Effects of menthol application on the skin during prolonged immersion in cool and cold water

The aim of the study was to compare the effect of skin surface menthol application on rectal temperature (Tre) during prolonged immersion in cool and cold water. We hypothesized that menthol application would lead to a slower Tre decline due to the reduced heat loss as a consequence of the menthol‐induced vasoconstriction and that this effect would be attenuated during cold‐water immersion. Six male subjects were immersed for 55 minutes in stirred cool (24°C) or cold (14°C) water immediately after attaining a Tre of 38°C by cycling at 60% of maximum heart rate on two occasions: without (ΝM) and with (M) whole‐body skin application of menthol cream. Tre, the proximal‐distal skin temperature gradient, and oxygen uptake were continuously measured. ANOVA with repeated measures was employed to detect differences among variables. Significance level was set at 0.05. The area under the curve for Tre was calculated and was greater in 24°C M (−1.81 ± 8.22 a.u) compared to 24°C NM (−27.09 ± 19.09 a.u., P  = .03, r  = .90), 14°C NM (−18.08 ± 10.85 a.u., P  = .03, r  = .90), and 14°C M (−11.71 ± 12.58 a.u, P  = .05, r  = .81). In cool water, oxygen uptake and local vasoconstriction were increased (P  ≤ .05) by 39 ± 25% and 56 ± 37%, respectively, with menthol compared to ΝM, while no differences were observed in cold water. Menthol application on the skin before prolonged immersion reduces heat loss resulting in a blunted Tre decline. However, such a response is less obvious at 14°C water immersion, possibly because high‐threshold cold‐sensitive fibers are already maximally recruited and the majority of cold receptors saturated.     

Physical and perceptual cooling: Improving cognitive function,mood disturbance and time to fatigue in the heat

This study investigated the effects of menthol swilling and crushed ice ingestion on cognitive function, total mood disturbance (TMD), and time to fatigue (TTF). Twelve male long-distance runners completed three counterbalanced running trials (3 × 30 minutes at 65% VO_2peak and a TTF run at 100% VO_2peak) in hot, humid conditions (35.3 ± 0.3°C, 59.2 ± 2.5% relative humidity). Trials consisted of precooling with crushed ice ingestion and mid-cooling by menthol swilling (MIX), precooling with water ingestion and mid-cooling by menthol swilling (MENTH), and control (CON). Swilling with either 25 mL of menthol solution or placebo occurred upon entry to the heat, at 15-minute intervals during the run and prior to the TTF run. Core temperature, forehead skin temperature, tympanic temperature, perceived thermal sensation, and TMD were significantly lower with MIX compared with MENTH and CON (P < .05). Thirst was satiated in MIX compared with CON; however, MENTH did not have a significant effect. After 90 minutes of running and post-TTF run, fewer errors occurred in the executive control task (P < .05), as well as decision-making and working memory (P > .05; d = 0.5-0.79) between MIX and CON; however, MENTH had no effect compared with CON. The TTF run was significantly longer with MENTH (34.38%; P = .02) and MIX (39.06%; P = .001) compared with CON, with no difference between MENTH and MIX (P = .618). The physical reduction in core and internal head temperature seen with crushed ice ingestion may lead to improvements in cognitive function; however, both MENTH and MIX were sufficient for improving exercise performance.     

Post‐exercise hot water immersion induces heat acclimation and improves endurance exercise performance in the heat

We examined whether daily hot water immersion (HWI) after exercise in temperate conditions induces heat acclimation and improves endurance performance in temperate and hot conditions. Seventeen non‐heat‐acclimatized males performed a 6‐day intervention involving a daily treadmill run for 40 min at 65% V?O_2max in temperate conditions (18 °C) followed immediately by either HWI (N = 10; 40 °C) or thermoneutral (CON, N = 7; 34 °C) immersion for 40 min. Before and after the 6‐day intervention, participants performed a treadmill run for 40 min at 65% V?O_2max followed by a 5‐km treadmill time trial (TT) in temperate (18 °C, 40% humidity) and hot (33 °C, 40% humidity) conditions. HWI induced heat acclimation demonstrated by lower resting rectal temperature (T_re, mean, ?0.27 °C, P < 0.01), and final T_re during submaximal exercise in 18 °C (?0.28 °C, P < 0.01) and 33 °C (?0.36 °C, P < 0.01). Skin temperature, T_re at sweating onset and RPE were lower during submaximal exercise in 18 °C and 33 °C after 6 days in HWI (P < 0.05). Physiological strain and thermal sensation were also lower during submaximal exercise in 33 °C after 6 days in HWI (P < 0.05). HWI improved TT performance in 33 °C (4.9%, P < 0.01) but not in 18 °C. Thermoregulatory measures and performance did not change in CON. Hot water immersion after exercise on 6 days presents a simple, practical, and effective heat acclimation strategy to improve endurance performance in the heat.     

Effects of capsaicin application on the skin during resting exposure to temperate and warm conditions

We investigated thermoregulatory and cardiovascular responses at rest in a temperate (20°C) and in a warm (30°C) environment (40% RH) without and with the application of capsaicin on the skin. We hypothesized that regardless of environmental temperature, capsaicin application would stimulate heat loss and concomitantly deactivate heat conservation mechanisms, thus resulting in rectal temperature (Tre) and mean blood pressure decline due to excitation of heat‐sensitive TRPV1. Ten male subjects were exposed, while seated, for 30 minutes to 20.8 ± 1.0°C or to 30.6 ± 1.1°C: without (NCA) and with (CA) application of capsaicin patches on the skin. Thermoregulatory (Tre, proximal‐distal skin temperature gradient) and cardiovascular variables (modelflow technique) as well as oxygen uptake were continuously measured. The area under the curve for Tre decline at 20°C was smaller in CA (?2.1 ± 1.3 a.u.) than in NCA (?0.6 ± 1.1 a.u., P < 0.01, r = 0.8). Likewise, at 30°C it was smaller in CA (?2.2 ± 2.1 a.u.) compared to NCA (?0.8 ± 2.0 a.u., P = 0.02, r = 0.7). Local vasomotor tone and oxygen uptake, were significantly lower by 36.7% ± 94.2% and 12.3% ± 12.3%, respectively, with capsaicin compared to NCA (P = 0.05 and P < 0.01, respectively). Additionally, in 30°C CA mean arterial pressure was lower by 10.7% ± 5.9%, 8.9% ± 5.9%, and 10.6% ± 7.0% compared to 30°C NCA, 20°C NCA, and 20°C CA, respectively (P < 0.01, P = 0.02, and P < 0.01, respectively, d = 1.4‐1.8). In conclusion, capsaicin application on the skin induced vasodilation and Tre decline. At 30°C CA, thermal responses were accompanied by arterial hypotension most likely due to the interactive effects of both stressors (warm environment and capsaicin) on cutaneous vascular regulation.     

Running performance and thermal sensation in the heat are improved with menthol mouth rinse but not ice slurry ingestion

The purpose of this study was to compare the effects of a cooling strategy designed to predominately lower thermal state with a strategy designed to lower thermal sensation on endurance running performance and physiology in the heat. Eleven moderately trained male runners completed familiarization and three randomized, crossover 5‐km running time trials on a non‐motorized treadmill in hot conditions (33 °C). The trials included ice slurry ingestion before exercise (ICE), menthol mouth rinse during exercise (MEN), and no intervention (CON). Running performance was significantly improved with MEN (25.3 ± 3.5 min; P = 0.01), but not ICE (26.3 ± 3.2 min; P = 0.45) when compared with CON (26.0 ± 3.4 min). Rectal temperature was significantly decreased with ICE (by 0.3 ± 0.2 °C; P < 0.01), which persisted for 2 km of the run and MEN significantly decreased perceived thermal sensation (between 4 and 5 km) and ventilation (between 1 and 2 km) during the time trial. End‐exercise blood prolactin concentration was elevated with MEN compared with CON (by 25.1 ± 24.4 ng/mL; P = 0.02). The data demonstrate that a change in the perception of thermal sensation during exercise from menthol mouth rinse was associated with improved endurance running performance in the heat. Ice slurry ingestion reduced core temperature but did not decrease thermal sensation during exercise or improve running performance.     

Effects of oral rehydration and external cooling on physiology,perception, and performance in hot,dry climates

Only limited research evaluates possible benefits of combined drinking and external cooling (by pouring cold water over the body) during exercise. Therefore, this study examined cold water drinking and external cooling on physiological, perceptual, and performance variables in hot, dry environments. Ten male runners completed four trials of walking 90 min at 30% VO_2max followed by running a 5‐km time trial in 33 ± 1 °C and 30 ± 4% relative humidity. Trials examined no intervention (CON), oral rehydration (OR), external cooling (EC), and oral rehydration plus external cooling (OR + EC). Investigators measured rectal temperature, skin temperatures, heart rate, thirst, thermal sensation, and ratings of perceived exertion (RPE). Oral rehydration (OR and OR + EC) significantly lowered heart rate (P < 0.001) and thirst (P < 0.001) compared with nondrinking (CON and EC) during low‐intensity exercise. External cooling (EC and OR + EC) significantly reduced chest and thigh temperature (P < 0.001), thermal sensation (P < 0.001), and RPE (P = 0.041) compared with non‐external cooling (CON and OR) during low‐intensity exercise. Performance exhibited no differences (CON = 23.86 ± 4.57 min, OR = 22.74 ± 3.20 min, EC = 22.96 ± 3.11 min, OR + EC = 22.64 ± 3.73 min, P = 0.379). Independent of OR, pouring cold water on the body benefited skin temperature, thermal sensation, and RPE during low‐intensity exercise in hot, dry conditions but failed to influence high‐intensity performance.     

Eccentric cycling is more efficient in reducing fat mass than concentric cycling in adolescents with obesity

The benefits of eccentric (ECC) training on fat mass (FM) remain underexplored. We hypothesized that in obese adolescents, ECC cycling training is more efficient for decreasing whole‐body FM percentage compared to concentric (CON) performed at the same oxygen consumption (VO₂). Twenty‐four adolescents aged 13.4 ± 1.3 years (BMI > 90th percentile) were randomized to ECC or CON. They performed three cyclo‐ergometer sessions per week (30 min per session) for 12 weeks: two habituation, 5 at 50% VO_2peak, and 5 at 70% VO_2peak. Anthropometric measurements, body composition, maximal incremental CON tests, strength tests, and blood samples were assessed pre‐ and post‐training. Whole‐body FM percentage decreased significantly after compared to pretraining in both groups, though to a larger extent in the ECC group (ECC: ?10% vs CON: ?4.2%, P < 0.05). Whole‐body lean mass (LM) percentage increased significantly in both groups after compared to pretraining, with a greater increase in the ECC group (ECC: 3.8% vs CON: 1.5%, P <0.05). The improvements in leg FM and LM percentages were greater in the ECC group (?6.5% and 3.0%, P = 0.01 and P < 0.01). Quadriceps isometric and isokinetic ECC strength increased significantly more in the ECC group (28.3% and 21.3%, P < 0.05). Both groups showed similar significant VO_2peak improvement (ECC: 15.4% vs CON: 10.3%). The decrease in homeostasis model assessment of insulin resistance index was significant in the ECC group (?19.9%). In conclusion, although both ECC and CON cycling trainings are efficient to decrease FM, ECC induces greater FM reduction, strength gains, and insulin resistance improvements and represents an optimal modality to recommend for obese adolescents.     

Broad‐spectrum health improvements with one year of soccer training in inactive mildly hypertensive middle‐aged women

The study tested the hypothesis that long‐term soccer training has positive impact on cardiovascular profile, body composition, bone health, and physical capacity in inactive, pre‐menopausal women with mild hypertension. The study applied a randomized controlled design in which physically inactive middle‐aged women were separated into a soccer training group (n=19; SOC) and a control group (n=12; CON). SOC performed 128±29 (±SD) one‐h small‐sided soccer training sessions over one year. Blood pressure, body composition, blood lipid profile, and fitness level were determined pre‐ and post‐intervention. Over one year, mean arterial pressure decreased more in SOC than in CON (?5±7 vs +4±5 mmHg; P<.05). Total‐body fat mass decreased more (P<.05) in SOC than in CON (?2.5±2.5 vs +0.6±3.2 kg; P<.05), while the change scores for lean body mass were not significantly different in SOC (2.6±2.7 kg) compared to CON (1.1±1.9 kg, P=.09). Over one year, change scores in whole‐body bone mineral density (0.004±0.032 vs ?0.019±0.026 g·cm²) as well as bone mineral content (30±70 vs ?39±113 g) were positive in SOC compared to CON (P<.05). Post‐intervention plasma triglycerides decreased more (?0.1±0.7 vs +0.2±0.2 mmol·L^?1) and HDL cholesterol increased more (0.2±0.7 vs ?0.2±0.2 mmol·L^?1) in SOC than in CON (P<.05). Yo‐Yo intermittent endurance level 1 (122±105 vs 2±21%) and 20‐m sprint performance (6±6 vs ?1±2%) increased more (P<.05) in SOC than in CON. In conclusion, long‐term soccer training resulted in broad‐spectrum improvements in the health profile of untrained, pre‐menopausal women with mild hypertension, including cardiovascular, metabolic, and musculo‐skeletal benefits.     

Optimal cooling strategies for players in Australian Tennis Open conditions

Objectives

We compared the utility of four cooling interventions for reducing heat strain during simulated tennis match-play in an environment representative of the peak conditions possible at the Australian Open (45 °C, <10% RH, 475 W/m² solar radiation).

The determinants of thermal comfort in cool water

Water‐based activities may result in the loss of thermal comfort (TC). We hypothesized that in cooling water, the hands and feet would be responsible. Supine immersions were conducted in up to five clothing conditions (exposing various regions), as well as investigations to determine if a “reference” skin temperature (T_sk) distribution in thermoneutral air would help interpret our findings. After 10 min in 34.5 °C water, the temperature was decreased to 19.5 °C over 20 min; eight resting or exercising volunteers reported when they no longer felt comfortable and which region was responsible. TC, rectal temperature, and T_sk were measured. Rather than the extremities, the lower back and chest caused the loss of overall TC. At this point, mean (SD) chest T_sk was 3.3 (1.7) °C lower than the reference temperature (P = 0.005), and 3.8 (1.5) °C lower for the back (P = 0.002). Finger T_sk was 3.1 (2.7) °C higher than the reference temperature (P = 0.037). In cool and cooling water, hands and feet, already adapted to colder air temperatures, will not cause discomfort. Contrarily, more discomfort may arise from the chest and lower back, as these regions cool by more than normal. Thus, T_sk distribution in thermoneutral air may help understand variations in TC responses across the body.     

Including arm exercise during a cold water immersion recovery better assists restoration of sprint cycling performance

Sprint (high‐intensity) exercise performance is reduced when immediately preceded by cold water immersion (CWI). We aimed to investigate whether this performance effect could be attenuated by combining an active recovery (arm exercise) with hip‐level CWI, and whether this attenuation may be related to an effect on core temperature (T_core). Participants (n = 8) completed three Wingate tests before (Ex1) and after (Ex2) four different 30‐min recovery interventions: CWI at 15 °C (CW15), arm exercise during CWI at 15 °C (CW15+AE), arm exercise during thermoneutral immersion at 34 °C (TW34+AE) and non‐immersed arm exercise (AE). After AE and TW34+AE, performance during Ex2 was not different from Ex1; while after CW15+AE and CW15, performance was reduced by 4.9% and 7.6%, respectively. Arm exercise maintained T_core during recovery in CW15+AE, while it declined to a larger extent upon commencement of Ex2 (?0.9 °C) when compared with CW15 (?0.6 °C). This suggests similar leg muscle cooling during recovery in CW15 and CW15+AE. Without any other significant effects (e.g., on blood lactate), these data suggest that the improvement in sprint performance following an active CWI recovery, over CWI alone, may be related to maintained T_core and its effect on neurophysiological mechanisms that drive muscle activation, but not by reduced muscle cooling.     

Ingestion of sodium plus water improves cardiovascular function and performance during dehydrating cycling in the heat

We studied if salt and water ingestion alleviates the physiological strain caused by dehydrating exercise in the heat. Ten trained male cyclists ( : 60 ± 7 mL/kg/min) completed three randomized trials in a hot‐dry environment (33 °C, 30% rh, 2.5 m/s airflow). Ninety minutes before the exercise, participants ingested 10 mL of water/kg body mass either alone (CON trial) or with salt to result in concentrations of 82 or 164 mM Na⁺ (ModNa⁺ or HighNa⁺ trial, respectively). Then, participants cycled at 63% of for 120 min immediately followed by a time‐trial. After 120 min of exercise, the reduction in plasma volume was lessened with ModNa⁺ and HighNa⁺ trials (?11.9 ± 2.1 and ?9.8 ± 4.2%) in comparison with CON (?16.4 ± 3.2%; P < 0.05). However, heat accumulation or dissipation (forearm skin blood flow and sweat rate) were not improved by salt ingestion. In contrast, both salt trials maintained cardiac output (～1.3 ± 1.4 L/min; P < 0.05) and stroke volume (～10 ± 11 mL/beat; P < 0.05) above CON after 120 min of exercise. Furthermore, the salt trials equally improved time‐trial performance by 7.4% above CON (～289 ± 42 vs 269 ± 50 W, respectively; P < 0.05). Our data suggest that pre‐exercise ingestion of salt plus water maintains higher plasma volume during dehydrating exercise in the heat without thermoregulatory effects. However, it maintains cardiovascular function and improves cycling performance.     

Partial-body cryotherapy (−135°C) and cold-water immersion (10°C) after muscle damage in females

This randomized controlled trial examined the effects of cold-water immersion (CWI), partial-body cryotherapy (PBC), or a passive control (CON) on physiological and recovery variables following exercise-induced muscle damage (EIMD, 5 × 20 drop jumps) in females. Twenty-eight females were allocated to PBC (30 seconds at −60°C, 2 minutes at −135°C), CWI (10 minutes at 10°C), or CON (10 minutes resting). Muscle oxygen saturation (SmO₂), cutaneous vascular conductance (CVC), mean arterial pressure (MAP), and local skin temperature were assessed at baseline and through 60 minutes (10-minute intervals), while delayed onset of muscle soreness (DOMS), muscle swelling, maximum voluntary isometric contraction (MVIC), and vertical jump performance (VJP) were assessed up to 72 hours (24-hour intervals) following treatments. SmO₂ was lower in PBC (Δ-2.77 ± 13.08%) and CWI (Δ-5.91 ± 11.80%) compared with CON (Δ18.96 ± 1.46%) throughout the 60-minute follow-up period (P < .001). CVC was lower from PBC (92.7 ± 25.0%, 90.5 ± 23.4%) and CWI (90.3 ± 23.5%, 88.1 ± 22.9%) compared with CON (119.0 ± 5.1 and 116.1 ± 6.6%, respectively) between 20 and 30 minutes (P < .05). Mean skin temperature was lower from CWI vs PBC (between 10 and 40 minutes, P < .05). Mean skin temperature was higher in CON compared with CWI up to 60 minutes and compared with PBC up to 30 minutes (P < .05). DOMS was lower following both PBC and CWI compared with CON through 72-hour (P < .05), with no difference between groups. No main group differences for swelling, MVIC, and VJP were observed. In conclusion, CWI elicited generally greater physiological effects compared with PBC while both interventions were more effective than CON in reducing DOMS in females, but had no effect on functional measures or swelling.     

The effect of heavy strength training on muscle mass and physical performance in elite cross country skiers

Aim: To investigate the effect of supplementing high‐volume endurance training with heavy strength training on muscle adaptations and physical performance in elite cross country skiers. Eleven male (18–26 years) and eight female (18–27 years) were assigned to either a strength group (STR) (n=9) or a control group (CON) (n=10). STR performed strength training twice a week for 12 weeks in addition to their normal endurance training. STR improved 1 repetition maximum (RM) for seated pull‐down and half squat (19±2% and 12±2%, respectively), while no change was observed in CON. Cross‐sectional area (CSA) increased in m. triceps brachii for both STR and CON, while there was no change in the m. quadriceps CSA. VO_2max during skate‐rollerskiing increased in STR (7±1%), while VO_2max during running was unchanged. No change was observed in energy consumption during rollerskiing at submaximal intensities. Double‐poling performance improved more for STR than for CON. Both groups showed a similar improvement in rollerski time‐trial performance. In conclusion, 12 weeks of supplemental heavy strength training improved the strength in leg and upper body muscles, but had little effect on the muscle CSA in thigh muscles. The supplemental strength training improved both VO_2max during skate‐rollerskiing and double‐poling performance.     

Ice slurry ingestion does not enhance self‐paced intermittent exercise in the heat

This study aimed to determine if ice slurry ingestion improved self‐paced intermittent exercise in the heat. After a familiarisation session, 12 moderately trained males (30.4 ± 3.4 year, 1.8 ± 0.1 cm, 73.5 ± 14.3 kg, O_2max 58.5 ± 8.1 mL/kg/min) completed two separate 31 min self‐paced intermittent protocols on a non‐motorised treadmill in 30.9 ± 0.9 °C, 41.1 ± 4.0% RH. Thirty minutes prior to exercise, participants consumed either 7.5 g/kg ice slurry (0.1 ± 0.1 °C) (ICE) or 7.5 g/kg water (23.4 ± 0.9 °C) (CONTROL). Despite reductions in T_c (ΔT_c: ?0.51 ± 0.3 °C, P < 0.05) and thermal sensation prior to exercise, ICE did not enhance self‐paced intermittent exercise compared to CONTROL. The average speed during the walk (CONTROL: 5.90 ± 1.0 km, ICE: 5.90 ± 1.0 km), jog (CONTROL: 8.89 ± 1.7 km, ICE: 9.11 ± 1.5 km), run (CONTROL: 12.15 ± 1.7 km, ICE: 12.54 ± 1.5 km) and sprint (CONTROL: 17.32 ± 1.3 km, ICE: 17.18 ± 1.4 km) was similar between conditions (P > 0.05). Mean T_sk, T_b, blood lactate, heart rate and RPE were similar between conditions (P > 0.05). The findings suggest that lowering T_c prior to self‐paced intermittent exercise does not translate into an improved performance.     

Fatigue is mediated by cholinoceptors within the ventromedial hypothalamus independent of changes in core temperature

We investigated brain mechanisms modulating fatigue during prolonged physical exercise in cold environments. In a first set of studies, each rat was subjected to three running trials in different ambient temperatures (T_a). At 8 °C and 15 °C, core body temperature (T_core) decreased and increased, respectively, whereas at 12 °C, the T_core did not change throughout the exercise. In another set of experiments, rats were randomly assigned to receive bilateral 0.2 μL injections of 2.5 × 10^?2 M methylatropine or 0.15 M NaCl solution into the ventromedial hypothalamic nuclei (VMH). Immediately after the injections, treadmill exercise was started. Each animal was subjected to two experimental trials at one of the following T_a: 5 °C, 12 °C or 15 °C. Muscarinic blockade of the VMH reduced the time to fatigue (TF) in cold environments by 35–37%. In all T_a studied, methylatropine‐treated rats did not present alterations in T_core and tail skin temperature compared with controls. These results indicate that, below the zone of thermoneutrality, muscarinic blockade of the VMH decreases the TF, independent of changes in T_core. In conclusion, our data suggest that VMH muscarinic transmission modulates physical performance, even when the effects of thermoregulatory adjustments on fatigue are minimal.     

The Estimation of Local Brain Temperature by in Vivo 1H Magnetic Resonance Spectroscopy

Brain temperature may be important for investigating pathology and cerebroprotective effects of pharmaceuticals and hypothermia. Two methods for estimating temperature using ¹H magnetic resonance spectroscopy are described: a partially water-suppressed binomial sequence and non-water-suppressed point-resolved spectroscopy. Relative to N-acetylaspartate (Naa), water chemical shift (θ_H2O-Naa) in piglet brain depended linearly on temperature from 30° to 40°C: temperature was 286.9–94.0 θ_H2O-Naa ° C. Thalamic temperature in six normal infants was 38.1° ± 0.4° C indicating that local brain temperature could be estimated with adequate sensitivity for studying pathologic and therapeutic changes.     

Cardiorespiratory fitness in aging men and women: the DR's EXTRA study

The aim of the study was to describe the levels and to create reference values of cardiorespiratory fitness, expressed as maximal oxygen consumption (VO_2max), maximal metabolic equivalents (METs) and maximal workload in aging men and women. We measured VO_2max directly by a breath‐by‐breath method during a maximal exercise stress test on a bicycle ergometer with a linear workload increase of 20 W/min in a representative population sample of 672 men and 677 women aged 57–78 years. We presented the age and sex‐specific categories of cardiorespiratory fitness (very low, low, medium, high and very high) based on variable distribution and non‐linear regression models of VO_2max, maximal METs and maximal workload. The linear age‐related decrement of VO_2max was ?0.047 L/min/year (?2.3%) and ?0.404 mL/kg/min/year (?1.6%) in men and ?0.027 L/min/year (?1.9%) and ?0.328 mL/kg/min/year (?1.6%) in women. After exclusion of diseased individuals, the rate of VO_2max decrement remained similar. The number of chronic diseases (0, 1, 2 or ≥3) was inversely associated with VO_2max in men (P<0.001) and women (P<0.001). The present study provides clinically useful reference values of cardiorespiratory fitness for primary and secondary prevention purposes in aging people.     

Effect of MRI strength and propofol sedation on pediatric core temperature change

Purpose:

To determine core body temperature variations in children undergoing MRI exams on 1.5 Tesla (T) and 3T magnetic field strengths and with and without propofol sedation.

Materials and Methods:

Temporal artery temperatures were prospectively collected on 400 consecutive patients undergoing 1.5 Tesla (T) or 3.0T MRI scans. A cumulative logistic regression model was created using age, weight, MRI protocol, sedation status, pre‐MRI temperature and MRI strength to assess risk of temperature change.

Results:

For patients with complete pre‐ and post‐MRI temperature data, mean temperatures did not significantly change (?0.0155°C, 95%CI, ?0.035, 0.064; n = 385). Temperature changes differed significantly between propofol‐sedated and nonsedated patients (?0.26°C ± .44 versus 0.24°C ± 0.42; P < 0.0001), as did temperature changes for patients on the 3T (0.076°C ± 0.52) versus 1.5T (?0.06°C ± 0.48; P = 0.011). Sedation status, age, MRI strength, and MRI protocol accounted for 44.17% of temperature variance. The temperatures of 15 patients' (3.9%) decreased >1°C; 12 were on the 1.5T. All 7 patients (1.8%) who increased >1°C were non‐sedates.

Conclusion:

Clinically significant core body temperature change is uncommon in children undergoing MRI with different magnetic field strengths, and with and without propofol sedation. J. Magn. Reson. Imaging 2011;33:950–956. © 2011 Wiley‐Liss, Inc.

     

Rapid body mass loss affects erythropoiesis and hemolysis but does not impair aerobic performance in combat athletes

Rapid body mass loss (RBML) before competition was found to decrease hemoglobin mass (Hb_mass) in elite boxers. This study aimed to investigate the underlying mechanisms of this observation. Fourteen well‐trained combat athletes who reduced body mass before competitions (weight loss group, WLG) and 14 combat athletes who did not practice RBML (control group, CON) were tested during an ordinary training period (t‐1), 1–2 days before an official competition (after 5–7 days RBML in WLG, t‐2), and after a post‐competition period (t‐3). In WLG, body mass (?5.5%, range: 2.9–6.8 kg) and Hb_mass (?4.1%) were significantly (P < 0.001) reduced after RBML and were still decreased by 1.6% (P < 0.05) and 2.6% (P < 0.001) at t‐3 compared with t‐1. After RBML, erythropoietin, reticulocytes, haptoglobin, triiodothyronine (FT₃), and free androgen index (FAI) were decreased compared with t‐1 and t‐3. An increase occurred in ferritin and bilirubin. Peak treadmill‐running performance and VO_2peak did not change significantly, but performance at 4‐mmol lactate threshold was higher after RBML (P < 0.05). In CON, no significant changes were found in any parameter. Apparently, the significant decrease in Hb_mass after RBML in combat athletes was caused by impaired erythropoiesis and increased hemolysis without significant impact on aerobic performance capacity.