The Executive Council of the International Society of Biomechanics has initiated and overseen the commemorations of the Society’s 50th Anniversary in 2023. This included multiple series of lectures at the ninth World Congress of Biomechanics in 2022 and XXIXth Congress of the International Society of Biomechanics in 2023, all linked to special issues of International Society of Biomechanics’ affiliated journals. This special issue of the Journal of Applied Biomechanics is dedicated to the biomechanics of the neuromusculoskeletal system. The reader is encouraged to explore this special issue which comprises 6 papers exploring the current state-of the-art, and future directions and roles for neuromusculoskeletal biomechanics. This editorial presents a very brief history of the science of the neuromusculoskeletal system’s 4 main components: the central nervous system, musculotendon units, the musculoskeletal system, and joints, and how they biomechanically integrate to enable an understanding of the generation and control of human movement. This also entails a quick exploration of contemporary neuromusculoskeletal biomechanics and its future with new fields of application.
David G. Lloyd, Ilse Jonkers, Scott L. Delp, and Luca Modenese
Catarina Morais, Clara Simães, A. Rui Gomes, and Beatriz M. Gonçalves
This study aimed to provide a framework for how athletes evaluate stress before a competition and how stress relates to cognitive appraisal, sport confidence, and expectations of performance. Participants were 327 youth male athletes, aged 15–19 years (M = 16.90; SD = 1.00), who competed in the Portuguese National Football League and completed a questionnaire 24–48 hr before their match, using the critical incident methodology. Results revealed that opponents were the main source of stress for athletes and that the more athletes stress about their opponents, the more they tend to perceive the situation as threatening (and less challenging), the lower their perceptions of coping and sport confidence which, in turn, predicted lower expectations of individual and collective performance. In sum, perceiving the stressful situation as either a challenge or a threat predicts young athletes’ sport confidence and, consequently, expected performance when dealing with stressful competitive situations.
Zahra S. Mahdian, Huawei Wang, Mohamed Irfan Mohamed Refai, Guillaume Durandau, Massimo Sartori, and Mhairi K. MacLean
Lower limb exoskeletons and exosuits (“exos”) are traditionally designed with a strong focus on mechatronics and actuation, whereas the “human side” is often disregarded or minimally modeled. Muscle biomechanics principles and skeletal muscle response to robot-delivered loads should be incorporated in design/control of exos. In this narrative review, we summarize the advances in literature with respect to the fusion of muscle biomechanics and lower limb exoskeletons. We report methods to measure muscle biomechanics directly and indirectly and summarize the studies that have incorporated muscle measures for improved design and control of intuitive lower limb exos. Finally, we delve into articles that have studied how the human–exo interaction influences muscle biomechanics during locomotion. To support neurorehabilitation and facilitate everyday use of wearable assistive technologies, we believe that future studies should investigate and predict how exoskeleton assistance strategies would structurally remodel skeletal muscle over time. Real-time mapping of the neuromechanical origin and generation of muscle force resulting in joint torques should be combined with musculoskeletal models to address time-varying parameters such as adaptation to exos and fatigue. Development of smarter predictive controllers that steer rather than assist biological components could result in a synchronized human–machine system that optimizes the biological and electromechanical performance of the combined system.
Blake W. Jones, John D. Willson, Paul DeVita, and Ryan D. Wedge
Chronic exposure to high tibiofemoral joint (TFJ) contact forces can be detrimental to knee joint health. Load carriage increases TFJ contact forces, but it is unclear whether medial and lateral tibiofemoral compartments respond similarly to incremental load carriage. The purpose of our study was to compare TFJ contact forces when walking with 15% and 30% added body weight. Young healthy adults (n = 24) walked for 5 minutes with no load, 15% load, and 30% load on an instrumented treadmill. Total, medial, and lateral TFJ contact peak forces and impulses were calculated via an inverse dynamics informed musculoskeletal model. Results of 1-way repeated measures analyses of variance (α = .05) demonstrated total, medial, and lateral TFJ first peak contact forces and impulses increased significantly with increasing load. Orthogonal polynomial trends demonstrated that the 30% loading condition led to a curvilinear increase in total and lateral TFJ impulses, whereas medial first peak TFJ contact forces and impulses responded linearly to increasing load. The total and lateral compartment impulse increased disproportionally with load carriage, while the medial did not. The medial and lateral compartments responded differently to increasing load during walking, warranting further investigation because it may relate to risk of osteoarthritis.
Marcos Quintana-Cepedal, Omar de la Calle, and Hugo Olmedillas
Clinical Scenario: Injuries that affect the groin region are among the most common in football players. To prevent this condition, studies have focused on strengthening the adductors, hip flexors, or abdominal muscles. Recent investigations have used an eccentric-biased exercise (Copenhagen Adduction Exercise [CAE]) that promotes functional and architectural adaptations in the muscle tissue, though its effect on injury risk reduction is unknown. Clinical Question: Can the Copenhagen Adduction Exercise prevent groin injuries in soccer players? Summary of Key Findings: The literature was searched for studies investigating the potential groin injury risk reduction effect of the CAE. (1) Three studies met the inclusion criteria and were used for this appraisal; (2) one study observed a significantly lower injury rate ratio favoring the group that used the CAE program; and (3) 2 studies found similar or higher injury rates in the intervention groups, not supporting the inclusion of the CAE as a preventative tool. Clinical Bottom Line: There is conflicting evidence that usage of the CAE is superior to not performing adductor strengthening exercises in mitigating the risk of sustaining groin injuries. Given the evidence supporting these findings, it is advisable to exercise caution when contemplating the incorporation of the CAE into training regimens aimed at preventing groin injuries. Strength of Recommendation: There is Grade B evidence to suggest that inclusion of the CAE may not be associated with reduced injury rates.
Aude S. Lefranc, Glenn K. Klute, and Richard R. Neptune
Gait asymmetry is a predictor of fall risk and may contribute to increased falls during pregnancy. Previous work indicates that pregnant women experience asymmetric joint laxity and pelvic tilt during standing and asymmetric joint moments and angles during walking. How these changes translate to other measures of gait asymmetry remains unclear. Thus, the purpose of this case study was to determine the relationships between pregnancy progression, subsequent pregnancies, and gait asymmetry. Walking data were collected from an individual during 2 consecutive pregnancies during the second and third trimesters and 6 months postpartum of her first pregnancy and the first, second, and third trimesters and 6 months postpartum of her second pregnancy. Existing asymmetries in step length, anterior–posterior (AP) impulses, AP peak ground reaction forces, lateral impulses, and joint work systematically increased as her pregnancy progressed. These changes in asymmetry may be attributed to pelvic asymmetry, leading to asymmetric hip flexor and extensor length, or due to asymmetric plantar flexor strength, as suggested by her ankle work asymmetry. Relative to her first pregnancy, she had greater asymmetry in step length, step width, braking AP impulse, propulsive AP impulse, and peak braking AP ground reaction force during her second pregnancy, which may have resulted from increased joint laxity.
Kestrel McNeill, Hana Marmura, Melanie Werstine, Greg Alcock, Trevor Birmingham, Kevin Willits, Alan Getgood, Marie-Eve LeBel, Robert Litchfield, Dianne Bryant, and J. Robert Giffin
Context: The long duration and high cost of anterior cruciate ligament reconstruction (ACLR) rehabilitation can pose barriers to completing rehabilitation, the latter stages of which progress to demanding sport-specific exercises critical for a safe return to sport. A staged approach shifting in-person physiotherapy sessions to later months of recovery may ensure patients undergo the sport-specific portion of ACLR rehabilitation. Design/Objective: To compare postoperative outcomes of knee function in patients participating in a staged ACLR physiotherapy program to patients participating in usual care physiotherapy through a randomized controlled trial. Methods: One hundred sixty-two patients were randomized to participate in staged (n = 80) or usual care physiotherapy (n = 82) following ACLR and assessed preoperatively and postoperatively at 2 weeks, 6 weeks, 3 months, and 6 months. The staged group completed the ACLR rehabilitation protocol at home for the first 3 months, followed by usual care in-person sessions. The usual care group completed in-person sessions for their entire rehabilitation. Outcome measures included the Lower Extremity Functional Scale, International Knee Documentation Committee Questionnaire, pain, range of motion, strength, and hop testing. Results: There were no statistically significant between-group differences in measures of knee function at 6 months postoperative. Patients in the usual care group reported significantly higher International Knee Documentation Committee scores at 3 months postoperative (mean difference = 5.8; 95% confidence interval, 1.3 to 10.4; P = .01). Conclusion: A staged approach to ACLR rehabilitation does not appear to impede knee function at 6 months postoperative but may result in worse patient reported outcomes at early follow-ups.
Sabrina Gomez Souffront, Angeliki M. Mavrantza, and Marcelo Bigliassi
The present study sought to investigate the effects of a self-talk intervention on free-throw performance under pressure. The experimental manipulation was designed using a video from a social media platform. Thirty male college basketball players were randomly assigned into two groups (i.e., control and experimental). The experimental protocol incorporated three trials of three free throws each. Psychophysiological stress was assessed by use of heart rate variability. The illusion of pressure was created using arena recordings of large crowds along with instructions for participants to visualize a high-pressure scenario. The results indicate that the self-talk intervention was sufficient to improve free throw shooting accuracy during the postintervention phase. Short-term heart rate variability reduced significantly for the control group and remained relatively stable for the experimental group. Self-talk appears to influence free throw accuracy during situations of psychosocial stress by inhibiting the influence of negative thoughts on peripheral physiological reactions and movement automaticity.
J.D. DeFreese, Daniel J. Madigan, and Henrik Gustafsson
Kathleen T. Mellano and Christine Pacewicz
The purpose of the current research was to examine the interaction of teammate and coach support on athlete burnout and engagement, and determine how type of teammate and coach support links with athlete burnout and engagement. Adolescent athletes (N = 176) completed measures of support, burnout, and engagement. Total teammate and coach support accounted for 14.9%–26.0% and 22.4%–36.7% explained variance across dimensions of burnout and engagement, respectively. No meaningful significant interaction was found. Teammate esteem support predicted reduced accomplishment, devaluation, confidence, and vigor (β = −0.31, −0.36, 0.28, and 0.28), while emotional and tangible support predicted dedication (β = 0.29 and 0.20) and enthusiasm (β = 0.30 and 0.22). Coach esteem support predicted reduced accomplishment (β = −0.59) and devaluation (β = −0.27). Findings suggest that support from one key agent can enhance youth athlete well-being, but types of support provided by agents differ in salience.