Joint work is not shifted proximally after a long run in rearfoot strike runners     

Jake A. Melaro  Allison H. Gruber 《Journal of sports sciences》2021,39(1):78-83

ABSTRACT

Distal-to-proximal redistribution of joint work occurs following exhaustive running in recreational but not competitive runners but the influence of a submaximal run on joint work is unknown. The purpose of this study was to assess if a long submaximal run produces a distal-to-proximal redistribution of positive joint work in well-trained runners. Thirteen rearfoot striking male runners (weekly distance: 72.6 ± 21.2 km) completed five running trials while three-dimensional kinematic and ground reaction force data were collected before and after a long submaximal treadmill run (19 ± 6 km). Joint kinetics were calculated from these data and percent contributions of joint work relative to total lower limb joint work were computed. Moderate reductions in absolute negative ankle work (p = 0.045, Cohen’s d = 0.31), peak plantarflexor torque (p = 0.004, d = 0.34) and, peak negative ankle power (p = 0.005, d = 0.32) were observed following the long run. Positive ankle, knee and hip joint work were unchanged (p < 0.05) following the long run. These findings suggest no proximal shift in positive joint work in well-trained runners after a prolonged run. Runner population, running pace, distance, and relative intensity should be considered when examining changes in joint work following prolonged running.  相似文献   

Could knee joint mechanics during the golf swing be contributing to chronic knee injuries in professional golfers?     

Howie Carson  Jim Richards  Simon G. S. Coleman 《Journal of sports sciences》2020,38(13):1575-1584

ABSTRACT

Full three-dimensional movements and external moments in golfers’ knees and the possible involvement in injuries have not been evaluated using motion capture at high sample frequencies. This study measured joint angles and external moments around the three anatomical axes in both knees of 10 professional golfers performing golf drives whilst standing on two force plates in a motion capture laboratory. Significant differences were found in the knee joint moments between the lead and trail limbs for the peak values and throughout all stages during the swing phase. A significantly higher net abduction moment impulse was seen in the trail limb compared with the lead limb (?0.518 vs. ?0.135 Nms.kg^?1), indicating greater loading over the whole swing, which could contribute to knee lateral compartment or anterior cruciate ligament injuries. A significant correlation (r = ?0.85) between clubhead speed at ball contact and maximum joint moment was found, with the largest correlations being found for joint moments at the top of the backswing event and at the end of the follow-through. Therefore, although knee moments can contribute to high clubhead speeds, the large moments and impulses suggest that they may also contribute to chronic knee injuries or exacerbate existing conditions.  相似文献   

Reviewing the Variability-Overuse Injury Hypothesis: Does Movement Variability Relate to Landing Injuries?     

Andrew D. Nordin  Janet S. Dufek 《Research quarterly for exercise and sport》2019,90(2):190-205

Purpose: Overuse injuries are common in sport, but complete understanding of injury risk factors remains incomplete. Although biomechanical studies frequently examine musculoskeletal injury mechanisms, human movement variability studies aim to better understand neuromotor functioning, with proposed connections between overuse injury mechanisms and changes in motor variability. Method: In a narrative review, we discuss the variability-overuse injury hypothesis, which suggests repeated load application leads to mechanical tissue breakdown and subsequent injury when exceeding the rate of physiological adaptation. Due to the multidisciplinary nature of this hypothesis, we incorporate concepts from motor control, neurophysiology, biomechanics, as well as research design and data analysis. We therefore summarize multiple perspectives while proposing theoretical relationships between movement variability and lower extremity overuse injuries. Results: Experimental data are presented and summarized from published experiments examining interactions between experimental task demands and movement variability in the context of drop landing movements, along with comparisons to previous movement variability studies. Conclusion: We provide a conceptual framework for sports medicine researchers interested in predicting and preventing sports injuries. Under performance conditions with greater task demands, we predict reduced trial-to-trial movement variability that could increase the likelihood of overuse injuries.  相似文献   

Effect of different loading conditions on running mechanics at different velocities     

Germán Carretero-Navarro  Doménico Cherubini  Wolfgang Taube 《European Journal of Sport Science》2019,19(5):595-602

Weighted vests are widely used to improve running economy and performance. However, it is not well-studied how running mechanics are adapted to counteract the higher peak vertical ground reaction forces (Fpeak) while running with such a device. Therefore, the present study aimed to investigate the effects of different loading conditions on running mechanics at different velocities. Thirteen subjects participated in two separate sessions one week apart. In the first session, maximal aerobic speed (MAS) was determined through a maximal incremental running test while in the second session, they were instructed to run during one minute under different loading (0%, +10% and +20% of body mass [BM]) and velocity (60%, 80% and 100% of MAS) conditions in a random order. Spatiotemporal data were recorded and then running mechanics modelled using the spring-mass model. The main results indicated that vertical and leg stiffness (Kvert and Kleg, respectively) were increased (P?P?>?.05) when load was changed. At the same time, alterations of the running kinematics were observed such as longer contact times, reduced flight times, stride frequencies and step lengths, as well as an increase of the centre of mass dynamics. Based on these results it is assumed that runners maintain a certain stiffness level for each velocity despite different loading conditions. As a consequence, Fpeak increases and this probably causes spatiotemporal adjustments in the movement kinematics.  相似文献   

Validity and reliability of a low-cost dynamometer to assess maximal isometric strength of upper limb     

Natalia Romero-Franco  Juan C Fernández-Domínguez  Juan A Montaño-Munuera  Javier Romero-Franco  Pedro Jiménez-Reyes 《Journal of sports sciences》2019,37(15):1787-1793

Muscle imbalance and deficit are key parameters for guiding rehabilitation and sports sessions and avoiding injuries. However, the high cost and non-portable nature of most instruments employed for muscle strength assessment frequently hamper an affordable evaluation in field conditions. This study evaluated the validity and reliability of a low-cost digital dynamometer to assess the maximal isometric strength of upper limb muscles. Fourteen physically active volunteers performed the main movements of the upper limb at maximal isometric strength: flexion-extension, internal-external rotation and abduction-adduction of the shoulder; and flexion-extension of both elbow and wrist. Validity was examined by comparing the strength values from the low-cost digital dynamometer and those measured by an isokinetic dynamometer, assumed as the gold standard. The correlation between both devices was perfect (r > 0.913), while Bland-Altman plots showed absolute agreement between both devices, the maximum range of the values of bias was ?0.99–1.00 N in wrist extension. Inter-tester and intra-tester reliability were excellent for all movements (ICC ≥ 0.855). The low-cost digital dynamometer showed strong validity and excellent reliability in assessing maximal isometric strength during the main movements of the upper limb. Professionals may use it for an affordable isometric muscle strength assessment in field situations.  相似文献   

Comparing the magnitude and direction of asymmetry during the squat,countermovement and drop jump tests in elite youth female soccer players     

Chris Bishop  Lucas A. Pereira  Valter P. Reis  Paul Read  Anthony N. Turner  Irineu Loturco 《Journal of sports sciences》2020,38(11-12):1296-1303

ABSTRACT

The aims of the present study were to provide an in-depth comparison of inter-limb asymmetry and determine how consistently asymmetry favours the same limb during different vertical jump tests. Eighteen elite female under-17 soccer players conducted unilateral squat jumps (SJ), countermovement jumps (CMJ) and drop jumps (DJ) on a portable force platform, with jump height, peak force, concentric impulse and peak power as common metrics across tests. For the magnitude of asymmetry, concentric impulse was significantly greater during the SJ test compared to CMJ (p = 0.019) and DJ (p = 0.003). No other significant differences in magnitude were present. For the direction of asymmetry, Kappa coefficients revealed fair to substantial levels of agreement between the SJ and CMJ (Kappa = 0.35 to 0.61) tests, but only slight to fair levels of agreement between the SJ and DJ (Kappa = ?0.26 to 0.18) and CMJ and DJ (Kappa = ?0.13 to 0.26) tests. These results highlight that the mean asymmetry value may be a poor indicator of true variability of between-limb differences in healthy athletes. The direction of asymmetry may provide a useful monitoring tool for practitioners in healthy athletes, when no obvious between-limb deficit exists.  相似文献   

基于差异沉降控制的桩基优化设计     

潘海龙 《石家庄铁路职业技术学院学报》2021,(1):62-66,83

为解决传统桩基承载力低的问题,基于差异沉降控制优化设计桩基。分析桩基设计存在的问题,主要包括:桩基支承刚度设定误差高、桩基差异沉降大、桩基结构设计不合理,通过设定桩基支承刚度,控制桩基差异沉降,采用桩基塌孔承桩断裂结构,实现对桩基的优化设计。设计实例分析,结果表明,设计的桩基承载力明显高于对照组,能够解决传统桩基承载力低的问题。  相似文献   

非协调轴对称杂交应力元单元刚度矩阵的准确建立     

田炯  田宗漱 《中国科学院研究生院学报》1994,(1)

给出新型三类用理性杂交模式、根据一种修正的Ｈｅｌｌｉｎｇｅｒ－Ｒｅｉｓｓｎｅｒ原理、建立高精度非协调轴对称实体旋转有限元时，其单元刚度矩阵的准确计算式。  相似文献   

Relationship between Achilles tendon properties and foot strike patterns in long-distance runners     

Keitaro Kubo  Daisuke Miyazaki  Shigeharu Tanaka  Shozo Shimoju  Naoya Tsunoda 《Journal of sports sciences》2015,33(7):665-669

The purpose of this study was to investigate the relationship between Achilles tendon properties and foot strike patterns in long-distance runners. Forty-one highly trained male long-distance runners participated in this study. Elongation of the Achilles tendon and aponeurosis of the medial gastrocnemius muscle were measured using ultrasonography, while the participants performed ramp isometric plantar flexion up to the voluntary maximum. The relationship between the estimated muscle force and tendon elongation during the ascending phase was fit to a linear regression, the slope of which was defined as stiffness. In addition, the cross-sectional area of the Achilles tendon was measured using ultrasonography. Foot strike patterns (forefoot, midfoot and rearfoot) during running were determined at submaximal velocity (18 km · h^?1) on a treadmill. The number of each foot strike runner was 12 for the forefoot (29.3%), 12 for the midfoot (29.3%) and 17 for the rearfoot (41.5%). No significant differences were observed in the variables measured for the Achilles tendon among the three groups. These results suggested that the foot strike pattern during running did not affect the morphological or mechanical properties of the Achilles tendon in long-distance runners.  相似文献   

The impact of data reduction on the intra-trial reliability of a typical measure of lower limb musculoskeletal stiffness     

Mark P. Moresi  Elizabeth J. Bradshaw  David A. Greene  Geraldine A. Naughton 《Journal of sports sciences》2015,33(2):180-191

Double-leg repeated jumping tasks are commonly used as measures of lower limb stiffness in exercise science research. Within similar stiffness calculations, variation in data-reduction criteria exists. The impact of these varied data-reduction methods on stiffness measures is unknown. Sixteen adolescent female participants from varied physical activity backgrounds performed 15 self-paced, bent-knee continuous jumps (CJb) on two force plates. Leg stiffness was calculated as the ratio of the peak force and the centre of mass displacement for each contact. Using combinations of criteria based on previous literature, 83 data-reduction methods were applied to the raw data. Data reduction suitability was assessed based on intra-trial reliability, the number of participants excluded and the average contacts excluded. Four data-reduction methods were deemed suitable for use with adolescent female populations, with three consecutive contacts within 1 SD of the average jump frequency considered optimal. The average individual stiffness values were not greatly influenced by the data-reduction method; however, for a single participant, a stiffness change of up to 6 kN · m^?1 (30%) was observed. The role and potential impact of data-reduction methods used to evaluate measures of lower limb stiffness during repeated jumping tasks warrants consideration.  相似文献