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A-46 Free Communication/Poster - Thermoregulation Responses to Heat/Cold Stress

Medicine & Science in Sports & Exercise: May 2013 - Volume 45 - Issue 5S - p 81–84
doi: 10.1249/01.mss.0000433621.97168.70

May 29, 2013, 7:30 AM - 12:30 PM

Room: Hall C

349 Board #202 May 29, 11:00 AM - 12:30 PM

Young versus Older Males’ Thermoregulatory Responses to Exercise in Humid Heat Under Two Air Velocities

Heather E. Wright1, Chad N. Phinney1, Stephen G. Hardcastle2, Tom M. McLellan, FACSM3, Joanie Larose1, Pierre Boulay4, Glen P. Kenny1. 1University of Ottawa, Ottawa, ON, Canada. 2CanmetMINING Natural Resources Canada, Sudbury, ON, Canada. 3TM McLellan Research Inc., Stouffville, ON, Canada. 4Champlain Diabetes Regional Coordination Centre, Ottawa, ON, Canada.

(No relationships reported)

Older adults have less evaporative heat loss than younger adults during exercise performed at a fixed rate of heat production under conditions which permit full sweat evaporation. However, when evaporative heat loss is restricted (i.e., high humidity, clothing insulation), such differences may not lead to expected differences in the level of thermal strain. Despite a greater evaporative capacity in younger adults, excessive sweat dripping that would result under such conditions may not provide any additional cooling benefit.

PURPOSE: To examine the effects of exercise in warm/humid heat under two different levels of air velocity to modify the level of evaporative cooling, on the heat stress responses of young versus older adults.

METHODS: Ten young (Mean±SE; Y: 24±1 yrs) and 10 older (O: 59±1 yrs) males, matched for body surface area and wearing work coveralls, performed 4 successive 15 min cycling bouts (15 min rest) at a fixed rate of heat production (400 W) in humid heat (35°C, 60% relative humidity) with 0.5 (Low) and 3.0 m/s (High) air velocity. Rectal temperature (Tre) was measured continuously. Blood and urine were analyzed prior to exercise (PRE) and the end of final recovery for hemoglobin, hematocrit, and Interleukin (IL)-6, and urine specific gravity (USG), respectively.

RESULTS: The change (Δ) in Tre (PRE-end of exercise) was similar between age groups under Low (Y: 1.11±0.09, O: 1.28±0.10°C) and High (Y: 0.76±0.08, O: 0.96±0.10°C) air velocities, however was greater in Low than High for both groups. Plasma volume Δ was similar between Y and O, however were greater under Low (Y: -10.9±1.3, O: -10.8±1.0%) than High (Y: -5.7±0.7, O: -6.9±0.8%). Despite elevated PRE IL-6 in O, no age-related differences were seen for the Δ IL-6 during Low (Y n=9: 4.47±1.04, O n=7: 3.72±0.98 pg/mL) or High (Y: 1.04±0.37, O: 1.32±0.38 pg/mL). IL-6 Δ was greater under Low than High. No age or condition differences in USG were seen.

CONCLUSION: Preliminary data indicate that young and older males show similar thermal strain and changes in hydration status following intermittent exercise in humid heat. High air velocity was effective in reducing strain within both age groups. Support: Workplace Safety and Insurance Board of Ontario & Canada Foundation for Innovation-Leaders Opportunity Fund (G.P. Kenny), MITACS Accelerate (H.E. Wright).

350 Board #203 May 29, 11:00 AM - 12:30 PM

Effects of Heat and Different Humidities on Aerobic and Anaerobic Exercise Performance in Athletes

Jiexiu Zhao1, Santiago Lorenzo2, Nan An1, Wenping Feng1, Lili Lai1, Shuqiang Cui3. 1China Institute of Sport Science, Beijing, China. 2Institute for Exercise and Environmental Medicine, Dallas, TX. 3Beijing Institute of Sport Science, Beijing, China.

(No relationships reported)

PURPOSE: Previous studies suggested that maximal oxygen uptake (VO2max) and Wingate Anaerobic Test performances are decreased in hot environments, but more research is needed to investigate whether humidity changes in hot environment further affect VO2max and Wingate Anaerobic Test.

METHODS: Nine trained, male athletes were recruited to participate. All participants performed VO2max and Wingate Anaerobic Tests in three different environmental conditions: 21°C/20% relative humidity (R.H.) (Control), 33°C/20% R.H. (Hot-dry), 33°C/80% R.H. (Hot-wet).

RESULTS: Compared to Control condition, Hot-dry, and Hot-wet had lower VO2max values (Control, 3779.0 ± 234.3 mlmin-1; Hot-dry, 3528.2± 467.4 mlmin-1; Hot-wet, 3595.9 ± 274.6 mlmin-1; P < 0.05). However, there was no difference in VO2max between Hot-dry and Hot-wet. A decrease in oral-to-skin temperature gradient of post-exercise was strongly correlated with decrease of VO2max (mlkg-1min-1) in all conditions (r = 0.835, P < 0.001). There was no significant difference between conditions in peak power (Control, 806.2 ± 95.7 W; Hot-dry, 825.8 ± 112.4 W; Hot-wet, 857.8 ± 164.7 W; P > 0.05), anaerobic capacity (Control, 577.7 ± 49.2 W; Hot-dry, 562.1 ± 61.7 W; Hot-wet, 553.3 ± 74.7 W; P > 0.05), or blood lactate maximum (Control, 13.7 ± 1.9 mmoll-1; Hot-dry, 13.8 ± 1.8 mmoll-1; Hot-wet, 12.3 ± 1.9 mmoll-1; P > 0.05) during the Wingate Anaerobic Test.

CONCLUSION: 1) VO2max was impaired in Hot-dry and Hot-wet condition compared with Control, but there was no difference between Hot-dry and Hot-wet conditions. 2) The oral-to-skin temperature gradient of post-exercise may explain approximately 70% of the variance in VO2max in all three different environmental conditions. 3) Wingate Anaerobic Test performance was not affected by either hot-dry or how-wet conditions when compared with a control environment.

351 Board #204 May 29, 11:00 AM - 12:30 PM

Profile of Elite Collegiate Men’s Soccer Players During a Preseason Match

Lesley W. Vandermark, Rebecca L. Stearns, Julie K. DeMartini, Robert A. Huggins, Douglas J. Casa, FACSM. University of Connecticut, Storrs, CT.

(No relationships reported)

Elite collegiate and professional soccer players undergo unique physiological demands during match play. Hydration status, distance covered (DC), and heart rate (HR) have been examined during match play in professional soccer players, but no such data exists for collegiate level players.

PURPOSE: Examine hydration status, gastrointestinal temperature (Tgi), and measures of intensity and performance including average HR (HRav) and global positioning system (GPS) data, in collegiate men’s soccer players during preseason match play.

METHODS: 16 elite Division I men’s soccer players participated (Mean±SD: age: 20±1 yrs, body mass: 77.6±5.4 kg, height: 187±2 cm). Data was collected during one preseason soccer match (113 min, WBGT: 20.23±1.36°C, wind speed: 3.22±0.13 ms-1). Measures were taken to monitor Tgi, HRav, percent body mass loss (%BML), hydration indices (urine color (UC) and urine specific gravity (USG)), and GPS data including DC and maximum velocity (Vmax). Tgi, %BML, and urine samples were taken before (PRE) and after (POST) the match. HR and GPS data were recorded constantly during the match. DC and Vmax were analyzed in the following zones: Walking (Walk) (0.7-7.2 km·h-1), low intensity running (LIR) (7.2-14.4 km·h-1), moderate intensity running (MIR) (14.4-19.8 km·h-1), high intensity running (HIR) (19.8-25.2 km·h-1), and sprinting (Sprint) (+25.2 km·h-1).

RESULTS: During match play HRav, Tgi, %BML, DC, and Vmax was 130±32 bpm; 38.57±0.49°C; 1.5±0.80%; 6737±3285 m; 28.3±2.6 km·h-1, respectively. Tgi rose significantly PRE (37.59±0.5°C) to POST (39.17±0.44°C; p≤0.001). PRE UC (4±1) was significantly lower than POST UC (5±1; p=0.013). PRE USG (1.019±0.008) was significantly lower than POST USG (1.025±0.004; p=0.005). Walk DC (2849±1439 m) was significantly greater than MIR (759±385 m), HIR (266±174 m), and Sprint (6±13 m; p≤0.001). Sprint DC was significantly less than all other zones (p≤0.001).

CONCLUSION: These collegiate soccer athletes performed intense exercise during match play as shown by a significant rise in core temperature and heart rate, despite covering the most distance while walking. These athletes maintained a lower level of dehydration than professional athletes (<2% BML), but were comparable on all other variables during match play.

352 Board #205 May 29, 11:00 AM - 12:30 PM

Physiological Responses And Performance In A 50k Trail Run In A Warm Environment

Candi D. Ashley1, Rebecca M. Lopez1, Eric E. Coris1, Lauren Noe2, Stephanie Clark1, Kelly Crews1. 1University of South Florida, Tampa, FL. 2Kent State University, Kent, OH. (Sponsor: Douglas J. Casa, FACSM)

(No relationships reported)

Competing in the heat poses a special challenge for ultra-runners. Due to research challenges, there is little information on physiological responses during ultra-running.

PURPOSE: To examine physiological responses in runners competing in a 50-km trail race in a warm environment.

METHODS: Seven runners participated. Runners were weighed and urine color and urine specific gravity (USG) were assessed pre- and post-race. Runners ingested the CorTemp pill to assess core temperature (Tc) 5-8 hours pre-race. Runners were outfitted with a Polar HR monitor and CorTemp pill receiver worn during the race. Participants kept a list of food and beverages consumed during the race. At start, every 12.5 km and finish, Tc and race time were recorded. HR was recorded at the start, 25 km and finish. Changes in HR, Tc, urine color and USG were analyzed using a one-way ANOVA. Correlations established relationships among variables.

RESULTS: WBGT varied from 17.5°C to 30.0°C. Mean race time was 407.14 ± 72.08 min. Mean HR was 133.8 ± 6.4 bpm and mean Tc was 38.2 ± 0.7°C.

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Calorie intake was 814.9 ± 477.4 kcals. Fluid intake was 4.77 ± 4.51 L. Urine color was darker and USG higher post race than pre-race (urine color = 7.0 ± 0.8 and 2.9 ± 1.3 and USG = 1.021 ± 0.01 and 1.011 ± 0.01, respectively, p < 0.05). Body mass loss was 2.9 ± 1.4%. There was a strong correlation between race pace and mean Tc (r = -.915, p < 0.05) and a trend for a higher HR with a lower fluid intake (p = 0.05).

CONCLUSION: Participants seemed to self-regulate Tc by decreasing running speed or possibly Tc was a limiting factor in performance. Variability among runners and range of ambient conditions during the race illustrate the need for environment-dependent, individualized dietary and fluid replacement plans.

353 Board #206 May 29, 11:00 AM - 12:30 PM

Relative Plasma Volume Changes, Osmolality and Electrolytes During and After an Ultra-Marathon in Extreme Heat

Renate M. Leithauser1, Heinz J. Roth2, Michael Doppelmayr3, Holger Finkernagel4, Serge P. von Duvillard, FACSM5, Lawrence A. Golding, FACSM6, Ralph Beneke, FACSM1. 1Philipps University, Marburg, Germany. 2Limbach Laboratory, Heidelberg, Germany. 3Salzburg University, Salzburg, Austria. 4Institute for Performance Testing, Bad Berleburg, Germany. 5University of Primorska, Koper, Slovenia. 6University of Nevada, Las Vegas, NV.

(No relationships reported)

Exercising in extreme heat places a very high demand on the human body’s thermoregulatory system to avoid hyperthermia. Under these conditions, evaporation related body water loss, which is closely linked with corresponding losses in plasma volume (PV) and electrolytes are an issue for performance and health. During endurance events lasting longer than 4h, dehydration but also hyperhydration and exercise-associated hyponatremia may impose potential risks. Most studies investigating fluid and electrolyte balance during exercise addressed mostly pre- to post-race comparisons. However, during longer lasting ultra-endurance events, the effects may not necessarily accumulate gradually over time but show different responses to given stages of exercise.

PURPOSE: To analyze relative PV alterations, plasma osmolality (OSM) and electrolyte concentrations after given sub-sections of a one-stage ultra-marathon race in extreme heat.

METHODS: Venous blood samples were obtained from five highly-trained male athletes (mean±SD: age 53.8±10.4 yrs, height 175.8±11.1 cm, body mass 75.9±8.4 kg) before the start of the race (KM0), after 42, 84, 126 km, and after termination of the race (KM216) for the analysis of OSM, sodium (Na+), potassium (K+) and chloride (Cl-) concentrations as well as hemoglobin and hematocrit for calculation of relative PV changes.

RESULTS: Only PV and Na+ revealed a significant time effect (p<0.05). Compared to KM0 (set 100%) PV appeared to be decreased at KM42 (94.3±5.1%), returned to pre-race level at KM84 (97.1±10.9%) and KM126 (98.4±9.3%), and was increased at KM216 (107.8±11.7%). Na+ appeared to decrease continuously from KM0 (139.0±1.4 mmol/l) to KM216 (134.6±3.7 mmol/l) whilst K+ and Cl- remained more or less stable throughout the race. OSM did not change significantly and remained in the middle of the reference range over time.

CONCLUSIONS: Calculated PV changes indicated a hemoconcentration effect during the first marathon distance, which could be compensated for during the middle part of the race. During the final part of the race runners tended to overcompensate fluid loss leading to hyperhydration and borderline low Na+. However, despite these changes athletes performed rather well to maintain OSM balance throughout the race.

(Supported by Limbach Laboratory, Heidelberg, Germany)

354 Board #207 May 29, 11:00 AM - 12:30 PM

Accuracy Of Skin Probes Vs. Infrared Imaging For Temperature Measurements In Three Different Environments

Richard H. Laird, David J. Elmer, Matthew D. Barberio, Khalil A. Lee, David D. Pascoe, FACSM. Auburn, Auburn, AL.

(No relationships reported)

Skin temperature probes (thermistors) are the primary means of determining skin temperatures (Tsk) at specific sites on the body and for estimating mean Tsk using various formulas, despite questionable accuracy due to single site estimates or regional temperatures and skin contact. Inaccuracies are potentially caused by thermistors affecting Tsk through contact with the skin.

PURPOSE: To examine the effect on Tsk due to thermistor contact with the skin at common mean Tsk formula sites.

METHODS: Thirty participants (15 males, 15 females) equilibrated in cool (20°C, 40% RH), neutral (30°C, 40% RH), and hot (40°C, 40% RH) environments, with measurement sites exposed. After 15 min, images were taken using infrared thermography (IR) of the right upper chest, right posterior upper arm, right anterior thigh, and right calf (IRpre). Thermistors were then attached at these sites for another 15 min equilibration. After thermistor measurement of Tsk, they were removed for a final series of IR images (IRpost). IRpre Tsk values were used as the true Tsk at a given site in response to an environment. IRpost and thermistor Tsk was compared to IRpre Tsk to determine the effect of thermistor contact with the skin.

RESULTS: There were significant differences in IRpre Tsk between sites, subjects, environments, and sexes (p < 0.05), so differences in Tsk measurements were analyzed within subjects for each site, environment, and sex. IRpre Tsk measures were compared to both IRpost and thermistor Tsk and analyzed via t-test. Thermistor measures were significantly different (p < 0.05) from IRpre at each site, in each condition, and for both males and females (all p < 0.0085), indicating the existence of a microenvironment created by thermistor contact with the skin. Changes in regional Tsk regulation due to thermistor application, as evidenced by significant differences (p < 0.05) in Tsk measured by IRpost and IRpre at each site, condition, and sex (all p < 0.0102) could also contribute to differences between IRpre and thermistor Tsk.

CONCLUSIONS: The potential errors associated with thermistor Tsk and their weighted value in mean Tsk formulas confounds our understanding of skin thermoregulation.

355 Board #208 May 29, 11:00 AM - 12:30 PM

Recovery From Cold Water Immersion Impairs Cognitive Function In Healthy Men

Yongsuk Seo, Chul-Ho Kim, Edward J. Ryan, John Gunstad, Ellen L. Glickman, FACSM, Matthew D. Muller. Kent State University, Kent, OH.

(No relationships reported)

PURPOSE: The physiological effects of immersion hypothermia and afterdrop are well-characterized but the psychological effects are less clear. The purpose of this study was to quantify changes in cognitive function during and after lower body water immersion.

METHODS: Nine young healthy men participated and were randomly assigned to both neutral (35 ± 1 °C) and cold (13 ± 1 °C) water immersion on separate mornings. Subjects rested in neutral air for 30 min followed by 60 min water immersion to the iliac crest and 15 min of recovery in neutral air. Rectal temperature and mean skin temperature were continuously monitored. Metabolic rate, the Stroop Color Word Test (SCWT), and the Profile of Mood State (POMS) were quantified at predetermined time intervals.

RESULTS: During immersion in cold water, rectal temperature was reduced but SCWT and POMS scores were unchanged relative to baseline. During recovery from cold immersion, rectal temperature was further reduced by ∼0.5 °C, shivering was noted, and metabolic rate increased two-fold. Coincident with this acute afterdrop, SCWT Color-Word performance (-4 ± 8 versus 7 ± 6 correct responses) and Interferences score (-2 ± 7 versus 4 ± 8) was impaired relative to recovery from neutral immersion (i.e. when core temperature and metabolic rate did not change).

CONCLUSION: Recovery from lower body cold water immersion elicits the afterdrop phenomenon and impairs selective attention as measured by the SCWT. Finding countermeasures to this predicament would likely improve medical care of people who are accidentally or occupationally exposed to the cold.

356 Board #209 May 29, 11:00 AM - 12:30 PM

Effect Of Neck Cooling On Body Weight, Sweat Rate, And Performance During Kendo

Jong Kwang Kim, Bong Yeon Hwang, Younsun Son, Dae Taek Lee. Kookmin University, Seoul, Republic of Korea.

(No relationships reported)

Purpose: This study examined whether the neck cooling during a drill practice of Kendo (DPK) would impact on body weight change, sweat rate, performance, and thermal responses.

METHODS: Seven competitive elite college Kendo players (20.4±1.4 yrs, 174.4±3.0 cm, 75.1±6.5 kg, 14.2±2.6 % body fat) underwent two randomized trials; 1) exercising Kendo in a normal condition (NC) and 2) exercising Kendo with neck cooling condition (CC), at an environment of 24.7±0.8°C and 56.2±5.4% of relative humidity. Each trial consisted of 4 phases; 1) 10 min rest, 2) DPK for 40-50 min, 3) 10 min recovery, and 4) exercise tolerance test (ETT). During DPK, they performed 10 different styles of attack, each style separated by 90 seconds, 3 sets per style, and 10 repetitions per set. During ETT, they played Kendo at 70% of their maximal capacity until volitional exhaustion, and the duration of exercise was recorded. Maximal capacity was determined while they practiced ‘Fast Head Hitting’ until exhaustion. Only during DPK in CC, subjects wore a neck cooling collar which maintained at 10-11°C. Before and after each trial, naked body weight and blood lactate were measured. During trials, heart rate, ratio of perceived exertion, neck and whole body thermal sensation (from 1 to 9, 9 is the hottest), and face, neck, and ear cannal temperatures were continuously monitored and recorded. Sweat rate was calculated.

RESULTS: Each trial lasted approximately 90-100 min. After trials, their naked body weight was reduced by 1.66% in CC and 1.67% in NC from the baseline (p>0.05). During DPK in CC, neck temperature (17.2±1.5°C in CC vs. 33.2±0.5°C in NC) and neck thermal sensation (3.6±0.4 in CC vs. 7.2±1.0 in NC) were lower than in NC. But no conditional differences were noticed in other measured variables. During ETT, subjects continued their exercise for 752±423 seconds in CC and 638±229 seconds in NC (p>0.05). The duration of exercise in ETT normalized by the weight change during a DPK was not different between CC (780±446 sec/kg) and NC (593±306 sec/kg).

CONCLUSION: Neck cooling device lowered neck temperature and thermal sensation. However, it did not provide any beneficial effects on body weight change, sweat rate, and subsequent Kendo practice duration.

357 Board #210 Withdrawn

358 Board #211 May 29, 11:00 AM - 12:30 PM

The Effect Of Exercising In The Cold On Markers Of Fluid Balance In Women

Kristen M. Cornachione, Daniel P. Heil, FACSM. Montana State University, Bozeman, MT.

(No relationships reported)

Numerous studies have been conducted examining the relationship between environmental temperature and hydration status in men and women. However, this is the first study, to the author’s knowledge, that examines the effect of cold exposure on markers of hydration status solely in women.

PURPOSE: To investigate and describe changes in markers of hydration status for women exercising in the cold (-5°C) as compared to exercising in a temperate environment (24°C) during the follicular phase of the menstrual cycle.

METHODS: Nine women completed a 90-minute submaximal cycling protocol in both a cold (-5°C) and temperate (24°C) environment. Heart rate (HR), systolic and diastolic blood pressure (SBP, DBP), ratings of perceived exertion (RPE), percent change in plasma volume (%ΔPV), and percent change in body mass (%ΔBM), were measure before, during, and after submaximal exercise. A two-way RMANOVA was used to detect differences over time and temperature condition. Dunnett’s 2-sided Multiple Comparison Test was used for post hoc analyses at the 0.05 alpha level to compare the two environmental conditions at discrete time points 0, 30, 60, 90 minutes, and post-test, with the 0-minute time point being the reference value.

RESULTS: There were no differences detected across condition for HR, SBP, DBP, or RPE. Mean %ΔPV values were significantly higher (P<0.05) at Pre60 in the temperate condition. Mean Δ%PV values were trending toward significantly higher (P<0.10) at Pre90 in the temperate condition. Mean Δ%BM values were significantly less (P<0.01) in the cold condition than in the temperate. There was no significant difference (P=0.34) in urine output.

CONCLUSIONS: During submaximal exercise and cold exposure, %ΔPV is greater in the cold environment, indicative of fluid shifts out of the plasma volume and into the extracellular space. However, %ΔPV was restored to initial levels post exercise, indicative of a return of fluid from the extracellular space to the vascular space. Submaximal exercise in the cold induces a transient fluid shift from the plasma volume to extracellular space that is restored upon termination of exercise and cold exposure.

359 Board #212 May 29, 11:00 AM - 12:30 PM

Mice Heat Chamber Calibration

Paula Y.S. Poh1, Aminul Islam2, Yifan Chen2, Patricia A. Deuster, FACSM2. 1University of Illinois at Urbana-Champaign, Urbana-Champaign, IL. 2Uniformed Services University of the Health Sciences, Bethesda, MD. (Sponsor: Steven J. Petruzzello, FACSM)

(No relationships reported)

Variation in the responses to heat exposure among humans and animals has been well documented. As a consequence, it is difficult to draw firm conclusions regarding the etiology of these differences since investigations have different experimental designs and methodological confounders, such as heat test chamber heating rates.

PURPOSE: (1) Validate the heat test protocol for mice models via cage location and orientation, and (2) determine the maximum number of cages that could be in the chamber without compromising individual heating rates.

METHODS: A mice temperature transponder was centrally positioned inside each mice cage, which was set in the environmental chamber. Two cage orientations (adjacent, left-to-right and parallel, front-to-back) with three set-ups (top shelf, bottom shelf and both shelves) were examined in triplicate and thermal results were averaged. Transponders equilibrated at room temperature (21.5°C) for the first 5 min, after which the temperature was set at 39.5°C and left on for a minimum of 60 min.

RESULTS: The adjacent (L-R) top shelf cage set-up had the smallest temperature difference across the duration of the heat test (Δ = 0.43°C vs. Δ = 2.2°C) and at minute 60 (Δ = 0.2°C, p > 0.05 vs. Δ = 1.8°C, p < 0.05). Both orientations for the bottom shelf cage set-up had a slower rise in temperature (0.04°C·min-1) than the other set-ups (0.3°C·min-1). When using both shelves, the top shelf cages were warmer than the bottom shelf cages (1.0-3.6°C) for adjacent (L-R) and parallel (F-B) orientations.

CONCLUSIONS: The adjacent (L-R) top shelf cage set-up should be utilized in order to enable uniform chamber heating rate and to standardize subject heat exposure for 2-cage set-up. Furthermore, 2-cage set-up should take precedence over a 4-cage set-up, since an increased number of cages may obstruct heat flow patterns. The bottom shelf alone is not recommended for use in heat tests due to poor heat rate performance caused by the heat rising paradigm.

360 Board #213 May 29, 11:00 AM - 12:30 PM

A Thermal Perception Scale for Use During Rest and Exercise in 37°C ambient air

Ellen L. Glickman, FACSM, Corey Peacock, John Gunstad, Lynn Kakos, Keith J. Burns, Brandon Pollock, Matthew Feeback, Yongsuk Seo. Kent State University, Kent, OH.

(No relationships reported)

Previous work has validated a thermal perception scale for use during exposure to cold in resting conditions (Glickman-Weiss et al. 1994). Thermal perception is a primary concern to athletes who cannot easily quantify physiologic or thermal parameters easily in the field and in a growing area of concern due to thermal injuries especially during heat exposure.

PURPOSE: This investigation introduces a new thermal perception scale (HTS) for use during protracted rest and exercise in the heat. The scale contains categories ranging consecutively from 0, i.e., “Nothing at all” to 10, “Very, very hot”.

METHODS: Ten male subjects (23.7±2.1 yrs) underwent two heat exposure protocols (37°C, 50% RH) including an exposure baseline period (30 min), an exercise period (2 hr), and a recovery period (60 min). The physiological variables of heart rate (HR: via polar HR monitor), rectal temperature (Tre) and VO2 (via Parvo metabolic cart) were assessed during both protocols. Modified Heat (HTS), Gagge (TS; Gagge et al. 1967), and Comfort (COM; Epstein, 1980) scales were analyzed to validate and predict the three physiological variables of HR, Tre and VO2.

RESULTS: TS and VO2 are positively correlated (r = 0.426), mixed model effects demonstrate that this relationship was significant (F = 6.8, P < 0.001). Also, COM and VO2 are negatively correlated (r = -0.480), mixed model effects demonstrate that this relationship is significant (F = 6.7, P < 0.001). Data demonstrated HTS and VO2 are positively correlated (r = 0.257), mixed model effects demonstrate that this relationship was significant (F = 7.4, P < 0.001). TS and HR are positively correlated (r=0.315) mixed model effects demonstrate this relationship significant (F=4.9, P < 0.001). Also, COM and HR are negatively correlated (r= -0.438), mixed model effects demonstrate this relationship significant (F=3.4, P < 0.001). Data demonstrated HTS and HR are positively correlated (r=0.207), mixed model effects demonstrate this relationship significant (F=4.3, P < 0.001). TS and Tre are negatively correlated (r = -0.276), however, TS was not a significant predictor of Tre (F=0.955, P = 0.490). No relationship existed between both COM and HTS in terms of Tre.

CONCLUSION: This data supports the use of the HTS scale as a reliable instrument for measuring HR and VO2 when at rest or exercising in 37°C.

361 Board #214 May 29, 11:00 AM - 12:30 PM

Clothing Bellows Effect Does Not Impact Thermal Sensation During Exercise In The Cold

Colin R. Carriker1, Timothy R. Burnham2, Vince M. Nethery2, Robert C. Pritchett2. 1University of New Mexico, Albuquerque, NM. 2Central Washington University, Ellensburg, WA.

(No relationships reported)

In the cold, a windproof outer-garment preserves clothing microenvironment temperature (CMET) by preventing disruption of the inner air layer from cold ambient air. During vigorous exercise, arm/leg pumping actions create a bellows effect in which CMET ventilation decreases mean skin temperature (Tsk).

PURPOSE: To investigate the impact of 5 min intervals of increased arm/leg movement on Tsk, CMET, and thermal sensation (TS) during exercise (45 min) in a cold ambient temperature, Ta (2±1°C; 66±6% humidity) with simulated wind (∼1.5 m/s).

METHODS: A randomized crossover design was employed for 2 treatment garments of different thickness: 20 Denier (20D) and 70 Denier (70D). Nine men (23±2 yr, 11.72±5.95 %Fat, VO2max 49.83±3.23 ml/kg/min) wore a treatment garment and baselayer pant/long sleeve shirt (100% polyester) 2-layer ensemble. No hat/gloves were permitted. Trials were scheduled >2 days apart at the same time of day, 2 hr post-prandial. Testing occurred during winter/early spring months. Exercise consisted of 3 consecutive series of the following: 10 min treadmill walking (TW) at 10% grade and 5 min intermittent bench stepping (IBS). Pace and cadence determined by ACSM walking/step equations at ∼50% METmax. A four site Tsk was employed. Core temperature (Tre) measured using a rectal thermistor probe. TS, ranged from -7 unbearably cold to +7 unbearably hot.

RESULTS: Heart rate (HR) during each IBS was significantly greater than each TW (p<0.05) for both treatments. Tsk after each IBS was lower than the previous TW for both 20D (p=0.064, 0.114, and 0.076; respectively) and 70D treatments (p<0.05, <0.05, .164; respectively). CMET after each IBS was lower than the previous TW for both the 20D (p<0.05, <0.05, 1.0; respectively) and 70D treatments (p<0.05, 0.97, 1.0; respectively). TS continued to increase throughout the 45 min bout. Tre increased similarly (p=0.563) for 20D and 70D over 45 min (1.23±0.31 and 1.12°C±0.25; respectively) and was greater than rest after 15 min (p<0.05) for both conditions. A moderate correlation was seen between Tre and TS (r=0.53, p<0.05).

CONCLUSION: During IBS, arm and leg pumping were increased causing a decline in Tsk, however, TS continued to increase throughout the 45 minute exercise bout. IBS causes a clothing bellows effect but does not appear to impact TS or Tre directly.

© 2013 American College of Sports Medicine