Effect of electric fan use in isolation or combined with ice slurry/cold water ingestion and lower-leg immersion in young men during intermittent physical activity in hot-humid conditions

Using a randomized crossover protocol, 10 young men completed four 180 min exposures (38 °C, 60% relative humidity), alternating between 30 min of walking and 30 min of sitting where fluid or ice slurry were served. Participants underwent four trials: (i) 5 mL·kg body mass-1 of 20 °C water (CON); (ii) 5 mL·kg body mass-1 of 20 °C water + fan at 4 m·s-1 (FAN); (iii) fan + 3 mL·kg body mass-1 of ice slurry + 2 mL·kg body mass-1 of 4 °C water (FAN + ISCW); and (iv) FAN + ISCW + lower-leg immersion in 20 °C water (FAN + ISCW + LLI). Sweat and body mass losses were higher with FAN than CON, FAN + ISCW, and FAN + ISCW + LLI. Mean and peak changes in Δrectal temperature, heart rate, and perceived heat and thirst from baseline were not statistically and practically different between FAN and CON. FAN + ISCW + LLI decreased sweat loss compared with FAN + ISCW and mean and peak changes in Δrectal temperature, heart rate, and perceived thirst compared with CON. FAN + ISCW + LLI also attenuated the changes in Δrectal temperature (peak) and thirst (mean and peak) compared with FAN. In conclusion, FAN slightly exacerbates fluid loss but does not attenuate the changes in Δrectal temperature, heart rate, and perceived heat and thirst during intermittent physical activity in hot-humid conditions. However, coupling ISCW or ISCW + LLI with the use of a fan attenuates the increase in these outcomes compared with no intervention and to a greater extent for rectal temperature and thirst when fan is coupled with ISCW + LLI than when it is used in isolation.

Repeatability of Ad Libitum Water Intake during Repeated 1 h Walking/Jogging Exercise Sessions Conducted under Hot Ambient Conditions

A drinking strategy aiming to replace a given percentage of the sweat losses incurred during exercise should result in reproducible fluid intake volume and, hence, fluid balance from one exercise session to the other performed under similar scenarios. Whether this may also be the case with ad libitum drinking during exercise is unclear. We characterized the repeatability of ad libitum water intake during repeated 1 h exercise sessions and examined its effect over time on fluid balance and selected physiological functions and perceptual sensations. Twelve (3 women) healthy individuals participated in this study. At weekly intervals, they completed four 2 × 30 min walking/jogging exercise bouts (55% V˙O2max, 40 °C, 20-30% relative humidity) interspersed by a 3 min recovery period. During exercise, participants consumed water (20 °C) ad libitum. There were no significant differences among the four exercise sessions for absolute water intake volume (~1000 mL·h-1), percent body mass loss (~0.4%), sweat rate (~1300 mL·h-1) and percent of sweat loss replaced by water intake (~80%). Heart rate, rectal temperature, and perceived thirst and heat stress did not differ significantly between the first and fourth exercise sessions. Perceived exertion was significantly lower during the fourth vs. the first exercise session, but the difference was trivial (<1 arbitrary unit). In conclusion, ad libitum water intake during four successive identical 1 h walking/jogging sessions conducted in the heat will result in similar water intake volumes and perturbations in fluid balance, heart rate, rectal temperature, and perceived thirst, heat stress and exertion.

CORE™ wearable sensor: Comparison against gastrointestinal temperature during cold water ingestion and a 5 km running time-trial

Five km running time-trials (TT) are associated with rapid and significant increases in core body temperature (T_C). For such races, real-time feedback from pre-exercise and exercise T_C may be helpful in the design of an optimal pacing strategy aimed at limiting the possibility of developing heat-related illnesses. This study compared measurements of T_C obtained with a wearable device, the CORE™, to those of a gastrointestinal pill (GI pill), during cold water ingestion and a 5 km running TT. Twelve participants (25 ± 4 yrs) ingested 7.5 mL/kg fat-free mass of 4 °C water over the first 5 min of a 120 min sitting period, after which they completed a 5 km running TT at 30 °C, 50% relative humidity. A T_C difference > ± 0.25 °C between sensors was deemed clinically unacceptable. Prior to water ingestion, the CORE-derived T_C was 0.49 ± 0.25 °C lower than the GI pill. The CORE was irresponsive to the 0.26 ± 0.22 °C peak decline in T_C captured with the GI pill 40 min following water ingestion. Prior to the TT, T_C was 0.30 ± 0.25 °C lower with the CORE than the GI pill. During the TT, the CORE underestimated the rate of increase in T_C by 0.0125 ± 0.019 °C/min compared with the GI pill, and mean absolute difference in T_C between sensors was of 0.47 ± 0.34 °C. In conclusion, the CORE does not capture the cooling effect of cold water ingestion and provides a clinically relevant underestimation of T_C during a 5 km running TT in the heat.

Effect of Pre-Exercise Caffeine Intake on Endurance Performance and Core Temperature Regulation During Exercise in the Heat: A Systematic Review with Meta-Analysis

BACKGROUND

Heat is associated with physiological strain and endurance performance (EP) impairments. Studies have investigated the impact of caffeine intake upon EP and core temperature (C_T) in the heat, but results are conflicting. There is a need to systematically determine the impact of pre-exercise caffeine intake in the heat.

OBJECTIVE

To use a meta-analytical approach to determine the effect of pre-exercise caffeine intake on EP and C_T in the heat.

DESIGN

Systematic review with meta-analysis.

DATA SOURCES

Four databases and cross-referencing.

DATA ANALYSIS

Weighted mean effect summaries using robust variance random-effects models for EP and C_T, as well as robust variance meta-regressions to explore confounders.

STUDY SELECTION

Placebo-controlled, randomized studies in adults (≥ 18 years old) with caffeine intake at least 30 min before endurance exercise ≥ 30 min, performed in ambient conditions ≥ 27 °C.

RESULTS

Respectively six and 12 studies examined caffeine's impact on EP and C_T, representing 52 and 205 endurance-trained individuals. On average, 6 mg/kg body mass of caffeine were taken 1 h before exercises of ~ 70 min conducted at 34 °C and 47% relative humidity. Caffeine supplementation non-significantly improved EP by 2.1 ± 0.8% (95% CI - 0.7 to 4.8) and significantly increased the rate of change in C_T by 0.10 ± 0.03 °C/h (95% CI 0.02 to 0.19), compared with the ingestion of a placebo.

CONCLUSION

Caffeine ingestion of 6 mg/kg body mass ~ 1 h before exercise in the heat may provide a worthwhile improvement in EP, is unlikely to be deleterious to EP, and trivially increases the rate of change in C_T.

Programmed vs. Thirst-Driven Drinking during Prolonged Cycling in a Warm Environment

We compared the effect of programmed (PFI) and thirst-driven (TDFI) fluid intake on prolonged cycling performance and exercise associated muscle cramps (EAMC). Eight male endurance athletes (26 ± 6 years) completed two trials consisting of 5 h of cycling at 61% V˙O2peak followed by a 20 km time-trial (TT) in a randomized crossover sequence at 30 °C, 35% relative humidity. EAMC was assessed after the TT with maximal voluntary isometric contractions of the shortened right plantar flexors. Water intake was either programmed to limit body mass loss to 1% (PFI) or consumed based on perceived thirst (TDFI). Body mass loss reached 1.5 ± 1.0% for PFI and 2.5 ± 0.9% for TDFI (p = 0.10). Power output during the 20 km TT was higher (p < 0.05) for PFI (278 ± 41 W) than TDFI (263 ± 39 W), but the total performance time, including the breaks to urinate, was similar (p = 0.48) between conditions. The prevalence of EAMC of the plantar flexors was similar between the drinking conditions. Cyclists competing in the heat for over 5 h may benefit from PFI aiming to limit body mass loss to <2% when a high intensity effort is required in the later phase of the race and when time lost for urination is not a consideration.

Impact of Repeated Acute Exposures to Low and Moderate Exercise-Induced Hypohydration on Physiological and Subjective Responses and Endurance Performance

This study aimed to examine whether repeated exposures to low (2%) and moderate (4%) exercise-induced hypohydration may reverse the potentially deleterious effect of hypohydration on endurance performance. Using a randomized crossover protocol, ten volunteers (23 years, V˙O_2max: 54 mL∙kg^-1∙min^-1) completed two 4-week training blocks interspersed by a 5-week washout period. During one block, participants replaced all fluid losses (EUH) while in the other they were fluid restricted (DEH). Participants completed three exercise sessions per week (walking/running, 55% V˙O_2max, 40 °C): (1) 1 h while fluid restricted or drinking ad libitum, (2) until 2 and (3) 4% of body mass has been lost or replaced. During the first and the fourth week of each training block, participants completed a 12 min time-trial immediately after 2% and 4% body mass loss has been reached. Exercise duration and distance completed (14.1 ± 2.7 vs. 6.9 ± 1.5 km) during the fixed-intensity exercise bouts were greater in the 4 compared to the 2% condition (p < 0.01) with no difference between DEH and EUH. During the first week, heart rate, rectal temperature and perceived exertion were higher (p < 0.05) with DEH than EUH, and training did not change these outcomes. Exercise-induced hypohydration of 2% and 4% body mass impaired time-trial performance in a practical manner both at the start and end of the training block. In conclusion, exercise-induced hypohydration of 2% and 4% body mass impairs 12 min walking/running time-trial, and repeated exposures to these hypohydration levels cannot reverse the impairment in performance.

Validity and Reliability of the Computrainer Lab™ During Simulated 40 and 100 km Time-Trials

The validity and reliability of the Computrainer Lab^™ (CT) was assessed, for the first time, using a high-precision motor-driven calibration rig during simulated variable intensity 40 and 100 km time-trials (TTs). The load patterns imposed by the CT were designed from previously published studies in trained cyclists and included multiple 1 or 4 km bursts in power output. For the 40 and 100 km TTs, cluster-based analyses revealed a mean measurement error from the true workload of respectively 0.7 and 0.9%. However, measurement errors were dependent upon the workload variations, fluctuating from 0.2 to 5.1%. Average biases between repeated trials were contained within ± 1.1% for both TTs. In conclusion, using 40 and 100 km TTs containing 1 or 4 km bursts in power output, the present results indicate that (1) the CT can reliably be used by scientists to determine differences between research interventions; (2) the CT provides valid results of power output when data are being analyzed as a whole to derive one mean value of power output and; (3) variations in workload make it difficult to determine at any one time the veracity of the true power output produced by the athlete.

Provision of instructions to drink ad libitum or according to thirst sensation: impact during 120 km of cycling in the heat in men

The terms drinking to thirst and ad libitum drinking are used interchangeably, but should they? We investigated the differences in how athletes consumed fluids during exercise when instructed to drink according to thirst or ad libitum. Using a randomized, crossover, and counterbalanced design, 10 males (27 ± 4 y) cycled 120 km (48 ± 4% of peak power, 33 °C, 40% relative humidity) on 2 occasions, while drinking water according to thirst or ad libitum. Participants covered the cycling trials in 222 ± 11 min (p = 0.29). Although the body mass loss at the end of exercise and total volume of water consumed were similar between trials, thirst perception before each sip and the volume consumed per sip were significantly higher with thirst than ad libitum drinking, whereas the total number of sips was significantly lower with thirst than ad libitum drinking. Perceived exertion, rectal temperature, and heart rate were all significantly higher with thirst than ad libitum drinking, but the difference was trivial. In conclusion, thirst and ad libitum drinking are associated with different drinking patterns, but equally maintain fluid balance during prolonged exercise. The terms drinking to thirst and ad libitum drinking can be used interchangeably to guide fluid intake during prolonged exercise. Novelty: Both strategies are associated with different patterns of fluid ingestion during prolonged exercise, but are equally effective in maintaining fluid balance. Perceived exertion, rectal temperature, and heart rate are regulated dissimilarly by thirst and ad libitum drinking, but the difference is trivial.

Validity and Reliability of the CorTempTM Telemetric Pill during 50 h of Reuse in a Circulating Water Bath

It has been shown that CorTemp^TM telemetric pills (CTTPs) provide valid measures of rectal temperature when used as suppositories. While encapsulated into a condom linked to a thread, CTTPs can be inserted in and extracted from the rectum and be reused. The validity and reliability of the CTTP throughout repeated use remains to be demonstrated. Three CTTPs were compared to a YSI 401 wired rectal probe inside a circulating water bath (temperatures varying from 36.5 to 39.4 °C) during 50 h of intermittent use. Each CTTP underwent 20 trials comprising 6 protocols of varying duration: 6 · 1 h, 5 · 2 h, 4 · 3 h, 3 · 4 h and 2 · 5 h. All CTTPs were washed, switched off and disinfected after each trial to reproduce real-life use. Acceptable agreement between sensors was taken as a mean bias within ±0.27 °C. None of the pills showed signs of deterioration following 50 h of reuse. As for relative validity, where all CTTPs showed robust coefficients of determination ranging from 0.98 to 0.99, absolute validity was excellent with each CTTP showing mean biases and typical errors of the estimate (TEE) within ±0.27 °C. Comparisons between the first and last trial each CTTP underwent resulted in means biases and TEEs within ±0.27 °C and coefficients of determination ranging from 0.97 to 0.99, which indicates strong absolute and relative reliability. The present results show that CTTPs can provide valid and reliable measurements of temperature when reused up to 50 h.

Permanent tattooing has no impact on local sweat rate, sweat sodium concentration and skin temperature or prediction of whole-body sweat sodium concentration during moderate-intensity cycling in a warm environment

PURPOSES

This study investigated the impact of permanently tattooed skin on local sweat rate, sweat sodium concentration and skin temperature and determined whether tattoos alter the relationship between local and whole-body sweat sodium concentration.

METHODS

Thirteen tattooed men (27 ± 6 years) completed a 1 h (66 ± 4% of [Formula: see text]) cycling trial at 32 °C, 35% relative humidity. Sweat rate and sweat sodium concentration were measured using the whole-body washdown and local absorbent patch techniques. Patches and skin-temperature probes were applied over the right/left thighs and tattooed/non-tattooed (contralateral) regions.

RESULTS

Local sweat rates did not differ (p > 0.05) between the right (1.11 ± 0.38) and left (1.21 ± 0.37) thighs and the permanently tattooed (1.93 ± 0.82) and non-tattooed (1.72 ± 0.81 mg cm^-2 min^-1) regions. There were no differences in local sweat sodium concentration between the right (58.2 ± 19.4) and left (55.4 ± 20.3) thighs and the permanently tattooed (73.0 ± 22.9) and non-tattooed (70.2 ± 18.9 mmol L^-1) regions. Difference in local skin temperature between the right and left thighs (- 0.043) was similar to that between the permanently tattooed and non-tattooed (- 0.023 °C) regions. Prediction of whole-body sweat sodium concentration for the permanently tattooed (41.0 ± 6.7) and the non-tattooed (40.2 ± 5.3 mmol L^-1) regions did not differ.

CONCLUSION

Permanent tattoos do not alter local sweat rate, sweat sodium concentration or local skin temperature during moderate-intensity cycling exercise in a warm environment. Results from a patch placed over a tattooed surface correctly predicts whole-body sweat sodium concentration from an equation developed from a non-tattooed region.

Impact of Mild Hypohydration on Muscle Endurance, Power, and Strength in Healthy, Active Older Men

Goulet, EDB, Mélançon, MO, Lafrenière, D, Paquin, J, Maltais, M, and Morais, JA. Impact of mild hypohydration on muscle endurance, power, and strength in healthy, active older men. J Strength Cond Res 32(12): 3414-3424, 2018-Under particular circumstances older persons may be vulnerable to developing mild chronic hypohydration. In young adults, hypohydration has been shown to impair muscle endurance, power and strength. Muscle performance declines with aging, a condition known as dynapenia. How hypohydration impacts muscle performance in older persons remains unclear. In this study, we examined this question, believing it may identify a factor exacerbating dynapenia. One-hour after having been passively exposed to heat where either a body mass loss of 1% was induced or euhydration maintained with fluid ingestion, 8 healthy, active older men (age: 68 ± 5 years) completed an exercise testing session where indices of muscle strength (30-second chair stand, grip strength, maximal isometric seated leg-press extension), endurance (seated leg-curl flexion + seated leg-press extension to exhaustion at 60% of 1 repetition maximum), and power (30-second Wingate test) were assessed. Gastrointestinal temperature before exercise testing was not significantly different from that measured before heat exposure with neither hydration regimen. Magnitude-based inferential statistics indicate that from a clinical perspective, the effect of hypohydration on 30-second chair stand (-1.0 ± 4.4%) is possibly harmful, for grip strength (-2.4 ± 4.1%), lower limbs endurance (-7.5 ± 11.2%), and anaerobic power (-3.9 ± 4.3%) likely detrimental, and unclear with respect to maximal isometric lower limb strength. Maintaining adequate hydration in older men is important, since hypohydration of only 1% body mass could impede muscle endurance, power and strength and, consequently, worsen the impact of dynapenia.

Considerations in the Use of Body Mass Change to Estimate Change in Hydration Status During a 161-Kilometer Ultramarathon Running Competition

Hydration guidelines found in the scientific and popular literature typically advise that body mass losses beyond 2% should be avoided during exercise. In this work, we demonstrate that these guidelines are not applicable to prolonged exercise of several hours where body mass loss does not reflect an equivalent loss of body water due to the effects of body mass change from substrate use, release of water bound with muscle and liver glycogen, and production of water during substrate metabolism. These effects on the body mass loss required to maintain body water balance are shown for a 161-km mountain ultramarathon running competition participant utilizing published data for the total energy cost, exogenous energy consumption and percentage from each fuel source, average participant body mass, and the extent of soft tissue fluid accumulation during an ultramarathon. We assumed that total energy derived from protein ranges from 5 to 10%, all exogenous energy is used to support the energy cost of the race, glycogen utilization ranges from 300 to 500 g, water linked with glycogen ranges from 1 to 3 g per g of glycogen, and the mass of the bladder and gastrointestinal tract is unchanged from pre-race to post-race body mass measurements. These calculations show that the average participant of 68.8 kg must lose 1.9-5.0% body mass to maintain the water supporting body water balance while also avoiding overhydration. Future hydration guidelines should consider these findings so that the proper hydration message is conveyed to those who participate in prolonged exercise.

Correction to: Considerations in the Use of Body Mass Change to Estimate Change in Hydration Status During a 161-Kilometer Ultramarathon Running Competition

In Table 2 of the original publication, an error was made in the calculations for endogenous substrate oxidation which, subsequently, altered the values for total change in body mass.

Measurement of sodium concentration in sweat samples: comparison of 5 analytical techniques

Sweat sodium concentration (SSC) can be determined using different analytical techniques (ATs), which may have implications for athletes and scientists. This study compared the SSC measured with 5 ATs: ion chromatography (IChr), flame photometry (FP), direct (DISE) and indirect (IISE) ion-selective electrode, and ion conductivity (IC). Seventy sweat samples collected from 14 athletes were analyzed with 5 instruments: the 883 Basic IC Plus (IChr, reference instrument), AAnalyst 200 (FP), Cobas 6000 (IISE), Sweat-Chek (IC), and B-722 Laqua Twin (DISE). Instruments showed excellent relative (intraclass correlation coefficient (ICC) ≥ 0.999) and absolute (coefficient of variation (CV) ≤ 2.6%) reliability. Relative validity was also excellent between ATs (ICC ≥ 0.961). In regards to the inter-AT absolute validity, compared with IChr, standard error of the estimates were similar among ATs (2.8-3.8 mmol/L), but CV was lowest with DISE (3.9%), intermediate with IISE (7.6%), and FP (6.9%) and highest with IC (12.3%). In conclusion, SSC varies depending on the AT used to analyze samples. Therefore, results obtained from different ATs are scarcely comparable and should not be used interchangeably. Nevertheless, taking into account the normal variability in SSC (∼±12%), the imprecision of the recommendations deriving from FP, IISE, IC, and DISE should have trivial health and physiological consequences under most exercise circumstances.

Comparison of Sodium Chloride Tablets-Induced, Sodium Chloride Solution-Induced, and Glycerol-Induced Hyperhydration on Fluid Balance Responses in Healthy Men

Savoie, FA, Asselin, A, and Goulet, EDB. Comparison of sodium chloride tablets-induced, sodium chloride solution-induced, and glycerol-induced hyperhydration on fluid balance responses in healthy men. J Strength Cond Res 30(10): 2880-2891, 2016-Sodium chloride solution-induced hyperhydration (NaCl-SolIH) is a powerful strategy to increase body water before exercise. However, NaCl-SolIH is associated with an unpleasant salty taste, potentially dissuading some athletes from using it and coaches from recommending it. Therefore, we evaluated the hyperhydrating potential of sodium chloride tablets-induced hyperhydration (NaCl-TabIH), which bypasses the palatability issue of NaCl-SolIH without sacrificing sodium chloride content, and compared it to NaCl-SolIH and glycerol-induced hyperhydration (GIH). Sixteen healthy males (age: 21 ± 2 years; fat-free mass (FFM): 65 ± 6 kg) underwent three, 3-hour long passive hyperhydration protocols during which they drank, over the first 60 minutes, 30-ml·kg FFM of an artificially sweetened solution. During NaCl-TabIH, participants swallowed 7.5, 1 g each, sodium chloride tablets with every liter of solution. During NaCl-SolIH, an equal quantity of sodium chloride tablets was dissolved in each liter of solution. With GIH, the glycerol concentration was 46.7 g·L. Urine production, fluid retention, hemoglobin, hematocrit, plasma volume, and perceptual variables were monitored throughout the trials. Total fluid intake was 1948 ± 182 ml. After 3 hour, there were no significant differences among treatments for hemoglobin, hematocrit, and plasma volume changes. Fluid retention was significantly greater with NaCl-SolIH (1150 ± 287 ml) than NaCl-TabIH (905 ± 340 ml) or GIH (800 ± 211 ml), with no difference between NaCl-TabIH and GIH. No differences were found among treatments for perceptual variables. NaCl-TabIH and GIH are equally effective, but inferior than NaCl-SolIH. NaCl-TabIH represents an alternative to hyperhydration induced with glycerol, which is prohibited by the World Anti-Doping Agency.

Reliability and validity of a low cost, pocket-sized and battery operated sodium analyzer in measuring urinary sodium concentration

BACKGROUND

The 24-h urine collection technique is the reference method for assessing sodium intake. Frequent assessments of urinary sodium excretion improve patients' motivation in adhering to sodium-restricted diets. No portable, inexpensive, user-friendly and reliable sodium analyzers are available on the market. Allowing field practitioners access to such an instrument could facilitate patients' monitoring of urinary sodium output, potentially improving patients care and overall population health.

OBJECTIVE

To determine the validity and intra- and inter-instruments reliability of two portable, easy-to-use and inexpensive sodium analyzers.

METHODS

Urine samples (N= 77) were collected from 31 men and compared against reference values of an ion chromatograph.

RESULTS

Both analyzers demonstrated excellent absolute (95% limits of agreement (LoA) of ± 3-4%) and relative intra-instrument reliability (intraclass correlation coefficients (ICC) of 1.00). Inter-instruments relative reliability was excellent (ICC: 0.99), whereas absolute reliability was good (95% LoA of ± 13%). Compared with results obtained by ion chromatography, relative validity was excellent for both analyzers. Absolute validity was good-to-moderate (95% LoAs ranging from ± 15% to ± 20%).

CONCLUSIONS

A low cost, portable analyzer can reliably be used by field practitioners to monitor changes in urinary sodium excretion across time and provide adequate guidance for individuals on sodium-restricted diets.

Validity and reliability of the Horiba C-122 compact sodium analyzer in sweat samples of athletes

Accurate sodium replacement during prolonged exercise is possible when sweat rate and sweat sodium content are directly measured. Few athletes have access to sweat sodium content measurement, as the equipment needed to perform such analyzes is costly, laboratory-based or requires technical skills. Using 70 sweat samples collected in 24 athletes from 3 anatomical sites, this study determined the reliability [single-trial and inter-day (7 samples over 3 days)] and validity (instrument error) of a pocket-sized, easy-to-use and low cost sodium analyzer (Horiba C-122, Kyoto, Japan) against reference values of an ion chromatograph, the 883 Basic IC plus (Metrohm AG, Herisau, Switzerland). The Horiba C-122 showed high single-trial reliability with an intraclass correlation coefficient (ICC) of 0.997, a typical error of measurement (EM) of 1.77 mmol/L and a coefficient of variation (CV) of 3.73%. As expected, the reliability of the 883 Basic IC plus was superior to that of the Horiba C-122 (ICC: 0.999; typical EM: 0.70 mmol/L; CV: 1.52%). The Horiba’s C-122 inter-day reliability was high (ICC: 1.00; typical EM: 0.35 mmol/L). An ICC of 0.975 indicates there was a strong relationship between results provided by both analyzers. Compared with reference values, the Horiba C-122 demonstrated a mean bias of 1.71 mmol/L, a pure EM of 7.52 mmol/L and 68% limits of agreement ranging from -5.81 to 9.23 mmol/L. We propose that the Horiba C-122 is sufficiently reliable to be used under field conditions where some degree of imprecision is acceptable, but not for research purposes where high accuracy is required.

Pre-exercise hyperhydration-induced bodyweight gain does not alter prolonged treadmill running time-trial performance in warm ambient conditions

This study compared the effect of pre-exercise hyperhydration (PEH) and pre-exercise euhydration (PEE) upon treadmill running time-trial (TT) performance in the heat. Six highly trained runners or triathletes underwent two 18 km TT runs (~28 °C, 25%–30% RH) on a motorized treadmill, in a randomized, crossover fashion, while being euhydrated or after hyperhydration with 26 mL/kg bodyweight (BW) of a 130 mmol/L sodium solution. Subjects then ran four successive 4.5 km blocks alternating between 2.5 km at 1% and 2 km at 6% gradient, while drinking a total of 7 mL/kg BW of a 6% sports drink solution (Gatorade, USA). PEH increased BW by 1.00 ± 0.34 kg (P < 0.01) and, compared with PEE, reduced BW loss from 3.1% ± 0.3% (EUH) to 1.4% ± 0.4% (HYP) (P < 0.01) during exercise. Running TT time did not differ between groups (PEH: 85.6 ± 11.6 min; PEE: 85.3 ± 9.6 min, P = 0.82). Heart rate (5 ± 1 beats/min) and rectal (0.3 ± 0.1 °C) and body (0.2 ± 0.1 °C) temperatures of PEE were higher than those of PEH (P < 0.05). There was no significant difference in abdominal discomfort and perceived exertion or heat stress between groups. Our results suggest that pre-exercise sodium-induced hyperhydration of a magnitude of 1 L does not alter 80–90 min running TT performance under warm conditions in highly-trained runners drinking ~500 mL sports drink during exercise.

Glycerol-induced hyperhydration: a method for estimating the optimal load of fluid to be ingested before exercise to maximize endurance performance

Glycerol-induced hyperhydration (GIH) has been shown to increase endurance performance (EP). However, EP starts declining at a dehydration level >2% body weight (BW). It thus appears that the use of GIH is only required when athletes anticipate that their fluid intake during exercise would not be sufficient to prevent a loss of BW >2%. In such a scenario, the optimal GIH load to be ingested before exercise would correspond to the amount of fluid that cannot be drunk during exercise and that would be just sufficient to keep the dehydration level <2% BW. No method exists enabling the estimation of the most optimal GIH load to be drunk before exercise to optimize EP. Here, such a method comprising 3 easy steps is presented. Step 1 provides a formula allowing users to determine relative exercise-induced dehydration level based on individual BW, exercise time, and estimated hourly sweat rate and fluid consumption during exercise. Step 2 takes into account the result of step 1 and provides a formula allowing determination of the minimal GIH load required before exercise to prevent a loss of BW >2%. Step 3 consists of identifying, among those pre-selected, a GIH protocol that increases body water by at least the amount computed in step 2. This method will remove much of the guess work involved in the decision-making process of the optimal amount of GIH that should be ingested before exercise by athletes for maximizing EP and will serve as a practical reference tool for all athletes using, and coaches, practitioners, and exercise physiologists recommending the utilization of, GIH as an ergogenic aid.

Frailty in the elderly is associated with insulin resistance of glucose metabolism in the postabsorptive state only in the presence of increased abdominal fat

Whether frail elderly subjects are more insulin resistant (IR) than non-frail is unclear. How obesity, muscle mass, inflammation, hormonal and lipid status, oxidative stress, antioxidant capacity and physical activity influences insulin sensitivity (IS) in frail elderly subjects remains uncertain. We determined (1) whether frail elderly persons are more IR than non-frail elderly and (2) the influence of abdominal fat mass (AFM), muscle mass index (MMI), inflammation (CRP), hormonal (cortisol, free IGF-1, DHEA) and lipid (FFA, triglyceride (TG)) status, oxidative stress (paraoxonase-1 (PON-1), malondialdehyde (MDA)), antioxidant capacity (vitamin C, E) and physical activity (PASE questionnaire) on IS (QUICKI) in 16 frail obese (FO), 17 frail lean (FL) and 21 healthy, non-obese (HN) elderly subjects. IS was lower in FO than FL, but there was no significant difference between HN and FO or FL. There were no significant differences among groups for CRP, cortisol, IGF-1, DHEA, FFA, TG, PON-1, MDA, vitamin C and E and PASE. Age, AFM and MMI significantly correlated with IS. Only AFM and MMI were significant predictors explaining, respectively, 18.5% and 8.5% of the variance in IS. Increased abdominal obesity is associated with IR in frail elderly. Non-obese frail persons are not more IR than their healthy counterparts.

No difference in insulin sensitivity between healthy postmenopausal women with or without sarcopenia: a pilot study

Insulin plays a pivotal role in skeletal muscle protein metabolism and its action decreases with age. A loss of muscle mass, termed sarcopenia, also occurs with age. The age-associated decline in insulin sensitivity (IS) may negatively alter muscle protein metabolism and, therefore, be implicated in the aetiology of sarcopenia. However, no studies have yet compared the level of IS between older individuals with or without sarcopenia. Thus, in this study, we compared the IS of 20 class I sarcopenics (CIS), 8 class II sarcopeniscs (CIIS), and 16 non-sarcopenics (NS), among a group of otherwise healthy, non-obese, postmenopausal women. IS was estimated with the quantitative IS check index (QUICKI). Muscle mass index (MMI), which was used to determine sarcopenia, was calculated as follows: (appendicular muscle massx1.19)-1.01/h2, where h=height. Fat-free mass (FFM), fat mass (FM), and trunk FM (TFM) were measured by dual-energy X-ray absorptiometry. Accelerometry and indirect calorimetry were used to estimate resting (REE), daily (DEE), and physical activity (PAEE) energy expenditure. A 3 d food record was used to determine total energy, protein (animal and vegetal), and carbohydrate intakes. As expected, MMI and FFM differed significantly among groups. However, no significant differences were found among groups for IS, FM, TFM, REE, DEE, PAEE, or total energy, protein (both animal and vegetable), and carbohydrate intakes. Using QUICKI, a surrogate measure of IS, the present results suggest that the action of insulin does not play an important role in the development and maintenance of sarcopenia in healthy, non-obese, postmenopausal women.

Relationship between antioxidant intakes and class I sarcopenia in elderly men and women

BACKGROUND

The effect of nutritional intake on sarcopenia has been mostly examined in class II sarcopenia, i.e. when muscle mass has sufficiently decreased to induce a loss in physical capacity. Although this provides important information regarding the treatment of sarcopenia, it may not help highlight mechanisms involved at the very beginning of its development.

HYPOTHESIS

We hypothesized that class I sarcopenia is associated with differences in antioxidant intakes (vitamins A, C, E and selenium) and status in healthy, older white men and women when physical activity and protein intake are taken into account.

DESIGN

Fat-free mass and total appendicular skeletal muscle mass was determined by dual-energy X-ray absorptiometry in 50 healthy, older white men (n = 16) and women (n = 34) aged 60-75 yrs. Physical activity energy expenditure (PAEE) was determined using a Caltrac accelerometer over a 3-d period. Dietary protein and antioxidant intakes were estimated from a 3-d food record and serum total antioxidant activity (TAA) was measured by a ferrylmyoglobin- ABTS assay.

RESULTS

The prevalence of class I sarcopenia was 23.5 % in women and 25.0 % in men; 12 participants were thus considered sarcopenic (4 men and 8 women) and 38 participants were considered nonsarcopenic (12 men and 26 women). Our results showed that PAEE, serum albumin concentrations, TAA, and the four antioxidants intake levels were similar between groups. On the other hand, our results showed that total protein intake was significantly higher (P < 0.01) in the non-sarcopenic group than in the sarcopenic group. Also, the number of Recommended Dietary Allowances (RDAs) reached for the antioxidant nutrients and protein intakes by the non-sarcopenic group was significantly higher (P < 0.01) than in the sarcopenic group.

CONCLUSIONS

Although there were no significant differences between the sarcopenic and the non-sarcopenic group when antioxidant intakes were considered individually, we observed that the number of RDAs reached for antioxidant micronutrients and protein in healthy, older white men and women was lower in sarcopenic than nonsarcopenic individuals. Our results also suggest that a higher total dietary protein intake is associated with the preservation of muscle mass loss although both groups displayed values above actual RDAs. Obviously, prospective studies are needed to determine the minimum amount of protein in the diet needed to prevent class I sarcopenia and to examine the utility of antioxidant intake to combat the age-related loss in skeletal muscle mass.

Effect of sarcopenia on cardiovascular disease risk factors in obese postmenopausal women

OBJECTIVE

To compare sarcopenic-obese and obese postmenopausal women for risk factors predisposing to cardiovascular disease (CVD) and determine whether there may be a relationship between muscle mass and metabolic risk in obese postmenopausal women.

RESEARCH METHODS AND PROCEDURES

In this cross-sectional study, 22 healthy obese postmenopausal women (mean age, 66 +/- 5 years; mean BMI, 27 +/- 3 kg/m(2)) were divided into two groups matched for age (+/-2 years) and fat mass (FM) (+/-2%). Sarcopenia was defined as a muscle mass index of <14.30 kg fat-free mass (FFM)/m(2) (which corresponds to 1 standard deviation below the values of a young reference population), and obesity was defined as an FM of >35% (which corresponds to the World Health Organization guidelines). FM, FFM (measured by DXA), daily energy expenditure (accelerometry), dietary intake (3-day dietary record), and blood biochemical analyses (lipid profile, insulin, glucose, and C-reactive protein) were obtained. Visceral fat mass (VFM) was calculated by the equation of Bertin, which estimates VFM from DXA measurements.

RESULTS

Obese women had more FFM (p = 0.006), abdominal FM (p = 0.047), and VFM (p = 0.041) and a worse lipid profile [p = 0.040 for triglycerides; p = 0.004 for high-density lipoprotein (HDL); p = 0.026 for total cholesterol/HDL] than sarcopenic-obese postmenopausal women. Obese women also ingested significantly more animal (p = 0.001) and less vegetal proteins (p = 0.013), although both groups had a similar total protein intake (p = 0.967).

DISCUSSION

Sarcopenia seems to be associated with lower risk factors predisposing to CVD in obese postmenopausal women. With the increase in the number of aging people, the health implications of being sarcopenic-obese merit more attention.

Effect of glycerol-induced hyperhydration on thermoregulatory and cardiovascular functions and endurance performance during prolonged cycling in a 25°C environment

We compared the effect of glycerol-induced hyperhydration (GIH) to that of water-induced hyperhydration (WIH) on cardiovascular and thermoregulatory functions and endurance performance (EP) during prolonged cycling in a temperate climate in subjects consuming fluid during exercise. At weekly intervals, 6 trained male subjects ingested, in a randomized, double-blind, counterbalanced fashion, either a glycerol (1.2 g glycerol/kg bodyweight (BW) with 26 mL/kg BW of water - aspartame-flavored fluid) or placebo solution (water - aspartame-flavored fluid only) over a 2 h period. Subjects then performed 2 h of cycling at 66% of the maximal oxygen consumption (VO2 max) and 25 °C while drinking 500 mL/h of sports drink, which was followed by a step-incremented cycling test to exhaustion. Levels of hyperhydration did not differ significantly between treatments before exercise. During exercise, GIH significantly reduced urine production by 246 mL. GIH did not increase sweat rate nor did it decrease heart rate, rectal temperature, or perceived exertion during exercise as compared with WIH. EP was not significantly different between treatments. Neither treatment induced undesirable side effects. It is concluded that, compared with WIH, GIH decreases urine production, but does not improve cardiovascular or thermoregulatory functions, nor does it improve EP during 2 h of cycling in a 25 °C environment in trained athletes consuming 500 mL/h of fluid during exercise.Key words: prolonged exercise, fluid balance, heart rate, rectal temperature, exercise capacity.

Aerobic training improves insulin sensitivity 72–120 h after the last exercise session in younger but not in older women

The regular practice of aerobic training (AT) induces an improvement in insulin sensitivity (IS) in healthy younger women that persists until 96-120 h after the last exercise bout. Due to the dearth of research data, it still remains unclear whether a regular AT program can improve IS for such a period of time after the last training bout in healthy older women. To address this issue, we trained 14 younger and 8 older women 3 days per week during 6 months, and measured IS 3-5 days after the last training bout. AT consisted of 25-60 min sessions of running at 60-95% of maximal heart rate. Fat mass decreased (8%) in older women only. VO(2max) and fat-free mass increased in both groups. Only older women decreased bodyweight (4%) and subcutaneous adipose tissue (19%). Visceral adipose tissue decreased in none of the groups. The IS improved only in younger women (relative: 22%; absolute: 24%). The present findings suggest that in older women the improvement in IS following AT is short-lived and results mainly from the acute effect of the last training bout, whereas in younger women the chronic adaptations induced by AT are implicated, as the improvement in IS is maintained beyond the residual effect of the last training bout. From a clinical standpoint, our findings suggest that in older women AT should be performed every day to improve glucose metabolism, whereas in younger women an AT frequency (three times per week) allowing to induce and maintain chronic minimal physiological adaptations would be required.

No Sustained Effect of Aerobic or Resistance Training on Insulin Sensitivity in Nonobese, Healthy Older Women

It is unclear whether long-term aerobic (AT) or resistance (RT) training can improve insulin sensitivity (IS) beyond the residual effect of the last training bout in older women (54–78 years). Therefore, a group of nonobese, healthy older women underwent 6 months of AT (n= 8) or RT (n= 10), and the authors measured IS 4 days after the last training bouts using the hyperinsulinemic-euglycemic clamp technique. Women trained 3 days/week. AT consisted of 25- to 60-min sessions of walking/jogging at 60–95% of maximal heart rate. RT consisted of three sets of nine exercises repeated 10 times at 80% of 1 repetition maximum. AT decreased fat mass, whereas both AT and RT increased fat-free mass. Neither training program, however, improved absolute or relative rates of glucose disposal. The authors therefore concluded that nonobese, healthy older women should perform AT or RT on a daily basis in order to improve IS and maintain the improvement.

HRT provides no additional beneficial effect on sarcopenia in physically active postmenopausal women: a cross-sectional, observational study

OBJECTIVES

Physical activity can prevent or retard the loss of muscle mass associated with aging. On the other hand, it has been suggested that HRT may also help prevent sarcopenia in postmenopausal women. We thus examined if HRT provides additional beneficial effect in physically active postmenopausal women.

METHODS

Forty postmenopausal women aged between 55 and 65 years old (normal weight, healthy and no medication) were recruited. Seventeen women were already taking HRT for at least one year whereas 23 were never submitted to HRT. Body composition was measured by DXA and physical activity metabolism was obtained by the use of accelerometry. Subjects were divided in tertile groups based on their daily physical activity energy expenditure (PAEE).

RESULTS

Physical activity groups were similar for age, HRT users distribution, BMI, trunk fat-free mass (FFM), and all fat mass (FM) components. The group of women who were the most physically active significantly displayed greater total FFM, appendicular FFM, and muscle mass index (MMI) compared to the group of less active women (P < 0.05) whereas HRT added no additional effect on any FFM components.

CONCLUSIONS

Our results suggest that in active postmenopausal women, HRT does not provide any additional beneficial effect on body composition.

Assessment of the Effects of Eleutherococcus Senticosus on Endurance Performance

The use of nutritional ergogenic aids containing Eleutherococcus senticosus (ES), a plant which is also known as ciwujia or Siberian ginseng, is relatively common among endurance athletes. Eleutherococcus senticosus has been suggested to improve cardiorespiratory fitness (CF) and fat metabolism (FAM) and, therefore, endurance performance (EP). This article reviews the studies that evaluated the effects of ES during endurance exercise, three of which suggest that ES substantially improves CF, FAM, and EP. However, each of these reports contains severe methodological flaws, which seriously threaten their internal validity, thereby rendering hazardous the generalization of the results. On the other hand, 5 studies that used rigorous research protocols show no benefit of ES on CF, FAM, and EP. It is therefore concluded that ES supplementation (up to 1000 to 1200 mg/d for 1 to 6 wk) offers no advantage during exercise ranging in duration from 6 to 120 min.