The Association Between Hip-Shoulder Separation Angles and Technique Characteristics in World-Class High Jumpers

Hip-shoulder separation (H-Ssep) has been widely researched in many sporting activities (e.g., golf) to provide information on the contribution of torso rotation to performance and injury. Although it is necessary for high jumpers to generate significant long-axis rotation to successfully clear the bar, limited information exists on H-Ssep for high jump athletes. As such, this study aimed to (a) characterize the H-Ssep of world-class high jump athletes during competition, (b) determine if differences exist between male and female athletes and (c) to examine the relationship between H-Ssep and the biomechanical parameters used to describe high jump technique. Twenty-nine world-class high jumpers (17 males, 12 females) were video recorded (frame rate: 120–200 Hz) during the 2017 and 2018 World Athletics Championship finals. H-Ssep was quantified at touchdown (TD) and take-off (TO) following manual digitizing (SIMI motion) and a number of other common biomechanical parameters were computed. The observed levels of H-Ssep at TD (−46±12°) and TO (16 ±11°) were in line with those reported previously for other sports. The magnitude of H-Ssep varied between individuals and showed significant associations with other approach and take-off characteristics. Significant differences in H-Ssep were not evident between male and female athletes despite significant differences in other performance- and technique-related parameters. These findings highlight the divergent take-off characteristics of world-class performers and their reliance on hip-shoulder interactions when generating long axis rotation. Coaches should be mindful of the mechanical and physical consequences of H-Ssep when developing technical models, conditioning interventions and coaching strategies

Different inertial properties between static and dynamic rowing ergometers cause acute adaptations in coordination patterns

With ergometers being frequently used in training programmes of rowers, consensus is needed to identify which design most closely reproduces the biomechanics of on-water rowing. Discussion exists about the movement allowed to the stretcher, with static designs fixating it, while dynamic models allowing displacement. To investigate how this affects muscular and kinematic coordination patterns, a group of nine male rowers were analysed whilst exercising on three ergometer designs, a static ergometer and two dynamic versions. 3D motion analysis was applied to measure displacement of body segments, joint angles and angular velocities. Electromyography was used to record activation patterns of major muscles. All participants were measured on all three ergometer designs; data were analysed using repeated measures ANOVA. Duration of the stroke phase turned out to be longer on the static ergometer and tibialis anterior and biceps femoris coordination patterns differed between static and dynamic ergometers. Kinematic data showed a more squatted posture at the end of recovery on the static ergometer. These differences were interpreted as distorted movement coordination resulting from the more inert moving mass on the static ergometer

Kinematic factors associated with start performance in World-class male sprinters

The aim was to investigate the kinematic factors associated with successful performance in the initial acceleration phase of a sprint in the best male athletes in the World at the 2018 World Indoor Athletics Championships. High speed video (150 Hz) was captured for eight sprinters in the men's 60 m final. Spatio-temporal and joint kinematic variables were calculated from the set position to the end of the first ground contact post-block exit (GC1). Normalised average horizontal external power (NAHEP) defined performance and was the dependent variable for a series of regression analyses. Clear relationships were found between GC1 NAHEP and 10-m time, 60-m time, change in velocity, acceleration and contact time in the first ground contact (r = –0.74, –0.64, 0.96, 0.91 and –0.56, respectively). Stepwise multiple linear regression of joint kinematic variables in the first ground contact revealed that trunk angle at take-off and thigh separation angle at take-off explained nearly 90% of variation in GC1 NAHEP (R2 = 0.89). The athletes’ projection at take-off with a forward leaning trunk and large thigh separation is characteristic therefore of excellent initial acceleration performance and this will be a good visual guide for technical coaching instruction. This was the first study of its kind to adopt such a research design in a World-class sample in a representative environment. Future studies that combine detailed kinematic and kinetic data capture and analysis in such a setting will add further insight to the findings of this investigation.</p