Effects of ambient temperatures and exercise modality on neuromuscular excitability in people with multiple sclerosis

Grover, Geetika (2016) Effects of ambient temperatures and exercise modality on neuromuscular excitability in people with multiple sclerosis. Masters thesis, Memorial University of Newfoundland.

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Abstract

The objective of this thesis was to examine how ambient temperatures ((Cool (16°C) vs. Room (21°C)) and exercise modality ((upright (Treadmill) vs. recumbent stepper (NuStep)) effects the neuromuscular excitability in people with Multiple Sclerosis (PwMS). Fourteen heat sensitive MS patients (10 Females), 49.28 ± 13.56 years of age with relapsing remitting MS and baseline expanded disability status scores ranging from 3.4 ± 2.37 participated in the study. Transcranial magnetic stimulation (TMS) elicited motor evoked potentials (MEPs) were recorded and assessed prior to and following aerobic exercise interventions at 65% of VO₂max. Tibial nerve stimulation elicited maximal muscle compound action potential (Mmax). Measurements were taken from the tibialis anterior, lateral gastrocnemius and soleus muscle of the weakest limb, both at rest and during a torque equivalent to 10% of maximal voluntary contraction (MVC). Participants attended four randomized experimental sessions including temperature ((Cool (16°C) and Room (21°C)) and exercise modality ((Treadmill (T) and NuStep (N)). Therefore, the experimental sessions were T in cool (TC), T in room (TR), N in cool (NC) and N in room (NR).MEP amplitudes were made relative toMmax amplitudes for analysis. The results showed that exercising on a NuStep in a cool ambient temperature resulted in greater MVC and peak twitch (PT) torque, reduced half relaxation time (HRT) and no change in Mmax indicating that exercising in a cool environment enhances voluntary contraction and electrically evoked contractile properties of the muscle in PwMS. Furthermore, MEPs were elicited more readily following exercise using the NuStep as compared to the treadmill. Regardless of ambient temperature and/or exercise modality; the number of MEPs elicited was strongly correlated with the neurological disability measured through the EDSS (i.e., the occurrence of MEPs was reduced significantly with increasing motor impairments). Strong correlations were also observed with neurological disability for: 1) MVC and 2) EMG of the LG and SOL. Furthermore, post exercise aural temperatures recorded did not change after exercising in cool (16°C) ambient temperature conditions, but were increased in room (21°C) temperature conditions. Overall, the experiment demonstrated that neuromuscular excitability of the lower limb is affected by the exercise modality and ambient temperature conditions, and PwMS should exercise in a cooler temperature conditions on non-weight bearing exercise modality such as NuStep.

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