A time-saving method to assess power output at lactate threshold in well-trained and elite cyclists

Durability in Youth Squad Triathletes-Influence of Strenuous Cycling on Subsequent Running Performance, Economy, and Substrate Utilization

PURPOSE

This study aimed to investigate oxygen/energy cost (OC/EC) of running and substrate utilization before and after strenuous cycling in well-trained junior triathletes and the relevance of changes in these variables for fatigued running performance.

METHODS

Nineteen junior squad triathletes (4 female, 15 male; 17.2 [1.8] y; maximal oxygen uptake (V˙O2peak) 61.4 [5.1] mL·kg-1·min-1) completed 3 submaximal running steps (2.8 m·s-1, +0.4 m·s-1, and 5 min) under fresh conditions, followed by an incremental cycling test (∼2 W·kg-1, +20 W, and 3 min) to exhaustion. Afterward, they performed another incremental running test to exhaustion under fatigued conditions for V˙O2peak, OC, and time-to-exhaustion assessment. During both runs, OC, EC, and carbohydrate/fat oxidation (CHO/FO) were assessed.

RESULTS

Contrary to trivial/small average changes in OC (210 [15] to 209 [14] mL·kg-1·km-1, P = .71) and EC (4.75 [0.33] to 4.59 [0.29] kJ·kg-1·km-1, P = .02), CHO decreased (2.96 [0.68] to 2.08 [0.68] g·min-1) while FO increased (0.15 [0.13] to 0.48 [0.22] g·min-1) significantly from fresh to fatigued running (P < .001). Besides V˙O2peak (r = .68, P = .002), the changes in CHO (r = -.60, P = .01) and FO (r = .67, P = .003) were significantly correlated with fatigued time to exhaustion (1715 [172] s). Multiple regression and commonality analysis identified V˙O2peak, OC, and the change in FO as the best model for time to exhaustion (R2 = 88%).

CONCLUSION

Despite trivial/small changes in OC/EC from fresh to fatigued running, a pronounced shift in substrate utilization from CHO to FO was evident in junior triathletes, which was also associated with fatigued running performance.

Comparison of modeled lactate threshold 2 with maximal lactate steady state in running and cycling

This study investigated (1) the agreement of modeled lactate threshold 2 using peak oxygen uptake, cost of locomotion, and fractional utilization of peak oxygen uptake at lactate threshold 2 with the maximal lactate steady state in running and cycling; (2) the impact of different cost of locomotion determination methods on the accuracy of the model and (3) the contributions of peak oxygen uptake, cost of locomotion, and fractional utilization of peak oxygen uptake at lactate threshold 2 to the work rate at maximal lactate steady state. Thirty-four endurance-trained athletes (27.7±6.9 y, 56.2±5.5 ml∙kg-1∙min-1) completed an incremental step test on a treadmill or a cycling ergometer. Peak oxygen uptake, cost of locomotion at lactate threshold 1, at 80% of peak oxygen uptake, and at lactate threshold 2, and fractional utilization of peak oxygen uptake at lactate threshold 2 were assessed. Two to five 30-minute constant work rate tests were performed for maximal lactate steady state determination. Moderate to good agreement was found between modeled work rate corresponding to lactate threshold 2 and the maximal lactate steady state for running and cycling (intraclass correlation coefficient≥0.698) with the smallest mean difference (±limits of agreement) for cost of locomotion determined at lactate threshold 2 with -2.0±5.2 and -0.9±6.0%, respectively. Overall, 83 and 79% of the variance in the maximal lactate steady state was explained by peak oxygen uptake, cost of locomotion determined at lactate threshold 2, and fractional utilization of peak oxygen uptake at lactate threshold 2, respectively. Peak oxygen uptake and cost of locomotion determined at lactate threshold 2 contributed the most to the regression R 2 in running (54 and 40%) and cycling (74 and 51%), while fractional utilization of peak oxygen uptake at lactate threshold 2 had the smallest contribution (4 and 5%). Based on the high accuracy of the model with the major contribution of peak oxygen uptake and cost of locomotion determined at lactate threshold 2, the work rate corresponding to the maximal lactate steady state could be improved focusing on these two variables during training.

Elite Aerobic Endurance Performance: Is It Really Related to Lactate Threshold Expressed Relative to Peak Oxygen Uptake?

PURPOSE

The purpose of this study was to investigate how lactate threshold (LT), expressed as a percentage (LT%) of peak oxygen uptake (VO2peak), is related to aerobic endurance performance in a large group of aerobic endurance athletes from 3 demanding aerobic endurance sports.

METHODS

A total of 292 (212 male and 80 female) aerobic endurance athletes competing in long-distance running, cycling, and cross-country skiing participated in the present study. Based on their competitive history, they were divided into 3 performance-level groups: elite (n = 71), national (n = 158), and regional (n = 63). VO2peak and LT tests were conducted on the same day for all athletes, with similar testing protocols.

RESULTS

In the large group of endurance athletes, LT% did not differ between performance levels (78.9% [6.4%], 79.9% [6.7%], and 80.3% [7.1%] for elite, national, and regional level, respectively). The same nonsignificant difference was observed within males and females as well. VO2peak differed significantly (P < .01) between performance levels (71.1 [6.5], 65.5 [8.0], and 58.1 [6.4] mL·kg-1·min-1 in elite, national, and regional level, respectively). This was also displayed within males and females separately, although not when expressed in liters per minute.

CONCLUSIONS

The findings of similar LT% between different performance levels in the large group of endurance athletes challenges the realm of LT% being considered one of the primary determinants of aerobic endurance performance. This study also confirms the importance of VO2peak as a primary predictor of aerobic endurance performance in a large group of aerobic endurance athletes.

Modeling lactate threshold in cycling-influence of sex, maximal oxygen uptake, and cost of cycling in young athletes

PURPOSE

Understanding physiological determinants of lactate threshold 2 (LT2) is crucial for tracking adaptations and deriving individualized training recommendations in cycling. Therefore, the study investigated: 1. the accuracy of modeling power output at LT2 in young athletes of both sexes using maximal oxygen uptake (V ˙ O 2 peak ), fractional utilization ofV ˙ O 2 peak (%V ˙ O 2 peak ), and oxygen cost of cycling (Cc); 2. the influence of Cc determination on the model accuracy; 3. the influence of the model predictors and inclusion of maximal lactate accumulation rate (c ˙ L a max ) on power at LT2 depending on sex.

METHODS

Eighty-three cyclists and triathletes (22 females, 61 males; age [median and IQR]: 14.6 [13.8-17.6] years,V ˙ O 2 peak [mean ± SD]: 59.2 ± 6.5 mL⋅kg-1⋅min-1) performed an incremental test to determine power at LT2,V ˙ O 2 peak , %V ˙ O 2 peak at LT2, and Cc (assessed at 3 W⋅kg-1, 75%V ˙ O 2 peak , and 90% LT2).

RESULTS

Modeled and experimentally determined power at LT2 demonstrated excellent agreement for all, male and female athletes (ICC ≥ 0.961), with Cc at 90% LT2 providing the highest accuracy (ICC ≥ 0.986). The three physiological determinants explained ≥ 98% of the variance in power at LT2, with the largest unique contribution fromV ˙ O 2 peak (62 and 67% of total R 2 ), followed by Cc (8 and 34%) and %V ˙ O 2 peak at LT2 (5 and 12%) in males and females, respectively, whilec ˙ L a max did not improve the regression.

CONCLUSION

V ˙ O 2 peak , %V ˙ O 2 peak at LT2 and Cc accurately predict power at LT2 in young cycling athletes independent of sex, with determination of Cc at 90% LT2 providing the highest accuracy. WhileV ˙ O 2 peak contributes most to LT2 in both sexes, Cc appears more important in young females.

Setting Treadmill Intensity for Rat Aerobic Training Using Lactate and Gas Exchange Thresholds

PURPOSE

To open up new horizons of translational research, we studied the lactate threshold (LT)-dependent physiological responses and adaptations to exercise in rats, highlighting the importance of intensity-specific studies for optimizing exercise prescriptions. LT is physiologically related to the noninvasive gas exchange threshold (GET), and both thresholds are moderate-heavy-intensity boundary indices in determining an effective intensity of aerobic training in humans. Although their practical utility is presumed to extend to rats, the actual existence of GET, the thresholds' relations to maximal oxygen consumption (V̇O 2max ), and whether aerobic adaptations by training differ around the LT intensity remain uncertain.

METHODS

This study sought to identify the GET using our previously established rat LT model by combining the use of a metabolic chamber and the V-slope method, and to confirm the thresholds' relations to V̇O 2max . We investigated changes in the thresholds and V̇O 2max following 6 wk of endurance training at below or above LT intensity.

RESULTS

GET and LT were significantly correlated and agreed with high precision, although with a fixed bias. Untrained rats exhibited GET and LT at 56% and 52% of their V̇O 2max , respectively. Endurance training at supra-, but not below-, the LT intensity significantly improved V̇O 2max and both thresholds; however, their %V̇O 2max remained unaltered.

CONCLUSIONS

GET in rats is identifiable as a threshold associated with LT using the V-slope method. Furthermore, both thresholds can serve as moderate-heavy-intensity boundary indices for the aerobic training of rats. This study advances our understanding of exercise intensity regulation in rats, thereby contributing to the development of a more nuanced and effective model for exercise prescription, with implications for human health and fitness.

Short-time cycling performance in young elite cyclists: related to maximal aerobic power and not to maximal accumulated oxygen deficit

Purpose

To explore the relationships between performance variables and physiological variables in a short-time (2-3 min) cycling time trial (TT) on a cycle ergometer.

Methods

Fifteen young elite cyclists (age: 17.3 ± 0.7 years, maximal oxygen uptake (VO2max): 76.6 ± 5.2 mL⋅kg-1⋅min-1) participated in this study. Maximal aerobic power (MAP), maximal anaerobic power (MANP), time to exhaustion at 130% of maximal aerobic power (TTE), maximal accumulated oxygen deficit (MAOD) in the TT, anaerobic power reserve (APR) and lactate threshold (LT) was tested. MAP was calculated as VO2max/oxygen cost of cycling (CC), MANP was determined as mean power output (W) during a 10 s maximal cycling sprint test, and MAOD was calculated as (VO2 demand - VO2 measured) ∙ time. APR was calculated as the relative difference between MAP and MANP.

Results

There was a strong correlation between MAP and TT time (r = -0.91, p < 0.01) with a standard error of estimate (SEE) of 4.4%, and a moderate association between MANP and TT time (r = -0.47, p = 0.04). Neither MAOD, TTE, LT nor APR correlated with TT.

Conclusion

MAP was highly correlated with TT with a SEE of 4.4%. Since neither TTE nor MAOD correlated with TT, this indicates that these two variables do not play a significant role in differentiating short-time endurance cycling performance. We suggest training for improving MAP and, or MANP to improve short-time endurance cycling performance.

Lactate thresholds and role of nitric oxide in male rats performing a test with forced swimming to exhaustion

The present study assessed a complex of biochemical parameters at the anaerobic threshold (AT) in untrained male Wistar rats with different times to exhaustion (Tex ) from swimming. The first group of rats was randomly divided into six subgroups and subjected to a swimming test to exhaustion without a load or with a load of 2%-10% of body weight (BW). In the first group, we established that for untrained rats, the load of 4% BW in the swimming to exhaustion test was optimal for endurance assessment in comparison with other loads. The second group of rats went through a preliminary test with swimming to exhaustion at 4% BW and was then divided into two subgroups: long swimming time (LST, Tex  > 240 min) and short swimming time (SST, Tex  < 90 min). All rats of the second group performed, for 6 days, an experimental training protocol: swimming for 20 min each day with weight increasing each day. We established that the AT was 3% BW in SST rats and 5% BW in LST rats. The AT shifted to the right on the lactate curve in LST rats. Also, at the AT in the LST rats, we found significantly lower levels of blood lactate, cortisol, and NO.

Modeling lactate threshold in young squad athletes: influence of sex, maximal oxygen uptake, and cost of running

PURPOSE

This study aimed to investigate: 1. The influence of sex and age on the accuracy of the classical model of endurance performance, including maximal oxygen uptake ([Formula: see text]), its fraction (LT2_%), and cost of running (C_R), for calculating running speed at lactate threshold 2 (vLT2) in young athletes. 2. The impact of different C_R determination methods on the accuracy of the model. 3. The contributions of [Formula: see text], LT2_%, and C_R to vLT2 in different sexes.

METHODS

45 male and 55 female young squad athletes from different sports (age: 15.4 ± 1.3 years; [Formula: see text]: 51.4 ± 6.8 [Formula: see text]) performed an incremental treadmill test to determine [Formula: see text], LT2_%, C_R, and vLT2. C_R was assessed at a fixed running speed (2.8 [Formula: see text]), at lactate threshold 1 (LT1), and at 80% of [Formula: see text], respectively.

RESULTS

Experimentally determined and modeled vLT2 were highly consistent independent of sex and age (ICC [Formula: see text] 0.959). The accuracy of vLT2 modeling was improved by reducing random variation using individualized C_R at 80% [Formula: see text] (± 4%) compared to C_R at LT1 (± 7%) and at a fixed speed (± 8%). 97% of the total variance of vLT2 was explained by [Formula: see text], LT2_%, and C_R. While [Formula: see text] and C_R showed the highest unique (96.5% and 31.9% of total [Formula: see text], respectively) and common (- 31.6%) contributions to the regression model, LT2_% made the smallest contribution (7.5%).

CONCLUSION

Our findings indicate: 1. High accuracy of the classical model of endurance performance in calculating vLT2 in young athletes independent of age and sex. 2. The importance of work rate selection in determining C_R to accurately predict vLT2. 3. The largest contribution of [Formula: see text] and C_R to vLT2, the latter being more important in female athletes than in males, and the least contribution of LT2_%.

Relationships Between Maximal Aerobic Speed, Lactate Threshold, and Double Poling Velocity at Lactate Threshold in Cross-Country Skiers

Purpose

To investigate the relationships between maximal aerobic speed (MAS), lactate threshold in per cent of peak oxygen uptake (LT) and velocity at LT (LT_v) in cross-country skiers. Secondly, we aimed to explore the fit of an equation previously used in cyclists and runners in a cohort of well-trained, competitive cross-country skiers for calculation of LT_v. Thirdly, we aimed to investigate if a new LT_v could still be calculated after a period of regular training only by providing a new MAS.

Methods

Ninety-five competitive cross-country skiers (65 males and 30 females) were tested for maximal oxygen uptake (VO_2max), peak oxygen uptake in double poling (DP-VO_2peak), oxygen cost of double poling (C_DP), LT, and LT_v. Thirty-five skiers volunteered to be tested 3 months later to evaluate potential changes in LT and LT_v.

Results

Velocity at LT was mainly determined by MAS (r = 0.88, p < 0.01). LT did not show a significant impact on LT_v. The product of MAS·LT precisely predicted LT_v at baseline (r = 0.99, SEE = 2.4%), and by only measuring MAS, a new LT_v could be accurately calculated (r = 0.92, SEE = 6.8%) 3 months later in a sub-set of the initial 95 skiers (n = 35).

Conclusion

The results suggest that LT has minor impact on LT_v in DP tested in a laboratory. LT_v seemed to be predominantly determined by MAS, and we suggest to put more focus on MAS and less on LT and LT_v in regular testing to evaluate aerobic performance capacity in DP.

Steeper or Faster? Tactical Dispositions to Minimize Oxygen Cost in Ski Mountaineering

Purpose

Investigate the effect of speed, inclination, and use of heel elevator on the oxygen cost of vertical climbing (C_vert) in ski mountaineering.

Methods

In this study, 19 participants who were (3 women and 16 men) moderate- to well-trained recreational Norwegian ski mountaineers were involved. All participants were tested for VO_2max in running, and in a ski mountaineering test on a treadmill, to assess C_vert. The test protocol consisted of 12 4 min work periods at different inclinations from 13 to 23°, with continuous VO₂ measurements. After every second work period, the inclination increased by 2°, and speed was decreased accordingly. The speed reduction was based on the equation V_vert = speed · sin(α), where α represents the angle of inclination. V_vert was thus held constant for each work period (854 m·h⁻¹). All work periods were completed twice, with and without a heel elevator. Half of the subjects started with the smallest inclination, and the other half started with the steepest inclination.

Results

The results showed that C_vert was unchanged at all inclinations except 13°, where there was a significantly higher C_vert, at the same V_vert. Only at 13°, C_vert was higher with the use of heel elevator. There was also a significant trend indicating lower C_vert with use of heel elevator with steeper inclination.

Conclusions

There seemed to be nothing to gain by choosing detours if the inclination was 13° or less. The use of heel elevator was more advantageous, the steeper the inclination, but at 13° there was a negative effect of using heel elevator.

Factors Influencing Running Velocity at Lactate Threshold in Male and Female Runners at Different Levels of Performance

BACKGROUND

The primary aim was to examine the relationship between lactate threshold (LT) expressed as percentage of maximal oxygen uptake (VO2max) and running velocity at LT (LTV). A secondary aim was to investigate to what extent VO2max, oxygen cost of running (CR), and maximal aerobic speed (MAS) determined LTV. A third aim was to investigate potential differences in LT and LTV between elite, national and recreational runners, as well as possible gender differences regarding VO2max, CR, LT, and LTV.

METHODS

Seventy-five competitive runners (37 males and 38 females) with an average VO2max of 63.0 ± 9.3 mL⋅kg-1⋅min-1, and an average LTV of 13.6 ± 2.3 km⋅h-1 were tested for VO2max, LT, LTV, MAS, and CR.

RESULTS

Lactate threshold did not correlate with LTV. With an r - value of 0.95 (p < 0.001) and a standard error of estimate of 4.0%, the product of MAS and individual LT determined 90% of LTV, outside a range of ±0.27 km⋅h-1. LTV increased with higher performance level. However, LT did not differ between elite, national and recreational runners. Female runners had 2.5% higher LT, 8% lower LTV, and 21% lower VO2max, but 9% better CR than male runners.

CONCLUSION

Lactate threshold did not correlate with LTV. The product of MAS and LT correlated strongly with LTV. There were no differences between elite, national and recreational runners regarding LT, but female runners had higher LT than the male runners. Female runners at the same relative performance level had lower LTV and VO2max, but better CR than male runners.

No Change - No Gain; The Effect of Age, Sex, Selected Genes and Training on Physiological and Performance Adaptations in Cross-Country Skiing

The aim was to investigate the effect of training, sex, age and selected genes on physiological and performance variables and adaptations before, and during 6 months of training in well-trained cross-country skiers. National-level cross-country skiers were recruited for a 6 months observational study (pre - post 1 - post 2 test). All participants were tested in an outside double poling time trial (TT_DP), maximal oxygen uptake in running (RUN-VO_2max), peak oxygen uptake in double poling (DP-VO_2peak), lactate threshold (LT) and oxygen cost of double poling (C_DP), jump height and maximal strength (1RM) in half squat and pull-down. Blood samples were drawn to genetically screen the participants for the ACTN3 R577X, ACE I/D, PPARGC1A rs8192678, PPARG rs1801282, PPARA rs4253778, ACSL1 rs6552828, and IL6 rs1474347 polymorphisms. The skiers were instructed to train according to their own training programs and report all training in training diaries based on heart rate measures from May to October. 29 skiers completed all testing and registered their training sufficiently throughout the study period. At pre-test, significant sex and age differences were observed in TT_DP (p < 0.01), DP-VO_2peak (p < 0.01), C_DP (p < 0.05), MAS (p < 0.01), LT_v (p < 0.01), 1RM half squat (p < 0.01), and 1RM pull-down (p < 0.01). For sex, there was also a significant difference in RUN-VO_2max (p < 0.01). No major differences were detected in physiological or performance variables based on genotypes. Total training volume ranged from 357.5 to 1056.8 min per week between participants, with a training intensity distribution of 90-5-5% in low-, moderate- and high-intensity training, respectively. Total training volume and ski-specific training increased significantly (p < 0.05) throughout the study period for the whole group, while the training intensity distribution was maintained. No physiological or performance variables improved during the 6 months of training for the whole group. No differences were observed in training progression or training adaptation between sexes or age-groups. In conclusion, sex and age affected physiological and performance variables, with only a minor impact from selected genes, at baseline. However, minor to no effect of sex, age, selected genes or the participants training were shown on training adaptations. Increased total training volume did not affect physiological and performance variables.

Stronger Is Better: The Impact of Upper Body Strength in Double Poling Performance

The purpose of the present study was to compare time results from a roller-skiing double poling (DP) time trial with different physiological variables, muscular strength variables, and DP characteristics in both male and female young competitive skiers with the same relative training background. In order to do this, 28 (16 women and 12 men) well-trained 16–25-year-old cross-country skiers from three Norwegian high schools for skiers, as well as local high performance competitive skiers from the South-East of Norway were recruited to participate in the study. All participants were tested for; maximal oxygen uptake in running, Peak oxygen uptake in DP, lactate threshold in DP, DP economy, time to voluntary exhaustion in DP, force analyses in DP, one repetition maximum and power output in pulldown, and leg press and a time trial during DP roller skiing. The results expressed strong correlations between roller skiing time trial performance and maximal strength in pull-down, both independent (r_xy = −0.83, p < 0.01) and dependent (r_xy–z = −0.50, p < 0.02) of sex. Higher maximal upper body strength was related to higher DP peak forces (PF) (r_xy = 0.78, p < 0.02), lower DP frequency (r_xy = −0.71, p < 0.01), and shorter DP contact time (CT) (r_xy = −0.48, p < 0.02). The practical implications of the present study is to acknowledge maximal upper body strength as a performance determining factor in DP. This point at the importance of including maximal strength training in cross-country skiers training programs.

High-intensity aerobic interval training improves aerobic fitness and HbA1c among persons diagnosed with type 2 diabetes

PURPOSE

It remains to be established how high-intensity aerobic interval training (HAIT) affects risk factors associated with type 2 diabetes (TD2). This study investigated effects of HAIT on maximal oxygen uptake (VO_2max), glycated Hemoglobin type A1C (HbA1c), insulin resistance (IR), fat oxidation (FatOx), body weight (BW), percent body fat (%BF), lactate threshold (LT), blood pressure (BP), and blood lipid profile (BLP) among persons with T2D. Results were compared to the effects after a moderate-intensity training (MIT) program.

METHODS

Thirty-eight individuals with T2D completed 12 weeks of supervised training. HAIT consisted of 4 × 4 min of walking or running uphill at 85-95% of maximal heart rate, and MIT consisted of continuous walking at 70-75% of maximal heart rate.

RESULTS

A 21% increase in VO_2max (from 25.6 to 30.9 ml kg^-1 min^-1, p < 0.001), and a reduction in HbA1c by -0.58% points (from 7.78 to 7.20%, p < 0.001) was found in HAIT. BW and body mass index (BMI) was reduced by 1.9% (p < 0.01). There was a tendency towards an improved FatOx at 60% VO_2max (14%, p = 0.065). These improvements were significant different from MIT. Both HAIT and MIT increased velocity at LT, and reduced %BF, waist circumference, hip circumference, and BP, with no significant differences between the two groups. Correlations were found between change in VO_2max and change in HbA1c when the two intervention groups were combined (R = -0.52, p < 0.01).

CONCLUSION

HAIT is an effective exercise strategy to improve aerobic fitness and reduce risk factors associated with T2D.