Differences in leg muscle activity during running and cycling in humans

Abstract

Delta (D) efficiency is defined as the ratio of an increment in the external mechanical power output to the increase in metabolic power required to produce it. The purpose of the present study was to investigate whether differences in leg muscle activity between running and cycling can explain the observed difference in D efficiency between the two activities. A group of 11 subjects performed incremental submaximal running and cycling tests on successive days. The D efficiencies during running and cycling were based on five exercise stages. Electromyograph (EMG) measurements were made of three leg muscles (gastrocnemius, vastus lateralis and biceps femoris). Kendall's correlation coefficients between the mean EMG activity and the load applied were calculated for each muscle, for both running and cycling. As expected, the mean D efficiency during running (42%) was significantly greater than that during cycling (25%). For cycling, all muscles showed a significant correlation between mean EMG activity and the load applied. For running, however, only the gastrocnemius muscle showed a significant, but low correlation (r=0.33). The correlation coefficients of the vastus lateralis and biceps femoris muscles were not significantly different from 0. The results were interpreted as follows. In contrast to cycling, which includes only concentric contractions, during running up inclines eccentric muscle actions play an important role. With steeper inclines, more concentric contractions must be produced to overcome the external force, whereas the amount of eccentric muscle actions decreases. This change in the relative contribution of concentric and eccentric muscle actions, in combination with the fact that eccentric muscle actions require much less metabolic energy than concentric contractions, can explain the difference between the running and cycling D efficiency.

Effects of interval time between high-intensity intermittent aerobic exercise on strength performance: analysis in individuals with different training background

“…Although there are no studies evaluating the impact of different mode of aerobic exercises (cycling, running, rowing etc.) on the subsequent strength exercise performance, it is possible to infer that the cycling exercise result in higher local fatigue than running (Bijker et al, 2002), although a chronic study demonstrated the opposity, in which the interference generated by running exercise was greater than that generated by cycling when compared to strength training only (Gergley, 2009). …”

Efficiency in cycling: a review

“…Nevertheless, theoretically impossible efficiency values indicate a flaw in the calculations. For example, Bijker et al (2001Bijker et al ( , 2002 report a delta efficiency for running of around 50%, which seems to be an unlikely, if not impossible, true efficiency. Note that we do not claim that the use of delta efficiency is meaningless; rather we claim that it is not a measure for efficiency.…”

“…In cycling, this requirement is fulfilled by using the same cadence. Furthermore, it is expected that the energy cost-work rate relationship is linear, which has been substantiated empirically in many studies (e.g., Bijker et al 2001Bijker et al , 2002Chavarren and Calbet 1999;HintzyCloutier et al 2003;Widrick et al 1992; see also the literature results gathered in this review, Fig. 2), although it should be noted that for sustained work rates that exceed the lactate threshold this relationship may become nonlinear because of the influence of the so-called ''slow component'' of oxygen uptake (e.g., Poole et al 1994;Whipp and Rossiter 2005).…”

“…Delta efficiency is not, by definition, an integral measure for the entire energy conversion process. It will be independent of the protocol (work rate increments) only if the metabolic cost-work rate relationship is linear (e.g., Bijker et al 2001Bijker et al , 2002Chavarren and Calbet 1999;see also Fig. 2).…”

“…It is only a small step from work efficiency to delta-efficiency (e.g., Bijker et al 2001Bijker et al , 2002Chavarren and Calbet 1999;Coyle et al 1992;Garry and Wishart 1931;Marsh et al 2000;Mora-Rodriguez and Aguado-Jimenez 2006;Nickleberry and Brooks 1996;Sidossis et al 1992) defined as:…”