Purpose To explore sex-based differences in energy substrate utilization during moderate-intensity aerobic exercise; to identify the underpinning candidate physiological mechanisms. Methods Three databases were searched from inception to August 2020. Pertinent studies quantifying the utilization of substrates during moderate aerobic exercise in healthy men and reproductive-age women were considered. Studies conducted on sedentary/recreationally active and athletic populations were included and analyzed separately. Results Thirty-five studies entered the meta-analysis (21 in sedentary/recreationally active, 14 in athletic populations). Compared to women, the respiratory exchange ratio was significantly higher both in sedentary (mean difference, MD: + 0.03; p < 0.00001) and athletic men (MD: + 0.02; p < 0.0001). Greater carbohydrate oxidation was observed both in sedentary (standardized MD, SMD: 0.53; p = 0.006) and athletic men (SMD: 1.24; p < 0.00001). Regarding lipid substrates, sedentary men oxidized less fat than women (SMD:  − 0.77; p = 0.0002), while no sex-based differences in fat oxidation were observed in athletes (SMD: 0.06; p = 0.77). Paucity of data prevented robust meta-analyses for protein sources. Sex hormones and different adrenergic activation were the most cited mechanisms to discuss sex-based differences. Conclusions Meta-analyses confirmed that men display greater reliance on carbohydrates while women rely more on lipids to sustain moderate aerobic exercise. The latter finding was not confirmed in athletes, a novel aspect of the present study. Mechanistically driven research is needed to further dissect the physiological underpinnings of sex differences in substrate utilization during aerobic exercise, especially for proteins, which are still less investigated than other substrates.

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Abstract Objective To date, no attention has been devoted to the employment of eccentric contractions to manage spasticity in multiple sclerosis. This single-system case series aimed to explore the effects of eccentric training on spasticity-related resistance to passive motion in people with multiple sclerosis with elbow flexor spasticity. Methods Six people with multiple sclerosis (median Expanded Disability Status Scale score = 4.8, range = 2.0–5.5; Modified Ashworth Scale [MAS] score ≤ 3) underwent a 6-week eccentric strength training of the spastic muscles. Before and after the intervention, the following outcomes were assessed: resistive peak torque (RPT), isometric strength, resting limb position, passive range of motion and active range of motion, severity of hypertonia by MAS, and numerical rating scale. At baseline, the primary outcome (RPT) was tested over 3 time points to ensure a stable measurement. The 2-SD method was used to test pre-post training effects at individual level. Group-level analyses were also performed. Results Following the intervention RPT decreased by at least 2 SDs in all participants but 1, with a significant reduction at group level of 41.6 (29.6)%. Four people with multiple sclerosis reported a reduction in perceived spasticity severity. No changes in MAS score were detected. Group-level analyses revealed that maximal strength increased significantly in the trained elbow flexors (+30.9 [9.1]%). Elbow flexion at rest was found to be significantly reduced (−35.5 [12.4]%), whereas passive range of motion (+4.6%) and active range of motion (+11.8%) significantly increased. Conclusion Eccentric training is feasible and safe to manage spasticity in people with multiple sclerosis. Preliminary data showed that this protocol can reduce resistance to passive motion, also improving strength, spasticity-free range of motion, and limb positioning. Impact Patients with multiple sclerosis–related spasticity and moderate-to-severe disability can benefit from adding slow submaximal eccentric contractions to the conventional management of spasticity.

Objective Research on muscle performance testing reliability in people with multiple sclerosis (PwMS) has focused on limb performance while less is known about trunk strength and endurance. The objective is to 1) establish test–retest reliability of Trunk Flexion, Lateral Flexion and Extension strength tests, and Plank, Side-Bridge and Biering-Sorensen endurance tests in PwMS and matched healthy controls (HC); 2) analyze known-groups validity of these tests in PwMS and HC; 3) to compare groups for side-to-side differences; 4) to describe the relationships between trunk performance and functional mobility tests. Methods Fifteen PwMS (median EDSS = 3) and 15 HC underwent two trunk isometric strength and endurance testing sessions. Mobility was evaluated by Timed Up-and-Go (TUG) test. Intraclass correlation coefficient (ICC), standard error of measurement (SEM) and minimal detectable change (MDC) were calculated. Between-group differences in trunk performance were tested using the Student’s t-test for independent measures. Between-group differences in an asymmetry index were analyzed by independent t-test. Bivariate correlations between trunk tests and mobility were also examined. Results All trunk tests showed good-to-excellent relative reliability in both groups (ICC &gt; 0.71). Regarding absolute reliability, strength tests were associated with low intersession variability in both groups (MDC: MS, 11.23–36.45%; HC, 26.60–31.98%). Conversely, endurance tests showed higher variability scores in PwMS (MDC: MS, 69.55–116.50%; HC, 29.57–54.40%). PwMS displayed significantly lower trunk performance. Likewise, the asymmetry index showed significantly higher scores in PwMS for endurance assessment but not in strength tests. Significant correlations were detected in PwMS between TUG and several trunk tests (r = 0.63–0.70). Conclusions SEM and MDC scores revealed similar consistency and variability between groups for strength tests, while higher variability was observed for endurance tests in PwMS. Trunk strength tests are reliable and present discriminant validity to distinguish mildly-disabled PwMS from HC. Conversely, the high measurement error and variability of the endurance tests may hinder their application in intervention programs. Impact Determining the reliability and validity of the tests currently used to assess trunk function is of utter importance for PwMS (who not only show impaired trunk function but also wide fluctuations in performance) as it requires consistent and accurate measurements that are sensitive enough to detect minimal changes induced by rehabilitation.

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