Objective: To examine the selective influences of distinct acceleration profiles on the neuromuscular efficiency, force, and power during concentric and eccentric phases of isoinertial squatting exercise. Design: Cross-sectional study. Setting: Biomechanics laboratory of the university. Participants: A total of 38 active adults were divided according to their acceleration profiles: higher (n = 17; >2.5 m/s2) and lower acceleration group (n = 21; <2.5 m/s2). Intervention: All subjects performed squats until failure attached to an isoinertial conic pulley device monitored by surface electromyography of rectus femoris, vastus medialis, vastus lateralis, biceps femoris, and semitendinosus. Main Outcome Measures: An incremental optical encoder was used to assess maximal and mean power and force during concentric and eccentric phases. The neuromuscular efficiency was calculated using the mean force and the electromyographic linear envelope. Results: Between-group differences were observed for the maximal and mean force (P range = .001–.005), power (P = .001), and neuromuscular efficiency (P range = .001–.03) with higher significant values for the higher acceleration group in both concentric and eccentric phases. Conclusion: Distinct acceleration profiles affect the neuromuscular efficiency, force, and power during concentric and eccentric phases of isoinertial squatting exercise. To ensure immediate higher levels of power and force output without depriving the neuromuscular system, acceleration profiles higher than 2.5 m/s2 are preferable. The acceleration profiles could be an alternative to evolve the isoinertial exercise.
Denys Batista Campos, Isabella Christina Ferreira, Matheus Almeida Souza, Macquiden Amorim Jr, Leonardo Intelangelo, Gabriela Silveira-Nunes, and Alexandre Carvalho Barbosa
Kyung-eun Lee, Seung-min Baik, Chung-hwi Yi, Oh-yun Kwon, and Heon-seock Cynn
Context: Side bridge exercises strengthen the hip, trunk, and abdominal muscles and challenge the trunk muscles without the high lumbar compression associated with trunk extension or curls. Previous research using electromyography (EMG) reports that performance of the side bridge exercise highly activates the gluteus medius (Gmed). However, to the best of our knowledge, no previous research has investigated EMG amplitude in the hip and trunk muscles during side bridge exercise in subjects with Gmed weakness. Objective: The purpose of this study was to examine the EMG activity of the hip and trunk muscles during 3 variations of the side bridge exercise (side bridge, side bridge with knee flexion, and side bridge with knee flexion and hip abduction of the top leg) in subjects with Gmed weakness. Design: Repeated-measures experimental design. Setting: Research laboratory. Patients: Thirty subjects (15 females and 15 males) with Gmed weakness participated in this study. Intervention: Each subject performed 3 variations of the side bridge exercise in random order. Main Outcome Measures: Surface EMG was used to measure the muscle activities of the rectus abdominis, external oblique, longissimus thoracis, multifidus, Gmed, gluteus maximus, and tensor fasciae latae (TFL), and Gmed/TFL muscle activity ratio during 3 variations of the side bridge exercise. Results: There were significant differences in Gmed (F 2,56 = 110.054, P < .001), gluteus maximus (F 2,56 = 36.416, P < .001), and TFL (F 2,56 = 108.342, P < .001) muscles among the 3 side bridge exercises. There were significant differences in the Gmed/TFL muscle ratio (F 2,56 = 20.738, P < .001). Conclusion: Among 3 side bridge exercises, the side bridge with knee flexion may be effective for the individuals with Gmed weakness among 3 side bridge exercises to strengthen the gluteal muscles, considering the difficulty of the exercise and relative contribution of Gmed and TFL.
Bruno Augusto Lima Coelho, Helena Larissa das Neves Rodrigues, Gabriel Peixoto Leão Almeida, and Sílvia Maria Amado João
Context: Restriction in ankle dorsiflexion range of motion (ROM) has been previously associated with excessive dynamic knee valgus. This, in turn, has been correlated with knee pain in women with patellofemoral pain. Objectives: To investigate the immediate effect of 3 ankle mobilization techniques on dorsiflexion ROM, dynamic knee valgus, knee pain, and patient perceptions of improvement in women with patellofemoral pain and ankle dorsiflexion restriction. Design: Randomized controlled trial with 3 arms. Setting: Biomechanics laboratory. Participants: A total of 117 women with patellofemoral pain who display ankle dorsiflexion restriction were divided into 3 groups: ankle mobilization with anterior tibia glide (n = 39), ankle mobilization with posterior tibia glide (n = 39), and ankle mobilization with anterior and posterior tibia glide (n = 39). Intervention(s): The participants received a single session of ankle mobilization with movement technique. Main Outcome Measures: Dorsiflexion ROM (weight-bearing lunge test), dynamic knee valgus (frontal plane projection angle), knee pain (numeric pain rating scale), and patient perceptions of improvement (global perceived effect scale). The outcome measures were collected at the baseline, immediate postintervention (immediate reassessment), and 48 hours postintervention (48 h reassessment). Results: There were no significant differences between the 3 treatment groups regarding dorsiflexion ROM and patient perceptions of improvement. Compared with mobilization with anterior and posterior tibia glide, mobilization with anterior tibia glide promoted greater increase in dynamic knee valgus (P = .02) and greater knee pain reduction (P = .02) at immediate reassessment. Also compared with mobilization with anterior and posterior tibia glide, mobilization with posterior tibia glide promoted greater knee pain reduction (P < .01) at immediate reassessment. Conclusion: In our sample, the direction of the tibia glide in ankle mobilization accounted for significant changes only in dynamic knee valgus and knee pain in the immediate reassessment.
Arthur Alves Dos Santos, James Sorce, Alexandra Schonning, and Grant Bevill
This study evaluated the performance of 6 commercially available hard hat designs—differentiated by shell design, number of suspension points, and suspension tightening system—in regard to their ability to attenuate accelerations during vertical impacts to the head. Tests were conducted with impactor materials of steel, wood, and lead shot (resembling commonly seen materials in a construction site), weighing 1.8 and 3.6 kg and dropped from 1.83 m onto a Hybrid III head/neck assembly. All hard hats appreciably reduced head acceleration to the unprotected condition. However, neither the addition of extra suspension points nor variations in suspension tightening mechanism appreciably influenced performance. Therefore, these results indicate that additional features available in current hard hat designs do not improve protective capacity as related to head acceleration metrics.
Siobhan K. Fitzpatrick and Janine V. Olthuis
American student-athletes (SAs) are at heightened risk for hazardous alcohol consumption compared with their nonathlete peers. However, little is known about this risk or the influence of psychosocial predictors on drinking behavior among Canadian SAs. This study compared rates of alcohol use across Canadian SAs and nonathletes and investigated whether the use of athlete-specific psychosocial predictors can improve the prediction of alcohol use outcomes in SAs. Participants (179 varsity athletes and 366 nonathletes) completed anonymous self-report questionnaires. Results suggest that Canadian athletes are at a heightened risk for experiencing alcohol-related problems compared with nonathletes, with general psychosocial predictors explaining the majority of variance in SA alcohol use. However, and quite notably, athlete-specific positive reinforcement motives predicted SA binge drinking. This research provides some of the first evidence of drinking-related problems among Canadian SAs and supports the potential use of preventative efforts to help SAs develop safe strategies for alcohol use.
Katie Stephenson, Melissa N. Womble, Shawn R. Eagle, Philip Schatz, Tatiana Gervase, Brett Gustman, Eric Castor, Anthony P. Kontos, and R.J. Elbin
Objective: (1) To compare patient- and clinician-administered measurements of near point of convergence (NPC) distance including the percentage of patients exceeding clinical cutoffs among concussed adolescents and (2) to assess the reliability of patient- and clinician-measured NPC distances. Methods: A total of 762 patients (mean = 15.51, SD = 3.09 y) within 30 days of concussion participated. The NPC distance was measured consecutively with the patient and clinician controlling the fixation target. The differences between patient (PT) and clinician (CLIN) measurements and cases exceeding cutoffs (ie, ≥5 cm) were examined with a series of t tests and chi-square tests, respectively. Intraclass correlation coefficients and unbiased estimate of reliability were performed. Results: The NPC measurements were similar, t(761) = −.26, P = .79, between the PT (mean = 3.52, SD = 3.77 cm) and CLIN (mean = 3.54, SD = 3.97 cm) conditions. The number of measurements that exceeded cutoffs was similar among the PT (2.5%; 19/762) and CLIN conditions (3%; 23/762) (P = .10), and the number of measurements classified as abnormal/invalid was also similar among the PT (2.5%; 19/762) and CLIN conditions (3%; 23/762) (P = .10). There was excellent reliability between the methods (intraclass correlation coefficients = .85, unbiased estimate of reliability = .92). Conclusion: The findings support the application of this assessment in clinical settings where the clinician may not have direct contact with their patient and rely on the patient (eg, telehealth).
Carrie B. Scherzer, Jeremy Trenchuk, Meaghan Peters, and Robert Mazury
Athletes can be at elevated risk for developing eating disorders, the effects of which can be devastating. Few researchers have examined the influence of a predisposition toward an eating disorder on athletic injury. Exercise dependence might bridge the gap toward understanding this relationship. This study sought to examine the relationship between predisposition toward an eating disorder and exercise dependence and looked at both as predictors of athletic injury. College students (n = 132) completed the Eating Disorders Inventory and the Exercise Dependence Questionnaire, as well as provided demographic, activity, and injury information. Subscales of the Eating Disorders Inventory and Exercise Dependence Questionnaire were significant predictors of having at least one athletic injury in the preceding year. These findings suggest that both predisposition toward an eating disorder and exercise dependence may be contributing factors to injury.
Darjan Spudić, Janez Vodičar, Miha Vodičar, and Vedran Hadžić
Context: The importance of isometric trunk strength (ITS) among sport science professionals is higher than its actual reported effect size on either performance or low back pain (LBP) occurrence. Objective: To provide normative values of ITS and strength ratios, and to evaluate the effect of sex, sports discipline, and LBP status. Design: Crossover study. Setting: University research laboratory. Participants: Five hundred and sixty-seven elite athletes (186 females) with and without a history of LBP from different sports. Main Outcome Measure: Participants underwent ITS testing for trunk flexors, extensors, and lateral flexors. Normalized maximal strength (in newton meter per kilogram) and strength ratios were calculated. Differences between sex, LBP, and sport disciplines were assessed with 3-way analysis of variance (sex × LBP status × 7 sport categories) and partial eta-squared (
David G. Behm, Nehara Herat, Gerard M.J. Power, Joseph A. Brosky, Phil Page, and Shahab Alizadeh
Context: Both health professionals and consumers use menthol-based topical analgesics extensively for the temporary relief of pain from musculoskeletal ailments or injury. However, there are no reports of differences in the pain pressure threshold (PPT) or the relative effectiveness of topical analgesics to reduce pain in the upper and lower body muscles and tendons. The objective of this study was to investigate whether differences existed in PPT and relative pain attenuation associated with a menthol-based topical analgesic over a variety of upper and lower body muscles and tendons. Design: Randomized allocation, controlled, intervention study. Methods: Sixteen participants (10 females and 6 males) were tested on their dominant or nondominant side. The order of specific muscle/tendon testing was also randomized, which included upper body (middle deltoid, biceps brachii, and lateral epicondylar tendon) and lower body locations (quadriceps, hamstrings, gastrocnemius, lumbosacral erector spinae muscles, and patellar and Achilles tendons). The PPT was monitored before and 15 minutes following the application of a menthol-based topical analgesic. Results: A menthol-based topical analgesic increased PPT (decreased pain sensitivity) overall (P = .05; 11.6% [2.4%]; d = 1.05) and PPT was higher (P < .0001; 31.5%–44.2%; d = 1.03–1.8) for lower versus upper body locations. Conclusions: Health professionals and the public can be assured of similar reductions in pain sensitivity independent of the location of application of a menthol-based topical analgesic.
Tsz Lun (Alan) Chu, Bailey Sommerfeld, and Tao Zhang
Building on recent research examining athlete burnout trajectories, this study implemented the developmental model of sport participation to compare emotional and physical exhaustion, reduced sense of accomplishment, and sport devaluation between age groups (specializing [aged 13–15 years] vs. investment [aged 16–18 years]) and gender (boys vs. girls) among U.S. high school athletes. Participants were 367 high school athletes (M = 15.53; 212 males; 186 specializing) across various individual and team sports who completed a survey assessing their demographic information, sport backgrounds, and burnout perceptions. A 2 × 2 multivariate analysis of covariance, controlling for training hours, showed greater emotional and physical exhaustion and sport devaluation in the investment than the specializing group, but no developmental differences in reduced sense of accomplishment. Contrary to our hypothesis, no gender or interaction effects were found. Findings inform interventions and future research that address the role of developmental stages and gender in athlete burnout.