Sara M. Brice

Development and validation of a method to directly measure the cable force during the hammer throw

The development of cable force during hammer-throw turns is crucial to the throw distance. In this paper, we present a method that is capable of measuring cable force in real time and, as it does not interfere with technique, it is capable of providing immediate feedback to coaches and athletes during training. A strain gauge was mounted on the wires of three hammers to measure the tension in the wire and an elite male hammer thrower executed three throws with each hammer. The output from the gauges was recorded by a data logger positioned on the lower back of the thrower. The throws were captured by three high-speed video cameras and the three-dimensional position of the hammers head was determined by digitizing the images manually. The five best throws were analysed. The force acting on the hammers head was calculated from Newtons second law of motion and this was compared with the force measured via the strain gauge. Qualitatively the time dependence of the two forces was essentially the same, although the measured force showed more detail in the troughs of the force–time curves. Quantitatively the average difference between the measured and calculated forces over the five throws was 76 N, which corresponds to a difference of 3.8% for a cable force of 2000 N.

An analysis of the relationship between the linear hammer speed and the thrower applied forces during the hammer throw for male and female throwers

The purpose of this study was to investigate the relationship between the cable force and linear hammer speed in the hammer throw and to identify how the magnitude and direction of the cable force affects the fluctuations in linear hammer speed. Five male (height: 1.88 ± 0.06 m; body mass: 106.23 ± 4.83 kg) and five female (height: 1.69 ± 0.05 m; body mass: 101.60 ± 20.92 kg) throwers participated and were required to perform 10 throws each. The hammers linear velocity and the cable force and its tangential component were calculated via hammer head positional data. As expected, a strong correlation was observed between decreases in the linear hammer speed and decreases in the cable force (normalised for hammer weight). A strong correlation was also found to exist between the angle by which the cable force lags the radius of rotation at its maximum (when tangential force is at its most negative) and the size of the decreases in hammer speed. These findings indicate that the most effective way to minimise the effect of the negative tangential force is to reduce the size of the lag angle.

Use of inertial measurement units for measuring torso and pelvis orientation, and shoulder–pelvis separation angle in the discus throw:

Wearable technologies, such as inertial measurement units, are being increasingly utilised in sport to provide immediate feedback to athletes and coaches on movement dynamics. This study examines the validity of inertial measurement units for measuring data pertinent to discus throwing namely shoulder–pelvis separation angle, and torso and pelvis transverse plane orientation. Five discus throwers performed 10 throws, while shoulder–pelvis separation angle, and torso and pelvis transverse plane orientation were measured simultaneously using a motion capture system and inertial measurement unit system. Time-series torso and pelvis orientation data were compared to determine the validity of the inertial measurement unit system for measuring the segment orientation. Discrete shoulder–pelvis separation angle data were compared to determine the validity of the inertial measurement unit system for measuring the discrete data pertinent to discus throwers and coaches. Discrete data examined were magnitudes of separation that occurred when the torso was maximally rotated to the left and right. Data were compared using root mean square difference and root mean square relative to angle range (RMS%). Bland–Altman analyses were also performed. Torso (RMS% = 3%) and pelvis (RMS% = 2%) orientation data agreed closely. Agreement was lower for separation angle (maximum left rotation RMS% = 9%; maximum right rotation RMS% = 13%). Bland–Altman biases indicate inertial measurement units underestimated segment orientation, underestimated maximum right rotation, and overestimated maximum left rotation. The protocol described was valid for measuring the torso and pelvis orientation. Separation angle validity was low, indicating differences in underlying modelling approaches. Further investigation is needed to examine more optimal sensor positioning, and novel ways of examining shoulder–pelvis dynamics.

Analysis of the separation angle between the thorax and pelvis, and its association with performance in the hammer throw

The hammer throw is perhaps one of the most misunderstood and difficult events to learn in track and field. Improvements in technique are focused on strategies designed to increase implement release velocity. The purpose of this cross-sectional investigative study was to examine the association between the angle of separation between the thorax and pelvis and performance in the hammer throw. Two male and four female throwers were used to assess positional data of the hammer, thorax, and pelvis. Hammer positional data were used to determine linear hammer speed at release, release angle, and release height. Thorax and pelvis positional data were used to determine thorax rotation relative to the pelvis (separation angle). The association between values of separation angle at key instances and performance was examined. Performance was determined by distance thrown (55.69 ± 3.42 m). Release speeds (24.32 ± 0.70 m/s) were also examined as a contributory factor towards performance and were included to account for instances where throwers released the hammer using sub-optimal release heights and angles which negatively affected distance thrown. The separation angle at its smallest within each turn was found to have a strong negative association with the performance indicators, especially in the first two turns (significant correlates ranged from −0.82 to −0.97). This finding indicates when throwers reduced the separation to a smaller value, performance was enhanced. Separation angle was at its smallest in double support. This suggests that throwers may improve performance by reducing the separation angle during double support phases.