Running With Various Loads Causes Change in Subjective and Objective Physiological Variables

Abstract

There is little investigative evidence related to carrying one or two handheld bottles or a heavier pack and how these loads affect running performance and/or strategies related to finishing long endurance events. PURPOSE: To investigate the change in subjective and objective physiological variables while carrying various loads and running. METHODS: This study compared control (CON) to one of three load carrying conditions, including 1 handheld bottle with 24 oz of fluid + gel (1BOT) (2 lbs); 2 handheld bottles each with 24 oz of fluid + gel (2BOT) (3.5 lbs total); and a Nathan™ backpack holding 64 oz of liquid, gear, and 2 gels (PACK) (6.5 lbs total). Subjects (N = 5) reported to the HAPLab once for a VO2max test and 2-3 days later for 4 × 20-minute runs (randomized to CON, 1BOT, 2BOT, and PACK) at 63% of VO2max based on pace (min·mi-1). Each running bout was separated by 5-minutes of passive recovery with ingestion of 24 g of carbohydrate + 16 oz of water. Gas analysis was continuous during each bout and heart rate (HR), rating of perceived exertion (RPE), volume of oxygen uptake (VO2), minute ventilation (VE), and respiratory exchange ratio (RER) were constantly assessed. Comparisons between CON and each of the load conditions were conducted using a one-way ANOVA with significance set at p < 0.05. RESULTS: Subject characteristics (mean ± SD) included age (22.4 ± 1.7 yrs), height (69.7 ± 1.6 inch), body weight (147 ± 14.3 lbs), VO2max (66 ± 3.0 ml·kg-1·min-1), and running pace at 63% of VO2max (7.7 ±.6 min·mi-1). Versus CON, the greatest significant mean differences (p < 0.0004), respectively, occurred during the 2BOT condition for HR (135 ± 12 vs. 141 ± 12 bpm), RPE (9.9 ± 1.0 vs. 11.7 ± 1.1), VO2 (41.3 ± 2.9 vs. 43.3 ± 3.4 ml·kg-1·min-1), and VE (77.7 ± 6.3 vs. 83.7 ± 8.0 L·min-1. The greatest mean RER (.86 ±.04) occurred during the PACK run and was significantly different (p < 0.001) versus CON (.84 ±.03). CONCLUSION: Results indicated that 2BOT elicited the greatest HR, RPE, VO2, and VE, but not RER. The heavier PACK seemed to be more economical compared to 2BOT. CON was perceived as the easiest condition with the lowest reported values. Therefore, while competing in distance running events, especially ultra races, it might be desirable to carry light loads close to center mass and if allowed, let a pacer carry water and food during the later stages of the race.