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Reyes GF Dickin DC Crusat NJ Dolny DG 《Sports biomechanics / International Society of Biomechanics in Sports》2011,10(4):280-293
The purpose of this study was to evaluate the effects of whole-body vibration (WBV) on the muscle recruitment of selected upper and lower body muscles during the baseball swing. Participants were recreationally trained males (n = 16, 22 +/- 2 years, 181.4 +/- 7.4 cm, 84.7 +/- 9.0 kg), with previous baseball experience. Subjects participated in three randomized sessions on separate days, consisting of three sets of five swings offa hitting tee. Exercises (upper and lower body dynamic and static movements) with or without WBVexposure were performed between swing sets. During each swing, the gastrocnemius, biceps femoris, gluteus maximus, pectoralis major, latissimus dorsi, and triceps brachii were evaluated for electromyographic (EMG) activity. EMG values were normalized to EMG measured during maximal voluntary isometric contraction. Statistical analysis revealed no significant differences in EMG activity across the three treatments. In addition, the results displayed a specific muscle recruitment order during the swing, starting with the lower body followed by the upper body muscles. This study was the first to report the recruitment order during the baseball swing. Although acute exposure to WBV did not significantly alter the muscle recruitment, these results may prove useful for practitioners looking to enhance baseball swing performance. 相似文献
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Sweat lactate reflects eccrine gland metabolism. However, the metabolic tendencies of eccrine glands in a hot versus thermoneutral environment are not well understood. Sixteen male volunteers completed a maximal cycling trial and two 60-min cycling trials [30°C?=?30±1°C and 18°C?=?18±1°C wet bulb globe temperature (WBGT)]. The participants were requested to maintain a cadence of 60 rev?·?min?1 with the intensity individualized at ～ 90% of the ventilatory threshold. Sweat samples at 10, 20, 30, 40, 50 and 60?min were analysed for lactate concentration. Sweat rate at 30°C (1380±325?ml?·?h?1) was significantly greater (P<0.05) than at 18°C (632±311?ml?·?h?1). Sweat lactate concentration was significantly greater (P<0.05) at each time point during the 18°C trial, with values between trials tending to converge across time. During the 30°C trial, both heart rate (20, 30, 40, 50 and 60?min) and rectal temperature (30, 40, 50 and 60?min) were significantly higher than in the 18°C trial. Higher sweat lactate concentrations coupled with lower sweat rates may indicate a greater relative contribution of oxygen-independent metabolism within eccrine glands during exercise at 18°C. Decreases in sweat lactate concentration across time suggest either greater dilution due to greater sweat volume or increased reliance on aerobic metabolism within eccrine glands. The convergence of lactate concentrations between trials may indicate that time-dependent modifications in sweat gland metabolism occur at different rates contingent partially on environmental conditions. 相似文献
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Chia‐Chih DC Wang Makini L. King Nicholas R. Debernardi 《Journal of College Counseling》2012,15(2):101-116
This study examined the relationships between adult attachment, cognitive appraisal, and university students' behavioral and emotional reactions to infidelity situations in romantic relationships. Results based on 173 university students suggested that both attachment and cognitive appraisals significantly predicted distinct types of infidelity reactions and that participants' cognitive appraisal mediated the effects of attachment on behavioral and emotional reactions. Counseling applications for university counselors are discussed on the basis of attachment perspectives and cognitive appraisal models. 相似文献
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Meredith D. Wells D. Clark Dickin Jennifer Popp Henry Wang 《Sports biomechanics / International Society of Biomechanics in Sports》2020,19(3):333-341
ABSTRACTHill running is often used as a foundational training mechanism to build strength and speed. Distance runners in particular are at an increased likelihood of encountering steep hills during training runs. There is limited research regarding downhill running, and there is no research available on the biomechanics of females specifically during downhill running. The purpose of this study was to quantify the differences in loading when running downhill at different grades compared to a level surface in female distance runners to determine the potential risk for injury. Fifteen female distance runners (age: 23.5 ± 4.9 y), who ran 56.3 ± 20.9 km a week participated in this study. Participants ran on a force-instrumented treadmill at 4.0 m/s for 2 min at 0%, ?5%, ?10%, ?15%, and ?20% grades, with 5 min of rest between conditions. Study findings showed increased impact forces (p < 0.001), and increased loading rates (p < 0.001) with increasing downhill grades compared to level. These results indicate a significantly greater risk of overuse injury to the lower extremity with steeper downhill grades. Individuals need to be aware of these risks to plan and implement training programmes that will increase performance while minimising injury risk. 相似文献
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Department of Health, Physical Education, Recreation, and Dance at the University of Idaho. This study was performed to examine the effects of movement velocity and maximal concentric and eccentric actions on the bilateral deficit. Eighteen female participants performed maximal unilateral and bilateral knee extensions concentrically and eccentrically across six movement velocities (30, 60, 90, 120, 150, and 180 degrees/s). Repeated measures analyses of variance revealed significant differences (p < .025) between bilateral and summed unilateral contractions both concentrically and eccentrically at each velocity tested. Post hoc analyses revealed that the degree of bilateral deficit increased as movement velocity increased for concentric actions (e.g., 17-33% deficit, for 30 and 180 degrees/s, respectively), and an increasing trend was seen for eccentric actions (e.g., 18-25% deficit, for 30 and 180 degrees/s, respectively). These findings suggest that with increased velocity, a decreased or incomplete activation of fast twitch muscle fibers may have occurred in bilateral actions when compared to unilateral actions. 相似文献
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Scott R. Brown Henry Wang D. Clark Dickin Kaitlyn J. Weiss 《Sports biomechanics / International Society of Biomechanics in Sports》2014,13(4):351-361
This study examined the relationship between leg preference and knee mechanics in females during sidestepping. Three-dimensional data were recorded on 16 female collegiate footballers during a planned 45° sidestep manoeuvre with their preferred and non-preferred kicking leg. Knee kinematics and kinetics during initial contact, weight acceptance, peak push-off, and final push-off phases of sidestepping were analysed in both legs. The preferred leg showed trivial to small increases (ES = 0.19–0.36) in knee flexion angle at initial contact, weight acceptance, and peak push-off, and small increases (ES = 0.21–0.34) in peak power production and peak knee extension velocity. The non-preferred leg showed a trivial increase (ES = 0.10) in knee abduction angle during weight acceptance; small to moderate increases (ES = 0.22–0.64) in knee internal rotation angle at weight acceptance, peak push-off, and final push-off; a small increase (ES = 0.22) in knee abductor moment; and trivial increases (ES = 0.09–0.14) in peak power absorption and peak knee flexion velocity. The results of this study show that differences do exist between the preferred and non-preferred leg in females. The findings of this study will increase the knowledge base of anterior cruciate ligament injury in females and can aid in the design of more appropriate neuromuscular, plyometric, and strength training protocols for injury prevention. 相似文献
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This study examined the influences of generational status, self‐esteem, academic self‐efficacy, and perceived social support on 367 undergraduate college students' well‐being. Findings showed that 1st‐generation students reported significantly more somatic symptoms and lower levels of academic self‐efficacy than did non‐1st‐generation students. In addition, students' generational status was found to moderate predictive effects of perceived family support on stress. Implications for professional practices, limitations, and directions for future research are discussed. 相似文献