MyMedR

Displaying all 10 publications

Abstract:

Sort:

Decay of heat acclimation during exercise in cold and exposure to cold environment

Saat M, Sirisinghe RG, Singh R, Tochihara Y

Eur J Appl Physiol, 2005 Oct;95(4):313-20.
PMID: 16151840

Sixteen male students exercised for 14 days (1 h/day) in the heat for heat acclimation (HA). During deacclimation (DA) one group exercised in the cold (EXG, n=8) for 60 min/day (morning) and was exposed to the cold for another hour (afternoon) for 14 days. The other group was exposed to the cold (EPG, n=8) for 1 h each in the morning and afternoon (Ta: 18.0 degrees C, RH: 58%) over the same period. All returned to exercise in the heat for reacclimation (RA) for 10 days. Subjects were tested on days 1, 16, 21, 32, 36 and 44 on a bicycle ergometer for 60 min at 60% of VO(2max) in the heat (Ta: 31.1 degrees C, RH: 70%). Rectal temperature (T (re)) and heart rate (HR) at 40 min of exercise were used to determine the decay/gain of HA, which was calculated using the formula described by Pandolf et al. (Ergonomics, 20:399-408, 1977). After HA (day 16) T (re) and HR decreased significantly. During DA, EXG showed decay in T (re) of 24 and 35% and HR of 29 and 35% on days 21 and 32, respectively. For EPG the corresponding decay was of 2 and 9% for T (re) and 17 and 17% for HR. After 10 days of RA, EXG showed gains of 11% in T (re) and 12% in HR, while EPG showed gains of 47% in T (re) and 38% in HR. In conclusion, EXG had greater decay during DA and lower gains in RA compared to EPG. However, the differences between groups were significant only for T (re) after 4 days of DA.
Effects of short-term exercise in the heat on thermoregulation, blood parameters, sweat secretion and sweat composition of tropic-dwelling subjects

Saat M, Sirisinghe RG, Singh R, Tochihara Y

J Physiol Anthropol Appl Human Sci, 2005 Sep;24(5):541-9.
PMID: 16237263

This study investigates the effects of a short-term aerobic training program in a hot environment on thermoregulation, blood parameters, sweat secretion and composition in tropic-dwellers who have been exposed to passive heat. Sixteen healthy Malaysian-Malay male volunteers underwent heat acclimation (HA) by exercising on a bicycle ergometer at 60% of VO2max for 60 min each day in a hot environment (Ta: 31.1+/-0.1 degrees C, rh: 70.0+/-4.4%) for 14 days. All parameters mentioned above were recorded on Day 1 and at the end of HA (Day 16). On these two days, subjects rested for 10 min, then cycled at 60% of VO2max for 60 min and rested again for 20 min (recovery) in an improvised heat chamber. Rectal temperature (Tre), mean skin temperature (Tsk) heart rate (HR), ratings of perceived exertion (RPE), thermal sensation (TS), local sweat rate and percent dehydration were recorded during the test. Sweat concentration was analysed for sodium [Na+]sweat and potassium. Blood samples were analysed for biochemical changes, electrolytes and hematologic indices. Urine samples were collected before and after each test and analysed for electrolytes.After the period of acclimation the percent dehydration during exercise significantly increased from 1.77+/-0.09% (Day 1) to 2.14+/-0.07% (Day 16). Resting levels of hemoglobin, hematocrit and red blood cells decreased significantly while [Na+]sweat increased significantly. For Tre and Tsk there were no differences at rest. Tre, HR, RPE, TS, plasma lactate concentration, hemoglobin and hematocrit at the 40th min of exercise were significantly lower after the period of acclimation but mean corpuscular hemoglobin and serum osmolality were significantly higher while no difference was seen in [Na+]sweat and Tsk. It can be concluded that tropic-dwelling subjects, although exposed to prolonged passive heat exposure, were not fully heat acclimatized. To achieve further HA, they should gradually expose themselves to exercise-heat stress in a hot environment.
Rehydration after exercise with fresh young coconut water, carbohydrate-electrolyte beverage and plain water

Saat M, Singh R, Sirisinghe RG, Nawawi M

J Physiol Anthropol Appl Human Sci, 2002 Mar;21(2):93-104.
PMID: 12056182

This is to cross-over study to assess the effectiveness of fresh young coconut water (CW), and carbohydrate-electrolyte beverage (CEB) compared with plain water (PW) for whole body rehydration and blood volume (BV) restoration during a 2 h rehydration period following exercise-induced dehydration. Eight healthy male volunteers (mean age and VO2max of 22.4 +/- 3.3 years and 45.8 +/- 1.5 ml min kg-1 respectively) exercised at 60% of VO2max in the heat (31.1 +/- 0.03 degrees C, 51.4 +/- 0.1% rh) until 2.78 +/- 0.06% (1.6 +/- 0.1 kg) of their body weight (BW) was lost. After exercise, the subjects sat for 2 h in a thermoneutral environment (22.5 +/- 0.1 degrees C; 67.0 +/- 1.0% rh) and drank a volume of PW, CW and CEB on different occasions representing 120% of the fluid loss. A blood and urine sample, and the body weight of each subject was taken before and after exercise and at 30 min intervals throughout a rehydration period. Each subject remained fasted throughout rehydration. Each fluid was consumed in three portions in separate trials representing 50% (781 +/- 47 ml), 40% (625 +/- 33 ml) and 30% (469 +/- 28 ml) of the 120% fluid loss at 0, 30 and 60 min of the 2 h rehydration period, respectively. The drinks given were randomised. In all the trials the subjects were somewhat hypohydrated (range 0.08-0.18 kg BW below euhydrated BW; p > 0.05) after a 2 h rehydration period since additional water and BW were lost as a result of urine formation, respiration, sweat and metabolism. The percent of body weight loss that was regained (used as index of percent rehydration) during CW, PW, and CEB trials was 75 +/- 5%, 73 +/- 5% and 80 +/- 4% respectively, but was not statistically different between trials. The rehydration index, which provided an indication of how much of what was actually ingested was used for body weight restoration, was again not different statistically between trials (1.56 +/- 0.14, 1.36 +/- 0.13 and 1.71 +/- 0.21 for CW, CEB and PW respectively). Although BV restoration was better with CW, it was not statistically different from CEB and PW. Cumulative urine output was similar in all trials. There were no difference at any time in serum Na+ and Cl-, serum osmolality, and net fluid balance between the three trials. Urine osmolality decreased after 1 h during the rehydration period and it was lowest in the PW trial. Plasma glucose concentrations were significantly higher compared with PW ingestion when CW and CEB were ingested during the rehydration period. CW was significantly sweeter, caused less nausea, fullness and no stomach upset and was also easier to consume in a larger amount compared with CEB and PW ingestion. In conclusion, ingestion of fresh young coconut water, a natural refreshing beverage, could be used for whole body rehydration after exercise.
Fulltext The Incidence of Fracture-Related Infection in Open Tibia Fracture with Different Time Interval of Initial Debridement

Hadizie D, Kor YS, Ghani SA, Mohamed-Saat MA

Malays Orthop J, 2022 Nov;16(3):24-29.
PMID: 36589367 DOI: 10.5704/MOJ.2211.005

INTRODUCTION: The primary aim of open fracture management is to prevent fracture-related infection by early antibiotic administration, debridement and wound coverage. However, the timing of the initial debridement is still controversial, and 6 to 24 hours is commonly advocated. Studies have yet to provide substantial evidence regarding the best time for surgical debridement. Thus, this study was conducted to compare the incidence of fracture-related infection at different time intervals of initial debridement of the open tibia fracture.
MATERIALS AND METHODS: A total of 91 patients with grade I, II and IIIa open tibia fractures were recruited from 2016 to 2018, and their data were obtained from the consensus book and medical records. Participants were divided into four groups based on the time of initial debridement: (1) less than 6 hours, (2) 6 to less than 12 hours, (3) 12 to less than 24 hours, and (4) 24 hours and more. Fracture-related infection was determined by using Metsemakers confirmative criteria. Association between time and infection were determine by Binary Logistic Regression analysis by remerged the group into three; (1) less than 12 hours, (2) 12 to less than 24 hours and (3) 24 hours and more. The collected information was analysed using SPSS version 24 and Microsoft Excel 2010.
RESULTS: The mean age of the participants was 31.9 years old, with male predominant (n=80, 87.0%). Most participants had delayed initial debridement of more than 24 hours and predominantly Gustilo-Anderson type IIIa (n=47). A total of 8 fractures complicated with infection (8.7%), majority in grade IIIa and debridement performed within 12 to less than 24 hours. Binary logistic regression showed increased odds of infection with a delayed wound debridement both in clinical presentation and positive culture, but the association was not statistically significant. The commonest organism isolated was Pseudomonas aeruginosa.
CONCLUSION: Comparing to different time interval, initial wound debridement of more than 24 hours did not have strong association with increasing infection rate. However, even though statistically not significant, the odds of infection was increase with increasing time of initial wound debridement of an open tibia fracture, thus it should be performed early.
Fulltext A comparison of hydration effect on body fluid and temperature regulation between Malaysian and Japanese males exercising at mild dehydration in humid heat

Wakabayashi H, Wijayanto T, Lee JY, Hashiguchi N, Saat M, Tochihara Y

J Physiol Anthropol, 2014;33:5.
PMID: 24490869 DOI: 10.1186/1880-6805-33-5

This study investigated the effect of hydration differences on body fluid and temperature regulation between tropical and temperate indigenes exercising in the heat.
Ethnic differences in thermoregulatory responses during resting, passive and active heating: application of Werner's adaptation model

Lee JY, Wakabayashi H, Wijayanto T, Hashiguchi N, Saat M, Tochihara Y

Eur J Appl Physiol, 2011 Dec;111(12):2895-905.
PMID: 21437607 DOI: 10.1007/s00421-011-1912-5

For the coherent understanding of heat acclimatization in tropical natives, we compared ethnic differences between tropical and temperate natives during resting, passive and active heating conditions. Experimental protocols included: (1) a resting condition (an air temperature of 28°C with 50% RH), (2) a passive heating condition (28°C with 50% RH; leg immersion in a hot tub at a water temperature of 42°C), and (3) an active heating condition (32°C with 70% RH; a bicycle exercise). Morphologically and physically matched tropical natives (ten Malaysian males, MY) and temperate natives (ten Japanese males, JP) participated in all three trials. The results saw that: tropical natives had a higher resting rectal temperature and lower hand and foot temperatures at rest, smaller rise of rectal temperature and greater temperature rise in bodily extremities, and a lower sensation of thirst during passive and active heating than the matched temperate natives. It is suggested that tropical natives' homeostasis during heating is effectively controlled with the improved stability in internal body temperature and the increased capability of vascular circulation in extremities, with a lower thirst sensation. The enhanced stability of internal body temperature and the extended thermoregulatory capability of vascular circulation in the extremities of tropical natives can be interpreted as an interactive change to accomplish a thermal dynamic equilibrium in hot environments. These heat adaptive traits were explained by Wilder's law of initial value and Werner's process and controller adaptation model.
Comparison of thermoregulatory responses to heat between Malaysian and Japanese males during leg immersion

Wijayanto T, Wakabayashi H, Lee JY, Hashiguchi N, Saat M, Tochihara Y

Int J Biometeorol, 2011 Jul;55(4):491-500.
PMID: 20824480 DOI: 10.1007/s00484-010-0358-5

The objective of this study was to investigate thermoregulatory responses to heat in tropical (Malaysian) and temperate (Japanese) natives, during 60 min of passive heating. Ten Japanese (mean ages: 20.8 ± 0.9 years) and ten Malaysian males (mean ages: 22.3 ± 1.6 years) with matched morphological characteristics and physical fitness participated in this study. Passive heating was induced through leg immersion in hot water (42°C) for 60 min under conditions of 28°C air temperature and 50% RH. Local sweat rate on the forehead and thigh were significantly lower in Malaysians during leg immersion, but no significant differences in total sweat rate were observed between Malaysians (86.3 ± 11.8 g m(-2) h(-1)) and Japanese (83.2 ± 6.4 g m(-2) h(-1)) after leg immersion. In addition, Malaysians displayed a smaller rise in rectal temperature (0.3 ± 0.1°C) than Japanese (0.7 ± 0.1°C) during leg immersion, with a greater increase in hand skin temperature. Skin blood flow was significantly lower on the forehead and forearm in Malaysians during leg immersion. No significant different in mean skin temperature during leg immersion was observed between the two groups. These findings indicated that regional differences in body sweating distribution might exist between Malaysians and Japanese during heat exposure, with more uniform distribution of local sweat rate over the whole body among tropical Malaysians. Altogether, Malaysians appear to display enhanced efficiency of thermal sweating and thermoregulatory responses in dissipating heat loss during heat loading. Thermoregulatory differences between tropical and temperate natives in this study can be interpreted as a result of heat adaptations to physiological function.
Comparison of heat dissipation response between Malaysian and Japanese males during exercise in humid heat stress

Wakabayashi H, Wijayanto T, Lee JY, Hashiguchi N, Saat M, Tochihara Y

Int J Biometeorol, 2011 Jul;55(4):509-17.
PMID: 20949285 DOI: 10.1007/s00484-010-0374-5

This study investigated the differences in heat dissipation response to intense heat stress during exercise in hot and humid environments between tropical and temperate indigenes with matched physical characteristics. Ten Japanese (JP) and ten Malaysian (MY) males participated in this study. Subjects performed exercise for 60 min at 55% peak oxygen uptake in 32°C air with 70% relative humidity, followed by 30 min recovery. The increase in rectal temperature (T(re)) was smaller in MY during exercise compared to JP. The local sweat rate and total body mass loss were similar in both groups. Both skin blood flow and mean skin temperature was lower in MY compared to JP. A significantly greater increase in hand skin temperature was observed in MY during exercise, which is attributable to heat loss due to the greater surface area to mass ratio and large number of arteriovenous anastomoses. Also, the smaller increase in T(re) in MY may be explained by the presence of a significantly greater core-skin temperature gradient in MY than JP. The thermal gradient is also a major factor in increasing the convective heat transfer from core to skin as well as skin blood flow. It is concluded that the greater core-skin temperature gradient observed in MY is responsible for the smaller increase in T(re).
Effects of exercise in the heat on thermoregulation of Japanese and Malaysian males

Saat M, Tochihara Y, Hashiguchi N, Sirisinghe RG, Fujita M, Chou CM

J Physiol Anthropol Appl Human Sci, 2005 Jul;24(4):267-75.
PMID: 16079566

The effect of low-intensity exercise in the heat on thermoregulation and certain biochemical changes in temperate and tropical subjects under poorly and well-hydrated states was examined. Two VO2max matched groups of subjects consisting of 8 Japanese (JS) and 8 Malaysians (MS) participated in this study under two conditions: poorly-hydrated (no water was given) and well-hydrated (3 mL x Kg(-1) body weight of water was provided at onset of exercise, and the 15th, 35th and 55th min of exercise). The experimental room in both countries was adjusted to a constant level (Ta: 31.6+/-0.03 degrees C, rh: 72.3+/-0.13%). Subjects spent an initial 10 min rest, 60 min of cycling at 40% VO2max and then 40 min recovery in the experimental room. Rectal temperatures (Tre) skin temperatures (Tsk), heart rate (HR), heat-activated sweat glands density (HASG), local sweat rate (M sw-back) and percent dehydration were recorded during the test. Blood samples were analysed for plasma glucose and lactate levels.The extent of dehydration was significantly higher in the combined groups of JS (1.43+/-0.08%) compared to MS (1.15+/-0.05%). During exercise M sw-back was significantly higher in JS compared to MS in the well-hydrated condition. The HASG was significantly more in JS compared to MS at rest and recovery. Tre was higher in MS during the test. Tsk was significantly higher starting at the 5th min of exercise until the end of the recovery period in MS compared to JS. In conclusion, tropical natives have lower M sw-back associated with higher Tsk and Tre during the rest, exercise and recovery periods. However, temperate natives have higher M sw-back and lower Tsk and Tre during experiments in a hot environment. This phenomenon occurs in both poorly-hydrated and well-hydrated states with low intensity exercise. The differences in M sw-back, Tsk and Tre are probably due to a setting of the core temperature at a higher level and enhancement of dry heat loss, which occurred during passive heat exposure.
Cutaneous Warm and Cool Sensation Thresholds and the Inter-threshold Zone in Malaysian and Japanese Males

Lee JY, Saat M, Chou C, Hashiguchi N, Wijayanto T, Wakabayashi H, et al.

J Therm Biol, 2010 Feb;35(2):70-76.
PMID: 28799915 DOI: 10.1016/j.jtherbio.2009.11.002

The purpose of this study was to investigate ethnic differences in cutaneous thermal sensation thresholds and the inter-threshold sensory zone between tropical (Malaysians) and temperate natives (Japanese). The results showed that (1) Malaysian males perceived warmth on the forehead at a higher skin temperature (Tsk) than Japanese males (p<0.05), whereas cool sensations on the hand and foot were perceived at a lower Tsk in Malaysians (p<0.05); (2) Overall, the sensitivity to detect warmth was greater in Japanese than in Malaysian males; (3) The most thermally sensitive body region of Japanese was the forehead for both warming and cooling, while the regional thermal sensitivity of Malaysians had a smaller differential than that of Japanese; (4) The ethnic difference in the inter-threshold sensory zone was particularly noticeable on the forehead (1.9±1.2C for Japanese, 3.2±1.6°C for Malaysians, p<0.05). In conclusion, tropical natives had a tendency to perceive warmth at a higher Tsk and slower at an identical speed of warming, and had a wider range of the inter-threshold sensory zone than temperate natives.

Filters

Please provide feedback to Administrator (afdal@afpm.org.my)

External Links