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.
Erhan Seçer and Derya Özer Kaya
Context: Dynamic stretching (DS) is typically suggested during warm-up protocols. Also, foam rolling (FR), which is applied with a foam cylinder, has increased popularity in recent years. However, the combined effects of DS and FR in improving flexibility, dynamic balance, and agility performance are unclear in current literature. Therefore, this study aim to evaluate and compare the acute effects of DS as well as DS followed by FR (DS + FR) on flexibility, dynamic balance, and agility in male soccer players. Design: This study was a crossover study with a within-subject design. Methods: Thirty volunteer male soccer players (mean age 18.80 [0.66] y) were included in the study. Each participant performed the 2 sessions (DS and DS + FR) on separate occasions in a randomized order, with an interval of 72 hours. All sessions were performed in the indoor gym at the sports club. Flexibility was assessed by sit-and-reach test, dynamic balance was assessed by Y balance test, and agility was assessed by t test. Results: Compared with the pretest results, significant improvement in flexibility was observed in both groups (change = 0.55, percentage change = 2.05, effect size [ES] = 0.15, P = .041; change = 0.64, percentage change = 2.36, ES = 0.20, P = .025; respectively). Balance scores did not significantly improve in either group (change = 0.40, percentage change = 0.45, ES = 0.09, P = .342; change = 0.93, percentage change = 1.02, ES = 0.23, P = .103; respectively). Agility performance significantly improved in both groups (change = −0.12, percentage change = −1.18, ES = 0.19, P = .021; change = −0.21, percentage change = −2.18, ES = 0.38, P = .005; respectively). Conclusions: Both DS and DS + FR improved flexibility and agility and did not affect balance. DS + FR was not superior to DS at improving flexibility and agility as compared only with DS. Both methods are effective warm-up protocols to augment factors related to injury risk and performance. It seems that further studies that investigate the combined effects of FR and DS are needed.
Jeff M. Barrett, Colin D. McKinnon, Clark R. Dickerson, and Jack P. Callaghan
Relatively few biomechanical models exist aimed at quantifying the mechanical risk factors associated with neck pain. In addition, there is a need to validate spinal-rhythm techniques for inverse dynamics spine models. Therefore, the present investigation was 3-fold: (1) the development of a cervical spine model in OpenSim, (2) a test of a novel spinal-rhythm technique based on minimizing the potential energy in the passive tissues, and (3) comparison of an electromyographically driven approach to estimating compression and shear to other cervical spine models. The authors developed ligament force–deflection and intervertebral joint moment–angle curves from published data. The 218 Hill-type muscle elements, representing 58 muscles, were included and their passive forces validated against in vivo data. Our novel spinal-rhythm technique, based on minimizing the potential energy in the passive tissues, disproportionately assigned motion to the upper cervical spine that was not physiological. Finally, using kinematics and electromyography collected from 8 healthy male volunteers, the authors calculated the compression at C7–T1 as a function of the head–trunk Euler angles. Differences from other models varied from 25.5 to 368.1 N. These differences in forces may result in differences in model geometry, passive components, number of degrees of freedom, or objective functions.
Bryony Buck, Scott Beveridge, Gerard Breaden Madden, and Hans-Christian Jabusch
Background: High-speed drumming requires precise control over the timing, velocity, and magnitude of striking movements. Aim: To examine effects of tempo and expertise on unaccented repetitive drumming performance using 3D motion capture. Methods: Expert and amateur drummers performed unimanual, unaccented, repetitive drum strikes, using their dominant right hand, at five different tempi. Performance was examined with regard to timing variability, striking velocity variability, the ability to match the prescribed tempo, and additional variables. Results: Permutated multivariate analysis of variance (PERMANOVA) revealed significant main effects of tempo (p < .001) and expertise (p <.001) on timing variability and striking velocity variability; low timing variability and low striking velocity variability were associated with low/medium tempo as well as with increased expertise. Individually, improved precision appeared across an optimum tempo range. Precision was poorest at maximum tempo (400 hits per minute) for precision variables. Conclusions: Expert drummers demonstrated greater precision and consistency than amateurs. Findings indicate an optimum tempo range that extends with increased expertise.
Kristen M. Stearns-Reider, Rachel K. Straub, and Christopher M. Powers
Peak knee valgus has been shown to predict anterior cruciate ligament injury. The purpose of the current study was to compare peak rate of torque development (RTD) to peak isometric torque as a predictor of peak knee valgus during landing. Twenty-three healthy females participated. Hip abductor muscle performance was quantified using 2 types of isometric contractions: sustained and rapid. Peak isometric torque was calculated from the sustained isometric contraction. Peak RTD was calculated from the rapid isometric contraction (0–50 and 0–200 ms after force initiation). Kinematic data were collected during the deceleration phase of a double-leg drop jump task. Linear regression was used to assess the ability of hip abductor muscle performance variables to predict peak knee valgus. Increased peak RTD during the 0 to 50 milliseconds window after force initiation was found to significantly predict lower peak knee valgus (P = .011, R 2 = .32). In contrast, neither peak RTD from 0 to 200 milliseconds after force initiation window (P = .45, R 2 = .03) nor peak isometric torque (P = .49, R 2 = .03) predicted peak knee valgus. The inability of the hip abductors to rapidly generate muscular force may be more indicative of “at-risk” movement behavior in females than measures of maximum strength.
Takao Mise, Yosuke Mitomi, Saki Mouri, Hiroki Takayama, Yoshitomo Inoue, Mamoru Inoue, Hiroshi Akuzawa, and Koji Kaneoka
Context: The range of shoulder rotation is associated with shoulder pain in young male and female swimmers. However, the association between shoulder pain and shoulder complex mobility of the scapulothoracic and acromioclavicular joints has not yet been examined. Moreover, shoulder pain occurs more frequently in females than in males, but only a few studies have examined the relationship between shoulder pain and sex as a risk factor. This study aims to determine the association between shoulder complex mobility and shoulder pain in young male and female swimmers. Design: Prospective cohort design. Methods: The participants were competitive swimmers (n = 76; 37 males and 39 females) with a mean age of 14 years in Japan. The shoulder rotation width, which was the index of shoulder complex mobility, shoulder internal and external rotation range, and middle finger distance of the back-scratch test were measured. An examiner regularly visited the swimming clubs to evaluate the development of shoulder pain and swimming distance. Logistic regression analysis was used to determine the physical characteristics related to the overall development of shoulder pain in both female and male swimmers. The cutoff value was calculated using receiver operating characteristic curves. Results: Sixteen participants, composed of 8 males and 8 females, developed shoulder pain. The overall swimming distance of the male (odds ratio [OR]: 1.0007, P = .01) and female (OR: 1.0018, P = .02) swimmers and the shoulder rotation width of the male (OR: 1.0952, P = .04) and female (OR: 0.888, P = .03) swimmers were identified as risk factors for shoulder pain. The cutoff value for swimming distance was 6000 m. Shoulder rotation width was more than 88 cm in males and <54 cm in females. Conclusions: Hypomobility and hypermobility of the shoulder complex were identified as risk factors for shoulder pain in male and female swimmers, respectively.
Ashley M.B. Suttmiller and Ryan S. McCann
Context: Injury-related fear has recently been recognized to exist in ankle sprain populations. It is unclear, however, if injury-related fear levels differ between those who develop chronic ankle instability (CAI) and those who do not and the best tools for assessing these differences. Objective: The purpose of this study was to conduct a comprehensive systematic review investigating differences in injury-related fear between individuals with and without CAI. Evidence Acquisition: Relevant studies from CINAHL Plus with full text, PubMed, and SPORTDiscus through November 2020 were included. All studies used the Tampa Scale of Kinesiophobia, Fear-Avoidance Beliefs Questionnaire, or Athlete Fear Avoidance Questionnaire as either a descriptor or a main outcome and provided comparison data between a CAI group and ankle sprain copers (COP) or controls (CON). The authors independently assessed methodological quality using the modified Downs and Black Quality Index. Studies were then grouped by between-group comparisons including CAI and CON, CAI and COP, and COP and CON. The authors calculated Hedge g effect sizes and 95% confidence intervals to examine group differences. Evidence Synthesis: A total of 11 studies were included in this review. In total, 8 studies provided data for the CAI and CON comparison, 7 for CAI and COP comparisons, and 4 for COP and CON comparisons. Methodological quality scores ranged from 60.0% to 86.7%, with 2 high-, and 9 moderate-quality studies. Overall, the evidence suggests that physically active individuals with CAI report higher levels of injury-related fear when compared with both COP and CON. Although limited, ankle sprain COP do not seem to differ from CON. Conclusion: Available evidence emphasizes the importance of injury-related fear in individuals who develop chronicity after ankle sprain injury. The Fear-Avoidance Beliefs Questionnaire and Tampa Scale of Kinesiophobia are useful for the identification of injury-related fear in individuals after sustaining an ankle sprain and should be used to inform rehabilitation strategies and to monitor efficacy in fear reduction.