Effectiveness of multi-modal home-based videoconference interventions on sleep in older adults: study protocol for a randomized controlled trial.

Aging is characterized by substantial changes in sleep architecture that negatively impact fitness, quality of life, mood, and cognitive functioning. Older adults often fail to reach the recommended level of physical activity to prevent the age-related decline in sleep function, partly because of geographical barriers. Implementing home-based interventions could surmount these obstacles, thereby encouraging older adults to stay active, with videoconference administration emerging as a promising solution. Increasing the availability of biological rhythms synchronizers, such as physical activity, light exposure, or vestibular stimulation, represents a viable non-pharmacological strategy for entraining circadian rhythms and potentially fortifying the sleep-wake cycle, thereby enhancing sleep in aging. This study aims to (1) assess the impact of remote physical exercise training and its combination with bright light exposure, and (2) investigate the specific contribution of galvanic vestibular stimulation, to sleep quality among healthy older adults with sleep complaints. One hundred healthy older adults aged 60-70 years with sleep complaints will be randomly allocated to one of four groups: a physical exercise training group (n = 25), a physical exercise training combined with bright light exposure group (n = 25), a galvanic vestibular stimulation group (n = 25) or a control group (i.e., health education) (n = 25). While physical exercise training and health education will be supervised via videoconference at home, bright light exposure (for the physical exercise training combined with bright light exposure group) and vestibular stimulation will be self-administered at home. Pre-and post-tests will be conducted to evaluate various parameters, including sleep (polysomnography, subjective questionnaires), circadian rhythms (actigraphy, temperature), fitness (physical: VO2 peak, muscular function; and motor: balance, and functional mobility), cognition (executive function, long-term memory), quality of life and mood (anxiety and depression). The findings will be anticipated to inform the development of recommendations and non-pharmaceutical preventive strategies for enhancing sleep quality in older adults, potentially leading to improvements in fitness, cognition, quality of life, and mood throughout aging.

The mediating role of lower body muscle strength and IGF-1 level in the relationship between age and cognition. A MIDUS substudy.

OBJECTIVE: Aging is a natural process associated with a decline in cognition. However, the mediating effect of physical function and circulating myokines on this relationship has yet to be fully clarified. This study investigated how muscle strength and circulating insulin-like growth factor-1 (IGF-1) levels mediate the relationship between age and cognitive functions. SUBJECTS AND METHODS: A total of 1255 participants aged 25-74 years included in the Midlife in the United States II study were retrospectively analyzed. In this cross-sectional analysis, we applied a serial mediation model to explore the mediating effects of muscle strength and circulating IGF-1 levels on the relationship between age and cognitive functions. We included potential confounding factors related to sociodemographics, lifestyle, and health status as covariates in the model. RESULTS: The results showed that aging had both direct and indirect effects on cognition. As predicted, muscle strength and IGF-1 levels mediated the relationship between age and specific cognitive functions. In addition, mediation analyses indicated that the association between aging and cognitive flexibility, immediate and delayed memory, and inductive reasoning were partially mediated by muscle strength and IGF-1 levels in a serial manner. CONCLUSIONS: Our study demonstrated the serial multiple mediation roles of muscle strength and IGF-1 levels on the relationship between age and specific cognitive functions. Further longitudinal research should be performed to confirm the serial mediation results.

Changes in passive hamstring stiffness after primary anterior cruciate ligament reconstruction: A prospective study with comparison of healthy controls.

BACKGROUND: The mechanical properties of knee flexors muscles contribute to reducing anterior cruciate ligament loading. This case-control study evaluated the passive knee flexors stiffness after primary anterior cruciate ligament reconstruction with comparison of healthy controls. METHODS: After anterior cruciate ligament reconstruction, 88 participants (24.5 [8.6] years, 56,8% males) had two isokinetic tests at 4 and 8 postoperative months with measurement of the passive resistive torque of knee flexors and extensors/flexors strength. In the control group, 44 participants (24.5 [4.3] years, 56,8% males) had one visit with the same procedures. Passive knee flexors stiffness was calculated as the slope of the passive torque-angle curve on the last 10° of knee extension (Nm/°). We investigated the impact of timing and type of surgery (autograft and combined meniscus repair) and persistent knee extension deficits on knee flexors stiffness. FINDINGS: At 4 and 8 postoperative months, passive knee flexors stiffness was lower on the operated limb than on the non-operated limb (P < 0.001) but both limbs had significant lower values than controls (P < 0.001). Stiffness was positively correlated with knee flexors strength (P < 0.010), and knee flexors stiffness at 4 months was lower in individuals who underwent surgery <6 months from injury (P = 0.040). Knee extension deficit or the type of surgery did not have a significant influence on knee flexors stiffness. INTERPRETATION: Similarly to neuromuscular factors that are traditionally altered after anterior cruciate ligament reconstruction, evaluating passive knee flexors stiffness changes over time could provide supplementary insights into postoperative muscle recovery.

Effects of a 20-Week High-Intensity Strength Training Program on Muscle Strength Gain and Cardiac Adaptation in Untrained Men: Preliminary Results of a Prospective Longitudinal Study.

BACKGROUND: As strength sports gain popularity, there is a growing need to explore the impact of sustained strength training on cardiac biventricular structure and function, an area that has received less attention compared to the well-established physiological cardiac adaptation to endurance training. OBJECTIVE: This study aims to implement a 20-week high-intensity strength training program to enhance maximal muscle strength and evaluate its impact on cardiac biventricular adaptation in healthy, untrained men. METHODS: A total of 27 healthy and untrained young men (mean age 22.8, SD 3.2 years) participated in a strength training program designed to increase muscle strength. The training program involved concentric, eccentric, and isometric exercise phases, conducted over a consecutive 20-week time frame with a frequency of 3 weekly training sessions. Participants were evaluated before and after 12 and 20 weeks of training through body composition analysis (bioelectrical impedance), a 12-lead resting electrocardiogram, 3D transthoracic echocardiography, cardiopulmonary exercise testing, and muscle isokinetic dynamometry. The progression of strength training loads was guided by 1-repetition maximum (RM) testing during the training program. RESULTS: Of the initial cohort, 22 participants completed the study protocol. No injuries were reported. The BMI (mean 69.8, SD 10.8 kg/m² vs mean 72, SD 11 kg/m²; P=.72) and the fat mass (mean 15.3%, SD 7.5% vs mean 16.5%, SD 7%; P=.87) remained unchanged after training. The strength training program led to significant gains in 1-RM exercise testing as early as 4 weeks into training for leg extension (mean 69.6, SD 17.7 kg vs mean 96.5, SD 31 kg; P<.001), leg curl (mean 43.2, SD 9.7 kg vs mean 52.8, SD 13.4 kg; P<.001), inclined press (mean 174.1, SD 41.1 kg vs mean 229.2, SD 50.4 kg; P<.001), butterfly (mean 26.3, SD 6.2 kg vs mean 32.5, SD 6.6 kg; P<.001), and curl biceps on desk (mean 22.9, SD 5.2 kg vs mean 29.6, SD 5.2 kg; P<.001). After 20 weeks, the 1-RM leg curl, bench press, pullover, butterfly, leg extension, curl biceps on desk, and inclined press showed significant mean percentage gains of +40%, +41.1%, +50.3%, +63.5%, +80.1%, +105%, and +106%, respectively (P<.001). Additionally, the isokinetic evaluation confirmed increases in maximal strength for the biceps (+9.2 Nm), triceps (+11.6 Nm), quadriceps (+46.8 Nm), and hamstrings (+25.3 Nm). In this paper, only the training and muscular aspects are presented; the cardiac analysis will be addressed separately. CONCLUSIONS: This study demonstrated that a short-term high-intensity strength training program was successful in achieving significant gains in muscle strength among previously untrained young men. We intend to use this protocol to gain a better understanding of the impact of high-intensity strength training on cardiac physiological remodeling, thereby providing new insights into the cardiac global response in strength athletes. TRIAL REGISTRATION: ClinicalTrials.gov NCT04187170; https://clinicaltrials.gov/study/NCT04187170.

Changes in the Force-Velocity Relationship of Knee Muscles After Anterior Cruciate Ligament Reconstruction Using the Isokinetic 2-Point Model.

PURPOSE: After anterior cruciate ligament reconstruction (ACL-R), knee muscle strength symmetry is used as part of the return-to-sport criteria. However, little is known about the changes in the force-velocity (F-V) relationship, which could affect athletic performance. This study investigated the F-V relationship of knee muscles at 4 and 8 months after ACL-R, using the 2-point method tested by isokinetic dynamometry. METHODS: A total of 103 physically trained individuals (24.6 [9.3] y, 59.2% male) who underwent primary ACL-R were included. Demographic information and surgery characteristics were collected at 6 weeks postoperatively. Isokinetic knee flexors' and extensors' peak torques were measured at 60° and 240° per second in the concentric mode at 4 and 8 months postoperative. Peak torques and angular velocities were converted to force and linear velocity for calculating maximum isometric force (F0) and the slope of the regression line (F-V slope). RESULTS: At 4 and 8 months postoperative, F0 was significantly lower and F-V slope was significantly less steep (less negative) on the operated leg compared with the nonoperated leg for knee extensors (P < .001) and flexors (P < .001-.002). The limb symmetry index calculated using F0 was lower than the limb symmetry indexes assessed at 60° and 240° per second, especially for knee flexors (P < .001). The use of patellar tendon grafts was associated with lower F0 and a less steep F-V slope compared with hamstring tendon grafts (P < .010). CONCLUSION: The isokinetic 2-point model assessing the F-V relationship provides additional and relevant insight for evaluating knee muscle strength after ACL-R.

Shoulder muscle imbalance as a risk factor for shoulder injury in elite badminton players: A prospective study.

OBJECTIVES: To assess the impact of preseason shoulder testing on the risk of significant shoulder injury (SSI) in elite badminton players. DESIGN: Prospective cohort study. SETTING: Secondary care, academic medical center. PARTICIPANTS: Nineteen elite badminton players (19.37 ± 4.79 years, n = 13 males). MAIN OUTCOME MEASURES: At preseason, they had shoulder examination tests including the table-to-acromion distance and the glenohumeral rotation range of motion. The glenohumeral internal rotation deficit (GIRD) was calculated. Isokinetic internal and external rotator shoulder muscle strength was tested at 60°/s (concentric and eccentric modes) and 240°/s (concentric mode). Bilateral strength ratio (non-dominant:dominant) and unilateral agonist:antagonist conventional and functional ratios (FR: eccentric-to-concentric) were calculated. RESULTS: During the follow-up time of 38 weeks, SSIs were assessed by an experienced sport physician and 42% of the participants sustained at least one SSI at their dominant side. The preseason GIRD and FR at 240°/s (FR240) were independently associated with SSIs (G2 = 6.28, p = .012 and G2 = 6.23, p = .013, respectively). FR240 < 0.69 (odds ratio = 28.0) and GIRD> 14° (odds ratio = 36.14) were predictors for SSIs. CONCLUSIONS: Lower functional deceleration ratio and greater GIRD are associated with a higher risk of SSI at the dominant side in elite badminton players.

Exercise therapy in the treatment of anorexia nervosa: Its effects depending on the type of physical exercise-A systematic review.

Background and purpose: Clinical research focusing on the effectiveness of exercise therapy (ET) in patients with anorexia nervosa (AN) shows increasing interest in the last decade. The aim of this systematic review was to provide an overview of quantitative studies that have examined the impact of ET in AN patients and to examine its specific effects on physical and mental health according to the type of physical exercise (PE) practiced. Methods: The review was carried out based on the PRISMA 2020. Electronic databases PubMed, Web of Science, Embase, and Wiley were searched from inception to December 2021. Quantitative studies assessing the effects of ET interventions on AN patients were included and study quality was assessed using the PEDro scale. Results: A total of 27 studies were selected, including 13 randomized controlled trials. Regarding outcomes measured, results showed that aerobic and resistance exercise improved muscle strength, that mind-body PE decreased main symptoms of AN and mental health, and that combined PE reduced dysfunctional exercise and improved weight gain. Conclusion: The findings suggest that ET intervention can induce benefits and has no deleterious effects on patients. In addition, specific effects on anorexia symptoms and physical and mental health have been observed according to the type of PE. However, this review reported several methodological weaknesses, including a lack of control group or randomization and statistical misconduct. Finally, ET intervention parameters were heterogeneous, and ET intervention generally lacked details, making reproducibility and comparability difficult. All these limitations underscore the need for a more rigorous methodology for further research.

Shoulder Rotational Strength and Range of Motion in Unilateral and Bilateral Overhead Elite Athletes.

CONTEXT: Overhead athletes place tremendous demands on the shoulder complex, which result in adaptive kinematics but potential susceptibility to injury. This study aimed to compare shoulder glenohumeral range of motion (ROM) and rotator muscles strength in bilateral and unilateral overhead sports. DESIGN: Cross-sectional study; secondary care. METHODS: Forty-two elite athletes (17.7 [4.5] y; 42.9% female), including 18 swimmers and 24 badminton players, were included. Preseason glenohumeral rotation ROM and isokinetic shoulder internal and external rotator muscles strength was tested (60°·s-1). Bilateral (nondominant:dominant) and agonist:antagonist (external rotator:internal rotator) conventional and functional deceleration ratios (eccentric to concentric) were calculated. The impact of sport and number of competitive years on shoulder ROM and strength was tested. RESULTS: Badminton players had greater glenohumeral internal rotation deficit, total ROM deficit, and lower bilateral strength ratio than swimmers (P < .050). Rotational strength was positively associated with the competitive years, but greater in swimmers (P < .050) and on the internal rotator (P < .001). The functional deceleration ratio was negatively associated with the competitive years on the dominant side in swimmers and for both sides in badminton. CONCLUSIONS: Unilateral overhead athletes had greater ROM and rotational strength asymmetries than bilateral athletes. Interestingly, the functional deceleration ratio was lower over time on the dominant shoulder for both sports, but, surprisingly, also on the nondominant shoulder in badminton, potentially creating a greater risk for shoulder injuries.

Non-inferiority of a home-based videoconference physical training program in comparison with the same program administered face-to-face in healthy older adults: the MOTION randomised controlled trial.

BACKGROUND: older adults often fail to reach the recommended amount of physical activity to prevent the age-related decline in metabolic, cardiorespiratory and muscular function. Effective home-based physical training programs could neutralise barriers preventing older adults from being active, and administration/supervision through videoconference may be an optimal solution. The present randomised controlled trial aimed to test the non-inferiority of training program administered through videoconference against the same program administered face-to-face in healthy older adults. METHODS: participants were randomised in a no-training control group (n = 13), a face-to-face training group (n = 15) and a videoconference training group (n = 13). The intervention groups completed the same home-based, structured, progressive and combined training program for 16 weeks, 1-h twice a week. Pre-intervention and post-intervention evaluations included body composition, cardiorespiratory fitness and muscle function measures. RESULTS: non-inferiority of videoconferencing against face-to-face training was observed for changes in body weight (P < 0.01), fat mass (P = 0.015), maximal aerobic power (P = 0.013), maximal heart rate (P = 0.034), maximal oxygen consumption (P < 0.01), knee extension strength (P = 0.044) and lower limb power (P = 0.019), but not for muscle mass (P = 0.067), handgrip strength (P = 0.171), trunk extension strength (P = 0.241) and knee flexion strength (P = 0.462). CONCLUSION: a training program administered through videoconferencing was not inferior to the same program administered face-to-face for reducing body weight and fat mass, and for improving maximal aerobic power and oxygen consumption as well as lower limb power and knee extension strength in healthy older subjects. However, videoconferencing training was not as effective as face-to-face training for improving handgrip, trunk extension and knee flexion isometric strength.

Circadian rhythm of postural control, sleepiness and verticality perception in older adults.

INTRODUCTION: with ageing, the risk of falling increases. It has been reported that fall frequency may depend on the time of the day, suggesting a possible circadian rhythm of postural control. The objective was to test whether postural control in older adults followed a circadian rhythm. Then, in order to examine the possible functions involved in circadian variations in balance performances, circadian rhythm of sleepiness and vertical perception were also tested. METHODS: eight participants (70.7 ± 4.7 years) were included. Baseline circadian rhythm profile was assessed through continuous core temperature measurement. Static and dynamic balance, subjective sleepiness and fatigue, and verticality perception were measured at 2:00, 6:00, 10:00, 14:00, 18:00 and 22:00, on separate weeks in a random order. RESULTS: temperature followed a circadian rhythm, with lowest temperature occurring at 03:50. Circadian rhythm was detected for the centre of pressure displacement length and velocity, in dynamic condition eyes closed, with lowest performances occurring at 18:33 and 16:59, respectively. Subjective sleepiness and fatigue also followed circadian rhythm with lowest sleepiness occurring at 15:46 and 15:50, for the Karolinska Sleeping Scale and the Visual Analogic Scale of fatigue, respectively. Finally, the vertical perception was not significantly following a circadian rhythm. CONCLUSION: older adults present a circadian rhythm of balance, in particular in more challenging conditions, and the lowest performances occurred in the late afternoon These circadian rhythms could explain some of the falls happening at this time in community-dwelling older adults.

Knee strength symmetry at 4 months is associated with criteria and rates of return to sport after anterior cruciate ligament reconstruction.

BACKGROUND: Strength limb symmetry index (LSI) is a useful criterion to help in return-to-sport performance (RTP) after anterior cruciate ligament reconstruction (ACLR). OBJECTIVES: We aimed to assess whether knee extensor and flexor LSI values at 4 months after ACLR are associated with those recommended at 8 months after ACLR for RTP (80%, 85% and 90%) and with successful RTP after 2 years. METHODS: This was prospective cohort study of 113 participants who underwent primary ACLR. Personal factors such as demographic and sport information, injury and surgery characteristics were collected at 6 weeks after surgery. Isokinetic strength LSI (60°/s) was calculated at 4 months (LSI[4 m]) and 8 months (LSI[8 m]) for knee extensors (Q-LSI) and flexors (H-LSI). Participants were followed at 2 years after ACLR to determine their self-reported RTP. Multiple linear regression analysis was used to determine associations between personal factors and LSI at 4 and 8 months. Associations between passing the optimal cut-off thresholds and RTP were tested with chi-square tests and odds ratios (ORs) with effect sizes (ES). RESULTS: Among the 113 participants (mean age 25.2 [SD 9.7] years; 42% females), extended tourniquet time and lower level of pre-injury sport were associated with lower Q-LSI[4m] and H-LSI[4m]. Bone-patellar tendon-bone graft was associated with lower Q-LSI[4m] and Q-LSI[8m], and older age was associated with lower Q-LSI[4m]. For knee extensors, Q-LSI[4m] >59% was associated with Q-LSI[8m] >80% (OR= 31.50, p < 0.001, large ES) and increased odds of successful RTP (60% vs 31%, OR= 3.45, p = 0.003, medium ES). For knee flexors, H-LSI[4m] >72% was associated with H-LSI[8m] >90% (OR= 6.03, p < 0.001, large ES) and increased odds of successful RTP (53% vs 23%, OR= 3.76, p = 0.013, small-to-medium ES). CONCLUSIONS: After primary ACLR, 4-month post-operative strength symmetry was negatively associated with age, pre-injury sport and tourniquet time and bone-patellar tendon-bone graft. Four-month post-operative LSI was associated with 8-month post-operative LSI, and Q-LSI[4m] >59% or H-LSI[4m] >72% was associated with increased RTP rates after 2 years. CLINICALTRIALS: GOV: NCT04071912.

Kinematics or Kinetics: Optimum Measurement of the Vertical Variations of the Center of Mass during Gait Initiation.

BACKGROUND: During gait, the braking index represents postural control, and consequently, the risk of falls. Previous studies based their determination of the braking index during the first step on kinetic methods using force platforms, which are highly variable. This study aimed to investigate whether determining the braking index with a kinematic method, through 3D motion capture, provides more precise results. METHODS: Fifty participants (20 to 40 years) performed ten trials in natural and fast gait conditions. Their braking index was estimated from their first step simultaneously using a force platform and VICON motion capture system. The reliability of each braking index acquisition method was assessed by intraclass correlation coefficients, standard error measurements, and the minimal detectable change. RESULTS: Both kinetic and kinematic methods allowed good to excellent reliability and similar minimum detectable changes (10%). CONCLUSION: Estimating the braking index through a kinetic or a kinematic method was highly reliable.

Videoconference-Based Adapted Physical Exercise Training Is a Good and Safe Option for Seniors.

Videoconference-based adapted physical exercise combines the benefits of supervised exercise training with staying at home, when conventional training is inaccessible. However, exercising with the use of a screen can be considered an optokinetic stimulation, and could therefore induce changes in sensory processing, affecting postural stability. The objectives of this study were to compare the effectiveness of the training delivered Face-to-Face and by Videoconferencing in improving physical capacities of older adults, and to evaluate the possible effects of the Videoconference mode on the processing of sensory information that could affect postural control. Twenty eight older adults underwent the supervised exercise program for sixteen weeks either Face-to-Face or by Videoconference. Muscular strength of knee and ankle flexors and extensors, maximum oxygen uptake, postural stability and horizontal rotational vestibulo-ocular reflex were evaluated before and after the training. Both modes of training similarly increased the VO2 peak and strength of the motor muscles of lower limbs in all participants. The use of the Videoconference did not modify the vestibulo-ocular reflex in subjects or the importance of vision for postural control. Therefore, the Videoconference-based exercise training can be considered a safe and effective way to maintain good functional capacity in seniors.

Cycle more with virtual reality: a proof of concept study in an institutionalised able-bodied geriatric population.

BACKGROUND/OBJECTIVES: Physical activity (PA) has significant benefits for older adults. However, the recommended PA is rarely achieved in nursing homes. In this proof of concept study, we assessed whether virtual reality (VR) could help to increase spontaneous PA during a stationary cycling session. DESIGN: Prospective crossover proof of concept study. SETTING: Nursinghome. PARTICIPANTS: Twelve participants (10 men) aged 63-88, able-bodied but with moderate cognitive impairment. INTERVENTION: TWO stationary cycling sessions with and withoutVR. MEASUREMENTS: Cycling distance, pedalling duration, average speed, mean pedalling cadence and the modified Borg rating of perceived exertion scale. RESULTS: Cycling distance and duration were significantly higher in the VR condition. Most participants would rather repeat cycling sessions with VR than without. CONCLUSION: The use of VR seems feasible to help achieve PA recommendations for able-bodied people living in nursing homes, even with moderate cognitive impairments.

Ankle dorsiflexors and plantarflexors neuromuscular electrical stimulation training impacts gait kinematics in older adults: A pilot study.

BACKGROUND: While ankle muscles, highly affected by aging, are highly implicated in the changes in gait kinematics and involved in the limitation of seniors' mobility, whether neuromuscular electrical stimulation (NMES) training of these muscles could impact gait kinematics in older adults has not been investigated yet. RESEARCH QUESTION: What are the effects of 12 weeks of ankle plantar and dorsiflexors NMES training on strength and gait kinematics in healthy older adults? METHODS: Fourteen older adults (73.6 ± 4.9 years) performed a three-time per week, three months long NMES training of both ankle plantar and dorsiflexors. Before and after training, neuromuscular parameters, gait kinematic parameters, and daily physical activity were measured. RESULTS: The participants significantly increased their lower limb muscle mass and their plantar and dorsiflexors isometric strength after training. They reduced the hip abduction/adduction and the pelvic anterior tilt range of motion and variability during gait. However, the participants became less active after the training. SIGNIFICANCE: NMES training of ankle muscles, by increasing ankle muscle mass and strength,modified gait kinematics. NMES training of ankle muscles is feasible and effective to lower the hip implication and increment foot progression angle during gait. Further study should determine if this could lower the risk of falling.

Twenty-four-hour variation of vestibular function in young and elderly adults.

Animal and human studies demonstrate anatomical and functional links between the vestibular nuclei and the circadian timing system. This promotes the hypothesis of a circadian rhythm of vestibular function. The objective of this study was to evaluate the vestibular function through the vestibulo-ocular reflex using a rotatory chair at different times of the day to assess circadian rhythmicity of vestibular function. Two identical studies evaluating temporal variation of the vestibulo-ocular reflex (VOR) were performed, the first in young adults (age: 22.4 ± 1.5 y), and the second in older adults (70.7 ± 4.7 y). The slow phase velocity and time constant of the VOR were evaluated in six separate test sessions, i.e., 02:00, 06:00, 10:00, 14:00, 18:00, and 22:00 h. In both studies, markers of circadian rhythmicity (temperature, fatigue, and sleepiness) displayed expected usual temporal variation. In young adults, the time constant of the VOR showed variation throughout the day (p < .005), being maximum 12:25 h (06:00 h test session) before the acrophase of temperature circadian rhythm. In older adults, the slow phase velocity and time constant also displayed temporal variation (p < .05). Maximum values were recorded at 10:35 h (06:00 h test session) before the acrophase of temperature circadian rhythm. The present study demonstrates that vestibular function is not constant throughout the day. The implication of the temporal variation in vestibular system in equilibrium potentially exposes the elderly, in particular, to differential risk during the 24 h of losing balance and falling.

Shoulder Muscle Imbalance as a Risk for Shoulder Injury in Elite Adolescent Swimmers: A Prospective Study.

Muscle strength imbalances between the internal and external rotators of the shoulder are frequent in swimmers, but their role in shoulder injury remains unknown. We aimed to evaluate the association of shoulder rotator strength and injury in elite adolescent swimmers. Eighteen adolescent swimmers performed preseason isokinetic tests of the internal and external rotator muscles in concentric (con) and eccentric (ecc) modes. Conventional (conER:conIR and eccER:eccIR) and functional ratios (eccER:conIR and eccIR:conER) were calculated. Thirteen swimmers completed a weekly questionnaire about swimming habits and shoulder injuries throughout the season. Preseason testing showed a significant negative association between the functional eccER:conIR ratio and years of practice (p < 0.05). Over the season, 46% of athletes experienced at least one shoulder injury. At the end of the season, peak torques increased for both internal and external rotator muscles strength, but only concentrically, resulting in a decrease in the eccER:conIR functional ratio (p < 0.05). The receiver operating characteristic curve analysis highlighted good predictive power for the preseason functional eccER:conIR ratio, as values below 0.68 were associated with a 4.5-fold (95% CI 1.33-15.28, p < 0.05) increased risk of shoulder injuries during the season.

Effect of vestibular stimulation using a rotatory chair in human rest/activity rhythm.

The vestibular system is responsible for sensing every angular and linear head acceleration, mainly during periods of motor activity. Previous animal and human experiments have shown biological rhythm disruptions in small rodents exposed to a hypergravity environment, but also in patients with bilateral vestibular loss compared to a control population. This raised the hypothesis of the vestibular afferent influence on circadian rhythm synchronization. The present study aimed to test the impact of vestibular stimulation induced by a rotatory chair on the rest/activity rhythm in human subjects. Thirty-four healthy adults underwent both sham (SHAM) and vestibular stimulation (STIM) sessions scheduled at 18:00 h. An off-vertical axis rotation on a rotatory chair was used to ecologically stimulate the vestibular system by head accelerations. The rest/activity rhythm was continuously registered by actigraphy. The recording started one week before the first session (BASELINE), continued in the week between the two sessions and one week after the second session. Vestibular stimulation caused a significant decrease in the average activity level in the evening following the vestibular stimulation. A significant phase advance in the rest/activity rhythm occurred two days after the 18:00 h vestibular stimulation session. Moreover, the level of motion sickness symptoms increased significantly after vestibular stimulation. The present study confirms previous results on the effect of vestibular stimulation and the role of vestibular afferents on circadian biological rhythmicity. Our results support the hypothesis of the implication of vestibular afferents as non-photic stimuli acting on circadian rhythms.