Isometric versus isotonic contractions: Sex differences in the fatigability and recovery of isometric strength and high‐velocity contractile parameters

Ha, Phuong Hoai; Dalton, Benjamin E.; Alesi, Michaela G.; Smith, Tyler M; VanDusseldorp, Trisha A.; Feito, Yuri; Hester, Garrett M.

doi:10.14814/phy2.14821

Cited by 7 publications

(2 citation statements)

References 32 publications

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“…This, however, is misleading in that the diminished fatigability, or decline in force production over 5 min, is mainly due to the fact that relative to all other experimental groups, juvenile unloaded rats were already markedly weakened, and thus had little potential for further decline in strength during testing. Previously, it has been shown that muscles with small initial amounts of strength display less fatigue during an endurance test than those with higher levels of strength ( Hunter et al, 2006 ; Kent-Braun, 2009 ; Ha et al, 2021 ).…”

Section: Discussionmentioning

confidence: 99%

Juvenile Neuromuscular Systems Show Amplified Disturbance to Muscle Unloading

et al. 2021

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Muscle unloading results in severe disturbance in neuromuscular function. During juvenile stages of natural development, the neuromuscular system experiences a high degree of plasticity in function and structure. This study aimed to determine whether muscle unloading imposed during juvenile development would elicit more severe disruption in neuromuscular function than when imposed on fully developed, mature neuromuscular systems. Twenty juvenile (3 months old) and 20 mature (8 months old) rats were equally divided into unloaded and control groups yielding a total of four groups (N = 10/each). Following the 2 week intervention period, soleus muscles were surgically extracted and using an ex vivo muscle stimulation and recording system, were examined for neuromuscular function. The unloading protocol was found to have elicited significant (P ≤ 0.05) declines in whole muscle wet weight in both juvenile and mature muscles, but of a similar degree (P = 0.286). Results also showed that juvenile muscles displayed significantly greater decay in peak force due to unloading than mature muscles, such a finding was also made for specific tension or force/muscle mass. When examining neuromuscular efficiency, i.e., function of the neuromuscular junction, it again was noted that juvenile systems were more negatively affected by muscle unloading than mature systems. These results indicate that juvenile neuromuscular systems are more sensitive to the effects of unloading than mature ones, and that the primary locus of this developmental related difference is likely the neuromuscular junction as indicated by age-related differences in neuromuscular transmission efficiency.

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Section: Discussionmentioning

confidence: 99%

Juvenile Neuromuscular Systems Show Amplified Disturbance to Muscle Unloading

et al. 2021

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“…It is important to note, though, that hip abductor fatigue is used only as a surrogate of muscle weakness and is not an exact replication. Although isolated fatigue protocols decrease force production capacity [14,15], subjects with natural weakness can develop compensation mechanisms that may alter lower limb alignment [3]. However, fatigue-induced hip abductor weakness allows researchers to identify a cause-and-effect relationship between weakness and biomechanics, which is not possible when cross-sectionally evaluating subjects that already present hip-abductor weakness [5].…”

Section: Introductionmentioning

confidence: 99%

Effects of task and hip-abductor fatigue on lower limb alignment and muscle activation

et al. 2021

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Purpose Fatigue-induced hip-abductor weakness may exacerbate lower-limb misalignments during different dynamic single-leg tasks. We sought to evaluate the effects of fatigue and task on lower limb kinematics and muscle activation and to find associations between measurements obtained in two tasks. Methods One-group pretest–posttest design. Seventeen healthy adults (9 W) performed the single-leg squat (SLSQUAT) and the single-leg hop (SLHOP) before and after a hip-abduction fatigue protocol. Hip adduction, knee frontal plane projection angle (knee FPPA) and heel inversion displacement were measured during the eccentric phase of the SLSQUAT and the SLHOP, as well as activation of the gluteus medius (GMed), tensor fascia latae (TFL), peroneus longus (PER) and tibialis anterior (TA). Moments and tasks were compared using a repeated-measures two-way ANOVA. Correlation between tasks was evaluated using Spearman’s correlation. Results No differences in kinematics or activation were found between moments. Hip-adduction displacement (P = 0.005), GMed (P = 0.008) and PER (P = 0.037) activation were higher during SLSQUAT, while TA activation was higher during SLHOP (P < 0.001). No differences were found between tasks in knee FPPA and heel inversion. Hip-adduction and knee FPPA were not correlated between tasks, while ankle inversion displacement was positively correlated (rs = 0.524–0.746). Conclusion Different characteristics of SLSQUAT (slower and deeper) seem to have led to increased hip adduction displacement, GMed, and PER activation and decreased TA activation, likely due to higher balance requirements. However, hip-abductor fatigue didn’t influence lower-limb alignment during the tasks. Finally, evaluations should be performed with different single-leg tasks since they don’t give the same lower-limb alignment information.

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