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Open Access

Peer-reviewed

Research Article

The effect of flywheel training on strength and physical capacities in sporting and healthy populations: An umbrella review

Abstract

The aim of this umbrella review was to provide a detailed summary of how flywheel training enhances strength and physical capacities in healthy and athletic populations. The eleven reviews included were analyzed for methodological quality according to the Assessing the Methodological Quality of Systematic Review 2 (AMSTAR 2) and the Grading of Recommendations Assessment, Development and Evaluation (GRADE) criteria. Two were systematic reviews, six were systematic reviews with meta-analyses and three were narrative reviews. Although the included reviews support use of flywheel training with athletic and healthy populations, the umbrella review highlights disparity in methodological quality and over-reporting of studies (38 studies were included overall). Flywheel post-activation performance enhancement protocols can effectively enhance strength and physical capacities acutely with athletes and healthy populations. All relevant reviews support flywheel training as a valid alternative to traditional resistance training for enhancing muscular strength, power, and jump performance with untrained and trained populations alike. Similarly, reviews included report flywheel training enhances change of direction performance—although conclusions are based on a limited number of investigations. However, the reviews investigating the effect of flywheel training on sprint performance highlight some inconsistency in attained improvements with elite athletes (e.g., soccer players). To optimize training outcomes, it is recommended practitioners individualize (i.e., create inertia-power or inertia-velocity profiles) and periodize flywheel training using the latest guidelines. This umbrella review provides an analysis of the literature’s strengths and limitations, creating a clear scope for future investigations.

Citation: de Keijzer KL, Gonzalez JR, Beato M (2022) The effect of flywheel training on strength and physical capacities in sporting and healthy populations: An umbrella review. PLoS ONE 17(2): e0264375. https://doi.org/10.1371/journal.pone.0264375

Editor: Cristina Cortis, University of Cassino e Lazio Meridionale, ITALY

Received: October 27, 2021; Accepted: February 9, 2022; Published: February 25, 2022

Copyright: © 2022 de Keijzer et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Data Availability: The data are available online - it is an umbrella review, therefore, we have done a review of all previous reviews published on this topic. The papers used in this paper are reported in our manuscript and they can be found online.

Funding: The author(s) received no specific funding for this work.

Competing interests: The authors have declared that no competing interests exist.

Introduction

Flywheel devices were originally conceived to aid muscle mass maintenance of space travelers exposed to non-gravity environments [1]. More recently, the application of flywheel training as a resistance training method has elicited desirable neuromuscular and task specific adaptations across clinical [2] and sport performance contexts [3–5]. Flywheel devices utilize inertial disc(s) which rotate and store energy during the concentric portion according to the achieved rotational speed, inertial load, and machine characteristics [6, 7]. Subsequently, when the cord rewinds in the eccentric phase, the user is required to resist the rotating disc(s) [4]. The repetitive concentric-eccentric cycles can be performed in a variety of movements, allowing for versatility in training and application [8–10]. The flywheel paradigm is characterized by an unlimited resistance available during the entire range of motion [11, 12], with optimal muscle loading at any given joint angle [2]. If performed appropriately, flywheel exercise may provide a safe, effective, and more demanding eccentric phase (also termed eccentric-overload) than traditional resistance training [2, 4, 13]. Overall, flywheel exercise has been implemented as a valid training methodology to obtain acute and chronic physical capacity and sport performance related adaptations [3, 8, 14, 15].

Flywheel training may be especially beneficial for athletic populations [5, 14]. When applied within post-activation performance enhancement (PAPE) protocols, flywheel methods have shown to be very successful in enhancing strength and physical performance [8, 16–19]. Moreover, flywheel training has reported positive improvements in sport specific capacities after chronic application [20–22]—enhancing jump [23], sprint [24, 25], and change of direction (COD) ability of athletes [26, 27]. Flywheel training has also chronically improved neuromuscular capacity with healthy populations as well as reducing the likelihood of injury or falls and the negative impacts associated with limb disuse and ageing in other populations [2, 28]. With healthy populations, weekly improvements in force production (>2%) and muscle size (±1%) have been reported after only several weeks of training [12, 29–31]. Due to lacking evidence-based guidelines [10], a greater effort has been made towards developing guidelines for monitoring, testing, and periodization of flywheel training [5, 32, 33].

Initial reviews conducted on flywheel training have synthesized research and created practical recommendations and guidelines [4, 9], which provide key references for practitioners and aid decision making—optimizing prescription of training [3]. Yet, inconsistency in the literature exists regarding the effects of flywheel training on physical capacity (i.e., strength) and sport performance. For example, Maroto-Izquierdo et al. [4] reported a greater magnitude of muscle hypertrophy and physical performance after flywheel training in comparison to traditional resistance training. Conversely, Vicens-Bordas et al. [9] reported no differences between flywheel and traditional resistance training methods for enhancing strength. Several key factors may have influenced the pooled results and conclusions, including the number of databases searched, selection of search syntax, and the data analysis performed [34]. Not only does such inconsistency in the literature pose a challenge to creating definitive recommendations, but it also creates uncertainty regarding direction for future research. Given that some reviews and meta-analyses focus on slightly different aspects of sport performance (i.e., COD [15], PAPE [8], strength [14, 28]), an overall summary of the impact of flywheel training on physical capacities and strength is needed. Currently, no appropriate analysis or comparison of the quality of evidence supporting the use of flywheel training exists.

A proposed method to reduce the impact of limitations of individual reviews and meta-analyses is to synthesize and appraise them in the form of an umbrella review [34]. Umbrella reviews may help to better understand the evidence landscape by comparing conclusions based on all relevant published data. Umbrella reviews also allow for a greater analysis of bias in the literature which may implicitly affect the validity of the scientific evidence and misguide application [34]. Such analysis, although very important, is generally not performed in reviews and meta-analyses—meaning that bias often infiltrates practice undetected [35]. This umbrella review aims to provide a detailed summary of how flywheel training enhances strength and physical capacities in healthy and athletic populations. The quality and limitations of current evidence (expert-based reviews and meta-analytical evidence) are summarized, and important research avenues are set to explore.

Methods

Experimental approach to the problem

The present umbrella review was performed according to current umbrella review guidelines [34] and followed the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) statement guidelines [36]. Supporting information can be found in the S1 Checklist.

Search results

Two reviewers (KDK and MB) conducted a literature search on the following databases: PubMed, SPORTDiscus and Web of Science. The search syntaxes (including keywords and Boolean operators) have been reported here:

Pubmed search: ((((eccentric overload training) OR (flywheel training)) AND (sport performance [MeSH]) OR (muscular strength) Filters applied: Full text, Meta-Analysis, Review, Systematic Review, English; SportDiscus search: ((((eccentric overload training) OR (flywheel training)) AND (sport performance [MeSH]) OR (muscular strength); Web of Science search: TOPIC: (eccentric overload training) OR TOPIC: (flywheel training) AND TOPIC: (sport performance) OR TOPIC: (muscular strength).

ResearchGate was also utilized to find any other relevant texts not identified with the primary literature search. Screening of all bibliographies of selected texts was also performed. Duplicates were identified and removed by two reviewers separately (KDK and MB). The final search was conducted on September 15, 2021. Two reviewers (KDK and MB) independently screened titles and abstracts to identify studies that matched the research aim and inclusion criteria, with a third reviewer (JRG) consulted for discrepancies.

Inclusion criteria

Search records were limited to full-text articles in English. Utilizing the Participant-Intervention-Comparison-Outcome (PICO) process for evidence-based practice [37], the subsequent inclusion criteria were applied:

  1. Participants: Ranging from healthy adults and amateurs to professional sporting populations between the ages of 17–40.
  2. Interventions: Single and multi-component flywheel training programs aiming to enhance physical and/or strength capacity.
  3. Comparison group: Usual (no additional training) or alternative resistance training.
  4. Outcome measures: Jumping performance, sprinting performance, change of direction performance, swimming performance, isokinetic strength performance, eccentric hamstring strength performance, one-repetition maximum (1RM) strength, concentric power, eccentric power.

Supporting information and justification for exclusion can be found in S1 File.

Methodological quality and quality of the evidence assessment

The Assessing the Methodological Quality of Systematic Reviews 2 (AMSTAR 2) checklist was used to determine quality of reviews included [35]. Reviews were classified and scored by two reviewers (KDK and MB), if classification remained unclear, a third reviewer was included in the discussion (JRG). The 16 items of the checklist were answered with a ‘yes’ or ‘no’, with each ‘yes’ equaling 1 point. Reviews were classified as high (>80% items satisfied), moderate (40 to 80% items satisfied), or low quality (<40% items satisfied). An adapted form of the GRADE principles are applied to assess the quality of the evidence provided in the reviews included, as performed previously [38]. Reviews were classified into five GRADE categories: high; moderate; low; very low; no evidence from systematic review. A review was categorized as high quality if it consisted of at least two high-quality studies. Reviews with at least one high or two moderate quality studies were rated as moderate quality. If a review only includes moderate quality primary studies and/or primary studies presenting inconsistent results, that review was classified as low quality. Reviews are categorized as very low quality if they lack medium to high quality studies. Lastly, if the quality of the primary studies was not assessed by the reviewers, the GRADE system was not applied, and the review was classified as ‘no evidence from systematic review’.

Study coding and data extraction

The following moderator variables were extracted from the included reviews: (1) author details and year of publication, (2) main variables analyzed, (3) main objective of the review, (4) type of investigation, (5) review content (investigations and participants included as well as investigation duration), (6) main findings or conclusions reported. Data extraction, methodological quality assessment and quality of the evidence evaluation were performed independently by two authors (KDK and MB) and discrepancies between the authors were resolved in consultation with a third reviewer (JRG).

Results

Search results

The flow diagram (Fig 1) shows the retrieval process followed for this umbrella review. Initially, 2742 reviews were identified with the search criteria, while 1 additional review was found through a secondary search. Following this step, duplicate records were removed, and reviews were excluded based on their titles and/or abstracts. 18 full-text reviews were assessed, with 11 reviews included in the umbrella review.

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Fig 1. Flow diagram of the study retrieval process.

https://doi.org/10.1371/journal.pone.0264375.g001

Descriptive characteristics of the umbrella review

All of the studies that were included in the umbrella review are summarized in Table 1. These reviews were published between 2000 and 2021 and comprised of 38 primary studies corresponding to 608 participants in the experimental groups and 477 participants in the control groups. The 11 selected reviews either analyzed strength, chronic/acute physical capacity, or both. Studies that did not match the inclusion criteria were excluded. Specifically, key information for the reviews included can be found in Table 1. Two included reviews were systematic reviews [28, 39], six were systematic reviews with meta-analyses [4, 9, 14, 15, 40, 41], while three were narrative reviews [2, 8, 13].

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Table 1. Summary of reviews that investigated the effects of flywheel training on physical capacity and strength.

https://doi.org/10.1371/journal.pone.0264375.t001

Methodological quality assessment and quality of the evidence evaluation

The methodological quality of the 11 included reviews is presented in Tables 2 and 3. Two reviews were rated as high quality [9, 15], while six were considered moderate quality [4, 14, 28, 39–41] and three of low quality [2, 8, 13] using the AMSTAR 2 checklist. Critically, several AMSTAR 2 criteria were not met by a majority of reviews included [35]. Most reviews did not explicitly state that methods were established a priori (item 2). Reviews did not list excluded studies/justify exclusion (item 7), while all lacked a risk of bias assessment of individual studies included in their respective reviews (item 9). Furthermore, most reviews included did not consider the likelihood of publication bias (item 15). According to the adapted GRADE principles applied in the present umbrella review, five investigations were rated as high quality [4, 15, 28, 39, 40]. One review was rated as moderate quality [14], while the other five reviews did not critically appraise the included studies and could therefore not be assigned a GRADE rating [2, 8, 9, 13, 41].

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Table 2. Overall results of the AMSTAR 2 and GRADE recommendations for systematic reviews and meta-analyses.

https://doi.org/10.1371/journal.pone.0264375.t002

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Table 3. Overall results of the AMSTAR 2 and GRADE recommendations for narrative reviews.

https://doi.org/10.1371/journal.pone.0264375.t003

Discussion

This umbrella review provides a detailed summary of how flywheel training enhances strength and physical capacities in healthy and athletic populations and summarizes the quality and limitations of current evidence (expert-based reviews and meta-analytical evidence). The 11 included reviews and the 38 primary studies highlight important considerations for the implementation of flywheel training in sports (i.e., intensity, volume, frequency, modalities). Importantly, key texts within the current literature that significantly impact practice but are narrative reviews [2, 8, 13] were included.

Post-activation performance enhancement (PAPE)

The phenomenon defined as PAPE involves the enhancement of voluntary athletic performance following an activation activity (e.g., resistance exercise) [8, 42]. Phosphorylation of myosin regulatory light chains is suggested to be one of the main peripheral mechanisms associated with muscular performance enhancement [43]. Although the peripheral and central mechanisms underpinning PAPE remain debated [42–44], the research and application of flywheel PAPE protocols has seen a substantial increase over the past decade [8]. The present umbrella review reports that flywheel methods may be particularly effective when aiming to prepare for power-based tasks such as jumping and COD performance [8, 33, 45]. Interestingly, small acute improvements in isokinetic concentric and eccentric knee flexor strength have also been reported after flywheel PAPE protocols [8]. In support of such findings, a flywheel deadlift and squat PAPE protocol achieved moderate enhancements in eccentric isokinetic hamstring strength [16]. It is important to consider that PAPE protocols were traditionally developed to enhance rapid and power-based tasks more so than strength measures, possibly explaining the difference in literature on the topics [8, 46].

Similarly to strength outcomes, only one study in the umbrella review analyzed sprint speed, reporting a 0.7% (trivial) change in 20-meter sprint time [8]. In agreement with the review, another study reported no improvement in 5-meter acceleration performance after a similar flywheel half-squat PAPE protocol [47]. Although single set protocols enhanced diving performance and force parameters of a mixed cohort of swimmers [19, 48, 49], it remains unclear if a single set is sufficient to enhance other physical performance parameters [18]. A greater amount of research has been performed on COD and jumping tasks. The review supports the use of 3–4 sets of 6 repetitions of flywheel half-squats at a variety of inertial loads (0.03–0.11 kg·m2) and rest periods (3–9 min) to enhance performance of such measures [17, 47, 50–52]. If practitioners are unsure about optimal inertia selection with flywheel methods, an individualized PAPE protocol and minimal recommended rest periods should be employed [8]. Nonetheless, a large amount of variation in response to PAPE protocols has been noted in the literature, highlighting the importance of modulating factors (i.e., familiarization and experience) [46]. While similarity between the conditioning activity and subsequent athletic task does not appear to be a key factor for PAPE [16, 44, 53], flywheel training experience may be especially important for optimizing protocols and outcomes [8].

The brief review encapsulates seven studies (110 participants) relative to performance of various physical tasks (Table 1). Its aims were to synthesize preliminary literature, create methodological guidelines [8], and develop flywheel PAPE literature [16, 54]. Nonetheless, the conclusions of this review have some limitations considering the AMSTAR 2 checklist. Neither study selection nor data extraction was performed in duplicate, and authors did not justify study exclusion from the review. The authors did not perform a risk of bias assessment nor consider the potential effects of missing such an analysis [35]. Although the present review is valuable [8], future investigations on flywheel PAPE protocols based on high level evidence are necessary [8, 33].

Chronic performance

Strength.

The development of muscular strength is paramount to improving key muscular qualities, such as rate of force development [45]. Such improvements play key roles in optimizing sport performance and neuromuscular function of athletic and healthy populations [2, 45]. The interest in investigating the benefits of flywheel training for enhancing strength are highlighted by the multiple systematic and narrative reviews on the topic [2, 9, 13].

Systematic reviews. All of the systematic reviews (moderate to high AMSTAR 2 and no rating to high GRADE) supported flywheel training for enhancement of strength performance [4, 9, 14, 28, 39, 41]. Most of the reviews conclude that flywheel training is a valid alternative to traditional resistance training [9, 14, 28, 41]. In fact, Petre at al. (2018) reported large improvements in maximal strength (ES = 1.33) when 1–3 sessions were performed per week [14]. Such improvements in strength also appear to occur alongside rapid changes in pennation angle and fascicle length [12, 29]. The reported improvements in strength after flywheel training may be due to the effective development of both peripheral and central mechanisms [14]. Specifically, greater muscle activation, alterations in muscle morphology and to the length-tension relationship may be key to enhancements seen in the literature following flywheel training [12, 29, 55]. Importantly, strength improvements are typically seen after 5 to 10 weeks of flywheel training [4, 9, 14, 39], with one review highlighting that well-trained individuals may benefit more so than untrained individuals when training with the flywheel method [14]. Although it remains unclear why this occurs, it is possible that greater training experience or strength may allow for greater activation and control of the musculature during intense eccentric contractions [56].

Discord between systematic reviews exists regarding flywheel training and whether it is more effective [4] or equivalent to traditional resistance training for enhancing strength [9, 14, 28, 41]. Such differences are most probably due to the difference in inclusion criteria (i.e., different control groups or tests/measurements) which alter the findings of the meta-analyses and conclusions drawn from the systematic reviews [4, 9]. It remains difficult to conclude whether or not flywheel training is more effective than traditional resistance training and whether it is more effective with well-trained populations. Conclusions are limited by lacking well designed studies directly comparing the two methodologies [9, 30], with future research needed to clarify if differences exist.

Narrative reviews. Narrative reviews included in this umbrella review conclude that flywheel training is a valid resistance training method for enhancing strength (low quality and no GRADE applied) [2, 13]. Specifically, investigations applying flywheel training in a weekly and bi-weekly manner have enhanced strength during the in-season period with athletic populations [20, 21, 57]. Flywheel training can elicit larger force, torque, and muscle activation during the eccentric phase in comparison to the concentric phase [11, 12, 58]. In support of this, several reviews highlight that such an “eccentric overload” can be particularly beneficial for strength outcomes [2]. The exposure to optimized loading during both concentric and eccentric phases experienced with flywheel training may partly explain the distinct adaptations experienced in such short periods of time [11, 12, 29]. Such improvements are very attractive when training frequency must be reduced [10, 59, 60]. Nonetheless, caution is also warranted with such outcomes largely dependent upon appropriate movement familiarization and technique [2, 13]. Although future investigation into the effects of training experience on strength outcomes is warranted [31], weekly or bi-weekly flywheel training can be considered a viable method to enhance strength with athletes [20, 21, 57, 61]. More recently, interventions individualizing and progressively increasing inertia have been performed—enhancing performance and strength measures similarly to traditional resistance training [61, 62]. Nonetheless, future investigation into the effects of optimal frequency, varying training specificity, individualization, and appropriate progression criteria are necessary to develop application [13].

Sprint.

Sprint performance is frequently investigated because of its relevance to sporting demands and more generally because of its role as a physical capacity [4, 40]. Nonetheless, no review has been specifically dedicated to solely investigating speed or sprinting ability, as performed with strength [9] or COD performance [15, 28].

Systematic reviews. Four systematic reviews [4, 14, 39, 40] (moderate or high quality) were included in the present umbrella review. Training protocols with varying training exposure elicited favorable adaptations amongst soccer players [21, 62] and team-sport athletes [23–25]. The versatility of flywheel training in team-based environments is supported by the enhancements in sprint performance after squat [63], leg curl [21], leg press [23], and multi-exercise flywheel programs [26]. Favorably, such improvements in performance are seen after 5–10 weeks of training [40]. Furthermore, the application of flywheel multi-planar and sport-specific movements may also be beneficial for enhancement of sprint performance [40]. Changes towards faster muscle phenotypes [64] or changes in rate of production and retention of power during sprint strides are among several justifications for the benefits seen in sprint performance associated with eccentric and flywheel training [14]. The enhancement of concentric and eccentric strength has been seen alongside enhancement of sprint performance in athletic populations [4, 25]. Nonetheless, some investigations have reported limited benefits or trivial enhancements in sprint performance after flywheel training [20, 22, 26, 27, 65]. Recently, a randomized control trial investigating the effects of flywheel lateral squat training on physical capacity of U16 elite soccer players reported no enhancement of sprint performance—possibly due to the low training dose used (a weekly session) [27]. Alternatively, differences in familiarization protocols or training experience of the athletes may be key factors impacting outcomes [40]. One review specifically suggests that variation in sprint test outcomes may be specifically related to varying distances and instructions during sprint tests [14]. The literature supports the notion that flywheel training must be appropriately dosed to optimize efficacy [14, 39], which may not be possible in the context of prolonged congested fixture periods in season, when limited training time is available for athletes [59]. Of the four systematic reviews, one had large heterogeneity (I2 = 89%) in the variable sprint performance [14] and only one review accounted for the reliability measures of included individual studies [39]. Further investigation of low-dose flywheel training is therefore warranted to determine the effects of manipulating different training parameters during in-season periods on sprint performance [20, 25].

Narrative reviews. Flywheel training programs included in the reviews are typically performed weekly or bi-weekly with team sport athletes [2, 13], reflecting flywheel training frequency reported in professional soccer [10]. Although Tesch et al. (2017) [2] reported that sprint performance can be enhanced after application of flywheel training, the other narrative review reported inconsistent findings in both shorter (<10 m) and longer sprints (>20 m) [13]. Although inconsistent findings in sprint performance have been reported after flywheel training, several investigations highlight that other resistance training methods were similarly ineffective for enhancing sprint performance during in-season periods. For example, neither flywheel squat nor 80%1RM squat training enhanced 10 m and 30 m sprint performance with semi-professional soccer players [20]. Similarly, neither plyometric and resistance training protocols nor the addition of flywheel training to such training enhanced sprint performance outcomes with young males [26, 65]. The present review highlights the need for further high-quality studies on the topic (i.e., randomized controlled trials) to better understand how to optimally implement flywheel training to develop sprint performance.

Change of direction (COD).

COD are often characterized by demanding braking actions followed by immediate and high propulsive forces required to re-accelerate in a new direction [66]. Such actions are commonly performed in sport and are predominantly of interest for team-based sport athletes more so than healthy populations [67, 68]. Flywheel devices have been utilized to replicate similar movement patterns and transition from eccentric to concentric phases, which are believed to be particularly beneficial for enhancing change of direction outcomes [69, 70]. Logically, improvements in COD ability are therefore expected after appropriate application of flywheel training with athletic populations.

Systematic reviews. Two systematic reviews and meta-analyses investigating this topic were rated moderate or high on both AMSTAR 2 and GRADE [15, 40]. Although only involving three studies, Raya-Gonzalez et al. (2020) [40] reported flywheel training elicits significantly favorable outcomes in comparison to control conditions amongst athletes. Similarly, Liu et al., (2020) [15] reported beneficial COD outcomes after flywheel training. Such improvements in COD performance with team-based sport athletes were reported in comparison to regular training [66] and to traditional resistance training [20, 23, 26, 71]. Flywheel training appears to improve performance by reducing braking time and enhancing braking impulse during COD movements [15]. A systematic review by Allen et al. (2021) [39] (rated moderate and high on AMSTAR 2 and GRADE) also supported the efficacy of flywheel training for enhancing COD ability with adult male soccer players. Specifically, a variety of protocols appeared effective for enhancing COD performance parameters with youth and semi-professional soccer players [20, 26, 66]. Even though such improvements are reported, appropriate familiarization and adequate flywheel training technique are key to ensure COD performance enhancement with athletes [39, 40].

Narrative reviews. Two narrative reviews (rated low on AMSTAR 2, no GRADE applied) reached similar conclusions to the systematic reviews previously mentioned [2, 13]. Specifically, the authors highlight that other practical limitations affect flywheel training frequency and suggest that weekly training may still be effective for obtaining COD adaptations [20, 26]. Similarly, Raya-Gonzalez et al. (2020) [13] propose at least 8–11 weeks (one training session a week) and 6 weeks (two training sessions a week) of flywheel training be performed to enhance COD performance. Individualizing inertia chosen may further enhance COD outcomes [2, 58], although the optimal method to determine appropriate exercise inertia (intensity) remains unclear [6]. Nonetheless, the various tests (L-drill, V-cut) included in the narrative reviews suggest that flywheel training can enhance different types of COD tasks required in team-based sports [2, 13]. Although the recommendations provided by the narrative reviews presented are useful, their methodological limitations should be considered by practitioners (Table 2).

Although the reviews performed on COD performance and flywheel training involve a variety of team-based sports, they are predominantly based on a limited amount of investigations [13, 15, 39, 40]. This reflects the smaller number of investigations assessing the effects of flywheel training programs on COD ability in comparison to other physical qualities (e.g., jump performance). The obtained enhancements of jump ability in athletic and healthy populations also seem to be more consistent when compared to COD outcomes, which may be explained by a greater variation and disparity in training doses and tests utilized.

Jump.

Jumping performance is often utilized as a key indicator for lower-limb power, strength and physical ability with both healthy and athletic populations [4, 72]. Improvements in energy production and storage during the stretch-shortening cycle may be related to the transition from eccentric to concentric phases during flywheel training [73]. Moreover, the high eccentric demands of flywheel exercise may be an effective method to stimulate lower limb strength and power parameters, which can have a positive transfer to jumping performance [40].

Systematic reviews. Four systematic reviews and meta-analyses have specifically investigated the impact of flywheel training on jumping performance [4, 14, 39, 40]. The first systematic review on the topic (rated moderate and high on AMSTAR 2 and GRADE, respectively) conducted by Maroto-Izquierdo et al., 2017 [4] reported significant improvements (p < 0.01) in jump ability after 4–10 weeks of flywheel training, although it only involved 3 studies. Petré et al. [14] and Raya-González et al. [40] meta-analyzed 7 and 8 studies, respectively. The greater number of studies included, and the quality of the reviews (rated as moderate and high) further enhances confidence in application of flywheel training for jump performance enhancement in both athletic and healthy populations. In agreement with previous findings [4], both reported enhancement of jump performance after flywheel training protocols spanning 5–24 weeks [14, 40]. Similarly, another systematic review investigating the effects of flywheel training on young female populations reported improvements in jump ability [28]. The systematic review focused on female populations reported a greater effect when participant level was lower (healthy adults vs. team-sport athletes) and when weekly frequency was increased (1 vs. 3 weekly sessions) [28]. The systematic review by Allen et al. (2021) [39] observed that flywheel training frequently enhanced jumping ability of soccer players (only 1 of 7 studies did not report improvements). Overall, despite the promising results of the aforementioned findings, the meta-analyses included a variety of participants (healthy adults and team-sport athletes) [14, 40]. In fact, one of the meta-analyses included also reported high heterogeneity (I2 = 81%) [14], limiting conclusions. Further investigation into how flywheel training can enhance jumping performance of athletic populations may help optimize practical recommendations and conclusions.

Narrative reviews. Two narrative reviews and commentaries discussed the application of flywheel training for jump performance enhancement [2, 13]. The narrative review by Tesch et al. [2] reported enhancement of jump ability in healthy populations after flywheel training but does not provide conclusions for healthy athletic populations. On the other hand, Raya-González et al. [13] reviewed the application of how the flywheel paradigm is used to enhance jumping performance specifically in team-sport athletes. This review reported 3–10% improvements in countermovement jump performance when 4–6 sets of 6–10 repetitions of all-out flywheel half-squats were performed [13]. Nonetheless, when multi-exercise programs (including flywheel training) were implemented, no significant improvements in jump ability were seen [13]. Differences in response to training highlight that training specificity and exercise selection may be important considerations when designing flywheel training programs. When implementing flywheel training, it is recommended that practitioners use lower inertias for power-based actions and individualize training (i.e. create inertia-velocity or inertia-power profiles) if feasible [6, 32].

Limitations and future directions. A limitation of the present umbrella review is that majority of the reviews included utilized the same primary studies, highlighting a considerable over-reporting among reviews. As addressed earlier in the umbrella review, several limitations related to the methodological quality of the systematic and narrative reviews included affect the conclusions on the efficacy of flywheel training for developing strength and physical capacity. To enhance future investigations, authors are recommended to report all loading parameters (i.e., inertia) utilized in their protocols to enhance application and reproducibility. Furthermore, it is recommended to avoid using the term “eccentric overload” to define flywheel training. Instead, the term “eccentric overload” should only be used when confirmed (with appropriate measurements, e.g., encoder) and should be defined as a larger eccentric output in comparison to the respective concentric output—in line with previous recommendations [2, 33]. The present review echoes the need for further high-quality studies on PAPE and chronic flywheel protocols with elite athlete and female populations to enhance application [3, 28]. Research into the differences between flywheel and traditional resistance training for strength and physical capacity parameters is of interest and necessitates specific attention [3, 9]. Finally, further investigation into loading parameters, training frequency, and familiarization will enhance the quality of training protocols and outcomes.

Conclusions

This umbrella review provides a detailed summary on the effects of flywheel training for strength and physical capacity parameters in healthy and athletic populations and summarizes the quality and limitations of current evidence. Moreover, it provides an analysis of the literature’s strengths and limitations, creating a clear scope for future investigations and reviews. The 11 included reviews (including 38 primary studies) highlight that application of flywheel training with sports and healthy populations varies in prescription of exercise intensity, volume, frequency, and exercises. The variation in populations, protocols utilized, and methodological quality ratings of reviews included should be individually considered when interpreting findings. The evidence on flywheel PAPE protocols highlights that such protocols are effective for enhancing isokinetic hamstring strength, jump, and COD performance with athletes, although further high-quality investigations are necessary to confirm current findings. All reviews support use of flywheel training for enhancing muscular strength, power, and jump performance with healthy and athletic populations. All systematic and narrative reviews also conclude flywheel training improves change of direction performance—although conclusions are limited to fewer investigations than the aforementioned parameters. The reviews investigating the effect of flywheel training on sprint performance report some inconsistency in attained improvements with elite athletes (e.g., soccer players). To optimize training outcomes, it is recommended practitioners individualize (i.e., create inertia-power or inertia-velocity profiles) and periodize flywheel training using the latest guidelines [5, 32].

Supporting information

S1 File. Excluded studies (with justification).

https://doi.org/10.1371/journal.pone.0264375.s001

(DOCX)

S1 Checklist. PRISMA 2020 checklist.

https://doi.org/10.1371/journal.pone.0264375.s002

(DOCX)

References

  1. 1. Berg HE, Tesch A. A gravity-independent ergometer to be used for resistance training in space. Aviat Space Environ Med. 1994;65: 752–6. Available: https://europepmc.org/article/med/7980338 pmid:7980338
  2. 2. Tesch PA, Fernandez-Gonzalo R, Lundberg TR. Clinical Applications of Iso-Inertial, Eccentric-Overload (YoYo™) Resistance Exercise. Front Physiol. 2017;8. pmid:28496410
  3. 3. Beato M, Dello Iacono A. Implementing flywheel (isoinertial) exercise in strength training: current evidence, practical recommendations, and future directions. Front Physiol. 2020;11. pmid:32581845
  4. 4. Maroto-Izquierdo S, García-López D, Fernandez-Gonzalo R, Moreira OC, González-Gallego J, de Paz JA. Skeletal muscle functional and structural adaptations after eccentric overload flywheel resistance training: a systematic review and meta-analysis. J Sci Med Sport. 2017;20: 943–951. pmid:28385560
  5. 5. Beato M, Maroto-Izquierdo S, Hernández-Davó JL, Raya-González J. Flywheel Training Periodization in Team Sports. Front Physiol. 2021;12. pmid:34819871
  6. 6. McErlain-Naylor SA, Beato M. Concentric and eccentric inertia–velocity and inertia–power relationships in the flywheel squat. J Sports Sci. 2020; 1–8. pmid:33337956
  7. 7. Núñez FJ, Galiano C, Muñoz-López A, Floria P. Is possible an eccentric overload in a rotary inertia device? Comparison of force profile in a cylinder-shaped and a cone-shaped axis devices. J Sports Sci. 2020;38: 1624–1628. pmid:32299296
  8. 8. Beato M, McErlain-Naylor SA, Halperin I, Dello Iacono A. Current evidence and practical applications of flywheel eccentric overload exercises as postactivation potentiation protocols: A brief review. Int J Sports Physiol Perform. 2020;15: 154–161. pmid:31743092
  9. 9. Vicens-Bordas J, Esteve E, Fort-Vanmeerhaeghe A, Bandholm T, Thorborg K. Is inertial flywheel resistance training superior to gravity-dependent resistance training in improving muscle strength? A systematic review with meta-analyses. J Sci Med Sport. 2018;21: 75–83. pmid:29107539
  10. 10. de Keijzer K, McErlain-Naylor SA, Brownlee TE., Raya-González J, Beato M. Perception and application of flywheel training by professional soccer practitioners. Biol Sport. 2022.
  11. 11. Norrbrand L, Pozzo M, Tesch PA. Flywheel resistance training calls for greater eccentric muscle activation than weight training. Eur J Appl Physiol. 2010;110: 997–1005. pmid:20676897
  12. 12. Norrbrand L, Fluckey JD, Pozzo M, Tesch PA. Resistance training using eccentric overload induces early adaptations in skeletal muscle size. Eur J Appl Physiol. 2007;102: 271–281. pmid:17926060
  13. 13. Raya-González J, Castillo D, Beato M. The flywheel paradigm in team sports: A soccer approach. Strength Cond J. 2021;43: 12–22.
  14. 14. Petré H, Wernstål F, Mattsson CM. Effects of flywheel training on strength-related variables: a meta-analysis. Sport Med—Open. 2018;4: 55. pmid:30547232
  15. 15. Liu R, Liu J, Clarke CV, An R. Effect of eccentric overload training on change of direction speed performance: A systematic review and meta-analysis. J Sports Sci. 2020;38: 2579–2587. pmid:32677542
  16. 16. Beato M, de Keijzer KL, Fleming A, Coates A, La Spina O, Coratella G, et al. Post flywheel squat vs. flywheel deadlift potentiation of lower limb isokinetic peak torques in male athletes. Sport Biomech. 2020; 1–14. pmid:33112722
  17. 17. Beato M, De Keijzer KL, Leskauskas Z, Allen WJ, Dello Iacono A, McErlain-Naylor SA. Effect of postactivation potentiation after medium vs. high inertia eccentric overload exercise on standing long jump, countermovement jump, and change of direction performance. J Strength Cond Res. 2019;Publish Ah: 1. pmid:31232831
  18. 18. de Keijzer KL, McErlain-Naylor SA, Dello Iacono A, Beato M. Effect of volume on eccentric overload–induced postactivation potentiation of jumps. Int J Sports Physiol Perform. 2020;15: 976–981. pmid:32109884
  19. 19. Cuenca-Fernández F, López-Contreras G, Mourão L, de Jesus K, de Jesus K, Zacca R, et al. Eccentric flywheel post-activation potentiation influences swimming start performance kinetics. J Sports Sci. 2019;37: 443–451. pmid:30070620
  20. 20. Coratella G, Beato M, Cè E, Scurati R, Milanese C, Schena F, et al. Effects of in-season enhanced negative work-based vs traditional weight training on change of direction and hamstrings-to-quadriceps ratio in soccer players. Biol Sport. 2019;36: 241–248. pmid:31624418
  21. 21. Askling C, Karlsson J, Thorstensson A. Hamstring injury occurrence in elite soccer players after preseason strength training with eccentric overload. Scand J Med Sci Sports. 2003;13: 244–250. pmid:12859607
  22. 22. de Hoyo M, Pozzo M, Sañudo B, Carrasco L, Gonzalo-Skok O, Domínguez-Cobo S, et al. Effects of a 10-week in-season eccentric-overload training program on muscle-injury prevention and performance in junior elite soccer players. Int J Sports Physiol Perform. 2015;10: 46–52. pmid:24910951
  23. 23. Maroto-Izquierdo S, García-López D, de Paz JA. Functional and muscle-size effects of flywheel resistance training with eccentric-overload in professional handball players. J Hum Kinet. 2017;60: 133–143. pmid:29339993
  24. 24. Gonzalo-Skok O, Tous-Fajardo J, Valero-Campo C, Berzosa C, Bataller AV, Arjol-Serrano JL, et al. Eccentric-overload training in team-sport functional performance: Constant bilateral vertical versus variable unilateral multidirectional movements. Int J Sports Physiol Perform. 2017;12: 951–958. pmid:27967273
  25. 25. Timmins RG, Filopoulos D, Nguyen V, Giannakis J, Ruddy JD, Hickey JT, et al. Sprinting, strength and architectural adaptations following hamstring training in Australian footballers. Scand J Med Sci Sports. 2021. pmid:33617061
  26. 26. Tous-Fajardo J, Gonzalo-Skok O, Arjol-Serrano JL, Tesch P. Enhancing change-of-direction speed in soccer players by functional inertial eccentric overload and vibration training. Int J Sports Physiol Perform. 2016;11: 66–73. pmid:25942419
  27. 27. Raya-González J, Castillo D, de Keijzer KL, Beato M. The effect of a weekly flywheel resistance training session on elite U-16 soccer players’ physical performance during the competitive season. A randomized controlled trial. Res Sport Med. 2021; 1–15. pmid:33401975
  28. 28. Raya-González J, de Keijzer KL, Bishop C, Beato M. Effects of flywheel training on strength-related variables in female populations. A systematic review. Res Sport Med. 2021; 1–18. pmid:33401963
  29. 29. Seynnes OR, de Boer M, Narici M V. Early skeletal muscle hypertrophy and architectural changes in response to high-intensity resistance training. J Appl Physiol. 2007;102: 368–373. pmid:17053104
  30. 30. Lundberg TR, García-Gutiérrez MT, Mandić M, Lilja M, Fernandez-Gonzalo R. Regional and muscle-specific adaptations in knee extensor hypertrophy using flywheel versus conventional weight-stack resistance exercise. Appl Physiol Nutr Metab. 2019;44: 827–833. pmid:30620623
  31. 31. Fernandez-Gonzalo R, Lundberg TR, Alvarez-Alvarez L, de Paz JA. Muscle damage responses and adaptations to eccentric-overload resistance exercise in men and women. Eur J Appl Physiol. 2014;114: 1075–1084. pmid:24519446
  32. 32. Maroto-Izquierdo S, Raya-González J, Hernández-Davó JL, Beato M. Load Quantification and Testing Using Flywheel Devices in Sports. Front Physiol. 2021;12. pmid:34777007
  33. 33. Muñoz-López A, de Souza Fonseca F, Ramírez-Campillo R, Gantois P, Javier Nuñez F, Nakamura FY. The use of real-time monitoring during flywheel resistance training programmes: how can we measure eccentric overload? A systematic review and meta-analysis. Biol Sport. 2021. pmid:34937974
  34. 34. Aromataris E, Fernandez R, Godfrey CM, Holly C, Khalil H, Tungpunkom P. Summarizing systematic reviews: Methodological development, conduct and reporting of an umbrella review approach. Int J Evid Based Healthc. 2015. pmid:26360830
  35. 35. Shea BJ, Reeves BC, Wells G, Thuku M, Hamel C, Moran J, et al. AMSTAR 2: A critical appraisal tool for systematic reviews that include randomised or non-randomised studies of healthcare interventions, or both. BMJ. 2017. pmid:28935701
  36. 36. Liberati A, Altman DG, Tetzlaff J, Mulrow C, Gotzsche PC, Ioannidis JPA, et al. The PRISMA statement for reporting systematic reviews and meta-analyses of studies that evaluate healthcare interventions: explanation and elaboration. BMJ. 2009;339: b2700–b2700. pmid:19622552
  37. 37. Schardt C, Adams MB, Owens T, Keitz S, Fontelo P. Utilization of the PICO framework to improve searching PubMed for clinical questions. BMC Med Inform Decis Mak. 2007;7: 16. pmid:17573961
  38. 38. Brunner R, Friesenbichler B, Casartelli NC, Bizzini M, Maffiuletti NA, Niedermann K. Effectiveness of multicomponent lower extremity injury prevention programmes in team-sport athletes: an umbrella review. Br J Sports Med. 2019;53: 282–288. pmid:30201793
  39. 39. Allen WJC, de Keijzer KL, Raya-González J, Castillo D, Coratella G, Beato M. Chronic effects of flywheel training on physical capacities in soccer players: a systematic review. Res Sport Med. 2021; 1–21. pmid:34315310
  40. 40. Raya-González J, Prat-Luri A, López-Valenciano A, Sabido R, Hernández-Davó JL. Effects of Flywheel Resistance Training on Sport Actions. A Systematic Review and Meta-Analysis. J Hum Kinet. 2021;77: 191–204. pmid:34168704
  41. 41. Nuñez Sanchez FJ, Sáez de Villarreal E. Does Flywheel Paradigm Training Improve Muscle Volume and Force? A Meta-Analysis. J Strength Cond Res. 2017;31: 3177–3186. pmid:29068866
  42. 42. Blazevich AJ, Babault N. Post-activation potentiation versus post-activation performance enhancement in humans: Historical perspective, underlying mechanisms, and current issues. Front Physiol. 2019;10. pmid:31736781
  43. 43. Tillin NA, Bishop D. Factors Modulating Post-Activation Potentiation and its Effect on Performance of Subsequent Explosive Activities. Sport Med. 2009;39: 147–166. pmid:19203135
  44. 44. Boullosa D, Beato M, Dello Iacono A, Cuenca-Fernández F, Doma K, Schumann M, et al. A new taxonomy for postactivation potentiation in sport. Int J Sports Physiol Perform. 2020. pmid:32820135
  45. 45. Suchomel TJ, Nimphius S, Stone MH. The importance of muscular strength in athletic performance. Sport Med. 2016;46: 1419–1449. pmid:26838985
  46. 46. Seitz LB, Haff GG. Factors Modulating Post-Activation Potentiation of Jump, Sprint, Throw, and Upper-Body Ballistic Performances: A Systematic Review with Meta-Analysis. Sport Med. 2016;46: 231–240. pmid:26508319
  47. 47. Beato M, Bigby AEJ, de Keijzer KL, Nakamura FY, Coratella G, McErlain-Naylor SA. Post-activation potentiation effect of eccentric overload and traditional weightlifting exercise on jumping and sprinting performance in male athletes. Clemente FM, editor. PLoS One. 2019;14: e0222466. pmid:31513671
  48. 48. Cuenca-Fernández F, López-Contreras G, Arellano R. Effect on swimming start performance of two types of activation protocols. J Strength Cond Res. 2015;29: 647–655. pmid:25226318
  49. 49. Cuenca-Fernández F, Ruiz-Teba A, López-Contreras G, Arellano R. Effects of 2 types of activation protocols based on postactivation potentiation on 50-m freestyle performance. J Strength Cond Res. 2020;34: 3284–3292. pmid:33105381
  50. 50. Timon R, Allemano S, Camacho-Cardeñosa M, Camacho-Cardeñosa A, Martinez-Guardado I, Olcina G. Post-activation potentiation on squat jump following two different protocols: Traditional vs. inertial flywheel. J Hum Kinet. 2019;69: 271–281. pmid:31666909
  51. 51. Beato M, Stiff A, Coratella G. Effects of postactivation potentiation after an eccentric overload bout on countermovement jump and lower-limb muscle strength. J Strength Cond Res. 2019;Publish Ah: 1. pmid:30615009
  52. 52. de Hoyo M, de la Torre A, Pradas F, Sañudo B, Carrasco L, Mateo-Cortes J, et al. Effects of eccentric overload bout on change of direction and performance in soccer players. Int J Sports Med. 2014;36: 308–314. pmid:25525954
  53. 53. Beato M, Madruga-Parera M, Piqueras-Sanchiz F, Moreno-Pérez V, Romero-Rodriguez D. Acute Effect of Eccentric Overload Exercises on Change of Direction Performance and Lower-Limb Muscle Contractile Function. J Strength Cond Res. 2019;Publish Ah: 1. pmid:31490430
  54. 54. Maroto-Izquierdo S, Bautista I, Rivera F. Post-activation performance enhancement (PAPE) after a single-bout of high-intensity flywheel resistance training. Biol Sport. 2020;37: 343–350. pmid:33343067
  55. 55. Presland JD, Opar DA, Williams MD, Hickey JT, Maniar N, Lee Dow C, et al. Hamstring strength and architectural adaptations following inertial flywheel resistance training. J Sci Med Sport. 2020;23: 1093–1099. pmid:32461050
  56. 56. Hody S, Croisier J-L, Bury T, Rogister B, Leprince P. Eccentric muscle contractions: Risks and benefits. Front Physiol. 2019;10. pmid:31130877
  57. 57. Gual G, Fort-Vanmeerhaeghe A, Romero-Rodríguez D, Tesch PA. Effects of in-season inertial resistance training with eccentric overload in a sports population at risk for patellar tendinopathy. J Strength Cond Res. 2016;30: 1834–1842. pmid:26670989
  58. 58. Martinez-Aranda LM, Fernandez-Gonzalo R. Effects of inertial setting on power, force, work, and eccentric overload during flywheel resistance exercise in women and men. J Strength Cond Res. 2017;31: 1653–1661. pmid:28538317
  59. 59. Harden M, Bruce C, Wolf A, Hicks KM, Howatson G. Exploring the practical knowledge of eccentric resistance training in high-performance strength and conditioning practitioners. Int J Sports Sci Coach. 2020;15: 41–52.
  60. 60. Cross R, Siegler J, Marshall P, Lovell R. Scheduling of training and recovery during the in-season weekly micro-cycle: Insights from team sport practitioners. Eur J Sport Sci. 2019;19: 1287–1296. pmid:30922202
  61. 61. Puustinen J, Venojärvi M, Haverinen M, Lundberg TR. Effects of Flywheel vs. Traditional Resistance Training on Neuromuscular Performance of Elite Ice Hockey Players. J Strength Cond Res. 2021;Publish Ah.
  62. 62. Sagelv EH, Pedersen S, Nilsen LPR, Casolo A, Welde B, Randers MB, et al. Flywheel squats versus free weight high load squats for improving high velocity movements in football. A randomized controlled trial. BMC Sports Sci Med Rehabil. 2020;12: 61. pmid:33024564
  63. 63. Sabido R, Hernández-Davó JL, Botella J, Navarro A, Tous-Fajardo J. Effects of adding a weekly eccentric-overload training session on strength and athletic performance in team-handball players. Eur J Sport Sci. 2017;17: 530–538. pmid:28152673
  64. 64. Friedmann-Bette B, Bauer T, Kinscherf R, Vorwald S, Klute K, Bischoff D, et al. Effects of strength training with eccentric overload on muscle adaptation in male athletes. Eur J Appl Physiol. 2010;108: 821–836. pmid:19937450
  65. 65. Nuñez FJ, de Hoyo M, López AM, Sañudo B, Otero-Esquina C, Sanchez H, et al. Eccentric-concentric Ratio: A key factor for defining strength training in soccer. Int J Sports Med. 2019;40: 796–802. pmid:31434138
  66. 66. de Hoyo M, Sañudo B, Carrasco L, Mateo-Cortes J, Domínguez-Cobo S, Fernandes O, et al. Effects of 10-week eccentric overload training on kinetic parameters during change of direction in football players. J Sports Sci. 2016;34: 1380–1387. pmid:26963941
  67. 67. Zamparo P, Zadro I, Lazzer S, Beato M, Sepulcri L. Energetics of shuttle runs: The effects of distance and change of direction. Int J Sports Physiol Perform. 2014;9: 1033–1039. pmid:24700201
  68. 68. Reynolds J, Connor M, Jamil M, Beato M. Quantifying and Comparing the Match Demands of U18, U23, and 1ST Team English Professional Soccer Players. Front Physiol. 2021;12. pmid:34276425
  69. 69. Tesch PA, Ekberg A, Lindquist DM, Trieschmann JT. Muscle hypertrophy following 5-week resistance training using a non-gravity-dependent exercise system. Acta Physiol Scand. 2004;180: 89–98. pmid:14706117
  70. 70. Madruga-Parera M, Bishop C, Fort-Vanmeerhaeghe A, Beato M, Gonzalo-Skok O, Romero-Rodríguez D. Effects of 8 Weeks of Isoinertial vs. Cable-Resistance Training on Motor Skills Performance and Interlimb Asymmetries. J Strength Cond Res. 2020;Publish Ah: [Epub ahead of print]. pmid:32379241
  71. 71. de Hoyo M, Sañudo B, Carrasco L, Domínguez-Cobo S, Mateo-Cortes J, Cadenas-Sánchez MM, et al. Effects of Traditional Versus Horizontal Inertial Flywheel Power Training on Common Sport-Related Tasks. J Hum Kinet. 2015;47: 155–167. pmid:26557200
  72. 72. McErlain-Naylor S, King M, Pain MTG. Determinants of countermovement jump performance: a kinetic and kinematic analysis. J Sports Sci. 2014. pmid:24875041
  73. 73. Norrbrand L, Tous-Fajardo J, Vargas R, Tesch PA. Quadriceps Muscle Use in the Flywheel and Barbell Squat. Aviat Space Environ Med. 2011;82: 13–19. pmid:21235100