Influence of forearm orientation on biceps brachii tendon mechanics and elbow flexor force steadiness

Smart, Rowan R.; Kohn, Sienna; Richardson, Cydney M.; Jakobi, Jennifer M.

doi:10.1016/j.jbiomech.2018.05.039

Cited by 11 publications

(20 citation statements)

References 27 publications

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“…Because women frequently have lower MVC than men in the elbow flexor muscles (2), it is difficult to determine whether the larger increase in CV of force in women during cognitive challenge trial is truly a sex difference or associated with strength alone. Although the CV of force calculation already accounts for the mean force during the task (i.e., CV ϭ standard deviation of force/mean of force), a negative association between MVC and CV of force during contraction without cognitive challenge was reported (5,43,(62)(63)(64). The reasons for this association require further examination, with potential factors including mechanical properties such as tendon stress that was shown to be negatively associated with CV of force (62,63).…”

Section: Motor Unit Behavior and Force Steadiness With Aging In Men Amentioning

confidence: 99%

Oscillations in neural drive and age-related reductions in force steadiness with a cognitive challenge

Pereira

Schlinder-Delap

Keenan

et al. 2019

Journal of Applied Physiology

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A cognitive challenge when imposed during a low-force isometric contraction will exacerbate sex- and age-related decreases in force steadiness, but the mechanism is not known. We determined the role of oscillations in the common synaptic input to motor units on force steadiness during a muscle contraction with a concurrent cognitive challenge. Forty-nine young adults (19–30 yr; 25 women, 24 men) and 36 old adults (60–85 yr; 19 women, 17 men) performed a cognitive challenge (counting backward by 13) during an isometric elbow flexion task at 5% of maximal voluntary contraction. Single-motor units were decomposed from high-density surface EMG recordings. For a subgroup of participants, motor units were matched during control and cognitive challenge trials, so the same motor unit was analyzed across conditions. Reduced force steadiness was associated with greater oscillations in the synaptic input to motor units during both control and cognitive challenge trials ( r = 0.45–0.47, P < 0.01). Old adults and young women showed greater oscillations in the common synaptic input to motor units and decreased force steadiness when the cognitive challenge was imposed, but young men showed no change across conditions (session × age × sex, P < 0.05). Oscillations in the common synaptic input to motor units is a potential mechanism for altered force steadiness when a cognitive challenge is imposed during low-force contractions in young women and old adults. NEW & NOTEWORTHY We found that oscillations in the common synaptic input to motor units were associated with a reduction in force steadiness when a cognitive challenge was imposed during low-force contractions of the elbow flexor muscles in young women and old men and women but not young men. Age- and sex-related muscle weakness was associated with these changes.

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Section: Motor Unit Behavior and Force Steadiness With Aging In Men Amentioning

confidence: 99%

Oscillations in neural drive and age-related reductions in force steadiness with a cognitive challenge

Pereira

Schlinder-Delap

Keenan

et al. 2019

Journal of Applied Physiology

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“…While a majority of literature focuses on fatigue at the muscle fiber level, far less focus is on the effects of muscular fatigue at the tendon. There has been a growing emphasis on the tendon and its role in force steadiness (Johannsson et al, 2015;Jakobi et al, 2018;Smart et al, 2018). In the presence of muscular fatigue, after an acute bout of submaximal dynamic exercise, the Achilles tendon has been shown to exhibit sex-dependent behaviors, in which females exhibit greater tendon elongation and reduced tendon stiffness (Joseph et al, 2014).…”

Section: The Effects Of Performance Fatigability On Tracking Metricsmentioning

confidence: 99%

“…In the presence of muscular fatigue, after an acute bout of submaximal dynamic exercise, the Achilles tendon has been shown to exhibit sex-dependent behaviors, in which females exhibit greater tendon elongation and reduced tendon stiffness (Joseph et al, 2014). This may not translate directly to the upper extremity due to differing roles between the two muscle groups, however, further evidence suggests that the tendon plays a significant role in force steadiness (Smart et al, 2018). It is possible that there were tendon modifications that occurred as a result of the fatiguing protocol, although further investigation would be required.…”

Section: The Effects Of Performance Fatigability On Tracking Metricsmentioning

confidence: 99%

Dynamic Wrist Flexion and Extension Fatigue Induced via Submaximal Contractions Similarly Impairs Hand Tracking Accuracy in Young Adult Males and Females

Kumar

Forman

et al. 2020

Front. Sports Act. Living

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We evaluated the effects of muscle fatigue on hand-tracking performance in young adults. Differences were quantified between wrist flexion and extension fatigability, and between males and females. Participants were evaluated on their ability to trace a pattern using a 3-degrees-of-freedom robotic manipulandum before (baseline) and after (0, 1, 2, 4, 6, 8, and 10 mins) a submaximal-intensity fatigue protocol performed to exhaustion that isolated the wrist flexors or extensors on separate days. Tracking tasks were performed at all time points, while maximal voluntary contractions (MVCs) were performed at baseline, and 2, 6-, and 10-mins post-task termination. We evaluated movement smoothness (jerk ratio, JR), shape reproduction (figural error, FE), and target tracking accuracy (tracking error, TE). MVC force was significantly lower in females (p < 0.05), lower than baseline for all timepoints after task termination (p < 0.05), with no muscle group-dependent differences. JR did not return to baseline until 10-mins post-task termination (most affected), while FE returned at 4-mins post-task termination, and TE at 1-min post-task termination. Males tracked the target with significantly lower JR (p < 0.05), less TE (p < 0.05), and less FE (p < 0.05) than females. No muscle group-dependent changes in hand-tracking performance were observed. Based on this work, hand tracking accuracy is similarly impaired following repetitive submaximal dynamic wrist flexion or extension. The differences between male and female fatigability was independent of the changes in our tracking metrics.

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“…Force steadiness (FS), the ability to maintain a pre-established force at a target level, is used as a measure of functional performance [ 2 , 6 , 7 ], and in persons with PD, FS is less than in non-PD controls, independent of tremor [ 8 , 9 , 10 , 11 ]. FS varies with age, sex, muscle strength, and limb position, and is influenced by the nervous system and neuromuscular factors such as motor unit properties and tendon mechanics [ 12 , 13 , 14 , 15 , 16 , 17 ]. Plantar flexion strength and FS are less in persons with PD than healthy controls [ 8 ], but the reasons for these differences are unclear.…”

Section: Introductionmentioning

confidence: 99%

“…In older adults—relative to young—the lower FS is associated with alterations in neural drive [ 14 , 18 ] and muscle-tendon mechanics [ 16 ]. During muscle contraction, a stiffer tendon elongates less per applied unit of force, which facilitates smooth transfer of force through a more rigid unit and enables a more consistent force output [ 15 , 16 , 17 , 19 ]. Evaluating contributions of muscle shortening and tendon mechanics to plantar flexion FS in persons with PD is important, as FS is a strong predictor of functional movement performance [ 2 , 6 , 7 ].…”

Section: Introductionmentioning

confidence: 99%

Importance of Maximal Strength and Muscle-Tendon Mechanics for Improving Force Steadiness in Persons with Parkinson’s Disease

et al. 2020

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Although plantar flexion force steadiness (FS) is reduced in persons with Parkinson’s disease (PD), the underlying causes are unknown. The aim of this exploratory design study was to ascertain the influence of maximal voluntary contraction (MVC) force and gastrocnemius-Achilles muscle-tendon unit behaviour on FS in persons with PD. Nine persons with PD and nine age- and sex-matched non-PD controls (~70 years, 6 females per group) performed plantar flexion MVCs and sub-maximal tracking tasks at 5, 10, 25, 50 and 75% MVC. Achilles tendon elongation and medial gastrocnemius fascicle lengths were recorded via ultrasound during contraction. FS was quantified using the coefficient of variation (CV) of force. Contributions of MVC and tendon mechanics to FS were determined using multiple regression analyses. Persons with PD were 35% weaker during MVC (p = 0.04) and had 97% greater CV (p = 0.01) with 47% less fascicle shortening (p = 0.004) and 38% less tendon elongation (p = 0.002) than controls. Reduced strength was a direct contributor to lower FS in PD (ß = 0.631), and an indirect factor through limiting optimal muscle-tendon unit interaction. Interestingly, our findings indicate an uncoupling between fascicle shortening and tendon elongation in persons with PD. To better understand limitations in FS and muscle-tendon unit behavior, it is imperative to identify the origins of MVC decrements in persons with PD.

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Influence of forearm orientation on biceps brachii tendon mechanics and elbow flexor force steadiness

Cited by 11 publications

References 27 publications

Oscillations in neural drive and age-related reductions in force steadiness with a cognitive challenge

Oscillations in neural drive and age-related reductions in force steadiness with a cognitive challenge

Dynamic Wrist Flexion and Extension Fatigue Induced via Submaximal Contractions Similarly Impairs Hand Tracking Accuracy in Young Adult Males and Females

Importance of Maximal Strength and Muscle-Tendon Mechanics for Improving Force Steadiness in Persons with Parkinson’s Disease

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