Trace A. Dominy1, Savanna N. Knight1, Lynnsey R. Bowling1, Mac J Carder2, Eric M. Scudamore2, Veronika Pribyslayska2,Hunter S. Waldman1, & Eric K. O’Neal1

1The University of North Alabama, Florence, Alabama; 2Arkansas State University, Jonesboro, Arkansas

Oxygen consumption (VO2) and respiratory exchange ratio (RER) are two metabolic components that are often assessed in running economy (RE) studies. However, for runners competing in shorter long-distance running events, such as collegiate cross-country runners, the slower paces often assessed may not be strongly related to competition velocity metabolic values. PURPOSE: To determine which percentage of VO2 and RER at sub-maximal race pace most strongly correlated with actual race pace velocity. METHODS: Sixteen NCAA Division I, male distance runners performed their habitual warm-up before completing four, 5-minute RE bouts at 70, 80, 90, and 100% of personal best 8-km respective race paces from their previous season in a counter-balanced order with 5 min of passive recovery between bouts. VO2 and RER were collected and averaged in 60 s increments across the final two minutes of each RE bout. Pearson’s r correlation coefficient was conducted to determine strength of these relationships with sub-maximal and personal best race pace values. RESULTS: VO2 r ranged from 0.84-0.88 for all submaximal paces (p < 0.05) signifying no preferable race pace to be used for assessment of VO2. However, RER of both 70% (r = -0.21; p = 0.44) and 80% (r = -0.04; p = 0.89) of race pace intensity produced not only weak but inverse relationships with race pace RER. Only 90% of race pace produced a weak-moderate positive relationship with RER at 100% race pace (r = 0.36; p = 0.17). CONCLUSIONS: Metabolic cost is a more comprehensive indicator of RE than VO2 alone but cannot be calculated if RER exceeds 1.00. Four runners (25%) in this study exceeded an RER of 1.00 when running at race pace. This study indicates when assessing RE for male runners that compete at shorter long-distance running events, VO2 alone may not be a valid indicator of RE, particularly at lower velocities.

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