The purpose of this study was to quantify the effect of different starting distances on 5-m sprint time and the accuracy of the initial timing gate. A single-beam timing gate system (1 m high) was used to measure 5-m sprint time in 13 male sports students. Each subject performed 3 valid trials for 3 starting distances: 0.3, 0.5, and 1.0 m from the initial timing lights, respectively. A high-speed video camera was used to track a reflective marker placed on the subjects' hip within a field of view around the initial timing gate. Accuracy of the initial timing gate was defined as the time between the initial timing light trigger and passing of the reflective marker by the initial timing gate. Sprint times were significantly faster for the 1.0-m starting distance (0.98 ± 0.06 seconds) than for the 0.5-m (1.05 ± 0.07 seconds) and the 0.3-m (1.09 ± 0.08 seconds) starting distances (p < 0.001). There were no differences in initial timing gate error between starting distances (p = 0.078). Hence, starting distance influenced sprint times but not the accuracy of the initial timing gate. Researchers and coaches should consider the effect of starting distance on 5-m sprint time and ensure consistent testing protocols. Based on the results of this study, we recommend a starting distance of 0.3 m that should be used for all sprint performance tests.

Two different computational approaches were used to predict Olympic distance triathlon race time of German male elite triathletes. Anthropometric measurements and two treadmill running tests to collect physiological variables were repeatedly conducted on eleven male elite triathletes between 2008 and 2012. After race time normalization, exploratory factor analysis (EFA), as a mathematical preselection method, followed by multiple linear regression (MLR) and dominance paired comparison (DPC), as a preselection method considering professional expertise, followed by nonlinear artificial neural network (ANN) were conducted to predict overall race time. Both computational approaches yielded two prediction models. MLR provided R² = 0.41 in case of anthropometric variables (predictive: pelvis width and shoulder width) and R² = 0.67 in case of physiological variables (predictive: maximum respiratory rate, running pace at 3-mmol·L -1 blood lactate and maximum blood lactate). ANNs using the five most important variables after DPC yielded R² = 0.43 in case of anthropometric variables and R² = 0.86 in case of physiological variables. The advantage of ANNs over MLRs was the possibility to take non-linear relationships into account. Overall, race time of male elite triathletes could be well predicted without interfering with individual training programs and season calendars.

Background and Objectives:Sit-to-Stand (STS) movements are fundamental activities of daily living. As STS movements can be physically demanding especially for the elderly, bi-and unilateral STS movements are frequently used in motor tests to measure lower limb strength. In contrast to bilateral STS movements, the knee joint loads occurring during unilateral STS movements as well as the influences of chair height or lower limb dominance are still unknown. Methods:In a randomized study approach knee joint loads during unilateral STS movements from three different chair heights have been analyzed using biomechanical motion analysis in a population of 19 healthy middle-aged adults. Additionally, the influence of lower limb dominance and the level of perceived exertion have been investigated. Results:Lower limb dominance had no effect on knee joint load. In contrast, chair height significantly affected the peak shear forces in anterior (high: 3.94 ± 0.63 N/kg; low: 4.09 ± 0.61 N/kg) and lateral (high: 1.52 ± 0.79 N/kg; low: 1.78 ± 0.88 N/kg) direction as well as the peak knee adduction moment (high: 0.56 ± 0.29 Nm/kg; low: 0.65 ± 0.32 Nm/kg). Additionally, chair height but not limb dominance significantly affected the level of perceived exertion (high: 11.1 ± 2.8; low: 12.5 ± 3.5). Conclusion:The detected knee joint loads occurring during a unilateral STS movements are similar to those of other activities of daily living like e.g. stair ascent and thus, unilateral STS movements are applicable for usage in motor tests for middle-aged subjects. While lower limb dominance has no impact on the knee joint load, lower chair heights increase the load on the knee joint. Therefore, chair height should be considered when using unilateral STS movements in motor tests.

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