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INDUCED ACCELERATION ANALYSIS IN WEIGHTLIFTING: A PILOT STUDY
Get PDFThe purpose of this pilot study was to determine the functional roles of the lower extremity joints during a weightlifting exercise. One participant performed the power clean exercise with 75% of one-repetition maximum while 3D motion capture and force plate data were recorded. Net joint moments were calculated via inverse dynamics analysis and used as inputs to an induced acceleration analysis that calculated joint-specific contributions to ground reaction forces (GRF). Results showed that all joints exhibited to phase-specific contributions to vertical GRF. Interestingly, the ankle plantarflexors produced primarily anterior GRF, whereas the knee extensors produced primarily posterior GRF. The results underscore joint- and phase-specific contributions to the production of vertical and horizontal GRF during the power clean
A 3D APPROACH TO BASEBALL PITCHING KINEMATIC SEQUENCE
Get PDFA proximal-to-distal sequence (PDS) in baseball pitching is theorized to be more efficient and can reduce upper limb joint loads. However, studies investigating PDS using timing of peak segment angular velocity magnitude did not identify the use of “full” PDS from pelvis to hand. This study investigated PDS by comparing the timings of peak angular velocities about each global axis for the pelvis, trunk, upper arm, forearm, and hand during fastballs thrown by professional pitchers (n=4). We found that pitchers demonstrated full PDS about the global left axis (from pitching mound to first base) in 67-100% of their trials, depending on the pitcher. No pitcher demonstrated full PDS about the other two global axes. Similar to prior studies, we also did not observe full PDS when using angular velocity magnitude. This could be explained by differences in body segment rotation sequences between global axes. We also preliminarily uncovered impacts of filtering on the kinematic sequence detected. Analyzing 3D angular velocities with carefully selected filters may advance our understanding of the dynamics of pitching
A COMPARISON OF PITCH LENGTH VARIATIONS AND THE ABILITY TO CONTROL LENGTH IN CRICKET FAST BOWLING
Get PDFThis study aimed to identify differences between ball release parameters and different pitch length deliveries in cricket fast bowling. A total of 707 fast bowling trials (bouncers, yorkers, stock balls) performed by 21 male fast bowlers were recorded and used to investigate the variations in ball release parameters. Ball release angle (p \u3c 0.05) was significantly different between all three deliveries, while resultant ball release speed and ball release height of the bouncer deliveries were significantly different (p \u3c 0.05) to yorker and stock deliveries. Furthermore, the success rates of bowlers achieving their intended variation highlighted a difficulty in delivering yorker deliveries compared to bouncer and stock deliveries. Results provide a foundation for coaching and future research, in particularly investigating the kinematic and kinetic factors linked with different length fast bowling deliveries
IS THE VELOCITY PERTURBATION METHOD SUITABLE FOR THE CALCULATION OF THE USEFUL MECHANICAL POWER OUTPUT OF SPRINT KAYAKERS IN OUTDOOR CONDITIONS?
Get PDFThis study assessed whether the Useful Mechanical Power Output (PMO) estimated using the Velocity Perturbation Method (VPM) would be a valid biomechanical measure of performance enhancement in sprint kayaking that would not be affected by changes in environmental conditions. Twelve national-age K1 sprint kayakers performed twelve trials each of 60m maximal effort sprints within two separate sessions, six of which were conducted while towing a hydrodynamic object of known resistance. The opposing wind condition in each trial was recorded and classified as either mild or strong. The sprint velocities at towing-free and towing conditions under similar wind velocities and the resistance of the hydrodynamic object were matched to estimate the PMO. Non-significant differences in PMO between mild and strong wind conditions were observed. However, the typical error of PMO in both wind conditions were larger than 26% of the mean values, which hindered the ability of the PMO to detect the smallest worthwhile enhancement that would be valuable for high-performance kayak sprinting
RELIABILITY AND VALIDITY OF A DEEP LEARNING ALGORITHM BASED MARKERLESS MOTION CAPTURE SYSTEM IN MEASURING SQUATS
Get PDFThis study aimed to compare the performance of a traditional marker-based motion capture system and a video-based markerless system in analyzing squats and to determine the reliability and validity of the markerless system. Twenty-one squats were recorded using a marker-based motion capture system and a 2D video camera. We analyzed the 2D video data using Sportip Motion 3D, a deep learning-based 3D human pose estimation algorithm based specifically on sports activities, and the peak lower limb joint angles were calculated by both systems. There was an excellent agreement between VICON and Sportip Motion 3D for all joint angles (hip intraclass correlation coefficient (ICC) = 0.96, knee ICC = 0.92, ankle ICC = 0.86), with average differences of less than 1.3°. These results indicate that squat analysis using Sportip Motion 3D is equally reliable and accurate as the conventional marker-based method
THE ASSOCIATION BETWEEN TRUNK ENERGY FLOW AND PEAK SHOULDER DISTRACTION FORCE IN COLLEGIATE SOFTBALL PITCHING
Get PDFThe purpose of the study was to determine the association between trunk energy flow (proximal energy inflow (IF) and distal energy outflow (OF) on the pitching arm side) and peak shoulder distraction force during the acceleration phase of the windmill softball pitch. Fifty-five collegiate softball pitchers participated. Regression analysis revealed proximal energy IF was not associated with peak shoulder distraction force during the acceleration phase of the pitch [F (1,53) = .026; p = .87), r = .02]. Distal trunk OF was also not associated with peak shoulder distraction force during the acceleration phase of the pitch [F (1,53) = .920; p = .342), r = .13]. Thus, it was concluded proximal trunk energy IF and distal trunk energy OF on the pitching arm side are not associated with peak shoulder distraction force during the acceleration phase of the pitch
ANALYZING INTRA-CYCLE VELOCITY PROFILE DURING WHEELCHAIR RACING PROPULSION: A PRELIMINARY STUDY
Get PDFRecent technological improvements made it possible to monitor manual wheelchair (MWC) racing intra-cycle velocity profile under in-situ conditions. Based on the hypothesis that the intra-cycle velocity profile is related to the contribution of the upper body in racing MWC propulsion, it could be used for in-situ technical analysis. Four elite MWC racing athletes were equipped with IMUs during a 400 m race, and propulsion cycles were studied once constant speed was reached. Trunk flexion angle and trunk flexion speed were monitored, as well as manual wheelchair linear velocity. This preliminary study shows that intra-cycle velocity profile appears to be athlete specific. Future research coupling such measurements with pushrim contact detection systems could help further understanding the complexity of MWC racing propulsion’s technique and timing
THE ISOKINETIC MUSCLE ASYMMETRY OF THE THIGH AT 1 YEAR AFTER ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTION WAS SIGNIFICANTLY ASSOCIATED WITH GAIT ASYMMETRY
Get PDFObjective: To study the correlation between muscle strength asymmetry and gait asymmetry in 1 year after （Anterior Cruciate Ligament Reconstruction， ACLR）.
Methods: Twenty-five ACLR patients were enrolled in the Department of Sports Medicine, Peking University Third Hospital. Data of isokinetic muscle strength test one year after ACLR were collected. The concentric and eccentric strength of extensor and flexor muscles at 60°/s, 180°/s and 300°/s on the uninjured side and the injured side were measured respectively, and the peak value of muscle strength was analyzed. The three dimensional motion information and ground reaction force during gait were collected, and the peaks of three dimensional joint angle and moments during gait stance phase were calculated by inverse dynamics analysis. The paired-samples T test was used to analyze the difference of gait parameters and isokinetic muscle strength peaks. Spearman correlation analysis was used to study the correlation between bilateral asymmetry index of isokinetic muscle strength and gait asymmetry index. Results: One year after ACLR, the isokinetic muscle strength peaks of the flexor and extensor muscles on the injured side were significantly lower than those on the uninjured side【60°/s extensor concentric, the injured side: (1.22 ± 0.4)Nm·kg-1, uninjured side: (1.73 ± 0.42)Nm·kg-1, bilateral difference: (-0.5 ± 0.39)Nm·kg-1, P \u3c 0.01; 60°/s flexor concentric, injured side: (0.84 ± 0.19)Nm·kg-1, uninjured side: (1.05 ± 0.23)Nm·kg-1, bilateral difference: (-0.21 ± 0.14)Nm·kg-1, P \u3c 0.01】. Compared with the uninjured side, the injured side showed insufficient knee extension at the time of maximum knee extension during stance phase 【injured side: (5.25 ± 4.17) °, uninjured side: (2.24 ± 3.11) °, bilateral difference: (3.01 ± 2.44) °, P \u3c 0.01】, and the peak extension moment decreased significantly 【injured side: (0.1 ± 0.09) Nm·kg-1·m-1, (0.15 ± 0.07) Nm·kg-1·m-1, (-0.05 ± 0.06) Nm·kg-1·m-1, P \u3c 0.01】. One year after ACLR, the asymmetry of 180°/s isokinetic extensor concentric strength was significantly correlated with the asymmetry of peak flexion moment (R = 0.449, P = 0.024). The asymmetry of 60°/s isokinetic extensor concentric strength was significantly correlated with the asymmetry of peak internal rotation moment (R = 0.421, P = 0.036). One year after ACLR, asymmetries of 180°/s, 300°/s isokinetic extensor concentric strength and 60°/s isokinetic flexor eccentric strength were significantly correlated with peak asymmetries during stance phase. Conclusion: There is a significant correlation between isokinetic muscle strength asymmetry of knee and gait asymmetry. This study suggests that ACLR patients still need regular rehabilitation training to improve muscle strength and motor function 1 year after ACLR, so as to reduce the risk of reinjury and secondary injury
A COMPARISON OF KINEMATICS BETWEEN ELITE HANDBALL PLAYERS WITH AND WITHOUT SHOULDER PAIN AFTER A FUNCTIONAL FATIGUE PROTOCOL
Get PDFShoulder pain are common in team handball, and players often continue playing despite pain. The aim of the study was to investigate whether a functional fatigue protocol(FFP) affects throwing kinematics, and whether this effect was different between players with and without shoulder pain. Thirty female players performed maximal standing throws before and after a FFP, while joint kinematics were measured with eight cameras (Vicon T40, Oxford, UK). The main findings were that fatigue affected throwing velocity positively. Some kinematic parameters in both groups were affected, but the effect on kinematics was not the same in both groups, especially timing of the maximal shoulder extension and minimal internal shoulder rotations seems to change differently between the groups after a FFP. No previous studies have investigated, whether functional fatigue influences throwing kinematic differently at team handball players who are playing with or without shoulder pain.
KEYWORDS: Throwing kinematics, Team Handball, Overhead athletes, fatigue protocol, shoulder pain, risk factor
MUSCLE INERTIA DURING RUNNING: A MASSIVE CHANGE OF MOMENTS?
Get PDFSkeletal muscles have substantial inertia that cause inertial forces working around joints. These inertial forces are not typically considered in musculoskeletal models used for sport biomechanics research, which can lead to considerable errors in estimated joint kinetics. How large these errors are in common sports movements is yet unclear. We therefore examined the role of shank muscle inertia on ankle joint moments during the swing phase of running at different speeds. Ankle moments were considerably affected when muscles were modelled as separate masses, with a general shift towards reduced dorsiflexion and higher plantarflexion moments. These results show that ignoring inertial muscle forces in musculoskeletal simulations can lead to under- or overestimations of structure-specific loads and possibly erroneous conclusions. We therefore encourage sport biomechanics researchers to consider the impact of muscle inertia on inverse dynamics calculations