Do baseline cognitive status, participant specific characteristics and EDSS impact changes of cognitive performance following aerobic exercise intervention in multiple sclerosis?

PURPOSE: Cognitive impairment is a common symptom of multiple sclerosis (MS). Physical exercise represents a promising non-pharmacological therapy option, however, potential predictors for successful cognitive improvements mediated by exercise remain to be elucidated in order to optimize targeted exercise training regimens. One of the most promising exercise training regime in this context is high-intensity interval training (HIIT). Against this backdrop, this study i) analysed the effects of a three-week HIIT compared to moderate continuous exercise on cognitive performance and ii) investigated potential predictors for changes of cognitive performance following a three-week aerobic exercise intervention. METHODS: Datasets of two randomized controlled trials (RCT) were pooled, resulting in a total sample size of n = 130 persons with MS (pwMS) who either performed HIIT or moderate intensity continuous (MCT) exercise 3-5x/ week for three weeks. Cognitive performance was assessed with the Brief International Cognitive Assessment for MS. I) Potential within (time) and interaction (time x group) effects for cognitive performance were investigated with univariate analyses of covariance (ANCOVA). II) Potential predictors for changes of cognitive performance were assessed by multiple linear regression models. RESULTS: ANCOVA revealed significant time effects for all cognitive outcomes and a time x group interaction for verbal learning (p=.045), with HIIT inducing superior effects compared to moderate continuous exercise (MCT). Cognitive status (impaired/intact cognition) (p= .008) and exercise regime (HIIT/moderate continuous) (p=.040) influenced changes of verbal learning. Cognitive status (p=.006) and EDSS (p=.048) affected changes of visuospatial memory in pwMS. The models accounted for 5.4% and 7.7% of the variance. CONCLUSION: Cognitive status, exercise regime and EDSS potentially impact changes of specific cognitive domains following aerobic exercise. Further predictors for changes of cognitive performance following an aerobic exercise intervention need to be investigated as current results accounted only for a limited amount of variance. RCTs that investigate effects of physical exercise on cognitive performance should include only pwMS with impaired baseline cognitive performance. To better understand the impact of exercise on cognitive performance, it is furthermore recommendable to include cognitive assessments in clinical routine.

Phosphorylation of αB-crystallin and its cytoskeleton association differs in skeletal myofiber types depending on resistance exercise intensity and volume.

αB-crystallin (CRYAB) is an important actor in the immediate cell stabilizing response following mechanical stress in skeletal muscle. Yet, only little is known regarding myofiber type-specific stress responses of CRYAB. We investigated whether the phosphorylation of CRYAB at serine 59 (pCRYABSer59) and its cytoskeleton association are influenced by varying load-intensity and -volume in a fiber type-specific manner. Male subjects were assigned to 1, 5, and 10 sets of different acute resistance exercise protocols: hypertrophy (HYP), maximum strength (MAX), strength endurance (SE), low intensity (LI), and three sets of maximum eccentric resistance exercise (ECC). Skeletal muscle biopsies were taken at baseline and 30 min after exercise. Western blot revealed an increase in pCRYABSer59 only following 5 and 10 sets in groups HYP, MAX, SE, and LI as well as following 3 sets in the ECC group. In type I fibers, immunohistochemistry determined increased pCRYABSer59 in all groups. In type II fibers, pCRYABSer59 only increased in MAX and ECC groups, with the increase in type II fibers exceeding that of type I fibers in ECC. Association of CRYAB and pCRYABSer59 with the cytoskeleton reflected the fiber type-specific phosphorylation pattern. Phosphorylation of CRYAB and its association with the cytoskeleton in type I and II myofibers is highly specific in terms of loading intensity and volume. Most likely, this is based on specific recruitment patterns of the different myofiber entities due to the different resistance exercise loadings. We conclude that pCRYABSer59 indicates contraction-induced mechanical stress exposure of single myofibers in consequence of resistance exercise. NEW & NOTEWORTHY We determined that the phosphorylation of αB-crystallin at serine 59 (pCRYABSer59) after resistance exercise differs between myofiber types in a load- and intensity-dependent manner. The determination of pCRYABSer59 could serve as a marker indirectly indicating contractile involvement and applied mechanical stress on individual fibers. By that, it is possible to retrospectively assess the impact of resistance exercise loading on skeletal muscle fiber entities.