Efficiency of human skeletal muscle in vivo: comparison of isometric, concentric, and eccentric muscle action

Abstract

The purpose of this study was to estimate the efficiency of ATP utilization for concentric, eccentric, and isometric muscle action in the human tibialis anterior and extensor digitorum longus in vivo. A dynamometer was used to quantitate muscle work, or tension, while simultaneous 31P-nuclear magnetic resonance data were collected to monitor ATP, phosphocreatine, inorganic phosphate, and pH. The relative efficiency of the actions was estimated in two ways: steady-state effects on high-energy phosphates and a direct comparison of ATP synthesis rates with work. In the steady state, the cytosolic free energy dropped to the lowest value with concentric activity, followed by eccentric and isometric action for comparative muscle tensions. Estimates of ATP synthesis rates revealed a mechanochemical efficiency [i.e., ATP production rate/work (both in J/s)] of 15.0 +/- 1.3% in concentric and 34.7 +/- 6.1% in eccentric activity. The estimated maximum ATP production rate was highest in concentric action, suggesting an activation of energy metabolism under these conditions. By using direct measures of metabolic strain and ATP turnover, these data demonstrate a decreasing metabolic efficiency in human muscle action from isometric, to eccentric, to concentric action.

Efeitos agudos de vários métodos de treinamento de força no lactato sanguíneo e características de cargas em homens treinados recreacionalmente

“…When comparing the FR to SIX methods it was found that blood lactate response were not different between them, despite executing 77% more repetitions and work (p < 0.01) and been submitted to 52,14% more TUT (p < 0.01) during the FR method. The fact that the FR method did not produce superior lactate responses when compared to SIX is in agreement with previous findings (17) and it is not unexpected, since eccentric contractions have been shown to induce a decreased metabolic stress (19,(27)(28)(29) . The rationale for using the FR method probably lies in the neuromuscular characteristics of eccentric actions.…”

Mechanics and energetics of level walking with powered ankle exoskeletons

“…We acknowledge that there are also metabolic costs associated with muscle activation, isometric muscle force production and negative muscle work (Beltman et al, 2004;Hogan et al, 1998;Ryschon et al, 1997), but evidence suggests that metabolic energy expenditure during walking is dominated by the cost of performing positive muscle work. Recent studies indicate that muscles perform substantially more positive work than negative work during level walking (DeVita et al, 2007;Umberger and Martin, 2007).…”

Effect of age on in vivo oxidative capacity in two locomotory muscles of the leg

“…This contrasts with two recent studies of active Y individuals, which found higher oxidative capacity in the MG than in the TA (Forbes et al 2009b;Gregory et al 2001), despite the higher percentage of type I fibers in the TA. The authors of both previous studies reasoned that the athletic events the active subjects participated in likely involved frequent concentric contractions of the gastrocnemius (Gottschall and Kram 2003), which are more energetically costly than the largely eccentric contractions of the TA (Ryschon et al 1997). Regular participation in these activities may be a strong stimulus for increasing oxidative capacity in the MG. By contrast, the largely eccentric action of the TA during these activities may be a less potent stimulus for adaptation, leading to comparatively modest increases in the TA.…”