The reliability of a portable steam sauna pod for the whole-body passive heating of humans.

INTRODUCTION: Passive heating is receiving increasing attention within human performance and health contexts. A low-cost, portable steam sauna pod may offer an additional tool for those seeking to manipulate physiological (cardiovascular, thermoregulatory and sudomotor) and perceptual responses for improving sporting or health profiles. This study aimed to 1) report the different levels of heat stress and determine the pods' inter-unit reliability, and 2) quantify the reliability of physiological and perceptual responses to passive heating. METHOD: In part 1, five pods were assessed for temperature and relative humidity (RH) every 5 min across 70 min of heating for each of the 9 settings. In part 2, twelve males (age: 24 ± 4 years) completed two 60 min trials of passive heating (3 × 20 min at 44 °C/99% RH, separated by 1 week). Heart rate (HR), rectal (Trectal) and tympanic temperature (Ttympanic) were recorded every 5 min, thermal comfort (Tcomfort) and sensation (Tsensation) every 10 min, mean arterial pressure (MAP) at each break period and sweat rate (SR) after exiting the pod. RESULTS: In part 1, setting 9 provided the highest temperature (44.3 ± 0.2 °C) and longest time RH remained stable at 99% (51±7 min). Inter-unit reliability data demonstrated agreement between pods for settings 5-9 (intra-class correlation [ICC] >0.9), but not for settings 1-4 (ICC <0.9). In part 2, between-visits, high correlations, and low typical error of measurement (TEM) and coefficient of variation (CV) were found for Trectal, HR, MAP, SR, and Tcomfort, but not for Ttympanic or Tsensation. A peak Trectal of 38.09 ± 0.30 °C, HR of 124 ± 15 b min-1 and a sweat loss of 0.73 ± 0.33 L were reported. No between-visit differences (p > 0.05) were observed for Trectal, Ttympanic, Tsensation or Tcomfort, however HR (+3 b.min-1) and MAP (+4 mmHg) were greater in visit 1 vs. 2 (p < 0.05). CONCLUSION: Portable steam sauna pods generate reliable heat stress between-units. The highest setting (44 °C/99% RH) also provides reliable but modest adjustments in physiological and perceptual responses.

The elderly's physiological and perceptual responses to cooling during simulated activities of daily living in UK summer climatic conditions.

OBJECTIVES: The elderly are the most at-risk population for heat-related illness and mortality during the periods of hot weather. However, evidence-based elderly-specific cooling strategies to prevent heat-illness are limited. The aim of this investigation was to quantify the elderly's physiological and perceptual responses to cooling through cold water ingestion (COLD) or an L-menthol mouth rinse (MENT) during simulated activities of daily living in UK summer climatic conditions. STUDY DESIGN: Randomised, controlled repeated measures research design. METHODS: A total of ten participants (men n = 7, women n = 3: age; 69 ± 3 yrs, height; 168 ± 10 cm, body mass; 68.88 ± 13.72 kg) completed one preliminary and three experimental trials; control (CON), COLD and MENT. Experimental trials consisted of 40 min rest followed by 30 min of cycling exercise at 6 metabolic equivalents and a 6-min walk test (6MWT), within a 35 °C, 50% relative humidity environment. Experimental interventions (every 10 min); cold water (4 °C) ingestion (total of 1.5L) or menthol (5 ml mouth swill for 5 s, menthol concentration of 0.01%). RESULTS: Peak rectal temperature (Tre) was significantly (P < 0.05) lower in COLD compared with CON (-0.34 ± 0.16 °C) and MENT (-0.36 ± 0.20 °C). End exercise heart rate (HR) decreased in COLD compared with CON (-7 ± 9 b min-1) and MENT (-6 ± 7 b min-1). There was no difference in end exercise thermal sensation (TS) (CON; 6.1 ± 0.4, COLD; 6.0 ± 0.4, MENT; 6.4 ± 0.6) or thermal comfort (TC) (CON; 4 ± 1, COLD; 4 ± 1, MENT; 4 ± 1) between trials. The participants walked significantly further during the COLD 6MWT compared with CON (40 m ± 40 m) and MENT (40 m ± 30 m). There was reduced physiological strain in the COLD 6MWT compared with CON (Tre; -0.21 ± 0.24 °C, HR; -7 ± 8 b min-1) and MENT (Tre; -0.23 ± 0.24 °C, HR; -4 ± 7 b min-1). CONCLUSION: The elderly have reduced physiological strain (Tre and HR) during activities of daily living and a 6MWT in hot UK climatic conditions, when they drink cold water. Furthermore, the elderly's perception (TS and TC) of the hot environment did not differ from CON at the end of exercise with COLD or MENT interventions. Menthol provided neither perceptual benefit to exercise in the heat nor functional gain. The TS data indicate that elderly may be at increased risk of heat illness, due to not feeling hot and uncomfortable enough to implement physiological strain reducing strategies such as cold-water ingestion.

Physiological and perceptual responses in the elderly to simulated daily living activities in UK summer climatic conditions.

OBJECTIVES: The elderly population is at an increasingly significant health risk to heat-related illnesses and mortality when compared with younger people in the same conditions. This is due to an increased frequency and severity of heatwaves, attributed to climate change, and reduced ability of elderly individuals to dissipate excess heat. Consequently, most excess deaths and emergency visits during heatwaves occur in people aged more than 65 years. The aim of this investigation was to assess the physiological and perceptual responses of elderly people during exercise sessions equating to activities of daily living in UK summer climatic conditions. STUDY DESIGN: Mixed-method, randomised research design. METHODS: Twenty-eight participants (17 males, 10 females and 1 transgender female) were randomly assigned into three experimental groups; 15°C, 25°C or 35°C, with 50% relative humidity. Participants completed one preliminary and three experimental trials within their assigned environment. The data from the preliminary incremental recumbent cycling test was used to calculate participant's individual exercise intensities equating to 2, 4 and 6 metabolic equivalents (METs) for the subsequent trials. During experimental trials, participants completed 30-min seated rest and 30-min cycling. RESULTS: No change was observed in thermal comfort ([TC] just uncomfortable in both trials), and only modest changes in ratings of perceived exertion (14 ± 2 vs 15 ± 2) at 6 METs in 25°C compared with those in 35°C were observed. In contrast, thermal strain markers did significantly increase (P < 0.05) across the same conditions, including change in rectal temperature (ΔTre) during exercise (0.27 ± 0.17°C vs 0.64 ± 0.18°C) and peak skin temperature ([Tskin] 32.94 ± 1.15°C vs 36.11 ± 0.44°C). CONCLUSION: When completing exercise that equates to activities of daily living, elderly people could have a decreased perceptual awareness of the environment even though physiological markers of thermal strain are elevated. Consequently, the elderly could be less likely to implement behavioural thermoregulation interventions (i.e. seek shade and/or remove excess layers) due to a decreased awareness of an increasingly thermally challenging environment.

The time course of endogenous erythropoietin, IL-6, and TNFα in response to acute hypoxic exposures.

Erythropoietin (EPO) rapidly decreases on return to sea level (SL) after chronic altitude exposure. Acute hypoxia may provide an additional stimulus to prevent the decline in EPO. Proinflammatory cytokines, interleukin-6 (IL-6), and tumor necrosis factor alpha (TNFα) have been shown to inhibit EPO production. Optimal normobaric hypoxic exposure has not been established; therefore, investigation of methods eliciting the greatest response in EPO to limit physiological stress is required. Eight men (age 27 ± 4 years, body mass 77.5 ± 9.0 kg, height 179 ± 6 cm) performed four passive exposures to different normobaric hypoxic severities [FiO2 : 0.209 (SL), FiO2 : ~0.135 (3600 m), FiO2 : ~0.125 (4200 m) and FiO2 : ~0.115 (4800 m)] in a hypoxic chamber for 2 h. Venous blood was drawn pre-exposure and then at 1, 2, 4, 6, and 8 h to determine EPO concentration ([EPO]), IL-6, and TNFα. During 4200 and 4800 m, [EPO] increased from 5.9 ± 1.5 to 8.1 ± 1.5 mU/mL (P = 0.009) and 6.0 ± 1.4 to 8.9 ± 2.0 mU/mL (P = 0.037), respectively, with [EPO] increase peaking at 4 h (2 h post-exposure). There were no differences in IL-6 or TNFα during or post-exposure. Increased [EPO] was found 2 h post hypoxic exposure as result of 2 h of normobaric hypoxia ≥4200 m. There was no dose-response relationship in [EPO] between simulated hypoxia severities.

The effects of single versus twice daily short term heat acclimation on heat strain and 3000m running performance in hot, humid conditions.

Endurance performances are impaired under conditions of elevated heat stress. Short term heat acclimation (STHA) over 4-6 days can evoke rapid adaptation, which mitigate decrements in performance and alleviate heat strain. This study investigated the efficacy of twice daily heat acclimation (TDHA) compared to single session per day heat acclimation (SDHA) and normothermic training, at inducing heat acclimation phenotype and its impact upon running performance in hot, humid conditions. Twenty one, moderately trained males were matched and assigned to three groups; SDHA (mean±SD) (peak oxygen consumption [V̇O2peak] 45.8±6.1mLkg(-1)min(-1), body mass 81.3±16.0kg, stature 182±3cm), TDHA (46.1±7.0mLkg(-1)min(-1), 80.1±11.9kg, 178±4cm) or control (CON) (47.1±3.5mLkg(-1)min(-1), 78.6±16.7kg, 178±4cm). Interventions consisted of 45min cycling at 50% V̇O2peak, once daily for 4d (SDHA) and twice daily for 2d (TDHA), in 35°C, 60% relative humidity (RH), and once daily for 4 days (CON) in 21°C, 40% RH. Participants completed a pre- and post-intervention 5km treadmill run trial in 30°C, 60% RH, where the first 2km were fixed at 40% V̇O2peak and the final 3km was self-paced. No statistically significant interaction effects occurred within- or between-groups over the 2-4 days intervention. While within-group differences were found in physiological and perceptual measures during the fixed intensity trial post-intervention, they did not statistically differ between-groups. Similarly, TDHA (-36±34s [+3.5%]) and SDHA (-26±28s [+2.8%]) groups improved 3km performances (p=0.35), but did not differ from CON (-6±44s [+0.6%]). This is the first study to investigate the effects of HA twice daily and compare it with traditional single session per day STHA. These STHA protocols may have the ability to induce partial adaptive responses to heat stress and possibly enhance performance in environmentally challenging conditions, however, future development is warranted to optimise the administration to provide a potent stimuli for heat adaptation in athletic and military personnel within a rapid regime.

Leukocyte Hsp72 mRNA transcription does not differ between males and females during heat acclimation.

Purpose: Thermotolerance is an acquired state of increased cytoprotection achieved following single or repeated exposures to heat stress, in part characterized by changes in the intracellular 72 kda heat shock protein (HSP72; HSPA1A). Females have demonstrated reduced exercise induced HSP72 in comparison to males. This study examined sex differences in heat shock protein 72 messenger ribonucleic acid (Hsp72 mRNA) transcription during heat acclimation (HA) to identify whether sex differences were a result of differential gene transcription. Methods: Ten participants (5M, 5F) performed 10, 90 min controlled hyperthermia [rectal temperature (Tre) ≥ 38.5°C] HA sessions over 12 d. Leukocyte Hsp72 mRNA was measured pre and post D1, D5, and D10, via Reverse transcription polymerase chain reaction (RT-QPCR). Results: HA was evidenced by a reduction in resting Tre (-0.4 ± 0.5°C) and resting heart rate [(HR); -13 ± 7 beats.min-1] following HA (p ≤ 0.05). During HA no difference (p > 0.05) was observed in ΔTre between males (D1 = 1.5 ± 0.2°C; D5 = 1.6 ± 0.4°C; D10 = 1.8 ± 0.3°C) and females (D1 = 1.5 ± 0.5°C; D5 = 1.4 ± 0.2°C; D10 = 1.8 ± 0.3°C). This was also true of mean Tre demonstrating equality of thermal stimuli for mRNA transcription and HA. There were no differences (p > 0.05) in Hsp72 mRNA expression between HA sessions or between males (D1 = +1.8 ± 1.5-fold; D5 = +2.0 ± 1.0 fold; D10 = +1.1 ± 0.4-fold) and females (D1 = +2.6 ± 1.8-fold; D5 = +1.8 ± 1.4-fold; D10 = +0.9 ± 1.9-fold). Conclusions: This experiment demonstrates that there is no difference in Hsp72 mRNA increases during HA between sexes when controlled hyperthermia HA is utilised. Gender specific differences in exercise-induced HSP72 reported elsewhere likely result from post-transcriptional events.

The reliability of a heat acclimation state test prescribed from metabolic heat production intensities.

Acclimation state indicates an individual's phenotypic response to a thermally stressful environment, where changes in heat dissipation capacity are determined during a heat acclimation state test (HAST). Variations in thermoregulatory and sudomotor function are reported while exercising at intensities relative to maximal oxygen uptake. This inter-individual variation is not true when intensity is prescribed to elicit a fixed rate of metabolic heat production (Hprod). This study investigated the reliability of peak Tre and two composite measures (sweat gain and sweat setpoint) derived from indices of thermosensitivity during a HAST prescribed from Hprod intensities. Fourteen participants (mean±SD; age 23±3 years, stature 174±7cm, body mass 75.0±9.4kg, body surface area 1.9±0.1m(2), peak oxygen consumption [V̇O2peak] 3.49±0.53Lmin(-1)) completed a lactate threshold-V̇O2peak test and two duplicate Hprod HASTs on a cycle ergometer. The HAST consisted of three, 30-min periods of exercise at fixed Hprod intensities relative to body mass (3, 4.5 and 6Wkg(-1)), within hot dry conditions (44.7±1.8°C and 18.1±4.7% relative humidity). Peak Tre (38.20±0.36 vs. 38.16±0.42°C, p=0.54), sweat setpoint (36.76±0.34 and 36.79±0.38°C, p=0.68) and sweat gain (0.37±0.14 and 0.40±0.18gs(-1)°C(-1), p=0.40) did not differ between HASTs. Typical error of measurement (TEM), coefficient variation (CV) and intra-class coefficient of correlation (ICC) were 0.19°C, 0.5% and 0.80 for peak Tre, 0.21°C, 0.6% and 0.65 for sweat setpoint and 0.09gs(-1)°C(-1), 28% and 0.68 for sweat gain, respectively. The use of fixed Hprod intensities relative to body mass is a reliable method for measuring Tre and ascertaining sweat setpoint during a HAST, whereas, sweat gain displays greater variability. A Hprod HAST appears sufficiently reliable for quantifying heat acclimation state, where TEM in peak Tre and sweat setpoint are small enough to identify physiologically meaningful improvements post-intervention.

Physiological responses to incremental exercise in the heat following internal and external precooling.

Twelve males completed three incremental, discontinuous treadmill tests in the heat [31.9(1.0) °C, 61.9(8.9)%] to determine speed at two fixed blood lactate concentrations (2 and 3.5 mmol/L), running economy (RE), and maximum oxygen uptake ( V ˙ O 2 m a x ). Trials involved 20 min of either internal cooling (ICE, 7.5 g/kg ice slurry ingestion) or mixed-methods external cooling (EXT, cold towels, forearm immersion, ice vest, and cooling shorts), alongside no intervention (CON). Following precooling, participants ran 0.3 km/h faster at 2 mmol/L and 0.2 km/h faster at 3.5 mmol/L (P = 0.04, partial η(2) = 0.27). Statistical differences were observed vs CON for ICE (P = 0.03, d = 0.15), but not EXT (P = 0.12, d = 0.15). There was no effect of cooling on RE (P = 0.81, partial η(2) = 0.02), nor on V ˙ O 2 m a x (P = 0.69, partial η(2) = 0.04). An effect for cooling on physiological strain index was observed (P < 0.01, partial η(2) = 0.41), with differences vs CON for EXT (P = 0.02, d = 0.36), but not ICE (P = 0.06, d = 0.36). Precooling reduced thermal sensation (P < 0.01, partial η(2) = 0.66) in both cooling groups (P < 0.01). Results indicate ICE and EXT provide similar physiological responses for exercise up to 30 min duration in the heat. Differing thermoregulatory responses are suggestive of specific event characteristics determining the choice of cooling. Precooling appears to reduce blood lactate accumulation and reduce thermoregulatory and perceptual strain during incremental exercise.

A comparison of males and females' temporal patterning to short- and long-term heat acclimation.

The current study assessed sex differences in thermoregulatory and physiological adaptation to short-term (STHA) and long-term heat acclimation (LTHA). Sixteen (eight males; eight females) participants performed three running heat tolerance tests (RHTT), preceding HA (RHTT1), following 5 days HA (RHTT2) and 10 days HA (RHTT3). The RHTT involved 30-min running (9 km/h, 2% gradient) in 40 °C, 40% relative humidity. Following STHA, resting rectal temperature (Trrest ) (males: -0.24 ± 0.16 °C, P ≤ 0.001; females: -0.02 ± 0.08 °C, P = 0.597), peak rectal temperature (Trpeak ) (males: -0.39 ± 0.36 °C, P ≤ 0.001; females -0.07 ± 0.18 °C, P = 0.504), and peak heart rate (males: -14 ± 12 beats/min, P ≤ 0.001; females: -5 ± 3 beats/min, P = 0.164) reduced in males, but not females. Following STHA, sweat rate relative to body surface area (SRBSA ) increased (428 ± 269 g/h/m(2) , P = 0.029) in females, but not males (-11 ± 286 g/h/m(2) , P = 0.029). Following LTHA, Trrest (males: -0.04 ± 0.15 °C, P = 0.459; females: -0.22 ± 0.12 °C, P ≤ 0.01) and Trpeak (males: -0.05 ± 0.26 °C, P = 0.590; females: -0.41 ± 0.24 °C, P ≤ 0.01) reduced in females, but not males. Following LTHA, SRBSA increased in males (308 ± 346 g/h/m(2) , P = 0.029), but not females (44 ± 373 g/h/m(2) , P = 0.733). Males and females responded to STHA; however, females required LTHA to establish thermoregulatory and cardiovascular stability. HA protocols should be designed to target sex differences in thermoregulation for optimal adaptation.

Isothermic and fixed-intensity heat acclimation methods elicit equal increases in Hsp72 mRNA.

Thermotolerance, to which heat shock protein-72 (Hsp72) contributes, is an acquired state achieved following heat acclimation (HA), eliciting cellular adaption and protection against thermal stress. Optimal HA methods achieving the greatest heat shock response (HSR) are equivocal; therefore, investigation of methods provoking the greatest sustained HSR is required to optimize cellular adaptation. Twenty-four males performed short-term HA (STHA; five sessions) and long-term HA (LTHA; STHA plus further five sessions) utilizing fixed-intensity (FIXED; workload = 50% V ˙ O 2 p e a k ), continuous isothermic HA [ISOCONT ; target rectal temperature (Trec ) = 38.5 °C], or progressive isothermic HA (ISOPROG ; target Trec = 38.5 °C for STHA then target Trec = 39.0 °C for LTHA). Leukocyte Hsp72 mRNA was measured pre- and post day 1, day 5, and day 10 of HA via reverse transcription quantitative polymerase chain reaction to determine the HSR. Hsp72 mRNA increased (P < 0.05) pre- to post day 1, pre- to post day 5, and pre to post day 10 in FIXED, ISOCONT , and ISOPROG , but no differences were observed between methods (P > 0.05). The equal Hsp72 mRNA increases occurring from consistent, reduced, or increased endogenous strain following STHA and LTHA suggest that transcription occurs following attainment of sufficient endogenous criteria. These data give confidence that all reported HA methods increase Hsp72 mRNA and are capable of eliciting adaptations toward thermotolerance.

Reliability and validity of skin temperature measurement by telemetry thermistors and a thermal camera during exercise in the heat.

New technologies afford convenient modalities for skin temperature (TSKIN) measurement, notably involving wireless telemetry and non-contact infrared thermometry. The purpose of this study was to investigate the validity and reliability of skin temperature measurements using a telemetry thermistor system (TT) and thermal camera (TC) during exercise in a hot environment. Each system was compared against a certified thermocouple, measuring the surface temperature of a metal block in a thermostatically controlled waterbath. Fourteen recreational athletes completed two incremental running tests, separated by one week. Skin temperatures were measured simultaneously with TT and TC compared against a hard-wired thermistor system (HW) throughout rest and exercise. Post hoc calibration based on waterbath results displayed good validity for TT (mean bias [MB]=-0.18 °C, typical error [TE]=0.18 °C) and reliability (MB=-0.05 °C, TE=0.31 °C) throughout rest and exercise. Poor validity (MB=-1.4 °C, TE=0.35 °C) and reliability (MB=-0.65 °C, TE=0.52 °C) was observed for TC, suggesting it may be best suited to controlled, static situations. These findings indicate TT systems provide a convenient, valid and reliable alternative to HW, useful for measurements in the field where traditional methods may be impractical.

Comparison of total haemoglobin mass measured with the optimized carbon monoxide rebreathing method across different Radiometer™ ABL-80 and OSM-3 hemoximeters.

A new Radiometer™ hemoximeter (ABL-80) has recently become available to measure carboxyhaemoglobin concentration for the optimized CO-rebreathing method (oCOR-method). Within the English Institute of Sport (EIS), hemoximeters are used in three different laboratories; therefore, precision and agreement of total haemoglobin mass (tHbmass) determination across sites is essential, and comparison to the previous model OSM-3 is desirable. Six male and one female (age 30 ± 6 years, body mass 78.1 ± 10.6 kg) undertook the oCOR-method. Venous blood (~2 ml) was sampled immediately before and at 7 min during the oCOR-method; with seven replicates from each time point simultaneously analysed on five different Radiometer™ hemoximeters [OSM-3(1), OSM-3(2), ABL-80(1), ABL-80(2) and ABL-80(3)]. There were no differences (p > 0.05) between Δ%HbCO or mean tHbmass analysed with five different hemoximeters (OSM-3(1): 886 ± 167 g; OSM-3(2): 896 ± 160 g: ABL-80(1): 904 ± 157 g; ABL-80(2): 906 ± 163 g: ABL-80(3): 906 ± 162 g). However, the Bland-Altman plot revealed that there was closer agreement between ABL-80 machines for tHbmass than for the OSM-3. The variance (i.e. % error) across replicate samples decreased as the number of samples increased, with the error derived from the 'worse-case' scenario (single samples) being 1.2 to 1.6 fold greater in the OSM-3 than the ABL-80. Although there were no differences in the average tHbmass measured with five different hemoximeters, the new ABL-80 were in better agreement with each other compared to the old OSM-3. Previously, five replicates were required to achieve a low error using the OSM-3; however, three replicates are sufficient with the ABL-80 model to produce an error of ≤ 1% in tHbmass.

Simulated moderate hypoxia reduces intermittent sprint performance in games players.

BACKGROUND: Exercise at altitude places additional physiological stress on the individual in comparison with sea-level performance. This study examines the effect of a moderate hypoxic environment (FiO2=~17%) on intermittent sprint exercise performance. METHODS: Nine male games players completed two consecutive sets of a 40 minute cycling intermittent sprint protocol (CISP×2) in a hypoxic (HYP; FiO2=~17%) and normoxic (NORM; FiO2=~21%) environment. During each sprint peak power output (PPO; the highest power during each 5 s sprint), mean power output (MPO; the average power during the 3 s sprint) were measured and total work done (WD; force applied from the highest 3 s period of power output) was calculated. Physiological responses were recorded throughout the testing procedure. RESULTS: Reductions were found in PPO (944±155 vs. 983±167 W), MPO (900±176 vs. 853±177 W) and WD (102±20 vs. 108±20 kJ) during the CISP×2 (P<0.05) at HYP compared to NORM. Reductions in PPO, MPO and WD were also found between the 1st half and 2nd half CISP (P<0.05) and there was a greater decline from the 1st half CISP to the 2nd half CISP in PPO, MPO and WD at HYP. Heart rate was higher and peripheral arterial oxygen saturation lower during HYP compared to NORM (P<0.05). CONCLUSION: Moderate hypoxia significantly reduced PPO (~4%), MPO (~5%) and WD (~5%) compared to normoxia. The results suggest athletes will be at a disadvantage when performing intermittent sprinting at moderate altitude.

The influence of carbon monoxide bolus on the measurement of total haemoglobin mass using the optimized CO-rebreathing method.

The optimized carbon monoxide (CO) rebreathing method (oCOR-method) is routinely used to measure total haemoglobin mass (tHbmass). The tHbmass measure is subject to a test-retest typical error of ~2%, mostly from the precision of carboxyhaemoglobin (HbCO) measurement. We hypothesized that tHbmass would be robust to differences in the bolus of CO administered during the oCOR-method. Twelve participants (ten males and two females; age 27 ± 6 yr, height 177 ± 11 cm and mass 73.9 ± 12.1 kg) completed the oCOR-method on four occasions. Different bolus of CO were administered (LOW: 0.6 ml kg(-1); MED1: 1.0 ml kg(-1) and HIGH: 1.4 ml kg(-1)); to determine the reliability of MED1, a second trial was conducted (MED2). tHbmass was found to be significantly less from the HIGH CO bolus (776 ± 148 g) when compared to the LOW CO (791 ± 149 g) or MED1 CO (788 ± 149 g) trials. MED2 CO was 785 ± 150 g. The measurement of tHbmass is repeatable to within 0.8%, but a small and notable difference was seen when using a HIGH CO bolus (1.4 to 1.9% less), potentially due to differences in CO uptake kinetics. Previously, an improved precision of the oCOR-method was thought to require a higher bolus of CO (i.e. larger Δ%HbCO), as commercial hemoximeters only estimate %HbCO levels to a single decimal place (usually ± 0.1%). With the new hemoximeter used in this study, a bolus of 1.0 ml kg(-1) allows adequate precision with acceptable safety.

Serum antibody titres to canine parvovirus, adenovirus and distemper virus in dogs in the UK which had not been vaccinated for at least three years.

Antibody titres to canine distemper (CDV), canine parvovirus (CPV) and canine adenovirus (CAV) were measured in 144 adult dogs that had not been vaccinated for between three and 15 years. Protective antibodies to CPV were present in 95 per cent of the population, to CDV in 71.5 per cent and to CAV in 82 per cent. The prevalence of protective titres did not decrease with increasing time interval from the last vaccination for any of the three diseases studied. Booster vaccination increased the dogs CAV titres. For comparative purposes, 199 puppies were sampled at the time of their first and second vaccination. In the case of CPV and CAV a significantly higher proportion of the adult dogs were protected than of the puppies immediately after they were vaccinated. Natural CPV boosting was strongly suspected because the dogs had significantly higher titres three years after their primary vaccination than two weeks after it and three unvaccinated dogs had acquired protective antibody levels uneventfully. There was no evidence of natural exposure to CDV.

Evaluation of the reliability and validity of a soccer-specific field test of repeated sprint ability.

The reliability and validity of a soccer-specific field test of repeated sprint ability was assessed. Seven male games players performed the repeated sprint test on six separate occasions. The temporal pattern of the mean sprint time was analysed by using coefficient of variation with confidence intervals (CI), and repeated measures ANOVA. A within subject mean coefficient of variation of 1.8% (95% CI, 1.5-2.4) was found for performance in the repeated sprint test across all six trials. The mean coefficient of variation across trials 2-4 was found to be 1.9% (95% CI, 1.3-3.1), compared to trials 4-6, where it was 1.4% (95% CI, 1.0-2.3). The ANOVA showed that a significant difference was present between the trials (F6,30 9.8. P<0.001). A Tukey post-hoc test showed that significant differences were present between trial I and trials 3-6, and trial 2 and trial 5. The learning effect was complete by trial 3. Performance in the repeated sprint test was compared to total running time averaged from two repeats of the maximal anaerobic running test laboratory protocol. Mean sprint time in the repeated sprint test and total running time in the laboratory protocol had a correlation coefficient of r = -0.298 (P = 0.516, n = 7), suggesting that the energetics of the two tests are not closely related. In conclusion, this soccer-specific field test demonstrated high reliability.

Intermittent running: muscle metabolism in the heat and effect of hypohydration.

PURPOSE: This study reports two studies that investigated the reason for a poorer intermittent supramaximal running performance previously found in the heat (Maxwell et al., The effect of climatic heat stress on intermittent supramaximal running performance in humans. Exp. Physiol. 81:833-845, 1996). The first study tested the hypothesis that it was due to different rates of substrate metabolism. The second study tested whether a greater level of hypohydration led to an earlier exhaustion time. METHODS: A maximal anaerobic running test (MART) was the exercise model used. This involved repeated 20-s runs, each at increasing intensities, with 100 s of passive recovery between runs. RESULTS: In study 1, eight male subjects performed the MART on two occasions at either 32.8+/-0.3 degrees C, 80.5+/-1.6% relative humidity (RH), or 21.3+/-0.4 degrees C, 48.8+/-2.2% RH. Needle biopsy samples were taken from the vastus lateralis muscle before and immediately after the MART. In study 2, 11 male subjects performed the MART in a moderately hypohydrated (HYPO) and euhydrated (EUH) state while in a cool environment. In study 1, performance was significantly worse in the hot compared with the cool environment (138+/-7 vs. 150+/-6 s, respectively, P<0.05). No differences were observed in the change in muscle glycogen (100.3+/-15.1 vs. 107.0+/-15.6 mmol glucosyl units x kg dry muscle(-1)) or muscle lactate (102.9+/-18.2 vs. 100.5+/-16.6 mmol x kg dry muscle(-1)) between the hot and cool environments, respectively. In study 2, performance was worse in the HYPO (148+/-9 s) compared with the EUH (154+/-9 s) trial (P<0.05). CONCLUSIONS: These results indicate that a reduced intermittent supramaximal running performance in the heat is not caused by greater muscle glycogenolysis or lactate accumulation. Further, a poorer intermittent sprinting performance is experienced in a hypohydrated compared with a euhydrated state.

The effect of climatic heat stress on intermittent supramaximal running performance in humans.

The purpose of this study was to test the hypothesis that intermittent supramaximal running would be negatively affected when performed in a hot humid environment. Twelve physically active, male volunteers took part in this study. The exercise model was performed under three environmental trial conditions, randomly assigned and separated by 1 week. This included performing: (a) a standardized warm-up in the cool environment and a repeated sprint test in the cool environment (CC); (b) a standardized warm-up in the cool environment and a repeated sprint test in a hot, humid environment (CH); and (c) a standardized warm-up in a hot, humid environment and a repeated sprint test in a hot, humid environment (HH). The repeated sprint test involved 20 s runs, each at increasing-intensity, with 100s passive recovery between successive sprints. Capillary blood samples were taken post-warm-up and at 1, 3 and 6 min post-repeated sprint test for the determination of plasma lactate, ammonia and glucose concentrations and the percentage change in plasma volume. Rectal, aural and mean skin temperature were measured continuously throughout each trial condition. Sweat loss was estimated from the change in body mass. Sweat loss was significantly greater in the HH trial than in the CH trial and in the CH trial than in the CC trial (P < 0.0001). Performance was significantly better in the CC trial than in the CH and HH trials (CC vs. CH and HH: 151 +/- 4 vs. 144 +/- 5 and 140 +/- 5 s, respectively, P = 0.02). For the post-exercise data, significant differences were found between the CC and the CH and HH trials in rectal (P = 0.007), aural (P < 0.001) and mean skin temperatures (P < 0.001). No significant differences were found in post-repeated sprint test lactate and ammonia concentrations, or in plasma volume among trial conditions, but glucose concentrations were higher in the CH and HH trials than in the CC trial (P = 0.005). No significant differences were found in performance, body temperature or any blood measurement between the CH and HH trials. Intermittent supramaximal running performance was detrimentally affected by a hot, humid environment, resulting in performance being significantly less in the CH and HH trials than in the CC trial.

Anaerobic capacity: a maximal anaerobic running test versus the maximal accumulated oxygen deficit.

The present investigation evaluates a maximal anaerobic running test (MART) against the maximal accumulated oxygen deficit (MAOD) for the determination of anaerobic capacity. Essentially, this involved comparing 18 male students performing two randomly assigned supramaximal runs to exhaustion on separate days. Post warm-up and 1, 3, and 6 min postexercise capillary blood samples were taken during both tests for plasma blood lactate (BLa) determination. In the MART only, blood ammonia (BNH3) concentration was measured, while capillary blood samples were additionally taken after every second sprint for BLa determination. Anaerobic capacity, measured as oxygen equivalents in the MART protocol, averaged 112.2 +/- 5.2 ml.kg-1.min-1. Oxygen deficit, representing the anaerobic capacity in the MAOD test, was an average of 74.6 +/- 7.3 ml.kg-1. There was a significant correlation between the MART and MAOD (r = .83, p < .001). BLa values obtained over time in the two tests showed no significant difference, nor was there any difference in the peak BLa recorded. Peak BNH3 concentration recorded was significantly increased from resting levels at exhaustion during the MART.