Is the joint-angle specificity of isometric resistance training real? And if so, does it have a neural basis?
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There are suggestions that isometric resistance training (RT) produces highly angle-specific changes in strength with the greatest changes at the training angle, but these effects remain controversial with limited rigorous evidence, and the possible underpinning physiological mechanism(s) remain opaque. This study investigated the extent of angle-specific changes in strength and neuromuscular activation after RT in comparison to a control group.
A RT group (n = 13) performed 14 isometric RT sessions at a knee-joint angle of 65° (0° is anatomical position) over a 4-week period, whilst a control group (CON, n = 9) maintained their habitual activity. Pre- and post-test sessions involved voluntary and evoked isometric knee extension contractions at five knee-joint angles (35°, 50°, 65°, 80° and 95°), while electromyography was recorded.
RT group increased maximum voluntary torque (MVT) at the training angle (65°; + 12%) as well as 80° (+ 7%), 50° (+ 11%) and 35° (+ 5%). Joint-angle specificity was demonstrated within the RT group (MVT increased more at some angles vs. others), and also by more rigorous between-group comparisons (i.e., larger improvements after RT vs. CON at some angles than others). For the RT group, normalized EMG increased at three of the same joint angles as strength, but not for CON. Importantly, however, neither within- or between-group analyses provided evidence of joint angle-specific changes in activation.
In conclusion, this study provides robust evidence for joint angle-specific strength gains after isometric RT, with weaker evidence that changes in neuromuscular activation may contribute to these adaptations.
KeywordsNeuromuscular activation Muscle contractile properties Torque production Angle specificity
Within-participant coefficient of variation
Explosive contraction training
Explosive voluntary contraction
Supramaximal muscle compound action potential
- MMAX P–P
MMAX peak-to-peak amplitude
Maximum voluntary contraction
Maximum voluntary torque
- Octet PT
Octet peak torque
- Octet T50
Octet torque measure at 50 ms after torque onset
Quadriceps femoris EMG epoch between 0 and 50 ms after EMG onset
Quadriceps femoris EMG epoch between 0 and 100 ms after EMG onset
Quadriceps femoris EMG epoch between 0 and 150 ms after EMG onset
Quadriceps femoris EMG at maximum voluntary torque
Sustained contraction training
Explosive torque at 50 ms after torque onset
Explosive torque at 100 ms after torque onset
Explosive torque at 150 ms after torque onset
- Twitch PT
Twitch peak torque
- Twitch T50
Twitch torque measure at 50 ms after torque onset
MBL, TGB, and JPF contributed to the design and implementation of the research to the analysis of the results and to the writing of the manuscript. All authors read and approved the manuscript.
Compliance with ethical standards
Conflict of interest
All authors declare that they have no conflicts of interest.
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