Effects of block start vs. standing start on force production during sprint performance


The primary muscles that provide force for a sprint start are the biceps femoris and gastrocnemius. However, the force generated might vary depending on the orientation of the hip, knee, and ankle joints. The lower limbs begin in a more flexed position in blocks than in a standing start. Muscles have a length tension relationship with force production. The goal of this investigation was to ascertain if joint angle impact may alter the maximal force output. For a sprint start, it was hypothesized that starting in a block stance rather than a standing stance would result in the most force due to the influence of the joint angles. Five participants, one female and four males were recruited. Subjects had little prior training in sprinting from blocks before beginning the study. The subjects then carried out a standing sprint and a sprint from the blocks. Delsys ® Trigno wireless electromyography (EMG) sensors were used to track the activation of the biceps femoris and gastrocnemius muscles in order to gauge the muscles' ability to produce force. The peak activation of each muscle was compared after computing the root mean square of the signal. Performance was video recording and joint angles were measured using Dartfish ®. When beginning from a block start position as opposed to a standing start stance, subjects exhibited greater activation in their lower leg muscles. When beginning from a block start posture, participants typically generated 1.01 J and 5.33 J in their Biceps Femoris and Gastrocnemius, as opposed to 0.6 J and 1.12 J when starting from a standing start stance. Hip angle in block stance was 48.7° and 110° in the standing start on average. Knee angle was 82.0° in the block stance and 120° in the standing stance on average. Ankle angle was 90° on average for both block and standing stances. The gastrocnemius and biceps femoris provide a large amount of force when a sprint is initiated from a block start position. The maximal force produced depends on the angle of the hip, knee, and ankle joints. The muscles produce greater force the more acutely the hip and knee joints are flexed. The paucity of test subjects and the fact that none of the participants had block start training both pose limitations to this investigation. Future studies should randomize conditions and compare experienced and non-experienced sprinters.

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