Impact of pre-cooling therapy on the physical performance and functional capacity of multiple sclerosis patients: A systematic review

Highlights

• Pre-cooling therapy generates improvements in the multiple sclerosis patients’ functional capacity.

• Pre-cooling methods are effective in reducing core temperature within 30 min to 1 h of cooling, while the reduction of core temperature varied from 0.37 to 1°C.

• Pre-cooling therapy can prevent the symptom worsening due to increased body temperature in multiple sclerosis patients without causing adverse effects.

Abstract

Patients with multiple sclerosis experience many complications that gradually lead them to comorbidity and disability. Exercise could prevent and ameliorate the symptoms that comorbidity or inactivity generate. However, until recently it was suggested that multiple sclerosis patients should not participate in exercise training programs because these patients are characterized by thermoregulatory failure and the heat stress due to physical work could exacerbate the disease symptoms. Furthermore, taken into account that 60–80% of the multiple sclerosis patients present adverse clinical symptoms when their body temperature is increased (not only due to physical working but even when immerse in hot water or by exposure to infrared lamps or to the sun), the need for the development of treatment strategies to overcome the thermoregulatory problem in these patients is crucial. Given that pre-cooling has been proposed as an effective method, the aim of this systematic review is to discuss the current knowledge for the effects of cooling therapy on the functional capacity of multiple sclerosis patients. The relevant literature includes many articles, but only a handful of studies published thus far have used a cooling intervention in multiple sclerosis patients and have examined the effects of pre-cooling on functional capacity. These studies used active cooling methods, namely garments or other material that are cooled by circulating liquid through a tube, as well as passive, cooling methods. Passive cooling methods include passive cooling garments or other material namely garments that have ice or gel packs inside them. Overall, the results of all the studies analysed in this review demonstrated that pre-cooling therapy can prevent the symptom worsening due to increased body temperature in multiple sclerosis patients without causing adverse effects. Therefore, such strategies could serve as a complimentary therapeutic approach in multiple sclerosis patients.

Introduction

Multiple sclerosis (MS) (Schwid et al., 2003) is an autoimmune degenerative disease of the central nervous system characterized by inflammation, demyelination, and axonal loss (Schwid et al., 2003). The high global prevalence of MS, which is currently 33 patients per 100,000 adults (Browne et al., 2014), classifies it as one of the most frequent neurological diseases. Europe, with more than 30 patients per 100,000 adults, is among the regions with the highest prevalence in MS (Kurtzke, 2000). Overall, the disease prevalence appears to be particularly high in geographical areas where Caucasian people of Nordic origin live and in high-income countries (Koch-Henriksen and Sorensen, 2010). MS is considered a debilitating disease that reduces lifespan by around 7 to 10 years (Trapp and Nave, 2008). At the disease onset, most patients experience relapsing phases of exacerbated neurological impairments followed by partial or full remission (Trapp and Nave, 2008). However, a variable number of years after disease diagnosis MS patients can enter a secondary progressive phase where neurologic symptoms gradually worsen leading to disability (Lublin & Reingold, 1996). Studies, which have discussed the disability induced by MS (Confavreux et al., 2003, Huang et al., 2017), refer that the survival prognosis of MS patients is unpredictable and it is strongly associated with the patient’s age at the disease onset and the number of relapses that the patient will experience during the first five years.

MS affects mostly young individuals aged between 20 to 40 years and is the leading cause of morbidity and disability in young adults (Koch-Henriksen and Sorensen, 2010). Most MS patients experience multiple motor symptoms that induce gait difficulty and increase the risk for falls (Noseworthy et al., 2000) and other physical, cognitive and neurological symptoms that reduce their quality of life (Noseworthy et al., 2000). Exercise training may prevent or ameliorate these symptoms by preventing deconditioning and other comorbidities (Petajan and White, 1999, Sa, 2014). As some of the disabilities that MS patients experience e.g. muscle weakness and atrophy, could be considered as a consequence of inactivity and not a result of the disease per se (Dalgas, Stenager, & Ingemann-Hansen, 2008), it has been demonstrated that exercise can reduce inactivity-related impairments (Gallien et al., 2007). Therefore, it seems logical to speculate that exercise may induce clinically significant improvements in MS patients as well as benefits in their quality of life. However, the results of the studies regarding the effects of exercise training on MS patients report contradictory results. Specifically, aerobic exercise training has been proved to induce improvements in gait (Newman et al., 2007), in some functional abilities (Pilutti et al., 2011) and fatigue (Rampello et al., 2007). On the contrary, other authors did not observe exercise-induced improvements on the functional capacity in MS patients (Dalgas et al., 2008, Rasova et al., 2006, Schulz et al., 2004). Similarly, the results of the studies that applied exercise programs with resistance training were also contradictory (Cakt et al., 2010, Taylor et al., 2006).

MS patients for many years were advised not to participate in exercise training programs because there was a perception that the exercise could increase their body temperature and accordingly worsen the disease symptoms transiently (Freal et al., 1984, Heesen et al., 2006). Indeed, 60–80% of the MS patients present adverse clinical symptoms when their body temperature is increased not only due to physical work but also when immersed in hot water or during exposure to infrared radiation via the sun or electric lamps (Guthrie and Nelson, 1995). This phenomenon is characterized by visual impairment and paresis (Flensner et al., 2011) and was first described in 1890 by Wilhelm Uhthoff (Guthrie and Nelson, 1995). It can lead to exacerbation of MS patients’ neurological symptoms when body temperature is increased by as little as 0.5°C (Flensner et al., 2011, Davis et al., 1985) probably due to nerve conduction block in the demyelinated axonal segments (Davis et al., 1985). In this light, it is necessary to develop methods that allow MS patients to exercise by reducing their exercise-induced hyperthermia. The increased interest to address this problem is exemplified by the fact that a simple PubMed search using the search terms “multiple sclerosis” and “temperature” reveals a total of 507 articles that appear with increasing frequency through time reaching a peak of 17 articles/year during the past five years. Fig. 1 illustrates the evolution of publications using the aforementioned search terms clearly showing a growing interest in this field.

One of the main methods put forth to minimize the effects of exercise-induced hyperthermia in MS patients is pre-cooling therapy, which is based on the application of heat-removing material (vests/hoods/pads using phase-change material, liquid conditioning garments covering different parts of the body, etc.) on the skin surface (Flouris and Cheung, 2006, White et al., 2000, Goldberger, 1993). Typically, pre-cooling is used to reduce body temperature by 0.5–1.0°C (White et al., 2000, Reynolds et al., 2011) prior to the commencement of exercise and has been shown promising results (White et al., 2000, Reynolds et al., 2011). Nevertheless, to date the relevant literature has not been systematically analysed in order to critically assess the impact of pre-cooling on alleviating the symptoms of exercise-induced hyperthermia. In this article, we systematically evaluate the available research evidence to assess the impact of pre-cooling therapy on the physical performance and functional capacity of MS patients.