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INFLUENCE OF LIGHT AVAILABILITY ON THE ENERGY EXPENDITURE OF RUNNING

Abstract

T.K. Tamanaha, T.S. Kailiuli, S.O. Henry, K.G. Bass.

Pacific University, Forest Grove, OR

The energy expenditure of running is dependent upon many factors, including vision. For example, trail running relies on visual input to enable the most appropriate and optimal gait pattern for navigating obstacles and avoiding injury. However, running is often performed under low-light conditions and concomitant reduction of vision. Under these conditions, it is possible a runner expends more energy to complete the same task. Surprisingly, few studies have examined the energy expenditure associated with running in low-light conditions. PURPOSE: Investigate the effect of light availability on energy expenditure of running. METHODS: Thirty-four volunteers (20 m, 14 f; 20 ± 1.2 years of age; 70 ± 22.1 kg mass; 171 ± 12.1 cm stature) completed the study. Estimated VO2max for each participant, obtained from a step test, was used to calculate an individualized running pace corresponding to 60% VO2max. After 3 minutes baseline (running), participants ran on a treadmill for 16 minutes at their specific, submaximal pace. In a ramp design, illuminance was cycled twice between light (3.5 ± 0.25 lux) and dark (0.5 ± 0.25 lux) during 16 minutes. Light, monitored by a lux meter, was altered using progressive dimming of monitor placed in front of treadmill. Using the same monitor, virtual obstacles were randomly presented to simulate trail running. Gas exchange, heart rate (HR), and rating of perceived exertion (RPE) data were collected. Using principles of indirect calorimetry, energy expenditure was calculated from VO2and VCO2. For data analysis, the two light conditions (1 min) and the dark conditions (1 min) were collapsed into means and compared via paired t-tests. RESULTS: Participants expended more energy running in dark condition (46.96 ± 13.91 kJ∙min-1) compared to light condition (45.49 ± 13.76 kJ∙min-1) (p<0.05). Similarly, heart rate was elevated in dark condition (155.1 ± 20.0 bpm) compared to light condition (153.9 ± 19.0 bpm) (p<0.05). RPE followed the same trend, with participants perceiving increased exertion in dark condition (3.1 ± 1.5) compared to light condition (2.8 ± 1.7) (p<0.05). CONCLUSION: Diminished light increased energy expenditure, heart rate, and RPE associated with a constant, submaximal running intensity.

Supported by Pacific University College of Arts and Sciences Research Grant.

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