Background: Previous studies have shown that passive-elastic exoskeletons with springs in parallel with the ankle can reduce the metabolic cost of walking. We developed and tested the use of an unpowered passive-elastic exoskeleton for walking that stores elastic energy in a spring from knee extension at the end of the leg swing phase, and then releases this energy to assist ankle plantarflexion at the end of the stance phase prior to toe-off. The exoskeleton uses a system of ratchets and pawls to store and return elastic energy through compression and release of metal springs that act in parallel with the knee and ankle, respectively. We hypothesized that, due to the assistance provided by the exoskeleton, net metabolic power would be reduced compared to walking without using an exoskeleton. Methods: We compared the net metabolic power required to walk when the exoskeleton only acts at the knee to resist extension at the end of the leg swing phase, to that required to walk when the stored elastic energy from knee extension is released to assist ankle plantarflexion at the end of the stance phase prior to toe-off. Eight (4 M, 4F) subjects walked at 1.25 m/s on a force-measuring treadmill with and without using the exoskeleton while we measured their metabolic rates, ground reaction forces, and center of pressure. Results: We found that when subjects used the exoskeleton with energy stored from knee extension and released for ankle plantarflexion, average net metabolic power was 11% lower than when subjects walked while wearing the exoskeleton with the springs disengaged (p = 0.007), but was 23% higher compared to walking without the exoskeleton (p < 0.0001). Conclusion: The use of a novel passive-elastic exoskeleton that stores and returns energy in parallel with the knee and ankle, respectively, has the potential to improve the metabolic cost of walking. Future studies are needed to optimize the design and elucidate the underlying biomechanical and physiological effects of using an exoskeleton that acts in parallel with the knee and ankle. Moreover, addressing and improving the exoskeletal design by reducing and closely aligning the mass of the exoskeleton could further improve the metabolic cost of walking.

Ageing is accompanied by a severe muscle function decline presumably caused by structural and functional adaptations at the central and peripheral level. Although researchers have reported an extensive analysis of the alterations involving muscle intrinsic properties, only a limited number of studies have recognised the importance of the central nervous system, and its reorganisation, on neuromuscular decline. Neural changes, such as degeneration of the human cortex and function of spinal circuitry, as well as the remodelling of the neuromuscular junction and motor units, appear to play a fundamental role in muscle quality decay and culminate with considerable impairments in voluntary activation and motor performance. Modern diagnostic techniques have provided indisputable evidence of a structural and morphological rearrangement of the central nervous system during ageing. Nevertheless, there is no clear insight on how such structural reorganisation contributes to the age-related functional decline and whether it is a result of a neural malfunction or serves as a compensatory mechanism to preserve motor control and performance in the elderly population. Combining leading-edge techniques such as high-density surface electromyography (EMG) and improved diagnostic procedures such as functional magnetic resonance imaging (fMRI) or high-resolution electroencephalography (EEG) could be essential to address the unresolved controversies and achieve an extensive understanding of the relationship between neural adaptations and muscle decline.

Training and rehabilitation programmes involving neuromuscular electrical stimulation superimposed onto voluntary contractions (NMES+) have gained popularity in the last decades. Yet, there is no clear consensus on the effectiveness of such intervention. The aim of this review was to evaluate the effect of chronic exposure to NMES+ on muscle strength and mass compared to conventional volitional training or passive electrical stimulation alone. Two authors conducted an electronic search to identify randomized controlled trials that investigated the effect of NMES+ training, involved healthy participants or orthopaedic patients, detailed a well‐defined NMES training protocol, and provided outcomes related to muscle strength and/or mass. The authors extracted data on participants, intervention characteristics, muscle‐related outcomes, and assessed the methodological quality of the studies. A total of twenty‐four studies were included in the review. The majority of these reported an increase in muscle strength following NMES+ training compared to an equivalent voluntary or passive NMES training. The highest improvements were found when NMES was superimposed on sub‐maximal exercises involving both concentric and eccentric contractions. Two studies reported an increase in muscle mass after NMES+, while two other studies exhibited no differences. This review indicated that chronic exposure to NMES+ determines muscle strength improvements greater or equal compared to volitional training alone. However, differences in the methodological characteristics of the stimulation and the type of exercise associated with NMES+ revealed significant discrepancies in the results. A deeper understanding of the neurophysiological adaptations to NMES+ is crucial to fully explain the muscle‐related enhancement resulting from such intervention.

The aim of this systematic review and meta-analysis was to evaluate the rate of return to sport in elderly patients who underwent anatomic (ATSA) and reverse (RTSA) total shoulder arthroplasty, to assess postoperative pain and functional outcomes and to give an overview of postoperative rehabilitation protocols. A systematic search in Pubmed-Medline, Cochrane Library, and Google Scholar was carried out to identify eligible randomized clinical trials, observational studies, or case series that evaluated the rate of return to sport after RTSA or ATSA. Six retrospective studies, five case series, and one prospective cohort study were included in this review. The overall rate of return to sport was 82% (95% CI 0.76–0.88, p < 0.01). Patients undergoing ATSA returned at a higher rate (90%) (95% CI 0.80–0.99, p < 0.01) compared to RTSA (77%) (95% CI 0.69–0.85, p < 0.01). Moreover, the results showed that patients returned to sport at the same or a higher level in 75% of cases. Swimming had the highest rate of return (84%), followed by fitness (77%), golf (77%), and tennis (69%). Thus, RTSA and ATSA are effective to guarantee a significative rate of return to sport in elderly patients. A slightly higher rate was found for the anatomic implant.

Introduction: The application of neuromuscular electrical stimulation superimposed on voluntary muscle contractions (NMES+) has demonstrated a considerable potential to enhance or restore muscle function in both healthy and individuals with neurological or orthopedic disorders. Improvements in muscle strength and power have been commonly associated with specific neural adaptations. In this study, we investigated changes in the discharge characteristics of the tibialis anterior motor units, following three acute exercises consisting of NMES+, passive NMES and voluntary isometric contractions alone.Methods: Seventeen young participants participated in the study. High-density surface electromyography was used to record myoelectric activity in the tibialis anterior muscle during trapezoidal force trajectories involving isometric contractions of ankle dorsi flexors with target forces set at 35, 50% and 70% of maximal voluntary isometric contraction (MVIC). From decomposition of the electromyographic signal, motor unit discharge rate, recruitment and derecruitment thresholds were extracted and the input-output gain of the motoneuron pool was estimated.Results: Global discharge rate increased following the isometric condition compared to baseline at 35% MVIC while it increased after all experimental conditions at 50% MVIC target force. Interestingly, at 70% MVIC target force, only NMES + led to greater discharge rate compared to baseline. Recruitment threshold decreased after the isometric condition, although only at 50% MVIC. Input-output gain of the motoneurons of the tibialis anterior muscle was unaltered after the experimental conditions.Discussion: These results indicated that acute exercise involving NMES + induces an increase in motor unit discharge rate, particularly when higher forces are required. This reflects an enhanced neural drive to the muscle and might be strongly related to the distinctive motor fiber recruitment characterizing NMES+.

Neuromuscular electrical stimulation superimposed on voluntary contractions (NMES+) is effective to improve motor performance in several populations. Here, we investigated the changes in cortical activation and reflex response following three acute conditions, including NMES+. Our results show that NMES+ has a greater excitatory effect at both spinal and cortical levels compared with passive stimulation and voluntary exercise alone. These results open up original perspectives for the implementation of NMES+ in neurorehabilitation and training environments.