Matthew Bubak

Impact of hot and cold exposure on human skeletal muscle gene expression

Many human diseases lead to a loss of skeletal muscle metabolic function and mass. Local and environmental temperature can modulate the exercise-stimulated response of several genes involved in mitochondrial biogenesis and skeletal muscle function in a human model. However, the impact of environmental temperature, independent of exercise, has not been addressed in a human model. Thus, the purpose of this study was to compare the effects of exposure to hot, cold, and room temperature conditions on skeletal muscle gene expression related to mitochondrial biogenesis and muscle mass. Recreationally trained male subjects (n = 12) had muscle biopsies taken from the vastus lateralis before and after 3 h of exposure to hot (33 °C), cold (7 °C), or room temperature (20 °C) conditions. Temperature had no effect on most of the genes related to mitochondrial biogenesis, myogenesis, or proteolysis (p > 0.05). Core temperature was significantly higher in hot and cold environments compared with room temperature (37.2 ± 0.1 °C, p = 0.001; 37.1 ± 0.1 °C, p = 0.013; 36.9 ± 0.1 °C, respectively). Whole-body oxygen consumption was also significantly higher in hot and cold compared with room temperature (0.38 ± 0.01 L·min-1, p < 0.001; 0.52 ± 0.03 L·min-1, p < 0.001; 0.35 ± 0.01 L·min-1, respectively). In conclusion, these data show that acute temperature exposure alone does not elicit significant changes in skeletal muscle gene expression. When considered in conjunction with previous research, exercise appears to be a necessary component to observe gene expression alterations between different environmental temperatures in humans.

Irisin and Fibronectin Type III Domain-Containing 5 Responses to Exercise in Different Environmental Conditions: 1051 Board #230 May 31 3

Fibronectin type III domain-containing 5 (FNDC5) is a skeletal muscle membrane-bound precursor to the myokine irisin. Irisin is involved in stimulating adipose tissue to become more metabolically active in order to produce heat. The purpose of this study was to determine the effects of exercise in a hot (33 °C), cold (7 °C), and room temperature (RT, 20 °C) environment on the skeletal muscle gene expression of FNDC5 and the plasma concentrations of irisin. Twelve recreationally trained males completed three separate, 1 h cycling bouts at 60% of Wmax in a hot, cold, and RT environment followed by three hours of recovery at room temperature. Blood samples were taken from the antecubital vein and muscle biopsies were taken from the vastus lateralis pre-, post-, and 3 h post-exercise. Plasma concentrations of irisin did not change from pre- (9.23 ± 2.68 pg·mL−1) to post-exercise (9.6 ± 0.2 pg·mL−1, p = 0.068), but did decrease from post-exercise to 3 h post-exercise (8.9 ± 0.5 pg·mL−1, p = 0.047) regardless of temperature. However, when plasma volume shifts were considered, no differences were found in irisin (p = 0.086). There were no significant differences between trials for irisin plasma concentrations (p > 0.05). No significant differences in FNDC5 were observed between the hot, cold, or RT or pre-, post-, or 3 h post-exercise time points (p > 0.05). These data indicate that the temperature in which exercise takes place does not influence FNDC5 transcription or circulating irisin in a human model.

Exercise-Induced Interleukin-6 and Metabolic Responses in Hot, Temperate, and Cold Conditions

The purpose of this study was to determine the effects of exercise in hot, cold, and temperate environments on plasma interleukin-6 (IL-6). Eleven recreationally trained males (age 5 25 ¡ 4 years, height 5 178 ¡ 5 cm, weight 5 79.4 ¡ 13.5 kg, body fat 5 14.7 ¡ 3.6%, VO2 peak 5 54.6 ¡ 11.5 ml kg 21 min) performed a 1 hr cycling bout in hot (33 C̊), cold (7 C̊), and temperate (20 C̊) environments at 60% of Wmax followed by 3 hr of supine recovery in temperate conditions. Expired gases were measured every 15 min during exercise and once every hour during recovery. Heart rate was continuously measured throughout the trials. Blood samples were obtained from the antecubital vein pre-exercise, immediately post-exercise, and 3 hr post-exercise. Blood samples were analyzed for plasma concentrations of IL-6 using a commercial ELISA kit. Plasma IL-6 concentrations were significantly higher immediately post-exercise (14.8 ¡ 1.6 pg ml, p 5 0.008) and 3 hr post-exercise (14.8 ¡ 0.9 pg ml, p 5 0.018) compared to pre-exercise (11.4 ¡ 2.4 pg ml), across all trials. There were no differences in plasma IL-6 concentrations (p 5 0.207) between temperature conditions. Oxygen consumption and heart rate were higher and respiratory exchange ratio was lower in the hot compared to other conditions (p , 0.05). These data indicate that the temperature in which exercise occurs does not affect acute plasma IL-6 response despite differences in metabolic state.

Validity Of Optical Blood Flow Heart Rate Monitors: 1010 May 27, 3

CONCLUSIONS METHODS INTRODUCTION RESULTS Physical Activity in Health Promotion • Heart rate (HR) monitors are a valuable device for individuals who are interested in improving and/or tracking fitness. • These devices can be worn on the wrist or forearm and detects HR by use of an optical blood flow sensor without a chest strap. However, little is known about the validity of these commercially available HR monitors. • The purpose of this study was to validate the Schoche (SC) (RhythmTM), Basis B1 Band (BB) (BASIS Science, Inc.), and Mio Alpha (MA) (Physical Enterprises, Inc.) wireless heart rate monitors. Instruments • All participants simultaneously wore the SC on left forearm, the BB on the right wrist, the MA on the left wrist, and Polar heart rate strap on their chest. • The Schoche (SC) (RhythmTM) measures HR, calories burned, distance, speed, pace, and controls your music. • The Basis B1 Band (BB) (BASIS Science, Inc.) contains a 3D accelerometer to measure movement and is able to measure skin temperature, the ambient temperature, and the galvanic skin response when engaged in activity. • The Mio Alpha (MA) (Physical Enterprises, Inc.) is accurate at high speeds, has 3 user-settable heart rate zones, shows time, and has an exercise timer. • All of these devices use optical sensors to measure blood flow, are waterproof, and use Bluetooth technology to connect to a smartphone or tablet to display results. Procedures • The exercise protocol consisted of one 30-minute bout of continuous walking and running in which the treadmill speed increased every 5 minutes. • HR was recorded every minute from each monitor including the Polar HR monitor as a criterion measure. • The results demonstrate that the wireless wrist-oriented heart rate monitors provide an accurate measurement of HR during exercise. • However, further research is needed to validate these monitors with a larger sample in different environments RESULTS • Fifteen college students participated in this study. METHODS Female (N=4) Range Male (N=11) Range Age (y) 26.5 ± 5.7 23 35 27.3 ± 5.1 22 37 Height (cm) 164.3 ± 6.7 158.5 174 181.3 ± 4.0 175 186.5 Weight (kg) 60.7 ± 7.1 52.5 69.7 84.8 ± 14.5 67.63 109.2 BMI (kg · m2) 22.4 ± 1.1 20.9 23.4 25.7 ± 4.0 21.3 33.9 6.1 % 11.7 % 18.2 %