title: Effects of load and gradient on energy cost of running.
abstract: This study quantified the interaction of electromyography (EMG) obtained from the vastus lateralis and metabolic energy cost of running (C(r); mL·[mass+load](-1)·meter(-1)), an index of running economy, during submaximal treadmill running. Experiments were conducted with and without load on the back on a motor-driven treadmill on the downhill, level and uphill slopes. The obtained EMG was full-wave rectified and integrated (iEMG). The iEMG was divided into eccentric (ECC) and concentric (CON) phases with a foot sensor and a knee-joint goniometer. The ratio of ECC to CON (ECC/CON ratio) was regarded as the muscle elastic capacity during running on each slope. The C(r) was determined as the ratio of the 2-min steady-state VO(2) to the running speed. We found a significant decrease in the C(r) when carrying the load at all slopes. The ECC/CON ratio was significantly higher in the load condition at the downhill and level slopes, but not at the uphill slope. A significant gradient difference was observed in the C(r) (down<level<up) and ECC/CON ratio (down=level>uphill). Thus, an alteration of Cr by the gradient and load was almost consistent with that of the ECC/CON ratio. The ECC/CON ratio, but not the rotative torque (T) functioning around the center of body mass, significantly correlated with C(r) (r=-0.41, p<0.05). These results indicated that the ECC/CON ratio, rather than T, contributed to one of the energy-saving mechanisms during running with load.
authors.affiliation: Biodynamics Laboratory, Center for Health and Sports Science, Kyushu Sangyo University, Fukuoka, Japan. abed@ip.kyusan-u.ac.jp
authors.forename: Daijiro
authors.initials: D
authors.lastname: Abe
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Fukuoka
authors.forename: Satoshi
authors.initials: S
authors.lastname: Muraki
authors.forename: Akira
authors.initials: A
authors.lastname: Yasukouchi
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Sakaguchi
authors.forename: Shigemitsu
authors.initials: S
authors.lastname: Niihata
mesh_terms: D001696:Biomechanical Phenomena / Q000502:physiology; D004576:Electromyography; D004734:Energy Metabolism / Q000502:physiology; D006801:Humans; D008297:Male; D012420:Running / Q000502:physiology*; D012815:Signal Processing, Computer-Assisted; D055815:Young Adult