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Purpose The purpose of this study was to develop and validate a method that would facilitate immediate feedback on linear hammer speed during training. Methods Three-dimensional hammer head positional data were measured and used to calculate linear speed (calculated speed) and cable force. These data were used to develop two linear regression models (shifted and non-shifted) that would allow prediction of hammer speed from measured cable force data (predicted speed). The accuracy of the two models was assessed by comparing the predicted and calculated speeds. Averages of the coefficient of multiple correlation (CMC) and the root mean square (RMS) of the difference between the predicted and calculated speeds for each throw of each participant were used to assess the level of accuracy of the predicted speeds. Results Both regression models had high CMC values (0.96 and 0.97) and relatively low RMS values (1.27 m/s and 1.05 m/s) for the non-shifted and shifted models, respectively. In addition, the average percentage differences between the predicted and calculated speeds were 6.6% and 4.7% for the non-shifted and shifted models, respectively. The RMS differences between release speeds attained via the two regression models and those attained via three-dimensional positional data were also computed. The RMS differences between the predicted and calculated release speeds were 0.69 m/s and 0.46 m/s for the non-shifted and shifted models, respectively. Conclusion This study successfully derived and validated a method that allows prediction of linear hammer speed from directly measured cable force data. Two linear regression models were developed and it was found that either model would be capable of predicting accurate speeds. However, data predicted using the shifted regression model were more accurate. [ABSTRACT FROM AUTHOR]

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 hammer's 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. [ABSTRACT FROM AUTHOR]

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 hammer's head was determined by digitizing the images manually. The five best throws were analysed. The force acting on the hammer's head was calculated from Newton's 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. [ABSTRACT FROM AUTHOR]