Spring-mass characteristics during human locomotion: Running experience and physiological considerations of blood lactate accumulation

Abstract

The aim of this study was to examine how running experience affects leg stiffness (K_leg) and spring-mass characteristics during running stages associated with the onset of blood lactate accumulation (OBLA). Seven trained (66.9 ± 4.8 kg; 182 ± 4.0 cm; 23.1 ± 3.1 years) and 13 untrained (78.5 ± 7.6 kg; 182 ± 3.0 cm; 20.3 ± 1.5 years) runners completed an incremental treadmill run. Running velocity was increased by 1 km^.h⁻¹ every four minutes and blood lactate samples were taken at every stage, in addition to a 10 s video recording using ‘Runmatic’. Once 4 mmolL⁻¹ (OBLA; the second lactate turn point) had been reached one more stage was completed. Spring-mass characteristics across groups and at pre-OBLA, OBLA and post-OBLA were compared. The velocity at OBLA was higher for the trained runners compared to the untrained runners (18 ± 0.7 vs 11 ± 1.3 km^.h⁻¹, p < 0.001). K_leg was similar between untrained and trained runners across each stage (15.8 ± 0.3 vs 14.3 ± 0.3 kN^.m) and did not change between stages, yet spring-mass characteristics differed between groups. Vertical stiffness increased in the trained runners from pre-OBLA to post-OBLA (45.5 ± 3.35–51.9 ± 3.61 kN⁻¹), but not in untrained runners (35.0 ± 5.2–39.6 ± 5.7 kN⁻¹). K_leg was strongly related to F_peak for trained runners only (r = 0.79; untrained runners, r = 0.34). K_leg was unaffected by physiological training status and was maintained across all OBLA stages. Trained runners appear to have optimised their spring-mass system in a homogenous manner, whilst less consistent spring-mass characteristics were observed in untrained runners.

Keywords:

• Physiology
• kinesiology
• biomechanics
• exercise
• performance

Acknowledgments

The authors would like to thank Mr Matthew Clowes and Mr James Turner for their help recruiting participants and conducting data collection.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

Funding was received from Welsh Crucible.