Differences In Blood Lactate Concentrations Research Articles

The Effects of 24-h Fasting on Exercise Performance and Metabolic Parameters in a Pilot Study of Female CrossFit Athletes.

Many studies have tested intermittent fasting (IF) in athletes, but its effects on female CrossFit athletes remain relatively unexplored in the existing literature. The aim of this study was to evaluate and compare the effects of 24-h IF on the physical performance of female CrossFit practitioners. Eleven female CrossFit athletes (age: 30.91 ± 3.42, weight: 65.26 ± 7.55 kg, height: 1.66 ± 0.05 m) participated in the study. The study used a crossover design with fasting and eating conditions. Participants completed an exercise test, standing long jump, and handgrip strength assessment. Hydration status, heart rate, blood lactate, blood glucose, rates of perceived exertion, and hunger were measured. Results showed significant differences in blood lactate concentration (F = 5.435, p = 0.042, η2p = 0.352). Resting blood lactate concentration was significantly lower in the fasting trial than in the eating trial (p < 0.001), but post-exercise blood lactate concentrations were higher in the fasting trial than in the eating trial (p < 0.001). No differences were found in performance times (p > 0.05). In conclusion, this pilot study of females suggests that 24-h fasting does not impair exercise performance or negatively affect physiological parameters in CrossFit athletes.

Similar fat and carbohydrate oxidation in response to arm cycling exercise in persons with spinal cord injury versus able-bodied

Context Persons with spinal cord injury (SCI) present with low fat oxidation that is associated with poor cardiometabolic health. This study compared changes in fat and carbohydrate (CHO) oxidation during moderate intensity continuous exercise in persons with SCI and able-bodied adults (AB). Design Repeated measures, within-subjects study. Setting University laboratory in San Diego, CA. Participants Nine men and women with SCI (age and time since injury = 32 ± 11 yr and 7 ± 6 yr) and 10 AB adults (age = 25 ± 8 yr). Interventions To assess peak oxygen uptake (VO2peak) and peak power output (PPO), participants performed progressive arm ergometry to volitional exhaustion. Subsequently, they completed 25 min of continuous exercise at 45%PPO. Outcome Measures Respiratory exchange ratio (RER), fat and CHO oxidation, and blood lactate concentration (BLa) were assessed. Results Data showed a similar RER (P = 0.98) during exercise in SCI (0.97 ± 0.04) versus AB (0.97 ± 0.03) reflecting high CHO use and no differences in BLa (3.5 ± 1.1 and 3.0 ± 0.9 vs. mM, P = 0.56) or fat and CHO oxidation between groups (P > 0.05). However, participants with SCI exercised at a higher relative intensity (P < 0.01, 84 ± 7 vs. 75 ± 7%HRpeak) versus AB. Conclusion Data confirm high reliance on CHO during arm ergometry in persons with SCI. To better compare substrate utilization to AB adults, we recommend that exercise be prescribed according to peak heart rate due to differences in cardiorespiratory fitness between groups.

Sex Differences In Blood Lactate Concentration And Changes In Lifting Velocity During And After Resistance Exercise For Strength Gain And Muscle Hypertrophy.

Strength training variants, such as load, repetition, and set, are manipulated for strength gain and muscle hypertrophy. However, there is little evidence of optimal training variants for women. PURPOSE: To investigate sex differences in blood lactate concentration and changes in lifting velocity during and after resistance exercise for strength gain and muscle hypertrophy, respectively. METHODS: Fourteen subjects (men=8, age 21.1±0.8 years, weight 70.9±7.2 kg, height 170.7±5.4 cm; women=6, age 20.7±1.1 years, weight 58.3±5.0kg, height 159.5±5.5 cm) with significant physical education and resistance training experience participated in this study. Participants performed four sets of parallel squats as part of two protocols, one for strength gain (four repetitions at 85% of 1RM) and one for muscle hypertrophy (10 repetitions at 70% of 1RM) using a cross over design. We measured blood lactate concentration before, during, and after the exercise. We also measured lifting velocity during exercise using a transducer (GymAware). RESULTS: Blood lactate concentration significantly increased after both protocols in both men (strength 1.4±0.7 to 4.1±1.7 mmol/l, p=0.001, hypertrophy 1.6±0.5 to 8.3±2.0 mmol/l, p<0.001) and women (strength 1.3±0.3 to 1.8±0.5 mmol/l,p=0.012, hypertrophy 1.5±0.3 to 4.0±2.0 mmol/l,p=0.269). The protocol for muscle hypertrophy, led to a more significant increase in blood lactate concentration in both men (p=0.001) and women (p=0.040) after exercise than the protocol for strength gain. After both protocols were applied, blood lactate concentration immediately after exercise was significantly higher in men than in women (strength p= 0.008, hypertrophy p=0.005, respectively). Lifting velocity showed a decreasing tendency for both protocols, especially for muscle hypertrophy, in men, but without any significant differences between men and women. CONCLUSIONS: Our results suggest that there are no significant sex differences in blood lactate concentration and lifting velocity during and after the application of the two protocols for strength gain and muscle hypertrophy. However, blood lactate concentration was significantly higher in men than in women.

Effects of Energy Gel Ingestion on Blood Glucose, Lactate, and Performance Measures During Prolonged Cycling.

Kozlowski, KF, Ferrentino-DePriest, A, and Cerny, F. Effects of energy gel ingestion on blood glucose, lactate, and performance measures during prolonged cycling. J Strength Cond Res 35(11): 3111-3119, 2021-Endurance athletes have long used carbohydrate supplementation during prolonged exercise (most recently with energy gels) to enhance performance. The purpose of this study was to determine the effect of carbohydrate energy gel ingestion schedules (e.g., manufacturer's recommendations vs. a more frequent ingestion schedule) during 2 hours of steady-state cycling exercise on (a) blood glucose, (b) blood lactate, and (c) performance of a subsequent 15-minute time trial (TT). Ten trained cyclists (5 men and 5 women, mean age = 28.4 ± 3.66 years; body mass = 68.9 ± 10.63 kg; and V̇o2max = 54.57 ± 9.45 mlO2·kg-1·min-1) performed 3 exercise trials in a randomized order. One gel was ingested 15 minutes before exercise during all trials. The 3 experimental trials included gel ingestion every 30 minutes (T1), every 45 minutes (T2) during exercise, and no gel ingested during exercise (T3). Subjects cycled at 70% of V̇o2max for 2 hours, followed by a 15-minute fixed gear TT. The blood glucose level at 60 minutes of exercise was higher during T1 (125.5 ± 30.96 mg·dl-1) and T2 (127.6 ± 14.82 mg·dl-1) compared with T3 (102.8 ± 15.85 mg·dl-1). Time trial distance was significantly greater for T1 (7.56 ± 0.77 km) and T2 (7.16 ± 0.92 km) than T3 (6.69 ± 0.74 km) (p = 0.003) with moderate to strong effect sizes between trials. There were no differences in blood lactate concentrations across trials. Ingestion of energy gels during prolonged cycling elevates blood glucose levels and enhances subsequent performance, whereas a more frequent ingestion elicits additional performance benefits.

Effect of Different Recoveries During HIIT Sessions on Metabolic and Cardiorespiratory Responses and Sprint Performance in Healthy Men.

Germano, MD, Sindorf, MAG, Crisp, AH, Braz, TV, Brigatto, FA, Nunes, AG, Verlengia, R, Moreno, MA, Aoki, MS, and Lopes, CR. Effect of different recoveries during HIIT sessions on metabolic and cardiorespiratory responses and sprint performance in healthy men. J Strength Cond Res 36(1): 121-129, 2022-The purpose of this study was to investigate how the type (passive and active) and duration (short and long) recovery between maximum sprints affect blood lactate concentration, O2 consumed, the time spent at high percentages of V̇o2max, and performance. Subjects were randomly assigned to 4 experimental sessions of high-intensity interval training exercise. Each session was performed with a type and duration of the recovery (short passive recovery-2 minutes, long passive recovery [LPR-8 minutes], short active recovery-2 minutes, and long active recovery [LAR-8 minutes]). There were no significant differences in blood lactate concentration between any of the recoveries during the exercise period (p > 0.05). The LAR presented a significantly lower blood lactate value during the postexercise period compared with LPR (p < 0.01). The LPR showed a higher O2 volume consumed in detriment to the active protocols (p < 0.001). There were no significant differences in time spent at all percentages of V̇o2max between any of the recovery protocols (p > 0.05). The passive recoveries showed a significantly higher effort time compared with the active recoveries (p < 0.001). Different recovery does not affect blood lactate concentration during exercise. All the recoveries permitted reaching and time spent at high percentages of V̇o2max. Therefore, all the recoveries may be efficient to generate disturbances in the cardiorespiratory system.

Effect of carrying a rifle on physiology and biomechanical responses in biathletes.

This study aimed to assess the effect of carrying a rifle on the physiological and biomechanical responses of well-trained biathletes. Ten elite biathletes (five men and five women) performed ski skating with (R) or without a rifle (NR) on a treadmill using the V2 (5° incline) and V1 techniques (8°) at 8 and 6 km·h(-1), respectively, as well as at racing intensity (approximately 95% of peak oxygen uptake (V˙O2peak), 10.7 ± 0.8 and 7.7 ± 0.9 km·h(-1), respectively). V˙O2, ventilation (V˙(E)), HR, blood lactate concentration (BLa), and cycle characteristics as well as pole and leg kinetics were evaluated during these trials. Metabolic data were all higher for R than for NR, as follows: V˙O2, +2.5%; V˙(E), +8.1%; RER, +4.2%; all P < 0.001; HR, +1.7%; and BLa, +15.1%; both P < 0.05. Biomechanically, carrying a rifle reduced cycle time and length, poling and arm swing times, and leg ground contact time and increased cycle rate, the peak and impulse of leg force, average cycle force, and impulse of forefoot force (all P < 0.05). With the exception of elevated pole forces when V2 skating at racing velocity, there were no differences between the peak and impulse of pole force. The difference in V˙(E) between R and NR was greater for the women than that for men (P < 0.05), and the difference in BLa also tended to be larger for the women (P < 0.1). Carrying a rifle elevated physiological responses, accelerated cycle rate, and involved greater leg work, with no differences between the V1 and V2 techniques.

High cycling cadence reduces carbohydrate oxidation at given low intensity metabolic rate.

Cycling cadence (RPM)-related differences in blood lactate concentration (BLC) increase with increasing exercise intensity, whilst corresponding divergences in oxygen uptake (O2) and carbon dioxide production (CO2) decrease. Aim of the present study was to test whether a higher RPM reduces the fraction (%) of the O2 used for carbohydrate oxidation (relCHO) at a given BLC. Eight males (23.9 ± 1.6 yrs; 177 ± 3 cm; 70.3 ± 3.4 kg) performed incremental load tests at 50 and 100 RPM. BLC, O2 and CO2 were measured. At respiratory exchange ratios (RER) < 1, relCHO were calculated and the constant determining 50 % relCHO (kCHO) was approximated as a function of the BLC. At submaximal workload O2, CO2, and relCHO were lower (all p < 0.002; η2 > 0.209) at 50 than at 100 RPM. No differences were observed in O2peak (3.96 ± 0.22 vs. 4.00 ± 0.25 l · min−1) and RERpeak (1.18 ± 0.02 vs. 1.15 ± 0.02). BLC was lower (p < 0.001; η2 = 0.680) at 50 than at 100 RPM irrespective of cycling intensity. At 50 RPM, kCHO (4.2 ± 1.4 (mmol · l−1)3) was lower (p = 0.043; η2 = 0.466) than at 100 RPM (5.9 ± 1.9 (mmol · l−1)3). This difference in kCHO reflects a reduced CHO oxidation at a given BLC at 100 than at 50 RPM. At a low exercise intensity, a higher cycling cadence can substantially reduce the reliance on CHO at a given metabolic rate and/or BLC.

Blood lactate concentrations in ponies and miniature horses with gastrointestinal disease

Clinical impression suggested that pony and miniature breeds (collectively referred to as ponies) presenting to a referral hospital for investigation of gastrointestinal disease had higher blood lactate concentrations on admission than large breed horses. The study tested the hypothesis that ponies with gastrointestinal disease had higher blood lactate concentrations on admission than large breed horses with similar disease severity. Retrospective case-control study. Medical records from September 2006 to July 2011 were reviewed for ponies with a primary presenting complaint of gastrointestinal disease. Two larger breed horses with gastrointestinal disease were selected as controls for each case. Data collected included case details, historical and clinicopathological findings, diagnosis and outcome. Information was collected on 50 ponies and 100 horses. Ponies had higher mean ± s.d. respiratory rates (27 ± 13 vs. 21 ± 13 beats/min; P = 0.01) and rectal temperatures (37.9 ± 0.6 vs. 37.4 ± 0.6°C; P = 0.006) and a longer median duration of clinical signs prior to presentation (10 h [1-72 h] vs. 6 h [1-120]; P<0.001). Median blood lactate concentrations on admission were higher in ponies than in horses (2.8 mmol/l [0.7-18.0] vs. 1.6 mmol/l [0.4-8.1]; P = 0.001). All other parameters relating to colic severity were not significantly different between groups, although more horses underwent exploratory laparotomy (19/50 ponies and 55/100 horses; P = 0.05). Median blood lactate concentrations in ponies with large intestinal disease, nonstrangulating lesions, undergoing medical treatment and surviving ponies were significantly higher than in horses in the same category. In contrast to horses, no differences in blood lactate concentrations exist between ponies with medical vs. surgical treatment, strangulating and nonstrangulating lesions and surviving and nonsurviving ponies. Ponies might present with higher blood lactate concentrations than horses and might falsely be suspected of having a surgical lesion or a poorer prognosis if veterinarians are not aware of breed differences.

The effect of an official match on repeated sprint ability in junior basketball players

The aim of this study was to investigate the effect of an official basketball match on repeated sprint ability indices in male junior players. Ten (16 ± 1 years old; 183.6 ± 7.0 cm; 76.6 ± 8.0 kg) starting players for their teams performed three repeated sprint ability tests, before, at half-time and immediately after an official match. Each repeated sprint ability test consisted of 10 shuttle-run sprints of 30 m (15 + 15 m) separated by 30 seconds of passive recovery. The matches were video-taped to determine the frequency of eight types of movement patterns, and blood lactate concentration was measured before and immediately after each repeated sprint ability test. Differences in total time, ideal time and percentage decrement between tests was assessed by a one-way analysis of variance (ANOVA) with repeated measures, while a two-way ANOVA with repeated measures was used to identify differences in blood lactate concentration. The main results indicated a significant decrease in total movement frequency (−9.9%), high-intensity activity frequency (−13.3%), run frequency (−13.0%) and sprint frequency (−23.3%) in the second compared to the first half, and significantly worse total time and ideal time at the end of the match, compared to the start and half-time (differences ranging from −2.1% to -2.9%, P < 0.05). The practical implications of these findings suggest that regional basketball players should participate in conditioning sessions that focus on the improvement of repeated sprint ability.

Cardiorespiratory and Metabolic Alterations During Exercise and Passive Recovery After Three Modes of Exercise

The objective of this study was to investigate the potential variations in cardiorespiratory and metabolic parameters and running performance among 3 modes of exercise of the same duration, namely, intermittent running with active recovery (AR) or passive recovery (PR) and continuous running (CR) and whether these variations could affect passive recovery time (PRT). Fifteen male physical education students with a subspecialty in soccer were studied (mean age 22.3 ± 2.5 years, training experience 12.3 ± 2.5 years) in the middle of the playing season. The results showed that during exercise, the highest heart rate (HR) and VO2 values were observed in CR, whereas the lowest values in PR followed by AR. Blood lactate (BLa) concentration was higher in PR by 38% compared to that in AR (p < 0.05). The exercise duration was similar between PR and AR tests and longer than in CR. With regard to PRT, the highest HR (186 ± 9 b · min(-1)), VO2 (55.5 ± 5.2 ml · kg(-1) · min(-1)), and BLa (5.1 ± 1.7 mmol · L(-1)) values were found in CR. No differences in HR and VO2 between PR and AR were detected. However, despite the differences in BLa concentration between AR and PR during exercise, the PRT BLa values between these 2 exercise modes were not different. Among the 3 running protocols, only CR appeared to have fully challenged the cardiorespiratory system inducing maximal HR and VO2 responses during exercise and high BLa values in PRT, yet these responses were not associated with better exercise performance compared to intermittent running. Therefore, intermittent exercise, regardless of implementing passive or active interval, might be the preferable exercise mode particularly in activities extended over 30 minutes.

Ventilatory response to moderate incremental exercise performed 24 h after resistance exercise with concentric and eccentric contractions

In order to test our hypothesis that muscle condition has an effect on the cognition of self-motion and consequently on the ventilatory response during exercise, six healthy subjects performed a moderate incremental exercise test (IET) on a cycle ergometer under two conditions [resistance exercise condition (REC) and control condition (CC)]. In the REC, resistance exercise (30 incline leg presses) was conducted during two sessions scheduled at 48 and then 24h prior to the IET. For the CC, the subjects were instructed to refrain from participating in strenuous exercise for a period of 2days prior to the IET. In the IET, the workload was increased from 78 to 118watts in steps of 8watts every 3min. Although the ventilatory response during the IET was significantly higher in the REC than in the CC, there were no significant differences in cognitive indexes (RPE and awareness of change in workload) between the two conditions. In addition, the magnitude of muscle soreness was significantly higher in the REC than in the CC. However, the level of soreness in the REC was very low, and there were no significant differences in blood lactate concentration and integrated EMG between the two conditions. These results suggest that a change in peripheral neural reflex is the primary cause of increased ventilatory response to moderate exercise after resistance exercise, although the role of a cognitive element cannot be absolutely excluded.

The Effect of a Secret Manipulation of Ambient Temperature on Heat Storage and Voluntary Exercise Intensity

The Central Governor Model (CGM) suggests that physiological afferents, such as changes in ambient temperature or perturbations in the rate of heat storage (HS), are centrally integrated in a dynamic feed-forward manner, with the end goal of regulating voluntary exercise intensity in order to maintain physiological homeostasis. One limitation of previous research into this model is that subjects have been aware of the existence of an environmental manipulation. Because of this, a placebo effect may have influenced the anticipatory planning before the start of exercise, making it difficult to isolate the dynamic integration during exercise itself. PURPOSE: To directly test the CGM by secretly manipulating ambient temperature (Tam) while cycling at a set rate of perceived exertion (RPE). METHODS: Using a single trial to remove between-trial variability, participants cycled at a constant RPE of 14 while Tam was manipulated in an A-B-A pattern at 20-minute intervals from 20°C to 35°C, then returned to 20°C. Participants were deceived, both to the true purpose of the study and the Tam manipulation, to elicit dynamic pacing strategies without conscious anticipation. Power output was measured continuously throughout each trial and its synchronicity with changes in HS and Tam were quantified using Auto-Regressive Integrated Moving Averages (ARIMA) analysis. Furthermore, blood lactate measurements were taken and A-B-A differences were analyzed using repeated measures ANOVA. RESULTS: Ten recreational to competitive cyclists (mean±SD, age: 35.1±13.5 y, mass: 72.5±15.9 kg, height: 174.9±9.1 cm, body fat: 11.2±5.6%, VO2peak 57.6±6.3 mL/kg/min, and peak power output: 332±53 W) participated. Exercise intensity decreased during the 35°C manipulation in all subjects and ARIMA analysis indicates that power output is significantly correlated to changes HS (r2 = 0.984, Ljung-Box statistic = 0.083). There were no significant differences in blood lactate concentration throughout each trial (p = 0.164) despite changes in Tam. CONCLUSIONS: Real time dynamic sensation of Tam and integration of HS directly influences voluntary pacing strategies during sub-maximal cycling at a constant RPE while non-significant changes in blood lactate suggest an absence of peripheral fatigue. Supported by NSERC Discovery 227912-2007.

Analysis of multiple factors in the resuscitation of hemorrhagic shock in rabbits

Objective To investigate the effects of two different resuscitation fluids of two different temperatures and two different target MAP on the outcome of hemorrhagic shock in rabbits. Methods Forty adult male rabbits weighing 2.3-3.2 kg were anesthetized with iv pentobarbital sodium 30-35 mg/kg and tracheostomized. Spontaneous breathing was maintained. Hemorrhagic shock was induced according to modified Wiggers method. used. The temperature of the fluids was 23 ℃ (B_1) and 45 ℃ (B_2) respectively. The target MAP was 60 mm Hg (C_1) and 80 mm Hg (C_2). Forty animals were randomly divided into 8 groups (n=5 each) : group A_1B_1C_1; group A_1B_1C_2; group A_1B_2C_1; group A_1B_2C_2; group A_2B_1C_1; group A_2B_1C_2 ; group A_2 B_2 C_1 and group A_2B_2C_2 .Arterial blood samples were obtained from femoral artery at 5 min before blood-withdrawal, immediately after shock was induced and at 1, 2, and 3 h of resuscitation for blood gas analysis and determination of blood lactate concentration and serum concentrations of TNF-α and IL-6. Hemodynamies and changes in mesenteric capillaries were continuously monitored. Results PaO_2 was significantly higher in animals resuscitated with HSD (A_2) than in animals resuscitated with HS (A_1). Blood lactate concentration was significantly higher in group A_1B_1 (HS-23℃) than in group A_2B_1 (HSD-23℃). There was no significant difference in blood lactate concentration between group A_1B_2 (HS-45℃) and group A_2B_2 (HSD-45℃). The 3 factors did not have different effects on mesenteric capillaries. The serum TNF-α and IL-6 concentrations were significantly higher in animals resuscitated with HS (A_1) than in animals resuscitated with HSD (A_2) .Conclusion The effect of resuscitation of hemorrhagic shock is better with HSD than with HS. The resuscitation fluid of 23 ℃ is superior to fluid of higher temperature. The target BP during resuscitation does not influence the outcome of resuscitation. Key words: Shock,hemorrhagic; Fluid therapy; Sodium chloride; Dextrans; Temperature; Blood pressure

No Difference In Substrate Utilisation At Given Exercise Intensities Between Males And Females

There is evidence that the relative number of slow muscle fibres is higher in women than in men. Fibre composition affects glycolysis, blood lactate concentration (BLC), aerobic carbohydrate and fatty acid combustion (CHO and FAO). It has been suggested that women use less CHO and more FAO at given exercise intensities. PURPOSE: To analyze potential differences in BLC and relative CHO (relCHO) between males and females. METHODS: 15 males (age: 24.5 ± 3.2 yrs, height: 179.9 ± 7.4 cm, weight: 77.1 ± 6.9 kg) and 14 females (22.4 ± 4.5 yrs, 163.3 ± 3.8 cm, 58.9 ± 7.5 kg) performed an incremental cycling test at a pedalling rate of 65 rpm. Exercise intensity was calculated as fraction of power output at test termination. BLC, oxygen uptake and carbon dioxide production were measured. CHO was determined using indirect calorimetry. relCHO was calculated as a fraction of the theoretical maximum CHO for a given oxygen uptake assuming a respiratory exchange ratio of 1.0. relCHO was described as a function of BLC. A constant that functionally represents the half-maximal activation of relCHO (kel) was approximated: relCHO = 100/(1 + kel/BLC2). RESULTS: There was a significant main effect of intensity (P < 0.05) on BLC and relCHO. No main effects of gender on BLC or relCHO nor any interactions between intensity and gender were found. kel (1.75 + 0.88 vs. 1.92 + 1.19; P > 0.05) was not different between males and females. CONCLUSION: The present study does not confirm differences in relCHO at given exercise intensities between males and females. Furthermore, the interrelation between BLC and relCHO was unaffected by gender.

Effect of Chain Wheel Shape on Crank Torque, Freely Chosen Pedal Rate, and Physiological Responses during Submaximal Cycling

The development of noncircular chain wheels for the enhancement of cycling performance has been in progress for a long time and continues apace. In this study we tested whether submaximal cycling using a non-circular (Biopace) versus a circular chain wheel resulted in lower peak crank torque at preset pedal rates as well as resulting in lower pedal rate and metabolic response at freely chosen pedal rate. Ten trained cyclists (mean+/-SD: 27+/-3 years of age, 182+/-4 cm tall, 77.5+/-7.0 kg of body mass, and peak oxygen uptake of 61.7+/-4.4 ml kg(-1) min(-1)) cycled with a Biopace and a circular chain wheel at 180 W at 65 and 90 rpm for recording of crank torque profiles, and at their freely chosen pedal rate for recording of pedal rate and metabolic response, including oxygen uptake and blood lactate concentration. Crank torque profiles were similar between the two chain wheels during cycling at preset pedal rates. During cycling at the freely chosen pedal rate (being 93+/-6 and 93+/-4 rpm for the Biopace and circular chain wheel, respectively), blood lactate concentration was significantly different between the two chain wheels, being on average 0.2 mmol l(-1) lower with the Biopace chain wheel. A musculoskeletal simulation model supported the idea that a contributing factor to the observed difference in blood lactate concentration may be slightly reduced muscle activity around the phase where peak crank torque occurs during cycling with the Biopace chain wheel. In that particular phase of the crank revolution, the observed slightly lower muscle activity may result from larger transfer of energy from the legs to the crank.

Effect of cold water immersion on repeat cycling performance and thermoregulation in the heat

To assess the effect of cold water immersion and active recovery on thermoregulation and repeat cycling performance in the heat, ten well-trained male cyclists completed five trials, each separated by one week. Each trial consisted of a 30-min exercise task, one of five 15-min recoveries (intermittent cold water immersion in 10°C, 15°C and 20°C water, continuous cold water immersion in 20°C water or active recovery), followed by 40 min passive recovery, before repeating the 30-min exercise task. Recovery strategy effectiveness was assessed via changes in total work in the second exercise task compared with that in the first. Following active recovery, a mean 4.1% (s = 1.8) less total work (P = 0.00) was completed in the second than in the first exercise task. However, no significant differences in total work were observed between any of the cold water immersion protocols. Core and skin temperature, blood lactate concentration, heart rate, rating of thermal sensation, and rating of perceived exertion were recorded. During both exercise tasks there were no significant differences in blood lactate concentration between interventions; however, following active recovery blood lactate concentration was significantly lower (P < 0.05; 2.0 ± 0.8 mmol · l−1) compared with all cold water immersion protocols. All cold water immersion protocols were effective in reducing thermal strain and were more effective in maintaining subsequent high-intensity cycling performance than active recovery.

Comparison of the Lactate Pro and Analox GM7 Blood Lactate Analysers

The purpose of this study was firstly, to determine the level of agreement between the Lactate Pro and Analox GM7 for the measurement of blood lactate, and secondly, to examine whether these analysers may be used interchangeably to identify lactate parameters routinely used in the physiological assessment of athletes. Twenty well-trained male cyclists performed an incremental cycle ergometry test; duplicate blood samples were taken simultaneously throughout the test for lactate determination using the two analysers. Power output and heart rate at LT, LT1, 2 mmol.L-1, and 4 mmol.L-1 were calculated from the lactate values obtained from the two analysers. There was a strong linear relationship between the two analysers (Lactate Pro=1.4541xAnalox GM7-0.1287; R2=0.969, p<0.001; SEE=0.704) though the Lactate Pro overestimated blood lactate when compared to the Analox GM7; 95% ratio limits of agreement (Lactate Pro/Analox GM7) were 1.40x//1.35. Differences were found between analysers for power output and heart rate at LT1 (p<0.01), 2 mmol.L-1 (p<0.001), and 4 mmol.L-1 (p<0.001); no differences were found between analysers for power output or heart rate at LT. In conclusion, the average difference in blood lactate concentration measured by the Lactate Pro and the Analox GM7 was 40%, with 95% of measures differing by between 4% and 89%. This poor level of agreement and the significant differences between the two analysers in power output and heart rate associated with a number of lactate parameters indicate that these analysers should not be used interchangeably.

Modeling the blood lactate kinetics at maximal short-term exercise conditions in children, adolescents, and adults

Whether age-related differences in blood lactate concentrations (BLC) reflect specific BLC kinetics was analyzed in 15 prepubescent boys (age 12.0 +/- 0.6 yr, height 1.54 +/- 0.06 m, body mass 40.0 +/- 5.2 kg), 12 adolescents (16.3 +/- 0.7 yr, 1.83 +/- 0.07 m, 68.2 +/- 7.5 kg), and 12 adults (27.2 +/- 4.5 yr, 1.83 +/- 0.06 m, 81.6 +/- 6.9 kg) by use of a biexponential four-parameter kinetics model under Wingate Anaerobic Test conditions. The model predicts the lactate generated in the extravasal compartment (A), invasion (k(1)), and evasion (k(2)) of lactate into and out of the blood compartment, the BLC maximum (BLC(max)), and corresponding time (TBLC(max)). BLC(max) and TBLC(max) were lower (P < 0.05) in boys (BLC(max) 10.2 +/- 1.3 mmol/l, TBLC(max) 4.1 +/- 0.4 min) than in adolescents (12.7 +/- 1.0 mmol/l, 5.5 +/- 0.7 min) and adults (13.7 +/- 1.4 mmol/l, 5.7 +/- 1.1 min). No differences were found in A related to the muscle mass (A(MM)) and k(1) between boys (A(MM): 22.8 +/- 2.7 mmol/l, k(1): 0.865 +/- 0.115 min(-1)), adolescents (22.7 +/- 1.3 mmol/l, 0.692 +/- 0.221 min(-1)), and adults (24.7 +/- 2.8 mmol/l, 0.687 +/- 0.287 min(-1)). The k(2) was higher (P < 0.01) in boys (2.87 10(-2) +/- 0.75 10(-2) min(-1)) than in adolescents (2.03 x 10(-2) +/- 0.89 x 10(-2) min(-1)) and adults (1.99 x 10(-2) +/- 0.93 x 10(-2) min(-1)). Age-related differences in the BLC kinetics are unlikely to reflect differences in muscular lactate or lactate invasion but partly faster elimination out of the blood compartment.

Effect of precooling on high intensity cycling performance.

OBJECTIVE: To examine the effects of precooling skin and core temperature on a 70 second cycling power test performed in a warm and humid environment (29 degrees C, 80% relative...

Regulation of exercise intensity using ratings of perceived exertion during passive visual distraction.

The purpose of this investigation was to determine if passive visual distraction altered ability to regulate exercise intensity as, assessed by ratings of perceived exertion during a 30-min. treadmill run. 10 trained females (VO2max, 52.7 ml.kg-1.min.-1) performed a graded exercise test on a treadmill to assess maximal aerobic power and rating of perceived exertion, oxygen uptake (VO2), heart rate, and running velocity at the 2.5 mmol.L-1 blood lactate concentration. Subjects then used the target rating of perceived exertion to regulate exercise intensity during a control condition, and two treatment runs with passive visual distractions. During the treatment sessions, the subjects ran on a treadmill while viewing a high-action or a low-action video with no audio. The subjects were allowed to adjust the treadmill speed throughout the run to maintain the target rating of perceived exertion; however, subjects were not allowed to view the speed setting. There were no significant differences in blood lactate concentration among the conditions for the control, low action, high action, or graded exercise test (p < or = .05). No significant differences in VO2 or running velocity were found within or among the 30-min. treatment runs and the graded exercise test. Heart rate at 5 min. of exercise during control (158 +/- 3 b.min.-1), low action (158 +/- 3 b.min.-1), and high action (159 +/- 2 b.min.-1) was significantly lower than the graded exercise test (169 +/- 3 b.min.-1). Based on the data collected, visual passive distraction did not alter regulation of intensity using ratings of perceived exertion during a 30-min. treadmill run.