scholarly journals Lactate threshold predicting time-trial performance: impact of heat and acclimation

2011 ◽  
Vol 111 (1) ◽  
pp. 221-227 ◽  
Author(s):  
Santiago Lorenzo ◽  
Christopher T. Minson ◽  
Tony G. Babb ◽  
John R. Halliwill
Keyword(s):  
Exercise Performance ◽  
Lactate Threshold ◽  
Time Trial ◽  
Heat Acclimation ◽  
Mean Power ◽  
Performance Impact ◽  
Time Trial Performance ◽  
Threshold Test ◽  
Before And After ◽  
Trial Performance

The relationship between exercise performance and lactate and ventilatory thresholds under two distinct environmental conditions is unknown. We examined the relationships between six lactate threshold methods (blood- and ventilation-based) and exercise performance in cyclists in hot and cool environments. Twelve cyclists performed a lactate threshold test, a maximal O2 uptake (V̇o2max) test, and a 1-h time trial in hot (38°C) and cool (13°C) conditions, before and after heat acclimation. Eight control subjects completed the same tests before and after 10 days of identical exercise in a cool environment. The highest correlations were observed with the blood-based lactate indexes; however, even the indirect ventilation-based indexes were well correlated with mean power during the time trial. Averaged bias was 15.4 ± 3.6 W higher for the ventilation- than the blood-based measures ( P < 0.05). The bias of blood-based measures in the hot condition was increased: the time trial was overestimated by 37.7 ± 3.6 W compared with only 24.1 ± 3.2 W in the cool condition ( P < 0.05). Acclimation had no effect on the bias of the blood-based indexes ( P = 0.51) but exacerbated the overestimation by some ventilation-based indexes by an additional 34.5 ± 14.1 W ( P < 0.05). Blood-based methods to determine lactate threshold show less bias and smaller variance than ventilation-based methods when predicting time-trial performance in cool environments. Of the blood-based methods, the inflection point between steady-state lactate and rising lactate (INFL) was the best method to predict time-trial performance. Lastly, in the hot condition, ventilation-based predictions are less accurate after heat acclimation, while blood-based predictions remain valid in both environments after heat acclimation.

scholarly journals Heat acclimation improves exercise performance

2010 ◽  
Vol 109 (4) ◽  
pp. 1140-1147 ◽  
Author(s):  
Santiago Lorenzo ◽  
John R. Halliwill ◽  
Michael N. Sawka ◽  
Christopher T. Minson
Keyword(s):  
Exercise Performance ◽  
Lactate Threshold ◽  
Time Trial ◽  
Heat Acclimation ◽  
Control Group ◽  
Time Trial Performance ◽  
Before And After ◽  
C 30 ◽  
The Impact ◽  
Trial Performance

This study examined the impact of heat acclimation on improving exercise performance in cool and hot environments. Twelve trained cyclists performed tests of maximal aerobic power (V̇o2max), time-trial performance, and lactate threshold, in both cool [13°C, 30% relative humidity (RH)] and hot (38°C, 30% RH) environments before and after a 10-day heat acclimation (∼50% V̇o2max in 40°C) program. The hot and cool condition V̇o2max and lactate threshold tests were both preceded by either warm (41°C) water or thermoneutral (34°C) water immersion to induce hyperthermia (0.8–1.0°C) or sustain normothermia, respectively. Eight matched control subjects completed the same exercise tests in the same environments before and after 10 days of identical exercise in a cool (13°C) environment. Heat acclimation increased V̇o2max by 5% in cool (66.8 ± 2.1 vs. 70.2 ± 2.3 ml·kg−1·min−1, P = 0.004) and by 8% in hot (55.1 ± 2.5 vs. 59.6 ± 2.0 ml·kg−1·min−1, P = 0.007) conditions. Heat acclimation improved time-trial performance by 6% in cool (879.8 ± 48.5 vs. 934.7 ± 50.9 kJ, P = 0.005) and by 8% in hot (718.7 ± 42.3 vs. 776.2 ± 50.9 kJ, P = 0.014) conditions. Heat acclimation increased power output at lactate threshold by 5% in cool (3.88 ± 0.82 vs. 4.09 ± 0.76 W/kg, P = 0.002) and by 5% in hot (3.45 ± 0.80 vs. 3.60 ± 0.79 W/kg, P < 0.001) conditions. Heat acclimation increased plasma volume (6.5 ± 1.5%) and maximal cardiac output in cool and hot conditions (9.1 ± 3.4% and 4.5 ± 4.6%, respectively). The control group had no changes in V̇o2max, time-trial performance, lactate threshold, or any physiological parameters. These data demonstrate that heat acclimation improves aerobic exercise performance in temperate-cool conditions and provide the scientific basis for employing heat acclimation to augment physical training programs.

Effect of 8 days of exercise-heat acclimation on aerobic exercise performance of men in hypobaric hypoxia

2020 ◽  
Vol 319 (1) ◽  
pp. R114-R122
Author(s):  
Roy M. Salgado ◽  
Kirsten E. Coffman ◽  
Karleigh E. Bradbury ◽  
Katherine M. Mitchell ◽  
Beau R. Yurkevicius ◽  
...  
Keyword(s):  
Steady State ◽  
Exercise Performance ◽  
Hypobaric Hypoxia ◽  
Acute Mountain Sickness ◽  
Time Trial ◽  
Heat Acclimation ◽  
Peak Oxygen Consumption ◽  
Time Trial Performance ◽  
Expansion Time ◽  
Trial Performance

Exercise-heat acclimation (EHA) induces adaptations that improve tolerance to heat exposure. Whether adaptations from EHA can also alter responses to hypobaric hypoxia (HH) conditions remains unclear. This study assessed whether EHA can alter time-trial performance and/or incidence of acute mountain sickness (AMS) during HH exposure. Thirteen sea-level (SL) resident men [SL peak oxygen consumption (V̇o2peak) 3.19 ± 0.43 L/min] completed steady-state exercise, followed by a 15-min cycle time trial and assessment of AMS before (HH1; 3,500 m) and after (HH2) an 8-day EHA protocol [120 min; 5 km/h; 2% incline; 40°C and 40% relative humidity (RH)]. EHA induced lower heart rate (HR) and core temperature and plasma volume expansion. Time-trial performance was not different between HH1 and HH2 after 2 h (106.3 ± 23.8 vs. 101.4 ± 23.0 kJ, P = 0.71) or 24 h (107.3 ± 23.4 vs. 106.3 ± 20.8 kJ, P > 0.9). From HH1 to HH2, HR and oxygen saturation, at the end of steady-state exercise and time-trial tests at 2 h and 24 h, were not different ( P > 0.05). Three of 13 volunteers developed AMS during HH1 but not during HH2, whereas a fourth volunteer only developed AMS during HH2. Heat shock protein 70 was not different from HH1 to HH2 at SL [1.9 ± 0.7 vs. 1.8 ± 0.6 normalized integrated intensities (NII), P = 0.97] or after 23 h (1.8 ± 0.4 vs. 1.7 ± 0.5 NII, P = 0.78) at HH. Our results indicate that this EHA protocol had little to no effect—neither beneficial nor detrimental—on exercise performance in HH. EHA may reduce AMS in those who initially developed AMS; however, studies at higher elevations, having higher incidence rates, are needed to confirm our findings.

scholarly journals Change in Exercise Performance and Markers of Acute Kidney Injury Following Heat Acclimation with Permissive Dehydration

Nutrients ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 841
Author(s):  
Arpie Haroutounian ◽  
Fabiano T. Amorim ◽  
Todd A. Astorino ◽  
Nazareth Khodiguian ◽  
Katharine M. Curtiss ◽  
...  
Keyword(s):  
Acute Kidney Injury ◽  
Kidney Injury ◽  
Time Trial ◽  
Heat Acclimation ◽  
Time Trial Performance ◽  
Neutrophil Gelatinase Associated Lipocalin ◽  
Before And After ◽  
Temperate Environment ◽  
Kidney Injury Molecule 1 ◽  
Trial Performance

Implementing permissive dehydration (DEH) during short-term heat acclimation (HA) may accelerate adaptations to the heat. However, HA with DEH may augment risk for acute kidney injury (AKI). This study investigated the effect of HA with permissive DEH on time-trial performance and markers of AKI. Fourteen moderately trained men (age and VO2max = 25 ± 0.5 yr and 51.6 ± 1.8 mL.kg−1.min−1) were randomly assigned to DEH or euhydration (EUH). Time-trial performance and VO2max were assessed in a temperate environment before and after 7 d of HA. Heat acclimation consisted of 90 min of cycling in an environmental chamber (40 °C, 35% RH). Neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule-1 (KIM-1) were assessed pre- and post-exercise on day 1 and day 7 of HA. Following HA, VO2max did not change in either group (p = 0.099); however, time-trial performance significantly improved (3%, p < 0.01) with no difference between groups (p = 0.485). Compared to pre-exercise, NGAL was not significantly different following day 1 and 7 of HA (p = 0.113) with no difference between groups (p = 0.667). There was a significant increase in KIM-1 following day 1 and 7 of HA (p = 0.002) with no difference between groups (p = 0.307). Heat acclimation paired with permissive DEH does not amplify improvements in VO2max or time-trial performance in a temperate environment versus EUH and does not increase markers of AKI.

scholarly journals Heat training increases exercise capacity in hot but not in temperate conditions: a mechanistic counter-balanced cross-over study

2015 ◽  
Vol 309 (5) ◽  
pp. H750-H761 ◽  
Author(s):  
Stefanie Keiser ◽  
Daniela Flück ◽  
Fabienne Hüppin ◽  
Alexander Stravs ◽  
Matthias P. Hilty ◽  
...  
Keyword(s):  
Blood Volume ◽  
Exercise Performance ◽  
Cerebral Perfusion ◽  
Time Trial ◽  
Albumin Solution ◽  
Exercise Tests ◽  
Time Trial Performance ◽  
Before And After ◽  
Trial Performance

The aim was to determine the mechanisms facilitating exercise performance in hot conditions following heat training. In a counter-balanced order, seven males (V̇o2max 61.2 ± 4.4 ml·min−1·kg−1) were assigned to either 10 days of 90-min exercise training in 18 or 38°C ambient temperature (30% relative humidity) applying a cross-over design. Participants were tested for V̇o2max and 30-min time trial performance in 18 (T18) and 38°C (T38) before and after training. Blood volume parameters, sweat output, cardiac output (Q̇), cerebral perfusion (i.e., middle cerebral artery velocity [MCAvmean]), and other variables were determined. Before one set of exercise tests in T38, blood volume was acutely expanded by 538 ± 16 ml with an albumin solution (T38A) to determine the role of acclimatization induced hypervolemia on exercise performance. We furthermore hypothesized that heat training would restore MCAvmean and thereby limit centrally mediated fatigue. V̇o2max and time trial performance were equally reduced in T38 and T38A (7.2 ± 1.6 and 9.3 ± 2.5% for V̇o2max; 12.8 ± 2.8 and 12.9 ± 2.8% for time trial). Following heat training both were increased in T38 (9.6 ± 2.1 and 10.4 ± 3.1%, respectively), whereas both V̇o2max and time trial performance remained unchanged in T18. As expected, heat training augmented plasma volume (6 ± 2%) and mean sweat output (26 ± 6%), whereas sweat [Na+] became reduced by 19 ± 7%. In T38 Q̇max remained unchanged before (21.3 ± 0.6 l/min) to after (21.7 ± 0.5 l/min) training, whereas MCAvmean was increased by 13 ± 10%. However, none of the observed adaptations correlated with the concomitant observed changes in exercise performance.

Effect of Repeated Sodium Phosphate Loading on Cycling Time-Trial Performance and VO2peak

2013 ◽  
Vol 23 (2) ◽  
pp. 187-194 ◽  
Author(s):  
Cameron P. Brewer ◽  
Brian Dawson ◽  
Karen E. Wallman ◽  
Kym J. Guelfi
Keyword(s):  
Sodium Phosphate ◽  
Time Trial ◽  
Peak Oxygen Uptake ◽  
Fat Free Mass ◽  
Mean Power ◽  
Time Trial Performance ◽  
Cycling Time Trial ◽  
Placebo Phase ◽  
Cycling Time ◽  
Trial Performance

Research into supplementation with sodium phosphate has not investigated the effects of a repeated supplementation phase. Therefore, this study examined the potential additive effects of repeated sodium phosphate (SP) supplementation on cycling time-trial performance and peak oxygen uptake (VO2peak). Trained male cyclists (N = 9, M ± SD VO2peak = 65.2 ± 4.8 ml · kg−1 · min−1) completed baseline 1,000-kJ time-trial and VO2peak tests separated by 48 hr, then ingested either 50 mg · kg fat-free mass−1 · d−1 of tribasic SP or a combined glucose and NaCl placebo for 6 d before performing these tests again. A 14-d washout period separated the end of one loading phase and the start of the next, with 2 SP and 1 placebo phase completed in a counterbalanced order. Although time-trial performance (55.3–56.5 min) was shorter in SP1 and SP2 (~60–70 s), effect sizes and smallest-worthwhile-change values did not differ in comparison with baseline and placebo. However, mean power output was greater than placebo during time-trial performance at the 250-kJ and 500-kJ time points (p < .05) after the second SP phase. Furthermore, mean VO2peak values (p < .01) were greater after the SP1 (3.5–4.3%), with further improvements (p < .01) found in SP2 (7.1–7.7%), compared with baseline and placebo. In summary, repeated SP supplementation, ingested either 15 or 35 d after initial loading, can have an additive effect on VO2peak and possibly time-trial performance.

scholarly journals Short-Term Heat Acclimation and Precooling, Independently and Combined, Improve 5-km Time Trial Performance in the Heat

2018 ◽  
Vol 32 (5) ◽  
pp. 1366-1375 ◽  
Author(s):  
Carl A. James ◽  
Alan J. Richardson ◽  
Peter W. Watt ◽  
Ashley G.B. Willmott ◽  
Oliver R. Gibson ◽  
...  
Keyword(s):  
Time Trial ◽  
Heat Acclimation ◽  
Short Term ◽  
Time Trial Performance ◽  
Trial Performance

Effects of Heat Acclimatization, Heat Acclimation, and Intermittent Exercise Heat Training on Time-Trial Performance

2021 ◽  
pp. 194173812110506
Author(s):  
Yasuki Sekiguchi ◽  
Courteney L. Benjamin ◽  
Ciara N. Manning ◽  
Jeb F. Struder ◽  
Lawrence E. Armstrong ◽  
...  
Keyword(s):  
Intermittent Exercise ◽  
Statistical Significance ◽  
Time Trial ◽  
Heat Acclimation ◽  
Peak Oxygen Consumption ◽  
Heat Acclimatization ◽  
Level Of Evidence ◽  
Time Trial Performance ◽  
Level 3 ◽  
Trial Performance

Background: The purpose of this study was to investigate effects of heat acclimatization (HAz) followed by heat acclimation (HA), and intermittent heat training (IHT) on time-trial performance. Hypothesis: Time-trial performance will improve after HA and will further improve with twice a week of IHT. Study Design: Interventional study. Level of Evidence: Level 3. Methods: A total of 26 male athletes (mean ± SD; age, 35 ± 12 years; body mass, 72.8 ± 8.9 kg; peak oxygen consumption [VO2peak], 57.3 ± 6.7 mL·kg−1·min−1) completed five 4-km time trials (baseline, post-HAz, post-HA, post-IHT4, post-IHT8) in the heat (ambient temperature, 35.4°C ± 0.3°C; relative humidity, 46.7% ± 1.2%) on a motorized treadmill. After baseline time trial, participants performed HAz (109 ± 10 days) followed by post-HAz time trial. Then, participants completed 5 days of HA, which involved exercising to induce hyperthermia (38.50°C-39.75°C) for 60 minutes. Participants were then divided into 3 groups and completed IHT either twice per week (IHTMAX), once per week (IHTMIN), or not at all (IHTCON) over an 8-week period. The exercise used for the IHT matched the HA. Four-kilometer time trials were performed after 4 weeks (post-IHT4) and 8 weeks of IHT (post-IHT8). Results: Time trial was faster in post-HA (17.98 ± 2.51 minutes) compared with baseline (18.61 ± 3.06 minutes; P = 0.037) and post-HAz (18.66 ± 3.12 minutes; P = 0.023). Percentage change in time trial was faster in IHTMAX (−3.9% ± 5.2%) compared with IHTCON (11.5% ± 16.9%) ( P = 0.020) and approached statistical significance with large effect (effect size = 0.96) compared with IHTMIN (1.6% ± 6.2%; P = 0.059) at post-IHT8. Additionally, IHTMAX (−2.2% ± 4.2%) was faster than IHTCON (3.6% ± 6.9%) ( P = 0.05) at post-IHT4. Conclusion: These results indicate that HA after HAz induces additional improvement in time-trial performance. IHT twice per week shows improvement after 8 weeks, while once per week maintains performance for 8 weeks. No IHT results in a loss of adaptations after 4 weeks and even greater losses after 8 weeks. Clinical Relevance: HA after HAz improves time-trial performance, twice a week of IHT improves performance further, and once a week of IHT maintains performance for at least 8 weeks.

Dietary Composition Influences Short-term Endurance Training–Induced Adaptations of Substrate Partitioning during Exercise

2004 ◽  
Vol 14 (1) ◽  
pp. 38-61 ◽  
Author(s):  
Kevin A. Jacobs ◽  
David R. Paul ◽  
Ray J. Geor ◽  
Kenneth W. Hinchcliff ◽  
W. Michael Sherman
Keyword(s):  
Endurance Training ◽  
Time Trial ◽  
Whole Body ◽  
High Fat ◽  
Short Term ◽  
Time Trial Performance ◽  
Glucose Flux ◽  
Before And After ◽  
Substrate Partitioning ◽  
Trial Performance

The purpose of the current study was to examine the influence of dietary composition on short-term endurance training–induced adaptations of substrate partitioning and time trial exercise performance. Eight untrained males cycled for 90 min at ~54% aerobic capacity while being infused with [6,62H]glucose before and after two 10-d experimental phases separated by a 2-week washout period. Time trial performance was measured after the 90-min exercise trials before and after the 2nd experimental phase. During the first 10-d phase, subjects were randomly assigned to consume either a high carbohydrate or high fat diet while remaining inactive (CHO or FAT). During the second 10-d phase, subjects consumed the opposite diet, and both groups performed identical daily supervised endurance training (CHO+T or FAT+T). CHO and CHO+T did not affect exercise metabolism. FAT reduced glucose flux at the end of exercise, while FAT+T substantially increased whole body lipid oxidation during exercise and reduced glucose flux at the end of exercise. Despite these differences in adaptation of substrate use, training resulted in similar improvements in time trial performance for both groups. We conclude that (a) 10-d high fat diets result in substantial increases in whole body lipid oxidation during exercise when combined with daily aerobic training, and (b) diet does not affect short-term training-induced improvements in high-intensity time trial performance.

Sign in / Sign up

Export Citation Format

Share Document