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The between and within day variation in gross efficiency.

Dionne A Noordhof1, Jos J de Koning, Teun van Erp

  • 1Department of Human Movement Sciences, VU University-Amsterdam, Van Der Boechorststraat 9, 1081 BT, Amsterdam, The Netherlands. d.noordhof@fbw.vu.nl

European Journal of Applied Physiology
|May 14, 2010
PubMed
Summary

Gross efficiency (GE) measurements are reliable for assessing exercise performance. This study found minimal day-to-day and within-day variations in GE, indicating robust and consistent results when using specific exercise intensity criteria.

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Area of Science:

  • Exercise Physiology
  • Human Performance
  • Metabolic Research

Background:

  • Assessing factors influencing gross efficiency (GE) requires understanding its test-retest and within-day reliability.
  • Gross efficiency (GE) is the ratio of mechanical power output (PO) to metabolic power input (PI).

Purpose of the Study:

  • To determine the test-retest reliability and within-day variation of gross efficiency (GE) measurements.
  • To establish if GE exhibits a circadian rhythm under specific exercise conditions.

Main Methods:

  • Physically active males (n=18) underwent maximal incremental exercise tests to determine VO2max and PVO2max.
  • Three experimental days involved seven submaximal cycling bouts (45%, 55%, 65% PVO2max) over 24 hours.
  • Oxygen consumption (VO2) and respiratory exchange ratio (RER) were measured to calculate GE (PO/PI x 100%).

Main Results:

  • GE at the highest intensity with RER <1.0 showed no significant difference between days (mean GE 20.2%, 95% LOA 19.6-20.8%).
  • Within-day variations in GE were minor and not statistically significant.
  • A change in GE of approximately 0.6% can be reliably detected.

Conclusions:

  • Measurement of GE during cycling at intensities approximating the ventilatory threshold (VT) is highly reliable.
  • GE does not exhibit a circadian rhythm when steady-state VO2 and RER <1.0 criteria are applied.