Effects of muscle – tendon length on joint moment and power during sprint starts

Abstract

The aim of this study was to examine the effects of muscle-tendon length on joint moment and power during maximal sprint starts. Nine male sprinters performed maximal sprint starts from the blocks that were adjusted either to 40 degrees or 65 degrees to the horizontal. Ground reaction forces were recorded at 833 Hz using a force platform and kinematic data were recorded at 200 Hz with a film camera. Joint moments and powers were analysed using kinematic and kinetic data. Muscle - tendon lengths of the medial gastrocnemius, soleus, vastus medialis, rectus femoris and biceps femoris were calculated from the set position to the end of the first single leg contact. The results indicated that block velocity (the horizontal velocity of centre of mass at the end of the block phase) was greater (P < 0.01) in the 40 degrees than in the 65 degrees block angle condition (3.39 +/- 0.23 vs. 3.30 +/- 0.21 m . s(-1)). Similarly, the initial lengths of the gastrocnemius and soleus of the front leg in the block at the beginning of force production until half way through the block phase were longer (P < 0.001) in the 40 degrees than in the 65 degrees block angle condition. The initial length and the length in the middle of the block phase were also longer in the 40 degrees than in the 65 degrees block angle condition both for both the gastrocnemius (P < 0.01) and soleus (P < 0.01-0.05) of the rear leg. In contrast, the initial lengths of the rectus femoris and vastus medialis of the front leg were longer (P < 0.05) in the 65 degrees than in the 40 degrees block angle condition. All differences gradually disappeared during the later block phase. The peak ankle joint moment (P < 0.01) and power (P < 0.05) during the block phase were greater in the 40 degrees than in the 65 degrees block angle condition for the rear leg. The peak ankle joint moment during the block phase was greater (P < 0.05) in the 40 degrees block angle for the front leg, whereas the peak knee joint moment of the rear leg was greater (P < 0.01) in the 65 degrees block angle condition. The results suggest that the longer initial muscle-tendon lengths of the gastrocnemius and soleus in the block phase at the beginning of force production contribute to the greater peak ankle joint moment and power and consequently the greater block velocity during the sprint start.

Biomechanical structure of sprint start and effect of biological feedback methods on sprint start performance

“…Horizontal velocity of the center of mass of athletes were analyzed and concluded that use of starting blocks with 40° angle was resulted in better sprint start performances compared to use of starting blocks with 65° angle. It was stated that 40° angle led to greater muscle-tendon lengths of gastrocnemius and soleus muscles at the onset of the sprint start that resulted in higher ankle joint forces and moments (32). According to this study, these factors played an important role in obtaining a greater block velocity.…”

“…Mero et al (32) showed that maximal rate of force development (highest force generated within the smallest time frame) was crucial in attaining maximal block velocity. Similarly, it was stated that propulsive force applied onto the starting blocks had direct effects on the block velocity and the first phase of acceleration after the sprint start (14,32).…”

“…Mero et al (32) showed that maximal rate of force development (highest force generated within the smallest time frame) was crucial in attaining maximal block velocity. Similarly, it was stated that propulsive force applied onto the starting blocks had direct effects on the block velocity and the first phase of acceleration after the sprint start (14,32). According to literature knowledge, it could be concluded that sprint performance is dependent on the sprint start performance that is directly related to propulsive force applied onto the starting blocks (16,19,27,30).…”

“…According to results of biomechanical studies conducted until now, reaction time, sprint start position and block velocity are identified as major factors contributing to sprint performance (11,16,19,27,32,33). All these factors are integrated and each of them depends on central movement regulation process, biomotor abilities, energy production processes and morphological characteristics (24,26).…”

“…Effects of muscle-tendon length on joint movements and joint forces during sprint start position were investigated in the study of Mero et al (32). Nine male sprint athletes used starting blocks with 40° and 65° angle during their sprint runs.…”