Ankle dorsiflexion asymmetry and the relationship with walking performance in people with multiple sclerosis.

BACKGROUND: Multiple sclerosis (MS) is a neurological disease characterized by demyelination disrupting the central nervous system. Persons with MS may exhibit symptomatic strength asymmetry (SA) that impacts motor gait and ankle mobility. The purpose of the present study was to investigate ankle dorsiflexion SA in people with MS and its relationship to functional performance. RESEARCH QUESTION: Is their a difference in dorsiflexion SA in MS participants compared to healthy individuals and does it impact functional performance? METHODS: 13 MS participants (EDSS 3.5 + 1.8) and 13 age matched NON-MS participants underwent maximal isometric (MVC) dynamometry testing for ankle dorsiflexion in both limbs to determine SA. Participants performed three functional tasks of walking performance. RESULTS: There was a significant intra-limb MVC difference in the MS group, and significantly greater isometric SA (p < 0.007) and isokinetic SA (p < 0.04) in the MS group compared to healthy individuals. The MS group exhibited significant correlations between outcomes of functional walking performance with isokinetic but not isometric SA. There was no significant correlation between disability status and functional task performance. SIGNIFICANCE: Ankle dorsiflexion SA is negatively correlated with functional performance in MS participants. MS disability status was not a predictor of functional task performance, and symptom testing may be appropriate to assess walking ability in persons with MS.

Relationship between soleus H-reflex asymmetry and postural control in multiple sclerosis.

BACKGROUND: Impaired postural control is a common symptom in people with multiple sclerosis. Multiple sclerosis frequently presents with asymmetric motor involvement. One measurement yet to be evaluated for asymmetry in people with multiple sclerosis is the soleus Hoffmann reflex. PURPOSE: To measure the soleus Hoffmann reflex between limbs and correlate reflex asymmetry with postural control. MATERIAL AND METHODS: 16 participants completed four sessions of Hoffmann reflex testing and one session of balance testing. RESULTS: Multiple sclerosis participants had significantly greater reflex asymmetry (p = 0.01). The multiple sclerosis group had a significantly lower overall sensory organization testing composite score (p < 0.05), indicating sensory interpretation conflict that resulted in greater postural instability. Multiple sclerosis participants produced a significantly shorter endpoint and maximum excursion (p < 0.01) during limits of stability testing. Hoffmann reflex asymmetry was negatively related to forward endpoint excursion (p < 0.05), maximum excursion (p ≤ 0.01). CONCLUSIONS: Multiple sclerosis participants had greater soleus Hoffmann reflex asymmetry, which appears to significantly influence forward postural control.Implications for rehabilitationSoleus Hoffmann reflex asymmetry appears to influence postural stability.The soleus Hoffmann reflex is capable of adapting to different modes of exercise; therefore, to reduce H-reflex asymmetry it is recommended to individualize physical rehabilitative programming.Assessing the soleus Hoffmann reflex in people with multiple sclerosis during health screenings could be of use to clinical and rehabilitative practitioners.

Eight Weeks of High-Volume Resistance Training Improves Onset of Blood Lactate in Trained Individuals.

Lantis, DJ, Farrell, JW, III, Cantrell, GS, and Larson, RD. Eight weeks of high volume resistance training improves onset of blood lactate in trained individuals. J Strength Cond Res 31(8): 2176-2182, 2017-The purpose of this study was to determine if onset of blood lactate (OBLA) using the fixed at 4 mmol·L method could be delayed by supplementing high-volume resistance training (HVRT) to existing endurance training programs. There were 20 male subjects who participated in the study; 11 experimental (EX) (22.8 ± 4.6 years) and 9 controls (CON) (23.2 ± 5.8 years). An incremental cycling test was performed to determine maximal oxygen uptake, OBLA, maximum power, and time to exhaustion. Additionally, strength of the leg press (LP), leg curl (LC), and leg extension (LE) was assessed in both groups. Participants continued their ongoing endurance training, whereas the EX group supplemented their training with HVRT twice weekly for 8 weeks, performing 4 sets of 15 repetitions of LP, LC, and LE. Change score (post-pre) analysis was measured, using t-tests to compare the differences between groups, to eliminate outside variables that may have affected testing performance. Significance was set at p ≤ 0.05. No significant group differences in baseline measures were observed. A significant difference was observed for OBLA at 4 mmol·L (EX: 18.17 ± 15.36 W and CON: -3.52 ± 20.13 W, p < 0.02). A significant difference was observed for LP (EX: 39.09 ± 25.87 kg and CON: 4.22 ± 34.65 kg, p < 0.02) and LC (EX: 22.84 ± 8.7 kg and CON: -1.47 ± 8.2 kg, p < 0.01). Supplementing HVRT in endurance-trained individuals delayed OBLA at 4 mmol·L and improved leg strength. The HVRT used in the current study may be a useful training style for endurance-trained individuals.

Maximal strength, power, and aerobic endurance adaptations to concurrent strength and sprint interval training.

PURPOSE: This study was designed to examine whether concurrent sprint interval and strength training (CT) would result in compromised strength development when compared to strength training (ST) alone. In addition, maximal oxygen consumption (VO2max) and time to exhaustion (TTE) were measured to determine if sprint interval training (SIT) would augment aerobic performance. METHODS: Fourteen recreationally active men completed the study. ST (n = 7) was performed 2 days/week and CT (n = 7) was performed 4 days/week for 12 weeks. CT was separated by 24 h to reduce the influence of acute fatigue. Body composition was analyzed pre- and post-intervention. Anaerobic power, one-repetition maximum (1RM) lower- and upper-body strength, VO2max and TTE were analyzed pre-, mid-, and post-training. Training intensity for ST was set at 85 % 1RM and SIT trained using a modified Wingate protocol, adjusted to 20 s. RESULTS: Upper- and lower-body strength improved significantly after training (p < 0.001) with no difference between the groups (p > 0.05). VO2max increased 40.9 ± 8.4 to 42.3 ± 7.1 ml/kg/min (p < 0.05) for CT, whereas ST remained unchanged. A significant difference in VO2max (p < 0.05) was observed between groups post-intervention (CT: 42.3 ± 7.1 vs. ST: 36.0 ± 3.0 ml/kg/min). A main effect for time and group was observed in TTE (p < 0.05). A significant main effect for time was observed in average power (p < 0.05). CONCLUSION: Preliminary findings suggest that performing concurrent sprint interval and strength training does not attenuate the strength response when compared to ST alone, while also improves aerobic performance measures, such as VO2max at the same time.

Muscle Activity in Single- vs. Double-Leg Squats.

Muscular activity, vertical displacement and ground reaction forces of back squats (BS), rear-leg elevated split squats (RLESS) and split squats (SS) were examined. Nine resistance-trained men reported for two sessions. The first session consisted of the consent process, practice, and BS 1-repetition maximum testing. In the second session, participants performed the three exercises while EMG, displacment and ground reaction force data (one leg on plate) were collected. EMG data were collected from the gluteus maximus (GMX), biceps femoris (BF), semitendinosus (ST), rectus femoris (RF), vastus lateralis (VL), vastus medialis (VM), tibialis anterior (TA), and medial gastrocnemius (MGas) of the left leg (non-dominant, front leg for unilateral squats). Load for BS was 85% one repetition maximum, and RLESS and SS were performed at 50% of BS load. Repeated measures ANOVA was used to compare all variables for the three exercises, with Bonferroni adjustments for post hoc multiple comparisons, in addition to calculation of standardized mean differences (ES). Muscle activity was similar between exercises except for biceps femoris, which was significantly higher during RLESS than SS during both concentric and eccentric phases (ES = 2.11; p=0.012 and ES= 2.19; p=0.008), and significantly higher during BS than the SS during the concentric phase (ES = 1.78; p=0.029). Vertical displacement was similar between all exercises. Peak vertical force was similar between BS and RLESS and significantly greater during RLESS than SS (ES = 3.03; p=0.001). These findings may be helpful in designing resistance training programs by using RLESS if greater biceps femoris activity is desired.