Influence of forearm orientation on biceps brachii tendon mechanics and elbow flexor force steadiness |
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| Institution: | 1. Cleveland Akron Shoulder & Elbow Fellowship (CASE), Cleveland Shoulder Institute, University Hospitals of Cleveland, 3999 Richmond Road, Beachwood, OH 44122, USA;2. Cleveland Shoulder Institute, University Hospitals of Cleveland, 3999 Richmond Road, Beachwood, OH 44122, USA;3. Cleveland Akron Shoulder & Elbow Fellowship (CASE), Cleveland Shoulder Institute, University Hospitals of Cleveland, 3999 Richmond Road, Beachwood, OH 44122, USA;1. Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, FL, United States;2. Department of Physical Therapy, University of Florida, Gainesville, FL, United States;3. Exercise Science Program, Department of Physical Therapy, Marquette University, Milwaukee, WI, United States;1. Institute for Sport Science, Graz University, Austria;2. Department of Movement, Human and Health Sciences, University of Rome Foro Italico, Italy;3. Cardiff School of Sport, Cardiff Metropolitan University, Wales, UK;4. Department of Experimental Medicine and Surgery University of Tor Vergata, Rome, Italy;1. Research Center of Health, Physical Fitness & Sports, Nagoya University, Furo, Chikusa, Nagoya, Aichi 4648601, Japan;2. Graduate School of Education and Human Development, Nagoya University, Furo, Chikusa, Nagoya, Aichi 4648601, Japan;3. Graduate School of Medicine, Nagoya University, 65 Tsurumai, Showa, Nagoya, Aichi 4668560, Japan;4. Department of Sports Research, Japan Institute of Sports Sciences, 3-15-1 Nishigaoka, Kita, Tokyo 1150056, Japan |
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| Abstract: | Achilles tendon mechanics influence plantar flexion force steadiness (FS) and balance. In the upper limb, elbow flexor FS is greater in supinated and neutral forearm orientations compared to pronated, with contributions of tendon mechanics remaining unknown in position-dependent FS. This study investigated whether distal biceps brachii (BB) tendon mechanics across supinated, neutral and pronated forearm orientations influence position-dependent FS of the elbow flexors. Eleven males (23 ± 3 years) performed submaximal isometric elbow flexion tasks at low (5, 10% maximal voluntary contraction (MVC)) and high (25, 50, 75% MVC) force levels in supinated, neutral and pronated forearm orientations. Distal BB tendon elongation and CSA were recorded on ultrasound to calculate mechanics of tendon stress, strain and stiffness. Relationships between FS, calculated as coefficient of variation (CV) of force, and tendon mechanics were evaluated with multiple regressions. Supinated and neutral were ～50% stronger and ～60% steadier than pronated (p < 0.05). Tendon stress was ～52% greater in supinated and neutral compared to pronated, tendon strain was ～36% greater in neutral than pronated (p < 0.05), while tendon stiffness (267.4 ± 78.9 N/mm) did not differ across orientations (p > 0.05). At low forces, CV of force was predicted by MVC (r2: 0.52) in supinated, and MVC and stress in neutral and pronated (r2: 0.65–0.81). At high force levels, CV of force was predicted by MVC and stress in supinated (r2: 0.49), and MVC in neutral (r2: 0.53). Absolute strength and tendon mechanics influence the ability of the BB tendon to distribute forces, and thus are key factors in position-dependent FS. |
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| Keywords: | Ultrasound Neuromuscular Tendon stress Strength |
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