Relationship between muscle strength, Power and stiffness and running economy in trained male runners

Purpose: In this study, a comparison was made between muscle strength, power and muscle and tendon (k_m and k_t respectively) stiffness of the triceps surae muscle group and running economy (RE) in trained male runners. Methods: Twelve welltrained male runners (age = 21 ± 2.7 y, height = 178.1 ± 7.1 cm, body mass = 66.7 ± 3.2 kg, VO ₂max = 68.3 ± 4.3 mL.kg^-1.min^-1, 5000-m time = 15:04 min:s) underwent passive stiffness testing using a free oscillation method. Muscle strength was determined via a maximal isometric squat test and power determined via a maximal countermovement jump (CMJ). On a separate day, subjects performed an incremental treadmill test and their RE, lactate threshold, and VO₂max were determined. Fingertip blood lactate was determined at the end of each 3-min stage. Lactate threshold was defined as a nonlinear increase in lactate accumulation. Results: A statistically significant correlation was found between k_m and VO₂ at stage 6 (r = -0.69, P = .01). In addition, statistically significant correlations were observed between CMJ peak force production and VO₂ at stage 2 (r = .66, P = .02), stage 3 (r = .70, P = .01), and stage 4 (r = .58, P = .04). No other statistically significant correlations were observed. Conclusion: These data suggest that greater muscle stiffness and less power are associated with greater RE. Future study in this area should focus on determining the mechanisms behind this relationship and how to best apply them to a running population through training techniques.