Drum, S. M., & Busing, J. K. (2010). Running with various loads causes change in subjective and objective physiological variables. Presentation 875 at the 2010 Annual Meeting of the American College of Sports Medicine, Baltimore, Maryland; June 2-5.

This study investigated changes in subjective and objective physiological variables while carrying various loads when running. A control condition was compared to three load carrying conditions, 1) one handheld bottle with 24 ounces of fluid + gel weighing 2 pounds; 2) two handheld bottles each with 24 counces of fluid + gel weighing 3.5 pounds; and 3) a Nathan™ backpack holding 64 ounces of liquid, gear, and 2 gels weighing 6.5 pounds. Ss (N = 5) were tested for VO2max and 2-3 days later for 4 x 20-minute runs at 63% of VO2max based on pace. Each running bout was separated by five minutes of passive recovery with ingestion of 24 g of carbohydrate + 16 ounces of water. Gas analysis was continuous during each bout and heart rate, rating of perceived exertion, volume of oxygen uptake, volume of oxygen uptake, and respiratory exchange ratio were constantly assessed.

Compared to the control condition, the greatest significant mean differences occurred during the two-bottle condition for heart rate, rating of perceived exertion, volume of oxygen uptake, and volume of oxygen uptake. The greatest mean respiratory exchange ratio occurred during the backpack run and was significantly different to the control condition.

Implication. Slight changes in load and load form produce significant changes in physiological costs. Therefore, while competing in distance running events, especially ultra races, it might be desirable to carry light loads close to the center mass and if allowed, let a pacer or support-staff carry water and food during the later stages of the race.

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