Eric D.B. Goulet

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.

Effect of exercise-induced dehydration on time-trial exercise performance: a meta-analysis

Objective To use the meta-analytical procedures to determine the magnitude of the effect of exercise-induced dehydration (EID) upon time-trial (TT) exercise performance. Methods Studies were located via database searches and cross-referencing. TT performance outcomes were converted to mean percentage changes in power output. Random-effects model meta-regressions, analogue to the ANOVA and weighted mean effect summaries were used to delineate the effect of the EID-associated body weight (BW) loss on TT performance. Results Five research articles, all using cycling TTs, were included, producing 13 effect estimates and representing 39 subjects. The mean ambient temperature, relative humidity, exercise intensity and duration of the exercise trials were 26.0±6.7°C, 61±9%, 68±14% of VO2max and 86±34 min, respectively. The effect of EID (mean BW loss of 2.20±1.0%) during self-paced exercise conditions was to produce a non-significant increase in endurance performance of 0.06±2.72% (p=0.94), compared with the maintenance of euhydration (mean BW loss of 0.44±0.48%). Meta-regression analyses revealed a statistically significant relationship between the percentage changes in power output and exercise intensity and duration, but not with the EID-associated percentage changes in BW loss. Drinking according to the dictate of thirst was associated with an increase in TT performance compared with a rate of drinking below (+5.2±4.6%, p=0.01) or above (+2.4±5.0%, p=0.40) thirst. The probability that drinking to thirst confers a real and meaningful advantage on TT performances conducted under field conditions compared with a rate of drinking below and above thirst sensation is of the order of 98% and 62%, respectively. Conclusions (1) Compared with euhydration, EID (up to 4% BW loss) does not alter cycling performances during out-of-door exercise conditions; (2) exercise intensity and duration have a much greater impact on cycling TT performances than EID and; (3) relying on thirst sensation to gauge the need for fluid replacement maximises cycling TT performances.

Effect of exercise-induced dehydration on endurance performance: evaluating the impact of exercise protocols on outcomes using a meta-analytic procedure

Objective It is purported that exercise-induced dehydration (EID), especially if ≥ 2% bodyweight, impairs endurance performance (EP). Field research shows that athletes can achieve outstanding EP while dehydrated > 2% bodyweight. Using the meta-analytic procedure, this study compared the findings of laboratory-based studies that examined the impact of EID upon EP using either ecologically valid (EV) (time-trial exercise) or non-ecologically valid (NEV) (clamped-intensity exercise) exercise protocols. Methods EP outcomes were put on the same scale and represent % changes in power output between euhydrated and dehydrated exercise tests. Random-effects model meta-regressions and weighted mean effect summaries, mixed-effects model analogue to the ANOVAs and magnitude-based effect statistics were used to delineate treatment effects. Main results Fifteen research articles were included, producing 28 effect estimates, representing 122 subjects. Compared with euhydration, EID increased (0.09±2.60%, (p=0.9)) EP under time-trial exercise conditions, whereas it reduced it (1.91±1.53%, (p<0.05)) with NEV exercise protocols. Only with NEV exercise protocols did EID ≥ 2% body weight impair EP (p=0.03). Conclusions Evidence indicates that (1) EID ≤ 4% bodyweight is very unlikely to impair EP under real-world exercise conditions (time-trial type exercise) and; (2) under situations of fixed-exercise intensity, which may have some relevance for military and occupational settings, EID ≥ 2% bodyweight is associated with a reduction in endurance capacity. The 2% bodyweight loss rule has been established from findings of studies using NEV exercise protocols and does not apply to out-of-doors exercise conditions. Athletes are therefore encouraged to drink according to thirst during exercise.

Protein Anabolic Responses to a Fed Steady State in Healthy Aging

BACKGROUNDnProtein anabolism in response to feeding may be impaired with aging. To determine if this could contribute to muscle loss, we studied fed-state metabolic responses in healthy, non-sarcopenic elderly women.nnnMETHODSnWhole-body [(3)H]glucose and protein ([(13)C]leucine) kinetics were measured, and muscle protein fractional synthesis rate ([(2)H(5)]phenylalanine) and signaling events were assessed from vastus lateralis biopsies in eight elderly (73 ± 3 years) and eight young women (24 ± 1 years), using a simulated fed steady-state clamp.nnnRESULTSnBoth groups had similar muscle and lean body mass indices and activity level. During insulin, glucose (8 mmol/L), and amino acid (AA; 2× fasting) infusions, serum insulin was lower in the elderly women and C-peptide increased less. Glucose uptake was stimulated, and production suppressed similarly. Suppression of whole-body protein breakdown was less in the elderly women, leading to lower AA infusion rates, oxidation, and net positive protein balance, but differences were not present when adjusted for serum insulin. Whole-body protein synthesis and muscle protein fractional synthesis rate increased similarly. Similar increases in phosphorylated Akt(Ser473), PRAS40(Thr246), FoxO3a(Thr32), and rpS6(Ser240/244) indicated no alterations in insulin/nutrient signaling with aging.nnnCONCLUSIONSnBoth whole-body and muscle fed-state protein anabolic responses were preserved, as was insulin sensitivity of glucose metabolism, in active, healthy elderly women. This is consistent with other factors such as sedentarity, low protein intake, and concurrent diseases, being responsible for the sarcopenia of aging.

Dehydration and endurance performance in competitive athletes

The field of research examining the link between dehydration and endurance performance is at the dawn of a new era. This article reviews the latest findings describing the relationship between exercise-induced dehydration and endurance performance and provides the knowledge necessary for competitive, endurance-trained athletes to develop a winning hydration strategy. Acute, pre-exercise body weight loss at or above 3% may decrease subsequent endurance performance. Therefore, endurance athletes should strive to start exercise well hydrated, which can be achieved by keeping thirst sensation low and urine color pale and drinking approximately 5-10 mL/kg body weight of water 2 h before exercise. During exercise lasting 1 h or less, dehydration does not decrease endurance performance, but athletes are encouraged to mouth-rinse with sports drinks. During exercise lasting longer than 1 h, in which fluid is readily available, drinking according to the dictates of thirst maximizes endurance performance. In athletes whose thirst sensation is untrustworthy or when external factors such as psychological stress or repeated food intake may blunt thirst sensation, it is recommended to program fluid intake to maintain exercise-induced body weight loss around 2% to 3%.

Half-marathon running performance is not improved by a rate of fluid intake above that dictated by thirst sensation in trained distance runners.

AbstractPurposenIt has been demonstrated that exercise-induced dehydration (EID) does not impair, and ad libitum drinking optimizes, cycling time-trial (TT) performance. However, the idea that EIDxa0≥xa02xa0% bodyweight (BW) impairs endurance performance is well ingrained. No study has tested the impact of EID upon running TT performance. We compared the effects of thirst-driven (TD) vs. programmed fluid intake (PFI) aimed at maintaining EID-associated BW loss <2xa0% on half-marathon performance.MethodsnTen trained distance runners underwent, in a randomized, crossover fashion, two, 21.1xa0km running TTs on a treadmill (30xa0°C, 42xa0% relative humidity) while facing a wind speed matching running speed and drinking water (1) according to thirst sensation (TD) or (2) to maintain BW loss <2xa0% of their pre-exercise BW (PFI), as recommended by the American College of Sports Medicine.ResultsDespite that PFI significantly reduced EID from 3.1xa0±xa00.6 (TD) to 1.3xa0±xa00.7xa0% BW (PFI), mean rectal temperature from 39.4xa0±xa00.4 to 39.1xa0±xa00.3xa0°C, mean body temperature from 38.1xa0±xa00.4 to 37.7xa0±xa00.2xa0°C and mean heart rate from 175xa0±xa09 to 171xa0±xa08xa0bpm, neither half-marathon time (TD 89.8xa0±xa07.7; PFI 89.6xa0±xa07.7xa0min) nor running pace (TD 4.3xa0±xa00.4; PFI 4.2xa0±xa00.4xa0min/km) differed significantly between trials.ConclusionAlbeit providing trivial cardiovascular and thermoregulatory advantages, in trained distance runners, PFI (1,380xa0±xa0320xa0mL/h) offers no performance benefits over TD fluid intake (384xa0±xa0180xa0mL/h) during a half-marathon raced under warm conditions.

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.

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 96–120xa0h 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 3xa0days per week during 6xa0months, and measured IS 3–5xa0days after the last training bout. AT consisted of 25–60xa0min sessions of running at 60–95% of maximal heart rate. Fat mass decreased (8%) in older women only. VO2max 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 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.

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.