Background: Chronic non-specific neck pain (CINP) is common, but the etiology remains unclear. This study aimed to examine the relationship between cervical muscle composition (cervical multifidus and longus capitis/longus colli), morphometry, range of movement, muscle function, and disability severity (Neck Disability Index) in patients with CINP. Methods: From September 2020 to July 2021, subjects underwent cervical MRI and clinical tests (cervical range of motion, cranio-cervical flexion test, neck flexor, and extensor muscle endurance). MRI analysis comprised muscle cross-sectional area, volume, and fat infiltration of multifidus and longus colli between C4 and C7 levels. Results: Twenty-five participants were included. Multiple linear regression analysis indicated that NDI was positively correlated with the volume percentage of fat infiltration of the multifidus (B = 0.496), negatively correlated with fat-free muscle volume of the multifidus normalized by subject height (B = −0.230), and accounted for 32% of the variance. There was no relationship between neck disability and longus capitis/longus colli morphology. We also found no relationship between neck disability scores, neck flexor or extensor muscle endurance, or the outcome motor control test of craniocervical flexion (p > 0.05). Conclusions: Neck disability was moderately correlated with the percentage of fat volume in the multifidus muscle and fat-free volume of the multifidus. There was no relationship between NDI scores and muscle function test outcomes or any fat or volume measures pertaining to the longus colli muscle.

Background: This systematic review aimed to provide a comprehensive overview of the effects of functional electrical stimulation (FES) on gait characteristics in healthy individuals. Methods: Six electronic databases (PubMed, Embase, Epistemonikos, PEDro, COCHRANE Library, and Scopus) were searched for studies evaluating the effects of FES on spatiotemporal, kinematic, and kinetic gait parameters in healthy individuals. Two examiners evaluated the eligibility and quality of the included studies using the PEDro scale. Results: A total of 15 studies met the inclusion criteria. The findings from the literature reveal that FES can be used to modify lower-limb joint kinematics, i.e., to increase or reduce the range of motion of the hip, knee, and ankle joints. In addition, FES can be used to alter kinetics parameters, including ground reaction forces, center of pressure trajectory, or knee joint reaction force. As a consequence of these kinetics and kinematics changes, FES can lead to changes in spatiotemporal gait parameters, such as gait speed, step cadence, and stance duration. Conclusions: The findings of this review improve our understanding of the effects of FES on gait biomechanics in healthy individuals and highlight the potential of this technology as a training or assistive solution for improving gait performance in this population.

In recent years, running has dramatically increased in children and adolescents, creating a need for a better understanding of running gait in this population; however, research on this topic is still limited. During childhood and adolescence multiple factors exist that likely influence and shape a child’s running mechanics and contribute to the high variability in running patterns. The aim of this narrative review was to gather together and assess the current evidence on the different factors that influence running gait throughout youth development. Factors were classified as organismic, environmental, or task-related. Age, body mass and composition, and leg length were the most researched factors, and all evidence was in favour of an impact on running gait. Sex, training, and footwear were also extensively researched; however, whereas the findings concerning footwear were all in support of an impact on running gait, those concerning sex and training were inconsistent. The remaining factors were moderately researched with the exception of strength, perceived exertion, and running history for which evidence was particularly limited. Nevertheless, all were in support of an impact on running gait. Running gait is multifactorial and many of the factors discussed are likely interdependent. Caution should therefore be taken when interpreting the effects of different factors in isolation.

In many sports, practitioners must reach their maximal jump height (h_max) under time constraints. This requires a reduction of the countermovement depth and so of the push-off distance (h_PO). The purpose of this study was to investigate how h_PO influences force–velocity (F–v) profiles (, , , and S_Fv) and performance. Eleven participants (age: 26 [5] y, height: 175.6 [11.2] cm, mass: 76 [15] kg; squat 1RM: 129 [34] kg) performed maximal countermovement jumps. Kinetic and kinematic measurements were used to assess individual F–v profiles for 3 different h_PO conditions (h_PO-SMALL, h_PO-MEDIUM, h_PO-LARGE) from countermovement jumps performed under different load conditions (bodyweight [BW], BW + 8 kg, BW + 17 kg, BW + 40%1RM, BW + 70%1RM). Results indicated that and changed across h_PO conditions, while remained constant. A lower h_PO led to a significantly higher and . These changes resulted in a steeper S_Fv leading to a more force-oriented profile, a lower optimal S_Fv and a greater F–v imbalance. Reducing h_PO and modifying F–v profile led, to some extent, to a reduction in h_max. Performance is a compromise between h_PO, , and F–v imbalance, all influenced by countermovement depth. This explains why reducing countermovement depth to meet time constraint may lower performance.

Context: Strength-endurance mainly depends on the power output, which is often expressed relative to the individual’s maximal power capability (P_max). However, an individual can develop the same power, but in different combinations of force and velocity (force-velocity condition). Also, at matched power output, changing the force-velocity condition results in a change of the velocity-specific relative power (P_maxv), associated with a change in the power reserve. So far, the effect of these changing conditions on strength-endurance remains unclear. Purpose: We aimed to test the effects of force-velocity condition and power output on strength-endurance. Methods: Fourteen sportsmen performed (i) force- and power-velocity relationships evaluation in squat jumps and (ii) strength-endurance evaluations during repeated squat jump tests in 10 different force-velocity-power conditions, individualized based on the force- and power-velocity relationships. Each condition was characterized by different (i) relative power (%P_max), (ii) velocity-specific relative power (%P_maxv), and (iii) ratio between force and velocity (R_Fv). Strength-endurance was assessed by the maximum repetitions (SJ_Rep), and the cumulated mechanical work (W_tot) performed until exhaustion during repeated squat jump tests. Intra and inter-day reliability of SJ_Rep were tested in one of the 10 conditions. The effects of %P_max, %P_maxv, and R_Fv on SJ_Rep and W_tot were tested via stepwise multiple linear regressions and two-way ANOVAs. Results: SJ_Rep exhibited almost perfect intra- and inter-day reliability (ICC=0.94 and 0.92, respectively). SJ_Rep and W_tot were influenced by %P_maxv and R_Fv (R² = 0.975 and 0.971; RSME=0.243 and 0.234, respectively; both p < 0.001), with the effect of R_Fv increasing with decreasing %P_maxv (interaction effect, p = 0.03). %P_max was not considered as a significant predictor of strength-endurance by the multiple regressions analysis. SJ_Rep and W_tot were higher at lower %P_maxv and in low force-high velocity conditions (i.e., lower R_Fv). Conclusion: Strength-endurance was almost fully dependent on the position of the exercise conditions relative to the individual force-velocity and power-velocity relationships (characterized by %P_maxv and R_Fv). Thus, the standardization of the force-velocity condition and the velocity-specific relative power should not be overlooked for strength-endurance testing and training, but also when setting fatiguing protocols.