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Ankle joint angle position sense (JPS) plays a crucial role in maintaining balance and coordinating movements, yet its changes across the lifespan remain unclear. This cross-sectional study aimed to investigate changes in ankle JPS across the lifespan using an ipsilateral reproduction task (IRT) and a contralateral concurrent matching task (CMT). One hundred and fifty eight individuals (6-92yrs) were allocated into 6 groups: Young-children (YC; n = 14) and Old-children (OC; n = 15), Young (Y: 19-39yrs; n = 33), Middle-aged (M: 40-59yrs; n = 41), Young-Old (YO: 60-5yrs; n = 24) and Old-Old (OO: >76yrs; n = 31) adults. The IRT consisted of reproducing a previously experienced ankle angle with the same limb. The CMT consisted of matching the passively held target ankle angle of one limb with the contralateral ankle. Both tests were performed blind-folded from 5° and 20° plantar flexion position to a 5° dorsiflexion target position. Error was expressed in absolute (AE) and constant (CE) values. In IRT, no difference was observed for AE and CE (p > 0.05) between groups, regardless of the initial position (5° or 20°). For the CMT, no age effect was observed for AE (p > 0.05), but children and older adults showed more positive (overestimation) and more negative (underestimation) CE, respectively, regardless of the initial position (p < 0.001). These results indicate that age affects the direction of the error (CE) rather than the magnitude of the error (AE), regardless of the angular range. They further suggest that CMT and CE could be more relevant when comparing ankle JPS between populations of different ages., Competing Interests: Declarations. Competing interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2025. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The purpose of this study was to show that velocity-specific training may be implicated in modifications in the level of coactivation of agonist and antagonist muscles. Healthy males (n = 20) were randomly placed in to two groups: one group trained using concentric contractions (n = 12), the other was an untrained control group (n = 8). The training group underwent unilateral resistance training at a level of 35 (5)% of a one-repetition maximal contraction of the elbow flexors, executed at maximal angular velocity. Training sessions consisted of six sets of eight consecutive elbow flexions, three times per weak for a total of seven weeks. The velocity of the ballistic movements executed during training were measured using an optoelectronic measuring device (Elite), both at the beginning and at the end of the training period. Subjects were tested pre- and post-training during isokinetic maximal elbow flexions with constant angular torque (CAT) at 90 degrees (0 degrees = full extension), and at different velocities (60, 120, 180, 240 and 300 degrees x s(-1)) for concentric actions, and -60 and -30 degrees x s(-1) for eccentric and isometric contractions at 90 degrees. In order to verify the levels of activation of the agonist biceps brachii (BB) muscles and antagonist triceps brachii (TB) muscles during maximal voluntary activation, their myoelectrical activities were recorded and quantified as root mean square (RMS) amplitudes, between angles of 75 and 105 degrees . The results show that mean angular velocities between elbow angles of 75 and 105 degrees were similar before [302 (32) degrees x s(-1)] and after [312 (27) degrees x s(-1)] the training period. CAT significantly increased measures at angular velocities of 240 and 300 degrees x s(-1) by 18.7% and 23.5%, respectively. The RMS activity of BB agonist muscles was not significantly modified by training. Post-training normalized RMS amplitudes of TB antagonist muscles were inferior to those observed at pre-training, but values were only significantly different at 300 x s(-1). In conclusion, in this study we attempted to show that an increase of CAT to 240 and 300 degrees x s(-1), though velocity-specific training, may be due, in part, to a lowering of the level of coactivation.

The aim of this study was to examine isokinetic torque produced by highly skilled (HS) and sedentary (S) human subjects, during knee extension, during maximal voluntary and superimposed electrical activation. To verify the level of activation of agonist (vastus lateralis, VL, and vastus medialis, VM) and antagonist muscles (semi-tendineous, ST), during maximal voluntary activation, their myo-electrical activities were detected and quantified as root mean square (rms) amplitude. Ten HS and ten S subjects performed voluntary and superimposed isometric actions and isokinetic knee extensions at 14 angular velocities (from -120 to 300 degrees*s(-1)). The rms amplitude of each muscle was normalized with respect to its rms amplitude when acting as agonist at 15 degrees*s(-1). Whatever the angular velocity considered, peak torque and constant angular torque at 65 degrees of HS were significantly higher (P <0.05) than those of S. Eccentric superimposed torque of S, but not HS, was significantly higher (P <0.05) than voluntary torque at -120, -90, - 60 and - 30 degrees*s(-1) angular velocities. For a given velocity, the rms amplitude of VL and VM were significantly lower (P <0.05), during eccentric than during concentric actions, in S, but not in HS. However, whatever the angular velocity, ST co-activation in HS was significantly lower (P < 0.05) than in S. We concluded that co-activation phenomenon could partly explain differences in isokinetic performances. Differences between voluntary and superimposed eccentric torques as well as lower agonist rms amplitude during eccentric action in S, support the possibility of the presence of a tension-regulating mechanism in sedentary subjects.