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Purpose: Delayed structural and functional recovery after a 20 km graded running race was analyzed with respect to the sex effect. Method s : Thirteen female and 14 male recreational runners completed the race and three test sessions: one before (PRE) and two after, once on Day 1 or 2 (D1‐2) and then on Day 3 or 4 (D3‐4). Muscle damage was assessed indirectly using ultrasonography to quantify changes in cross‐sectional area (CSA) of 10 lower‐limb muscles. Delayed onset of muscle soreness (DOMS) was assessed for three muscle groups. Functional recovery was quantified by kinetic analysis of a squat jump (SJ) and a drop jump (DJ) test performed on a sledge ergometer. Linear mixed models were used to assess control group reproducibility and recovery patterns according to sex. Results: Regardless of sex, DOMS peaked at D1‐2 for all muscle groups and resolved at D3‐4. CSA was increased in each muscle group until D3‐4, especially in the semimembranosus muscle. A specific increase was found in the short head of the biceps femoris in women. Regardless of sex, SJ and DJ performances declined up to D3‐4. Depending on the muscle, positive and/or negative correlations were found between structural and functional changes. Some of these were sex‐specific. Conclusion: Structural and functional recovery was incomplete in both sexes up to D3‐4, although DOMS had disappeared. More emphasis should be placed on hamstring muscle recovery. Highlighting the intermuscular compensations that can occur during multi‐joint testing tasks, the structural‐functional relationships were either positive or negative, muscle‐ and sex‐dependent. [ABSTRACT FROM AUTHOR]

Proprioception is the sense of position and movement of body segments. The widespread distribution of proprioceptors in human anatomy raises questions about proprioceptive uniformity across different body parts. For the upper limbs, previous research, using mostly active and/or contralateral matching tasks, has suggested better proprioception of the non-preferred arm, and at the elbow rather than the wrist. Here we assessed proprioceptive perception through an ipsilateral passive matching task by comparing the elbow and wrist joints of the preferred and non-preferred arms. We hypothesized that upper limb proprioception would be better at the elbow of the non-preferred arm. We found signed errors to be less variable at the non-preferred elbow than at the preferred elbow and both wrists. Signed errors at the elbow were also more stable than at the wrist. Across individuals, signed errors at the preferred and non-preferred elbows were correlated. Also, variable signed errors at the preferred wrist, non-preferred wrist, and preferred elbow were correlated. These correlations suggest that an individual with relatively consistent matching errors at one joint may have relatively consistent matching errors at another joint. Our findings also support the view that proprioceptive perception varies across upper limb joints, meaning that a single joint assessment is insufficient to provide a general assessment of an individual's proprioception. [ABSTRACT FROM AUTHOR]

In habitually shod recreational runners, we studied the combined influence of footwear and stretch-shortening cycle (SSC) fatigue on treadmill running pattern, paying special attention to neuro-mechanical adjustments in the acute and 2-day delayed recovery periods. The SSC exercise consisted of a series of 25 sub-maximal rebounds on a sledge apparatus repeated until exhaustion. The acute and delayed functional fatigue effects were quantified in a maximal drop jump test. The neuro-mechanical adjustments to fatigue were examined during two submaximal treadmill run tests of 3 min performed either barefoot or with shoes on. Surface electromyographic (EMG) activities, tibial accelerations and kinematics of the right lower limb were recorded during the first and last 15 s of each run. The main result was that neuro-mechanical differences between the shod and barefoot running patterns, classically reported in the absence of fatigue, persisted in the fatigued state. However, in the delayed recovery phase, rearfoot eversion was found to significantly increase in the shod condition. This specific footwear effect is considered as a potential risk factor of overuse injuries in longer runs. Therefore, specific care should be addressed in the delayed recovery phase of SSC fatigue and the use of motion control shoes could be of interest. [ABSTRACT FROM PUBLISHER]

A few years after their bilateral vestibular loss, patients usually show a motor repertoire that is almost back to normal. This recovery is thought to involve an upregulation of the visual and proprioceptive information that compensates for the lack of vestibular information. Here, we investigated whether plantar tactile inputs, which provide body information relative to the ground and to the Earth vertical, contribute to this compensation. More specifically, we tested the hypothesis that somatosensory cortex response to electric stimulation of the plantar sole in standing adults will be greater in humans ( n = 10) with bilateral vestibular hypofunction (VH) than in an age-matched healthy group ( n = 10). Showing significantly greater somatosensory evoked potentials (i.e., P 1 N 1 ) in VH than in control subjects, the electroencephalographic recordings supported this hypothesis. Furthermore, we found evidence that increasing the differential pressure between both feet, by adding a 1-kg mass at each pendant wrist, enhanced the internal representation of body orientation and motion relative to a gravitational reference frame. The large decrease in alpha power in the right posterior parietal cortex (and not in the left) is in line with this assumption. Finally, behavioral analyses showed that trunk oscillations were smaller than head oscillations in VH and showed a reverse pattern for healthy participants. These findings are consistent with a tactile-based postural control strategy in the absence of vestibular input and a vestibular-based control strategy in healthy participants where the head serves as a reference for balance control. NEW & NOTEWORTHY Somatosensory cortex excitability is greater in participants with bilateral vestibular hypofunction than in age-matched healthy humans. To control balance, healthy humans "locked" the head whereas participants with vestibular hypofunction "locked" their pelvis. For participants with vestibular hypofunction, increasing loading/unloading of the feet enhances the internal representation of body state in the posterior parietal cortex.

Amongst reduced gravity simulators, the lower body positive pressure (LBPP) treadmill is emerging as an innovative tool for both rehabilitation and fundamental research purposes as it allows running while experiencing reduced vertical ground reaction forces. The appropriate use of such a treadmill requires an improved understanding of the associated neuromechanical changes. This study concentrates on the runner's adjustments to LBPP-induced unweighting and reloading during running. Nine healthy males performed two running series of nine minutes at natural speed. Each series comprised three sequences of three minutes at: 100% bodyweight (BW), 60 or 80% BW, and 100% BW. The progressive unweighting and reloading transitions lasted 10 to 15 s. The LBPP-induced unweighting level, vertical ground reaction force and center of mass accelerations were analyzed together with surface electromyographic activity from 6 major lower limb muscles. The analyses of stride-to-stride adjustments during each transition established highly linear relationships between the LBPP-induced progressive changes of BW and most mechanical parameters. However, the impact peak force and the loading rate systematically presented an initial 10% increase with unweighting which could result from a passive mechanism of leg retraction. Another major insight lies in the distinct neural adjustments found amongst the recorded lower-limb muscles during the pre- and post-contact phases. The preactivation phase was characterized by an overall EMG stability, the braking phase by decreased quadriceps and soleus muscle activities, and the push-off phase by decreased activities of the shank muscles. These neural changes were mirrored during reloading. These neural adjustments can be attributed in part to the lack of visual cues on the foot touchdown. These findings highlight both the rapidity and the complexity of the neuromechanical changes associated with LBPP-induced unweighting and reloading during running. This in turn emphasizes the need for further investigation of the evolution over time of these neuromechanical changes., Competing Interests: The authors have declared that no competing interests exist.

Background: Since trunk morphology and curve types were reported to affect standing in adolescent idiopathic scoliosis (AIS), it is reasonable to assume that bracing could perturb standing balance in this population. The objective here was to use time- and frequency-domain analyses to test if the Boston brace affects balance in AIS., Material/methods: Fifteen AIS girls were fitted with a Boston brace. At the four-month follow-up, standing balance was assessed using center of pressure (COP) displacements measured from a force plate. The subjects were tested with and without the brace., Results: The mean position of the COP and the sway area were similar with and without the brace. Though the first peak in the power spectra was not statistically significant, the second peak was statistically smaller with the brace in the antero-posterior direction (p=0.012) and larger along the medio-lateral axis (p=0.022). In the antero-posterior direction there was a statistically significant shift towards higher mean (p=0.012) and median (p=0.003) frequencies with the brace, whereas no difference was noted in the medio-lateral direction. Time-domain parameters did not prove useful in differentiating between the in- and out-of-brace conditions in AIS individuals. The second peak in the power spectra could be associated with an inverse double-pendulum motion., Conclusions: The time-dependent parameters used in this study did not prove useful in differentiating between in-brace and out-of-brace conditions. Spectral analysis highlighted increased stiffness in the antero-posterior direction and less control in the medio-lateral axis in standing balance between in-brace and out-of-brace conditions in AIS.