Association of Hamstring Length With Speed, Strength, and Endurance Among Recreational Long-Distance Runners: A Cross-Sectional Study.

Context: Hamstring flexibility is crucial for athletes, as muscle imbalances can impair performance and lead to strain injuries. Understanding its influence on running performance is essential for optimizing training and minimizing injury risks. While some studies suggest a link between hamstring flexibility and athletic performance, the evidence is limited and controversial. This study aims to investigate the association between hamstring length and performance factors, such as speed, strength, and endurance in recreational long-distance runners.

Methods: Forty recreational long-distance runners (mean age: 33.88 [8.49]) were included. Hamstring length was assessed by passive knee extension test (90°) and, according to the value, divided into flexible and nonflexible groups and then assessed speed using a 30-m sprint test; the strength of hamstring and quadriceps muscles was assessed using isometric muscle strength testing while endurance by Cooper 1.5-mile run test.

Results: The study revealed a significant correlation between hamstring length with quadriceps strength and a moderate association with hamstring strength. However, no statistically significant correlation was found with speed and endurance. A comparison of all quantitative data between flexible and nonflexible and male and females was done by using the independent t test and Mann-Whitney z test, which showed that a nonflexible group has less quadriceps strength (P = .02 right, P = .03 left) than a flexible hamstring.

Conclusion: The study concluded that hamstring flexibility is associated with quadriceps muscle strength. However, it may not help in improving speed and endurance performance in recreational long-distance runners. This suggests that further studies are needed to explore this area for further understanding.