The Reliability of Measuring Gross Efficiency During High Intensity Cycling Exercise

in International Journal of Sports Physiology and Performance
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To evaluate the reliability of calculating gross efficiency (GE) conventionally and using a back extrapolation (BE) method during high intensity exercise (HIE).


12 trained participants completed two HIE bouts (P1 = 4-min 80% Maximal Aerobic Power (MAP); P2 = 4-min at 100%MAP). GE was calculated conventionally in the last 3 min of submaximal (50%MAP) cycling bouts performed before and after HIE (Pre50%MAP and Post 50%MAP). To calculate GE using BE (BGE), a linear regression of GE submaximal values post-HIE were back extrapolated to the end of the HIE bout.


BGE was significantly correlated with Post50%MAP GE in P1 (r= 0.64; P = 0.01), and in P2 (r = 0.85; P = 0.002). Reliability data for P1 and P2 BGE demonstrate a mean CV of 7.8% and 9.8% with limits of agreement of 4.3% and 4.5% in relative GE units respectively. P2 BGE was significantly lower than P2 Post50%MAP GE (18.1 ± 1.6% vs 20.3 ± 1.7%; P= 0.01). Using a declining GE from the BE method, there was a 44% greater anaerobic contribution compared to assuming a constant GE during 4 min HIE at 100%MAP.


HIE acutely reduced BGE at 100%MAP. A greater anaerobic contribution to exercise as well as excess post oxygen consumption at 100%MAP may contribute to this decline in efficiency. The BE method may be a reliable and valid tool in both estimating GE during HIE and calculating aerobic and anaerobic contributions.

Correspondence: Dr James Hopker School of Sport and Exercise Sciences University of Kent Medway Building Chatham Maritime Chatham, Kent ME4 4AG United Kingdom Tel: +441634 888814 Email:
International Journal of Sports Physiology and Performance

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