M. A. Brace, G. Kaur, C. Evans, T. Trachte, S. Seidel, & G. P. Van Guilder
South Dakota State University, Brookings, SD

Purpose: Ischemic preconditioning (IPC) of the skeletal muscle - induced by brief episodes of sublethal ischemia followed by reperfusion – improves exercise performance, particularly maximum oxygen uptake, lactate metabolism, and time trial performance. However, to date it is not clear if the performance benefits of IPC also affect exercise economy. The purpose of this study was to test the hypothesis that leg IPC improves running economy. Methods: Currently ongoing, a randomized single-blind crossover study was employed in which 5 young healthy adult men and women (age: 25±1 yr; BMI: 21.5±3 kg/m2) completed two, 3x5 min submaximal treadmill running protocols (ranging from 107–188 meters/min) to assess running economy (Parvo Medics, TrueOne 2400) in the absence and presence of IPC. The independent variable was conditioning group (IPC versus a sham control). IPC was induced using bilateral high pressure cuffs placed on the upper thighs and inflated to 220 mmHg (EC20 rapid cuff inflator, DE Hokanson, Inc.) for 5 min, followed by 5 min of reperfusion. The sham control was identical to the IPC trial except the pressure cuffs were inflated to 20 mmHg to avoid preconditioning. The trials were separated by at least one week. Statistical Analysis: A two-tailed paired t-test was used to assess differences in running economy (i.e., steady-state oxygen consumption, respiratory exchange ratio, and heart rate) in the absence and presence of IPC. Results: Oxygen uptake at each running velocity was, on average, 1 ml/kg/min lower following IPC (stage 3 IPC: 35.5±1.8 ml/kg/min) compared with the sham control (36.5±2.8 ml/kg/min). Similarly, although not statistical significant given the small sample size, running economy was generally better following IPC. At the highest velocity, IPC running economy was 204±1 ml/kg/km compared with sham (210±8.4 ml/kg/km), a difference of approximately 6 ml of oxygen for every kilometer ran (P=0.18). Moreover, respiratory exchange ratio was significantly lower (P=0.036) in the IPC trial (0.93±0.03) compared with the sham control (0.95±0.03). Lastly, heart rate was 2-7 bpm less with the IPC trials. Conclusions: Our preliminary data shows potential for leg IPC to enhance running economy. However, we are currently increasing the sample size from 5 to 20 subjects before any firm conclusions are drawn.

NACSM Professional Sponsor: Gary P. Van Guilder

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