Saima Timpmann

Time-divided ingestion pattern of casein-based protein supplement stimulates an increase in fat-free body mass during resistance training in young untrained men.

We hypothesized that during prolonged resistance training, time-divided ingestion pattern of casein-based protein supplement is of superior efficiency in comparison with the ingestion of the same supplement immediately before each training session. In a crossover study, 13 men aged 18 to 19 years were evaluated during 2 well-controlled, 8-week training and supplementation periods. In the time-focused supplementation regimen (TFR), the subjects consumed the supplement in the morning and in the afternoon, immediately before the training session. Time-divided supplementation regimen (TDR) included 1 morning dose, whereas the second dose was ingested in the evening, 5 hours after training. The daily dose of the supplement contained approximately 70 g of protein (82% casein) and less than 1 g of carbohydrate and fat. Body mass, body composition (dual-energy x-ray absorptiometry scanned), and one-repetition maximum (1RM) for bench press and squat were determined at the beginning and at the end of both 8-week training and supplementation periods. Training produced a significant increase in 1RM strength both in the bench press (9.4% and 7.2%) and the squat exercise (10.7% and 17.8%) in the TFR and TDR, respectively, with no differences between the supplementation regimens. Fat-free mass increased from 62.4 +/- 1.2 to 63.5 +/- 1.3 kg (P = .046) with TDR, whereas no change was evident with TFR. The increase in 1RM strength in the squat exercise was related to the increase in fat-free mass in TDR (r = 0.569; P = .041). These findings may have practical implications for the timing of ingestion of protein supplements to enhance the efficacy of resistance training.

Effect of creatine supplementation during rapid body mass reduction on metabolism and isokinetic muscle performance capacity.

Abstract Well-trained subjects (n=6) were studied before and after losing a mean 3.0%–4.3% of body mass to determine whether muscle performance could be maintained or even enhanced by dietary creatine supplementation. During a 5-day period of loss of mass the subjects were randomly assigned to a creatine or placebo supplemented diet. All the subjects were measured before and after loss of mass on both supplements for isokinetic peak torque (PT) and work at peak torque (WPT) of knee extensors, also for intermittent high intensity working capacity of the same muscle group. The latter test consisted of submaximal isokinetic knee extensions at an angular velocity of 1.57 rad · s−1 for 45 s at the rate of 30 contractions each min (submaximal work, Wsmax) followed by 15-s maximal effort (maximal work, Wmax). Total duration of the test was 3 min. Haematocrit was measured and haemoglobin, ammonia, lactate, glucose and urea concentrations were analysed in blood samples obtained at rest and after cessation of muscle performance tests. The results indicated that creatine supplementation in comparison with placebo treatment during rapid body mass reduction may help to maintain muscle PT and WPT at high angular velocities, not influencing Wmax and the rate of fatigue development during Wmax, but affecting adversely Wsmax. Within the limitations of the present study the reasons for the partially detrimental effect of creatine administration remain obscure, but it is suggested that impaired creatine uptake in muscle during body mass loss as well as creatine induced changes in muscle glucose and glycogen metabolism may be involved.

Effects of daily medium-chain triglyceride ingestion on energy metabolism and endurance performance capacity in well-trained runners

Abstract The purpose of this study was to assess the effect of medium-chain triglyceride (MCTG) supplementation on energy metabolism and endurance performance capacity in well-trained runners. Seven men (age 19.4±1.7 years, maximal O 2 uptake 67.5±4.8 ml · min −1 · kg −1 ) were tested before and after MCTG as well as placebo consumption daily for 7 days. The energy and nutrient intake of the subjects did not differ in MCTG and placebo trial. The running time to exhaustion after dietary intervention was respectively 3916±1225 s in placebo trial and 3498±559 s in MCTG trial. The concentration of β-hydroxybutyric acid in plasma was the highest (1.029±0.67 mmol · l −1 ) in post-test samples after MCTG supplementation, significantly differing from the pre-test concentration in the same trial as well as from that observed in post-test blood after placebo treatment. These results suggest that daily MCTG supplementation increases the availability of ketone bodies for oxidation in working muscle during high intensity endurance exercise, but does not improve endurance performance capacity.

The compression of perceived time in a hot environment depends on physiological and psychological factors

The human perception of time was observed under extremely hot conditions. Young healthy men performed a time production task repeatedly in 4 experimental trials in either a temperate (22 °C, relative humidity 35%) or a hot (42 °C, relative humidity 18%) environment and with or without a moderate-intensity treadmill exercise. Within 1 hour, the produced durations indicated a significant compression of short intervals (0.5 to 10 s) in the combination of exercising and high ambient temperature, while neither variable/condition alone was enough to yield the effect. Temporal judgement was analysed in relation to different indicators of arousal, such as critical flicker frequency (CFF), core temperature, heart rate, and subjective ratings of fatigue and exertion. The arousal-sensitive internal clock model (originally proposed by Treisman) is used to explain the temporal compression while exercising in heat. As a result, we suggest that the psychological response to heat stress, the more precisely perceived fatigue, is important in describing the relationship between core temperature and time perception. Temporal compression is related to higher core temperature, but only if a certain level of perceived fatigue is accounted for, implying the existence of a thermoemotional internal clock.

Heat acclimation decreases the growth hormone response to acute constant-load exercise in the heat

OBJECTIVE The major objective of this study was to elucidate the effect of heat acclimation on blood growth hormone (GH) response to moderate intensity exhausting exercise in the heat. In addition, the potential relationship between inter-individual differences in GH response to exercise and variability in exercise-induced sweat loss was investigated. DESIGN Twenty young men completed three exercise tests on a treadmill: H1 (walk at 60% VO₂peak until exhaustion at 42 °C), N (walk at 22 °C; duration equal to H1) and H2 (walk until exhaustion at 42 °C after a 10-day heat acclimation program). Core temperature (T(c)) was recorded continuously and venous blood samples were taken before, during and after each exercise test. Exercise-induced sweat production was calculated on the basis of body mass change taking into account water intake and the volume of blood samples drawn. RESULTS Lower pre-exercise T(c), lower rate of rise in T(c) during exercise, and prolonged time to exhaustion in H2 compared with H1 revealed that the subjects successfully achieved an acclimated state. Overall, serum GH level was higher in H1 compared with both N and H2 (p<0.001) but did not differ between the two latter trials (p>0.05). T(c) correlated with serum GH concentration (r=0.615, p<0.01). Analysis of the individual data revealed a group (n=9) possessing a threshold-like pattern of the relationship between T(c) and blood GH response, whereas a plateau-like pattern was evident in the rest of the subjects (n=11). Both sweat production (r=0.596; p<0.001) and the rate of sweat production (r=0.457; p<0.001) correlated with the growth hormone area under the curve. CONCLUSION Heat acclimation decreases the GH response to moderate intensity exhausting exercise in the heat. GH may have a modest stimulating effect on whole-body sweat production during exercise.

Hydration status of Greco-Roman wrestlers in an authentic precompetition situation

We assessed the urinary indexes of hydration status of Greco-Roman wrestlers in an authentic precompetition situation at the time of official weigh-in (OWI). A total of 51 of 89 wrestlers competing in the Estonian Championship in 2009 donated a urine sample. Questionnaire responses revealed that 27 wrestlers (body mass losers (BMLs)) reduced body mass before the competition, whereas 24 wrestlers (those who do not lose body mass (n-BMLs)) did not. In 42 wrestlers, values of urine specific gravity ≥1.020 and urine osmolality ≥700 mOsmol·kg(-1) revealed a hypohydrated status. The prevalence of hypohydration in the BMLs (96%) was higher than in the n-BMLs (67%) (χ(2) = 7.68; p < 0.05). The prevalence of serious hypohydration (urine specific gravity >1.030) was 5.3 times greater (χ(2) = 8.32; p < 0.05) in the BMLs than in the n-BMLs. In the BMLs, the extent of body mass gain during the 16-h recovery (2.5 ± 1.2 kg) was associated (r = 0.764; p < 0.05) with self-reported precompetition body mass loss (4.3 ± 2.0 kg) and exceeded the body mass gain observed in the n-BMLs (0.7 ± 1.2 kg; p < 0.05). We conclude that hypohydration is prevalent among Greco-Roman wrestlers at the time of OWI. The prevalence of hypohydration and serious hypohydration is especially high among wrestlers who are accustomed to reducing body mass before competition. These results suggest that an effective rehydration strategy is needed for Olympic-style wrestlers, and that changes in wrestling rules should be considered to reduce the prevalence of harmful body mass management behaviours.

Dietary sodium citrate supplementation enhances rehydration and recovery from rapid body mass loss in trained wrestlers

This study assessed the effects of dietary sodium citrate supplementation during a 16 h recovery from 5% rapid body mass loss (RBML) on physiological functions, affective state, and performance in trained wrestlers. Sixteen wrestlers performed an upper body intermittent sprint performance (UBISP) test under three conditions: before RBML, after RBML, and after a 16 h recovery from RBML. During recovery, the subjects ate a prescribed diet supplemented with sodium citrate (600 mg·kg(-1); CIT group, N = 8) or placebo (PLC group, N = 8) and drank water ad libitum. RBML reduced (p < 0.05) UBISP mean power and increased urine specific gravity (USG). Reduction in mean power was associated with changes in plasma volume (PV) (r = 0.649, p = 0.006) and USG (r = -0.553, p = 0.026). During the 16 h recovery, increases in body mass (BM) and PV were greater (p < 0.05) in the CIT group than in the PLC group. BM gain was associated with water retention in the CIT group (r = 0.899, p = 0.002) but not in the PLC group (r = 0.335, p = 0.417). Blood pH, HCO(3)(-) concentration, and base excess increased (p < 0.05) only in the CIT group. Changes in UBISP, general negative affect, and general positive affect did not differ in the two groups. In conclusion, ingestion of sodium citrate increases blood buffering capacity and PV and stimulates BM regain during a 16 h recovery from RBML in trained wrestlers. However, sodium citrate does not improve UBISP nor does it have an impact on the affective state.

Effect of creatine administration on blood urea level and postexercise glycogen repletion in liver and skeletal muscle in rats.

The aim of the present study was to assess the effect of creatinine administration on urea metabolism in sedentary and exercised Wistar rats and also on the rate of glycogen resynthesis in the liver and skeletal muscle of endurance-trained animals after exhausting exercise. Creatine treatment for 7 days significantly increased the concentration of urea in blood plasma of sedentary as well as exercised rats and this effect was also maintained in trained animals 24 h after exhausting swimming. The rate of glycogen resynthesis in the liver and skeletal muscle after glycogen-depleting exercise was not modified by creatine administration.

Effects of caffeine on endurance capacity and psychological state in young females and males exercising in the heat

Acute caffeine ingestion is considered effective in improving endurance capacity and psychological state. However, current knowledge is based on the findings of studies that have been conducted on male subjects mainly in temperate environmental conditions, but some physiological and psychological effects of caffeine differ between the sexes. The purpose of this study was to compare the physical performance and psychological effects of caffeine in young women and men exercising in the heat. Thirteen male and 10 female students completed 2 constant-load walks (60% of thermoneutral peak oxygen consumption on a treadmill until volitional exhaustion) in a hot-dry environment (air temperature, 42 °C; relative humidity, 20%) after caffeine (6 mg·kg-1) and placebo (wheat flour) ingestion in a double-blind, randomly assigned, crossover manner. Caffeine, compared with placebo, induced greater increases (p < 0.05) in heart rate (HR) and blood lactate concentrations in both males and females but had no impact on rectal or skin temperatures or on walking time to exhaustion in subjects of either gender. Caffeine decreased (p < 0.05) ratings of perceived exertion and fatigue in males, but not in females. In females, but not in males, a stronger belief that they had been administered caffeine was associated with a shorter time to exhaustion. In conclusion, acute caffeine ingestion increases HR and blood lactate levels during exercise in the heat, but it has no impact on thermoregulation or endurance capacity in either gender. Under exercise-heat stress, caffeine reduces ratings of perceived exertion and fatigue in males but not in females.

Effects of heat acclimation on time perception

Cognitive performance is impaired during prolonged exercise in hot environment compared to temperate conditions. These effects are related to both peripheral markers of heats stress and alterations in CNS functioning. Repeated-exposure to heat stress results in physiological adaptations, and therefore improvement in exercise capacity and cognitive functioning are observed. The objective of the current study was to clarify the factors contributing to time perception under heat stress and examine the effect of heat acclimation. 20 young healthy male subjects completed three exercise tests on a treadmill: H1 (at 60% VO(2)peak until exhaustion at 42°C), N (at 22°C; duration equal to H1) and H2 (walk until exhaustion at 42°C) following a 10-day heat acclimation program. Core temperature (T(C)) and heart rate (HR), ratings of perceived fatigue and exertion were obtained continuously during the exercise, and blood samples of hormones were taken before, during and after the exercise test for estimating the prolactin, growth hormone and cortisol response to acute exercise-heat stress. Interval production task was performed before, during and after the exercise test. Lower rate of rise in core temperature, heart rate, hormone response and subjective ratings indicated that the subjects had successfully acclimated. Before heat acclimation, significant distortions in produced intervals occurred after 60 minutes of exercise relative to pre-trial coefficients, indicating speeded temporal processing. However, this effect was absent after in acclimated subjects. Blood prolactin concentration predicted temporal performance in both conditions. Heat acclimation slows down the increase in physiological measures, and improvement in temporal processing is also evident. The results are explained within the internal clock model in terms of the pacemaker-accumulator functioning.