Heart rate based exercise intensity: influence of fan airflow on physiological responses the regulate adaptation

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Authors
Jones, Andrew Maurice
Advisor
Trappe, Todd A.
Issue Date
2022-07
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Thesis (Ph. D.)
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Abstract

Heart rate, which is altered with thermoregulatory stress, is a common physiologic parameter used to determine exercise training intensity for laboratory research studies and the general public completing structured aerobic exercise training. This study investigated the influence of altering thermoregulatory demand with a fan during stationary cycling at a fixed heart rate on power output, metabolic demand, substrate utilization, and sweat loss. Two studies were completed, a well-controlled pilot study (Study A) and a follow up study that was designed to expand on the pilot study findings (Study B). Study A methods: A group of ten men and women (28±2 y, VO2max: 3.73±0.21 L/min) cycled at 70% heart rate reserve for 40 minutes with (FAN) and without (NO FAN) a fan on two separate days (Room temperature: 20.6±0.2°C, Relative humidity: 66±1%) in a randomized, counterbalanced order. Heart rate was continuously monitored, and power output was adjusted to maintain heart rate (151±2 b/min). Oxygen consumption was measured every 10 min during each trial to assess metabolic demand and substrate utilization. Sweat loss was calculated from measurements of nude body weight before and after each exercise bout and corrected for respiratory weight loss. Study B examined similar physiological parameters over a 60-minute cycling exercise session and was ii terminated after completing four individuals due to the onset of the COVID-19 pandemic in March 2020 and the termination of human subjects research at Ball State University for a significant period of time. In study A, not using the fan over the 40 minutes of exercise reduced (P<0.05) the average power output (FAN: 186±14 W, NO FAN: 172±12 W; -8%), VO2 (FAN: 2.71±0.17 L/min, NO FAN: 2.50±0.16 L/min; -8%), %VO2max (FAN: 73±1%, NO FAN: 67±1%), O2 pulse (stroke volume) (FAN: 18.0±1.2 ml O2/beat, NO FAN: 16.5±1.1 ml O2/beat; -8%), and carbohydrate utilization (FAN: 86±10 g, NO FAN: 73±10 g; -15%), while increasing (P<0.05) sweat rate (FAN: 0.60±0.06 L/h, NO FAN: 0.96±0.11 L/h; +60%). Similar trends were noted for all the same parameters over the 60 minutes of exercise for the individuals that completed study B. In conclusion, the use of a fan during fixed heart rate based exercise training substantially alters the acute physiologic responses, which likely has implications for chronic exercise training adaptations.