Relationships between the stretch-shortening cycle ability of the lower extremity and performance among high school male middle- and long-distance runners

Middle- and long-distance running performance is determined mainly by physiological parameters such as maximal oxygen uptake, lactate threshold (LT) and running economy (RE). As RE is influenced by biomechanical factors, middle- and long-distance running performance is also influenced by the stretch-shortening cycle (SSC) ability of the lower extremity. However, the relationship between the SSC ability of the lower extremity represented as the repeated rebound jump (RJ) index or the vertical counter movement jump (CMJ) height and middle- and long-distance running performance among high school middle- and long-distance runners with various performance levels is unclear. Thus, the purpose of this study was to investigate the relationship between the SSC ability of the lower extremity and middle- and long-distance running performance and LT among high school male middle- and long-distance runners. A total of 41 high school male middle- and long-distance runners (age: 17.00 ± 0.82 years, height: 170.62 ± 5.63 cm, body mass: 54.39 ± 4.85 kg) participated. Their demographics, training profiles and seasonal best records over 1500 m and 5000 m (1500m SB and 5000m SB, respectively) were collected. Then they performed the RJ and CMJ test and an incremental running test with blood lactate measurements on an outdoor running track. The RJ index, CMJ height and running speeds corresponding to blood lactate concentrations of 2 mmol/L (vLT) and 4 mmol/L (vOBLA) were then calculated. The relationships between the variables were examined using Pearson's correlation coefficient at a significance level of p<0.05. The subjects' 1500m SB was within the range 3 '47-4'32, and their 5000m SB was within the range 14'09-16'04. The average values of the RJ index and CMJ height were 2.13 ± 0.36 and 31.14 ± 3.56, respectively. The RJ index was significantly correlated with 1500m SB (r=-0.55), vLT (r=0.33) and vOBLA (r=0.40), but was not significantly correlated with 5000m SB. 1500m SB and 5000m SB were significantly correlated with vLT and vOBLA, respectively (r=-0.71-0.87). CMJ height was not significantly correlated with 1500m SB, 5000m SB, vLT or vOBLA. The data indicated that fast SSC ability of the lower extremity is related to performance over a short competition time and distance, such as 1500 m, among high school middle- and long-distance runners, and also related to some physiological parameters at submaximal running speeds. Future research should consider how to effectively perform plyometric training for middle- and long-distance runners.