Test of the Classic Model for Predicting Endurance Running Performance

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.

Assessment of Aerobic Fitness and Repeated Sprint Ability in Elite Male Soccer: A Systematic Review of Test Protocols Used in Practice and Research

BACKGROUND

Soccer requires players to cover distances around 10-12 km, with numerous consecutive sprints throughout the 90-min game. As such, aerobic fitness and repeated sprint ability (RSA) are crucial physical qualities for the modern soccer player to cope with the demands of the game. However, a comprehensive and systematic search of aerobic fitness and RSA assessment procedures in elite soccer has yet to be conducted.

OBJECTIVES

The aims of this systematic review were to (1) identify the tests and outcome variables used to assess aerobic fitness and RSA of elite male soccer players, (2) provide normative values for the most common tests of aerobic fitness and RSA across different playing levels, and (3) report the reliability values of these aerobic fitness and RSA tests.

METHODS

A systematic review of the academic databases MEDLINE, CINAHL, SPORTDiscus, Web of Science, and OVID for studies published until August 2023 was conducted, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Studies were eligible for inclusion if (1) they were original research studies, published in a peer-reviewed journal, and written in English language; (2) they had the primary aim of assessing aerobic fitness and/or RSA; (3) players were male and older than 17 years of age (i.e. mean age of the group); and (4) their playing level was defined as 'professional', 'international', or 'elite'.

RESULTS

For aerobic fitness testing, 124 studies and 35 different tests were identified. Of those, 26 tests (74%) were field-based, whereas only nine (26%) were laboratory-based tests. The incremental treadmill test to exhaustion was the most commonly used aerobic fitness assessment method (56 studies, 45%), with maximal oxygen consumption ( V ˙ O2max) (mL/kg/min) being the most prevalent outcome variable (49 studies, 87%). The YYIR1 and YYIR2 were also commonly used tests, identified in 22 (18%) and ten studies (8%), respectively. The most frequently reported outcome variable in both tests was distance in metres, reported in 20 studies (91%) for YYIR1 and in all ten studies (100%) for YYIR2. For RSA testing, 27 studies and 18 different tests were identified. Substantial variability in the identified RSA testing protocols was observed in terms of direction (linear vs. multidirectional), sprint repetitions (6-15), sprint distance (20-40 m), type of recovery (active vs. passive), and recovery duration (10-30 s). The 6 × 40-m shuttle sprint protocol with a 180° change of direction and 20 s passive recovery was the most common RSA test, employed in eight studies (29%).

CONCLUSIONS

This systematic review provides a comprehensive overview of the testing methods used to assess aerobic fitness and RSA in elite male soccer players. A total of 35 different aerobic fitness tests and 18 RSA tests were identified, highlighting the diversity in methodologies used. The most prevalent aerobic test was the incremental treadmill testing to exhaustion, with a median V ˙ O2max value of 58 mL/kg/min. Field-based tests were preferred due to their practicality, cost-efficiency, and ability to assess multiple athletes simultaneously. A substantial variability in RSA testing protocols was identified in terms of sprint directions, distances, repetitions, and recovery types. Future research should focus on establishing the diagnostic accuracy of the most commonly used aerobic fitness tests to inform their utility in practice and bridge the gap between current testing practices and optimal fitness evaluation.

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.

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.

Decoding Ultramarathon: Muscle Damage as the Main Impediment to Performance

The biological determinants of performance have been well described for running races up to and including the marathon (42.2 km). Ultramarathon is more complex. Events range from 50 to 5000 km in single or multiple stages, are contested in various environments and terrains, and force athletes to contend with diverse performance-limiting issues such as fueling, hydrating, gastrointestinal distress, muscle damage, and sleep deprivation. Ultramarathons are not simply "long marathons." Nevertheless, scientific developments over the past decade have inched us toward a more complete picture of the psychophysiological factors underpinning performance. In this Current Opinion, we argue that muscle damage and associated fatigue is the main impediment to performance in long ultramarathons; more performance-limiting than aerobic capacity, running economy, or gastrointestinal distress. To assess an athlete's tolerance to ultramarathon-specific muscle damage and fatigue, we propose a lab-based protocol comprising downhill running with pre- to post-exercise measures of muscle contractile function following electrical or magnetic stimulation of the quadriceps muscles or their central nerves, muscle damage biomarkers (e.g., creatine kinase, lactate dehydrogenase, and myoglobin), and muscle morphology via imaging techniques. We close by offering training and racing advice on mitigating the deleterious effects of muscle damage. The twofold aims of this paper are (i) to enable athletes and their teams to better prepare for races and (ii) to help medical personnel identify the physiological milieu most likely to afflict the ultrarunner.

Sex differences in elite ski mountaineering aerobic performance

Ski mountaineering (SkiMo) sprints will debut as an Olympic sport in 2026, yet research on the discipline remains scarce compared to other winter sports. The demanding sprint format, with most of the race time spent on uphill sections, highlights the importance of body composition and maximal oxygen consumption (V˙O2max). While previous studies have primarily focused on male athletes, this study aimed to analyze sex differences in physiological parameters of elite SkiMo athletes, hypothesizing that differences in vertical velocities (vV) would surpass those in V˙O2 at ventilatory thresholds (VT1, VT2) and maximal intensity (MAX), respectively. Twenty elite/worldclass Swiss SkiMo athletes (6 women, 14 men, aged 20-32 years) participated in the study. They performed a graded exercise test to exhaustion on a treadmill set at a 25% slope, with breath-by-breath gas exchanges. Elite female SkiMo athletes had a V˙O2 value 13.6% lower at MAX (64.0 ± 3.8 vs. 72.8 ± 5.5 ml/kg/min; p = 0.002) and 15.5% lower at VT2 (54.8 ± 2.8 vs. 62.2 ± 5.8 ml/kg/min; p = 0.009) than their male counterparts. Interestingly, the sex-differences in vV at both MAX (1,825 ± 113 vs. 2,125 ± 156 m/h; p < 0.001; 16.4%) and VT2 (1,412 ± 56 vs. 1,696 ± 151 m/h; p < 0.001; 20.1%) intensities were consistently larger than the differences in V˙O2. Moreover, fat mass was higher in females (15.2 ± 1.0 vs. 6.6 ± 0.6%; p = 0.004). Additionally, vertical running energy cost at VT2 was significantly higher in females compared to males (2,329 ± 95 vs. 2,199 ± 60 ml/kg/kmv; p = 0.018). Sex differences in uphill velocities (16.4-20.1%) exceeded those in V˙O2 (13.6-16.5%). Investigation on the underlying mechanisms is required but several factors may contribute to this pronounced sex difference in uphill velocity beyond aerobic power alone. Overall, the present findings align with recent studies reporting a 16%-20% difference in performance times when investigating sex differences in uphill displacement. The performance gap between men and women appears to be larger in uphill sports.

A case report of the female world record holder from 1,500 m to the marathon in the 75+ age category

This study assessed the cardiorespiratory fitness, running biomechanics, muscle architecture, and training characteristics of a 76-yr-old female runner who currently holds the world record 1,500 m to marathon in the women's 75-79 yr age category. Maximum oxygen uptake (V̇o2max), running economy (RE), lactate threshold (LT), lactate turnpoint (LTP), maximal heart rate (HRmax), and running biomechanics were measured during a discontinuous treadmill protocol followed by a maximal incremental test. Muscle architecture was assessed using ultrasound. The testing was done in close proximity to her world record marathon performance in 2024. V̇o2max was 47.9 mL·kg-1·min-1, and HRmax was 180 beats·min-1. At marathon speed (11.9 km·h-1) her RE was 210 mL·kg-1·km-1 and her fractional utilization was 88% of V̇o2max. Fractional utilization at LT (11.1 km·h-1) and LTP (12.5 km·h-1) were 83% and 92% of V̇o2max, respectively. Average weekly distance was 115 and 84 km·wk-1 in the 6 wk prior to the marathon world record, and 2024 World Masters Athletics Championships (where she achieved 6 gold medals out of 6 events), respectively, with on average 90%, 9%, and 1% of training time performed in the moderate, heavy, and severe intensity domain, respectively. The 76-yr-old female world-record holder 1,500 m to marathon showed the highest V̇o2max ever recorded for a female >75 yr old, a very high fractional utilization of V̇o2max at LT, LTP, and marathon pace, while RE was found to be modest compared with other world-class master and younger elite runners.NEW & NOTEWORTHY This case study investigates the physiological determinants of exceptional performance in a 76-yr-old female world-record holder across distances from 1,500 m to the marathon. It reveals the highest V̇o2max ever recorded in females aged >75 yr and exceptional fractional utilization at metabolic thresholds and marathon speed, comparable to younger world-class distance runners. The modest running economy found can be partially explained by biomechanical and training data.

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.

The effects of plyometric versus resistance training on running economy and 5-km running time in middle-aged recreational runners

The effects of plyometric training (PT) versus resistance training (RT) on running economy and performance are unclear, especially in middle-aged recreational runners. We examined (1) the efficacy of PT versus RT on running economy and performance in middle-aged recreational runners and (2) the relationships between the main training outcomes. Twenty middle-aged recreational runners were randomly allocated to a PT or RT group (n = 10/group). Training was conducted twice/week for 10 weeks combined with daily running. PT included the countermovement jump (CMJ), rebound jump, hurdle hop, and drop jump. RT consisted of leg press, leg curl, and calf raise with 50%-90% of one-repetition maximum (1RM). Before and after the intervention, 1RM of the three lifting tasks, CMJ and drop jump performances, oxygen cost at 8-12 km/h, and 5 km running time were assessed. PT enhanced 1RM of leg curl only (8.5% and p = 0.007), whereas RT increased 1RM of the three lifting tasks (19.0%-21.1% and p < 0.001). Both groups improved CMJ height (6.4%-8.3% and p = 0.016) and drop jump performance (height: 9.7%-19.4%, p = 0.005, height/contact time: 11.4%-26.3% and p = 0.009) and oxygen cost regardless of running velocity (2.0% and p = 0.001) without significant group differences. However, neither group changed the 5-km running time (p ≥ 0.259). A significant correlation was found between the changes in calf raise 1RM and oxygen cost (r = -0.477 and p = 0.046) but not between the other measured variables. These results suggest that for middle-aged recreational runners, PT and RT can similarly improve running economy albeit not necessarily the 5-km running time, and enhancing plantarflexion strength may particularly contribute to improving running economy.

Estimate Anaerobic Work Capacity and Critical Power with Constant-Power All-Out Test

Background: The critical power model (CPM) is used extensively in sports to characterize fitness by estimating anaerobic work capacity (W') and critical power (CP). Traditionally, estimates of CP and W' require repeated, time-consuming tests. Alternatively, a 3 min all-out test yields good estimates of W' and CP. However, adoption of the 3 min protocol for regular fitness monitoring is deterred by the mentally/physically strenuous nature of the test. Objective: We propose to examine an alternative single-session testing protocol that can accurately estimate critical power model parameters. Methods: Twenty-eight healthy competitive athletes (cyclists or triathletes) (mean ± SD: age: 38.5 ± 10.4 years, height: 177.9 ± 8.6 cm, mass: 73.4 ± 9.9 kg) participated in 5 sessions on a Lode cycle ergometer in isokinetic mode within a 2-week period. A 3 min all-out test (3MT) was conducted on the first visit to determine CPM parameters from which power outputs for 4 subsequent constant-power plus all-out tests (CPT) were selected to result in exhaustion in 1-10 min. The subjects were to maintain the prescribed power output as consistently as possible at their preferred race cadence. Once the power output could no longer be maintained for more than 10 s, the subjects were instructed to produce an all-out effort. Tests were terminated after power output fell to an asymptote which was sustained for 2 min. Results: The CPM parameters for all of the CPT durations were compared to the traditional CP protocol (significant parameter differences were identified for all CPT durations) and the 3MT (only CPT durations > 3 min were different [3-6 min test, p < 0.01; >6 min test, p < 0.01]). CPT does not estimate traditional CP and W' parameters well. However, the CPT with a duration < 3 min accurately estimates both parameters of a 3MT. Conclusion: Therefore, CPT has the capacity to serve as an alternative tool to assess CP parameters.

The Relationship between Inflammatory Factors, Hemoglobin, and VO2 Max in Male Amateur Long-Distance Cross-Country Skiers in the Preparation Period

Background: Identifying factors affecting heart health in amateur athletes can significantly impact their health and help them achieve high performance. The current knowledge of these predictors is insufficient. The purpose of this study was to identify the biochemical determinants of maximal oxygen uptake (VO2 max) in male amateur long-distance cross-country skiers (37.9 ± 6.58 years, 51.08 ± 4.61 VO2 max ml/kg/min) in the preparation period. Methods: In this cross-sectional study, a time trial test was used to determine VO2 max and venous blood via biochemical markers. Descriptive statistics and Pearson correlation were used to analyze the data. The regression model determined the predictors. Results: VO2 max was significantly correlated with nine moderate or weak variables. Two regression models (R2 = 0.94 and R2 = 0.9) each identified two determinants of VO2 max, hemoglobin (p < 0.001) and C-reactive protein (p < 0.001), as well as erythrocyte sedimentation (p < 0.001) and platelets (p = 0.03). Only hemoglobin positive affected VO2 max. Conclusions: The results may indicate, in addition to results regarding hemoglobin concentration and its changes, the necessity to monitor the immune system, which may affect the capacity for amateur exercise. Biochemical monitoring is an essential tool for evaluating the individual adaptation to exercise and developing an effective training plan. The application of this knowledge can facilitate the achievement of optimal individual performance capabilities among cross-country skiing amateurs.

The Effect of Strength Training Methods on Middle-Distance and Long-Distance Runners' Athletic Performance: A Systematic Review with Meta-analysis

BACKGROUND

The running performance of middle-distance and long-distance runners is determined by factors such as maximal oxygen uptake (VO2max), velocity at VO2max (vVO2max), maximum metabolic steady state (MMSS), running economy, and sprint capacity. Strength training is a proven strategy for improving running performance in endurance runners. However, the effects of different strength training methods on the determinants of running performance are unclear.

OBJECTIVE

The aim of this systematic review with meta-analysis was to compare the effect of different strength training methods (e.g., high load, submaximal load, plyometric, combined) on performance (i.e., time trial and time until exhaustion) and its determinants (i.e., VO2max, vVO2max, MMSS, sprint capacity) in middle-distance and long-distance runners.

METHODS

A systematic search was conducted across electronic databases (Web of Science, PubMed, SPORTDiscus, SCOPUS). The search included articles indexed up to November 2022, using various keywords combined with Boolean operators. The eligibility criteria were: (1) middle- and long-distance runners, without restriction on sex or training/competitive level; (2) application of a strength training method for ≥ 3 weeks, including high load training (≥ 80% of one repetition maximum), submaximal load training (40-79% of one repetition maximum), plyometric training, and combined training (i.e., two or more methods); (3) endurance running training control group under no strength training or under strength training with low loads (< 40% of one repetition maximum); (4) running performance, VO2max, vVO2max, MMSS and/or sprint capacity measured before and after a strength training intervention program; (5) randomized and non-randomized controlled studies. The certainty of evidence was assessed using the GRADE (Grading of Recommendations Assessment, Development and Evaluation) approach. A random-effects meta-analysis and moderator analysis were performed using Comprehensive meta-analysis (version 3.3.0.70).

RESULTS

The certainty of the evidence was very low to moderate. The studies included 324 moderately trained, 272 well trained, and 298 highly trained athletes. The strength training programs were between 6 and 40 weeks duration, with one to four intervention sessions per week. High load and combined training methods induced moderate (effect size =  - 0.469, p = 0.029) and large effect (effect size =  - 1.035, p = 0.036) on running performance, respectively. While plyometric training was not found to have a significant effect (effect size =  - 0.210, p = 0.064). None of the training methods improved VO2max, vVO2max, MMSS, or sprint capacity (all p > 0.072). Moderators related to subject (i.e., sex, age, body mass, height, VO2max, performance level, and strength training experience) and intervention (i.e., weeks, sessions per week and total sessions) characteristics had no effect on running performance variables or its determinants (all p > 0.166).

CONCLUSIONS

Strength training with high loads can improve performance (i.e., time trial, time to exhaustion) in middle-distance and long-distance runners. A greater improvement may be obtained when two or more strength training methods (i.e., high load training, submaximal load training and/or plyometric training) are combined, although with trivial effects on VO2max, vVO2max, MMSS, or sprint capacity.

Is test specificity the issue in assessing aerobic fitness and performance of runners? A systematic review

INTRODUCTION

Various tests have been developed to evaluate aerobic fitness and performance of runners. However, a systematic understanding of which methods are more accurate is necessary to provide coaches and the sports sciences community with useful and confident outcomes. This study aims to summarize the evidence regarding the validity, reliability and sensitivity of tests for measuring aerobic fitness and performance in runners of several background of training.

EVIDENCE ACQUISITION

A systematic search was conducted of Web of Science, PubMed and Scopus up to 31st December 2022 according to PRISMA statement guidelines. Studies that reported findings about tests covering maximal aerobic speed, final velocity achieved during the test, average running speed or other method of evaluating the reference speed during the test were included. We evaluated the risk of bias in the included articles using the Risk of Bias Assessment Tool for Nonrandomized Studies (RoBANS). The tests were categorized into continuous incremental tests, intermittent tests and time-trial test.

EVIDENCE SYNTHESIS

A total of 23 studies met eligibility criteria. These studies contained three background of training: track and road runners (N.=15), trail runners (N.=7) and inexperienced runners (N.=1). Criterion validity was assessed in 73% of the studies, while only 41% of studies examined convergent validity. The majority of the reviewed studies (87%) ignored test-retest reliability. Test sensitivity was not reported in any study.

CONCLUSIONS

At least one aerobic fitness and performance test was identified for each types of background of training. However, some methodological aspects were not provided in the included articles. Most studies examined at least one aspect of validity (i.e., criterion or convergent-related validity), whilst few studies investigated test-retest reliability. Researchers and practitioners can use the information provided in this systematic review to select appropriate tests.

Locally applied heat stress during exercise training may promote adaptations to mitochondrial enzyme activities in skeletal muscle

There is some evidence for temperature-dependent stimulation of mitochondrial biogenesis; however, the role of elevated muscle temperature during exercise in mitochondrial adaptation to training has not been studied in humans in vivo. The purpose of this study was to determine the role of elevating muscle temperature during exercise in temperate conditions through the application of mild, local heat stress on mitochondrial adaptations to endurance training. Eight endurance-trained males undertook 3 weeks of supervised cycling training, during which mild (~ 40 °C) heat stress was applied locally to the upper-leg musculature of one leg during all training sessions (HEAT), with the contralateral leg serving as the non-heated, exercising control (CON). Vastus lateralis microbiopsies were obtained from both legs before and after the training period. Training-induced increases in complex I (fold-change, 1.24 ± 0.33 vs. 1.01 ± 0.49, P = 0.029) and II (fold-change, 1.24 ± 0.33 vs. 1.01 ± 0.49, P = 0.029) activities were significantly larger in HEAT than CON. No significant effects of training, or interactions between local heat stress application and training, were observed for complex I-V or HSP70 protein expressions. Our data provides partial evidence to support the hypothesis that elevating local muscle temperature during exercise augments training-induced adaptations to mitochondrial enzyme activity.

The effect of forward postural lean on running economy, kinematics, and muscle activation

BACKGROUND

Running economy, commonly defined as the metabolic energy demand for a given submaximal running speed, is strongly associated with distance running performance. It is commonly believed among running coaches and runners that running with increased forward postural lean either from the ankle or waist improves running economy. However, recent biomechanical research suggests using a large forward postural lean during running may impair running economy due to increased demand on the leg muscles.

PURPOSE

This study tests the effect of altering forward postural lean and lean strategy on running economy, kinematics, and muscle activity.

METHODS

16 healthy young adult runners (23±5 years, 8M/8F) ran on a motorized treadmill at 3.58m/s using three postural lean angles [upright, moderate lean (50% of maximal lean angle), and maximal lean] and two strategies (lean from ankle and lean from waist [trunk lean]). Metabolic energy consumption, leg kinematics, and muscle activation data were recorded for all trials.

RESULTS

Regardless of lean strategy, running with an increased forward postural lean (up to 8±2 degrees) increased metabolic cost (worsened economy) by 8% (p < .001), increased hip flexion (p < .001), and increased gluteus maximus (p = .016) and biceps femoris (p = .02) muscle activation during the stance phase. This relation between running economy and postural lean angle was similar between the ankle and trunk lean strategies (p = .743).

CONCLUSION

Running with a large forward postural lean reduced running economy and increased reliance on less efficient extensor leg muscles. In contrast, running with a more upright or moderate forward postural lean may be more energetically optimal, and lead to improved running performance.

Changes in running economy and attainable maximal oxygen consumption in response to prolonged running: The impact of training status

During prolonged running at moderate-to-high intensity, running economy (RE) deteriorates and attainable maximal oxygen consumption (VO2max) decreases. Whether these changes appear similarly in trained and untrained runners exercising at the same relative intensity is not clear. We recruited 10 trained runners (TR) and 10 active adults (AA), and compared RE and attainable VO2max before and after 1 h of running at 70% of VO2max. Submaximal VO2 increased more (p = 0.019) in AA (0.20 ± 0.13 L min-1) than in TR (0.07 ± 0.05 L min-1). Attainable VO2max decreased in AA (-0.21 ± 0.15 L min-1, p = 0.002), but remained unchanged in TR (-0.05 ± 0.10 L min-1, p = 0.18). Relative intensity (i.e., VO2/attainable VO2max), increased more (p = 0.001) in AA (8.3 ± 4.4%) than in TR (2.6 ± 1.9%). These results demonstrate that the ability to resist changes in RE and VO2max following prolonged running is superior in trained versus untrained runners, when exercising at the same relative intensity.

The Relationship Between Running Biomechanics and Running Economy: A Systematic Review and Meta-Analysis of Observational Studies

BACKGROUND

Running biomechanics is considered an important determinant of running economy (RE). However, studies examining associations between running biomechanics and RE report inconsistent findings.

OBJECTIVE

The aim of this systematic review was to determine associations between running biomechanics and RE and explore potential causes of inconsistency.

METHODS

Three databases were searched and monitored up to April 2023. Observational studies were included if they (i) examined associations between running biomechanics and RE, or (ii) compared running biomechanics between groups differing in RE, or (iii) compared RE between groups differing in running biomechanics during level, constant-speed, and submaximal running in healthy humans (18-65 years). Risk of bias was assessed using a modified tool for observational studies and considered in the results interpretation using GRADE. Meta-analyses were performed when two or more studies reported on the same outcome. Meta-regressions were used to explore heterogeneity with speed, coefficient of variation of height, mass, and age as continuous outcomes, and standardization of running shoes, oxygen versus energetic cost, and correction for resting oxygen or energy cost as categorical outcomes.

RESULTS

Fifty-one studies (n = 1115 participants) were included. Most spatiotemporal outcomes showed trivial and non-significant associations with RE: contact time r = - 0.02 (95% confidence interval [CI] - 0.15 to 0.12); flight time r = 0.11 (- 0.09 to 0.32); stride time r = 0.01 (- 0.8 to 0.50); duty factor r = - 0.06 (- 0.18 to 0.06); stride length r = 0.12 (- 0.15 to 0.38), and swing time r = 0.12 (- 0.13 to 0.36). A higher cadence showed a small significant association with a lower oxygen/energy cost (r = - 0.20 [- 0.35 to - 0.05]). A smaller vertical displacement and higher vertical and leg stiffness showed significant moderate associations with lower oxygen/energy cost (r = 0.35, - 0.31, - 0.28, respectively). Ankle, knee, and hip angles at initial contact, midstance or toe-off as well as their range of motion, peak vertical ground reaction force, mechanical work variables, and electromyographic activation were not significantly associated with RE, although potentially relevant trends were observed for some outcomes.

CONCLUSIONS

Running biomechanics can explain 4-12% of the between-individual variation in RE when considered in isolation, with this magnitude potentially increasing when combining different variables. Implications for athletes, coaches, wearable technology, and researchers are discussed in the review.

PROTOCOL REGISTRATION

https://doi.org/10.17605/OSF.IO/293 ND (OpenScience Framework).

Biomechanical, physiological and anthropometrical predictors of performance in recreational runners

Background

The maximal running speed (VMAX) determined on a graded treadmill test is well-recognized as a running performance predictor. However, few studies have assessed the variables that predict VMAX in recreationally active runners.

Methods

We used a mathematical procedure combining Fick's law and metabolic cost analysis to verify the relation between (1) VMAX versus anthropometric and physiological determinants of running performance and, (2) theoretical metabolic cost versus running biomechanical parameters. Linear multiple regression and bivariate correlation were applied. We aimed to verify the biomechanical, physiological, and anthropometrical determinants of VMAX in recreationally active runners. Fifteen recreationally active runners participated in this observational study. A Conconi and a stead-steady running test were applied using a heart rate monitor and a simple video camera to register the physiological and mechanical variables, respectively.

Results

Statistical analysis revealed that the speed at the second ventilatory threshold, theoretical metabolic cost, and fat-mass percentage confidently estimated the individual running performance as follows: VMAX = 58.632 + (-0.183 * fat percentage) + (-0.507 * heart rate percentage at second ventilatory threshold) + (7.959 * theoretical metabolic cost) (R2 = 0.62, p = 0.011, RMSE = 1.50 km.h-1). Likewise, the theoretical metabolic cost was significantly explained (R2 = 0.91, p = 0.004, RMSE = 0.013 a.u.) by the running spatiotemporal and elastic-related parameters (contact and aerial times, stride length and frequency, and vertical oscillation) as follows: theoretical metabolic cost = 10.421 + (4.282 * contact time) + (-3.795 * aerial time) + (-2.422 * stride length) + (-1.711 * stride frequency) + (0.107 * vertical oscillation).

Conclusion

Critical determinants of elastic mechanism, such as maximal vertical force and vertical and leg stiffness were unrelated to the metabolic economy. VMAX, a valuable marker of running performance, and its physiological and biomechanical determinants can be effectively evaluated using a heart rate monitor, treadmill, and a digital camera, which can be used in the design of training programs to recreationally active runners.

Peak Running Velocity vs. Critical Speed: Which One Is Better to Prescribe Endurance Training to Recreational Runners?

ABSTRACT

Figueiredo, DH, Figueiredo, DH, Manoel, FA, and Machado, FA. Peak running velocity vs. critical speed: which one is better to prescribe endurance training to recreational runners? J Strength Cond Res 37(9): 1783-1788, 2023-This study aimed to evaluate the effects of 5 weeks of training prescribed by peak running velocity obtained on the track (Vpeak_TR) and their respective time limit (Tlim), as well as by critical speed (CS), on physiological and endurance performance parameters in recreational runners. Twenty-two male runners were distributed into a Vpeak_TR group (GVP) and CS group (GCS) with a predefined program, alternating moderate-intensity continuous training and high-intensity interval training. Maximum oxygen uptake (V̇O2max), and its respective velocity (vV̇O2max), Vpeak_TR, Tlim at 100% Vpeak_TR, 5-km running performance, CS, and D' (maximum distance covered above CS) were assessed at pretraining and posttraining period. There was a significant increase from pretraining to posttraining in Vpeak_TR (GVP = 4.5 ± 3.1% vs. GCS = 7.5 ± 4.2%), vV̇O2max (GVP = 3.9 ± 3.8% vs. GCS = 8.6 ± 6.7%), and mean velocity 5-km (GVP = 5.6 ± 3.3% vs. GCS = 7.3 ± 3.5%) and decrease in 5-km time (GVP = -5.1 ± 3.0% vs. GCS = -6.8 ± 3.0%). CS and V̇O2max significantly improved in GCS (9.3 ± 8.4% and 6.0 ± 6.8%, respectively), with no difference for GVP (2.8 ± 5.6% and 1.3 ± 8.4%, respectively). No differences were observed between groups for all variables. These findings give further supports to the notion that both variables obtained on the track are valid tools to prescribed training in recreational runners.

Physiological Features of Olympic-Distance Amateur Triathletes, as Well as Their Associations with Performance in Women and Men: A Cross-Sectional Study

The purpose of this study was to verify the physiological and anthropometric determinants of triathlon performance in female and male athletes. This study included 40 triathletes (20 male and 20 female). Dual-energy X-ray absorptiometry (DEXA) was used to assess body composition, and an incremental cardiopulmonary test was used to assess physiological variables. A questionnaire about physical training habits was also completed by the athletes. Athletes competed in the Olympic-distance triathlon race. For the female group, the total race time can be predicted by V̇O₂max (β = -131, t = -6.61, p < 0.001), lean mass (β = -61.4, t = -2.66, p = 0.018), and triathlon experience (β = -886.1, t = -3.01, p = 0.009) (r² = 0.825, p < 0.05). For the male group, the total race time can be predicted by maximal aerobic speed (β = -294.1, t = -2.89, p = 0.010) and percentage of body fat (β = 53.6, t = 2.20, p = 0.042) (r² = 0.578, p < 0.05). The variables that can predict the performance of men are not the same as those that can predict the triathlon performance of women. These data can help athletes and coaches develop performance-enhancing strategies.

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_%.

Body and mind? Exploring physiological and psychological factors to explain endurance performance in cycling

Endurance athletes attribute performance not only to physiological factors, but also refer to psychological factors such as motivation. The goal of this study was to quantify the proportion of the variance in endurance performance that is explained by psychological factors in addition to the physiological factor VO₂max. Twenty-five athletes of the U17 Swiss Cycling national team (7f, 18 m, 15.3 ± 0.5 years) were examined in a cross-sectional study with psychological factors and VO₂max as independent variables and endurance performance in road cycling as dependent variable. Questionnaires were used to assess psychological factors (i.e. use of mental techniques, self-compassion, mental toughness, achievement motivation, and action vs. state orientation). VO₂max was measured by a step incremental cycle ergometer test of exhaustion. Endurance performance was measured in a cycling mountain time trial (1,320 m long, incline of 546 meters). A multiple regression model was created by using forward selection of regression model predictors. Results showed that higher VO₂max values (β = .48), being male (β = .26), and higher achievement motivation (i.e. perseverance, β = .11) were associated with a better endurance performance. A more frequent use of one particular mental technique (i.e. relaxation techniques, β = .03) was associated with a worse endurance performance. Our study shows that a physiological factor like VO₂max explains endurance performance to a large extent but psychological factors account for additional variance. In particular, one aspect of achievement motivation, namely perseverance, was associated with a better endurance performance. HIGHLIGHTSEndurance performance is explained by physiological (e.g. VO₂max) and psychological (e.g. perseverance) factorsVO₂max explains young cyclists' endurance performance to a large extentPerseverance explained performance beyond the influence of VO₂max.

The Energetic Costs of Uphill Locomotion in Trail Running: Physiological Consequences Due to Uphill Locomotion Pattern-A Feasibility Study

The primary aim of our feasibility reporting was to define physiological differences in trail running (TR) athletes due to different uphill locomotion patterns, uphill running versus uphill walking. In this context, a feasibility analysis of TR athletes' cardiopulmonary exercise testing (CPET) data, which were obtained in summer 2020 at the accompanying sports medicine performance center, was performed. Fourteen TR athletes (n = 14, male = 10, female = 4, age: 36.8 ± 8.0 years) were evaluated for specific physiological demands by outdoor CPET during a short uphill TR performance. The obtained data of the participating TR athletes were compared for anthropometric data, CPET parameters, such as V˙Emaximum, V˙O2maximum, maximal breath frequency (BF_max) and peak oxygen pulse as well as energetic demands, i.e., the energy cost of running (C_r). All participating TR athletes showed excellent performance data, whereby across both different uphill locomotion strategies, significant differences were solely revealed for V˙Emaximum (p = 0.033) and time to reach mountain peak (p = 0.008). These results provide new insights and might contribute to a comprehensive understanding of cardiorespiratory consequences to short uphill locomotion strategy in TR athletes and might strengthen further scientific research in this field.

Heavy Resistance Training Versus Plyometric Training for Improving Running Economy and Running Time Trial Performance: A Systematic Review and Meta-analysis

BACKGROUND

As an adjunct to running training, heavy resistance and plyometric training have recently drawn attention as potential training modalities that improve running economy and running time trial performance. However, the comparative effectiveness is unknown. The present systematic review and meta-analysis aimed to determine if there are different effects of heavy resistance training versus plyometric training as an adjunct to running training on running economy and running time trial performance in long-distance runners.

METHODS

Electronic databases of PubMed, Web of Science, and SPORTDiscus were searched. Twenty-two studies completely satisfied the selection criteria. Data on running economy and running time trial performance were extracted for the meta-analysis. Subgroup analyses were performed with selected potential moderators.

RESULTS

The pooled effect size for running economy in heavy resistance training was greater (g = - 0.32 [95% confidence intervals [CIs] - 0.55 to - 0.10]: effect size = small) than that in plyometric training (g = -0.13 [95% CIs - 0.47 to 0.21]: trivial). The effect on running time trial performance was also larger in heavy resistance training (g = - 0.24 [95% CIs - 1.04 to - 0.55]: small) than that in plyometric training (g = - 0.17 [95% CIs - 0.27 to - 0.06]: trivial). Heavy resistance training with nearly maximal loads (≥ 90% of 1 repetition maximum [1RM], g = - 0.31 [95% CIs - 0.61 to - 0.02]: small) provided greater effects than those with lower loads (< 90% 1RM, g = - 0.17 [95% CIs - 1.05 to 0.70]: trivial). Greater effects were evident when training was performed for a longer period in both heavy resistance (10-14 weeks, g = - 0.45 [95% CIs - 0.83 to - 0.08]: small vs. 6-8 weeks, g = - 0.21 [95% CIs - 0.56 to 0.15]: small) and plyometric training (8-10 weeks, g = 0.26 [95% CIs - 0.67 to 0.15]: small vs. 4-6 weeks, g = - 0.06 [95% CIs 0.67 to 0.55]: trivial).

CONCLUSIONS

Heavy resistance training, especially with nearly maximal loads, may be superior to plyometric training in improving running economy and running time trial performance. In addition, running economy appears to be improved better when training is performed for a longer period in both heavy resistance and plyometric training.

Maximum aerobic speed, maximum oxygen consumption, and running spatiotemporal parameters during an incremental test among middle- and long-distance runners and endurance non-running athletes

Background

Maximal aerobic speed (MAS) is a useful parameter to assess aerobic capacity and estimate training intensity in middle- and long-distance runners. However, whether middle- and long-distance runners reach different levels of MAS compared to other endurance athletes with similar V̇O_2max has not been previously studied. Therefore, we aimed to compare V̇O_2max, MAS and spatiotemporal parameters between sub-elite middle- and long-distance runners (n = 6) and endurance non-runners (n = 6). In addition, we aimed to compare the maximal blood lactate concentration [BLa] experienced by participants after conducting these tests.

Methods

Telemetric portable respiratory gas analysis, contact and flight time, and stride length and rate were measured using a 5-m contact platform during an incremental test at a synthetic athletics track. V̇O₂, heart rate, respiratory quotient values in any 15 s average period during the test were measured. [BLa] was analyzed after the test . Running spatiotemporal parameters were recorded at the last two steps of each 400 m lap. A coefficient of variation (%CV) was calculated for each spatiotemporal variable in each participant from 8 km h^-1 onwards.

Results

Whereas runners reported faster MAS (21.0 vs. 18.2 km h^-1) than non-runners (p  =  0.0001, ES = 3.0), no differences were found for V̇O_2max and maximum blood lactate concentration during the running tests (p > 0.05). While significant increases in flight time and stride length and frequency (p < 0.001, 0.52 ≤ η p 2 ≤ 0.8) were observed throughout the tests, decreases in contact time (p < 0.001, η p 2 = 0 . 9 ) were reported. Runners displayed a greater %CV (p = 0.015) in stride length than non-runners. We conclude that middle- and long-distance runners can achieve a faster MAS compared to non-running endurance athletes despite exhibiting a similar V̇O_2max. This superior performance may be associated to a greater mechanical efficiency. Overall, runners displayed a greater ability to modify stride length to achieve fast speeds, which may be related to a more mechanically efficient pattern of spatiotemporal parameters than non-runners.

Is the maximal lactate steady state concept really relevant to predict endurance performance?

PURPOSE

There is no convincing evidence for the idea that a high power output at the maximal lactate steady state (PO_{_MLSS}) and a high fraction of [Formula: see text]O_2max at MLSS (%[Formula: see text]O_{2_MLSS}) are decisive for endurance performance. We tested the hypotheses that (1) %[Formula: see text]O_{2_MLSS} is positively correlated with the ability to sustain a high fraction of [Formula: see text]O_2max for a given competition duration (%[Formula: see text]O_{2_TT}); (2) %[Formula: see text]O_{2_MLSS} improves the prediction of the average power output of a time trial (PO_{_TT}) in addition to [Formula: see text]O_2max and gross efficiency (GE); (3) PO_{_MLSS} improves the prediction of PO_{_TT} in addition to [Formula: see text]O_2max and GE.

METHODS

Twenty-one recreationally active participants performed stepwise incremental tests on the first and final testing day to measure GE and check for potential test-related training effects in terms of changes in the minimal lactate equivalent power output (∆PO_LEmin), 30-min constant load tests to determine MLSS, a ramp test and verification bout for [Formula: see text]O_2max, and 20-min time trials for %[Formula: see text]O_{2_TT} and PO_{_TT}. Hypothesis 1 was tested via bivariate and partial correlations between %[Formula: see text]O_{2_MLSS} and %[Formula: see text]O_{2_TT}. Multiple regression models with [Formula: see text]O_2max, GE, ∆PO_LEmin, and %[Formula: see text]O_{2_MLSS} (Hypothesis 2) or PO_{_MLSS} instead of %[Formula: see text]O_{2_MLSS} (Hypothesis 3), respectively, as predictors, and PO_{_TT} as the dependent variable were used to test the hypotheses.

RESULTS

%[Formula: see text]O_{2_MLSS} was not correlated with %[Formula: see text]O_{2_TT} (r = 0.17, p = 0.583). Neither %[Formula: see text]O_{2_MLSS} (p = 0.424) nor PO_{_MLSS} (p = 0.208) did improve the prediction of PO_{_TT} in addition to [Formula: see text]O_2max and GE.

CONCLUSION

These results challenge the assumption that PO_{_MLSS} or %[Formula: see text]O_{2_MLSS} are independent predictors of supra-MLSS PO_{_TT} and %[Formula: see text]O_{2_TT}.

Cultural variation in running techniques among non-industrial societies

Research among non-industrial societies suggests that body kinematics adopted during running vary between groups according to the cultural importance of running. Among groups in which running is common and an important part of cultural identity, runners tend to adopt what exercise scientists and coaches consider to be good technique for avoiding injury and maximising performance. In contrast, among groups in which running is not particularly culturally important, people tend to adopt suboptimal technique. This paper begins by describing key elements of good running technique, including landing with a forefoot or midfoot strike pattern and leg oriented roughly vertically. Next, we review evidence from non-industrial societies that cultural attitudes about running associate with variation in running techniques. Then, we present new data from Tsimane forager-horticulturalists in Bolivia. Our findings suggest that running is neither a common activity among the Tsimane nor is it considered an important part of cultural identity. We also demonstrate that when Tsimane do run, they tend to use suboptimal technique, specifically landing with a rearfoot strike pattern and leg protracted ahead of the knee (called overstriding). Finally, we discuss processes by which culture might influence variation in running techniques among non-industrial societies, including self-optimisation and social learning.

Physiological and Somatic Principal Components Determining VO2max in the Annual Training Cycle of Endurance Athletes

The purpose of the study was to assess the impact of training on the physiological variables achieved during the test effort in the macrocycle of road cyclists and their use in the maximal oxygen uptake (VO2max) prediction at individual training stages in the VO2max test. Nine well-trained male cyclists (age 25.6 ± 5.2 years and body weight 72.4 ± 7.35 kg) participated in the study and each phase of the macrocycle was followed by a time to exhaustion test (TTE) on the bicycle ergometer. The research showed that training loads significantly influence the maximum power (PPO), ventilation (VE) in the preparatory period (T1), time of the test (TTmax) at the start of the competition period (T2), percentage of body fat in total body weight (%FAT) and skeletal muscle mass (MMS) during the competition period (T3). Of the 16 variables taken for the analysis of the principal components (PC), the regression model determined one principal variable responsible for VO2max in the training macrocycle of cyclists, the relative value of maximum power (PPORV) and the accompanying variables in individual periods: breathing frequency (BF), delta blood lactate concentration (ΔLA), body fat (FAT) and MMS. Determining PC influencing the exercise capacity can be crucial in achieving the intended goals by athletes. Monitoring these indicators can help protect the health of professional athletes and provide guidelines in the training process, stimulate the body properly while protecting against overtraining.

Physiological and Performance Correlates of Squash Physical Performance

The physiological and performance attributes of elite squash players were investigated. Thirty-one players (21 males, world ranking [WR] 42-594; 10 females, WR 7-182) completed a battery of fitness tests which included an aerobic squash-specific physical performance test (SPPT), repeated-sprint ability (RSA), change-of-direction speed (COD), acceleration (5-m sprint), body composition and force development (countermovement jump) assessments. The SPPT provided a finishing lap score, V̇O_2max, average movement economy and the lap corresponding to a blood lactate concentration of 4 mM.L^-1. Players were ranked and assigned to HIGH or LOW performance tiers. Two-way ANOVA (performance level*sex) revealed higher ranked players performed better (p < 0.05) for SPPT final lap (d = 0.35), 4 mM.L^-1 lap (d = 0.52) and COD (d = 0.60). SPPT displayed a 'very-large' correlation with 4 mM.L^-1 lap (r = 0.86), 'large' correlations with COD (r = 0.79), RSA (r = 0.79), sum-of-7 skinfolds (r = 0.71) and V̇O_2max (r = 0.69), and a 'trivial' correlation with average movement economy (r = 0.02). Assessments of cardiovascular fitness (i.e. 4 mM.L^-1 lap), RSA, COD and body composition appear highly pertinent for performance profiling of squash players. Regular, submaximal assessment of the 4 mM.L^-1 lap during the SPPT may offer a practical athlete monitoring approach for elite squash players.

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.

Sex Differences in Endurance Running

In recent years, there has been a significant expansion in female participation in endurance (road and trail) running. The often reported sex differences in maximal oxygen uptake (VO_2max) are not the only differences between sexes during prolonged running. The aim of this narrative review was thus to discuss sex differences in running biomechanics, economy (both in fatigue and non-fatigue conditions), substrate utilization, muscle tissue characteristics (including ultrastructural muscle damage), neuromuscular fatigue, thermoregulation and pacing strategies. Although males and females do not differ in terms of running economy or endurance (i.e. percentage VO_2max sustained), sex-specificities exist in running biomechanics (e.g. females have greater non-sagittal hip and knee joint motion compared to males) that can be partly explained by anatomical (e.g. wider pelvis, larger femur-tibia angle, shorter lower limb length relative to total height in females) differences. Compared to males, females also show greater proportional area of type I fibres, are more able to use fatty acids and preserve carbohydrates during prolonged exercise, demonstrate a more even pacing strategy and less fatigue following endurance running exercise. These differences confer an advantage to females in ultra-endurance performance, but other factors (e.g. lower O₂ carrying capacity, greater body fat percentage) counterbalance these potential advantages, making females outperforming males a rare exception. The present literature review also highlights the lack of sex comparison in studies investigating running biomechanics in fatigue conditions and during the recovery process.

Alternative Metabolic Strategies are Employed by Endurance Runners of Different Body Sizes; Implications for Human Evolution

Objective

A suite of adaptations facilitating endurance running (ER) evolved within the hominin lineage. This may have improved our ability to reach scavenging sites before competitors, or to hunt prey over long distances. Running economy (RE) is a key determinant of endurance running performance, and depends largely on the magnitude of force required to support body mass. However, numerous environmental factors influence body mass, thereby significantly affecting RE. This study tested the hypothesis that alternative metabolic strategies may have emerged to enable ER in individuals with larger body mass and poor RE.

Methods

A cohort of male (n = 25) and female (n = 19) ultra-endurance runners completed submaximal and exhaustive treadmill protocols to determine RE, and V̇O2Max.

Results

Body mass was positively associated with sub-maximal oxygen consumption at both LT1 (male r=0.66, p<0.001; female LT1 r=0.23, p=0.177) and LT2 (male r=0.59, p=0.001; female r=0.23, p=0.183) and also with V̇O2Max (male r=0.60, p=0.001; female r=0.41, p=0.046). Additionally, sub-maximal oxygen consumption varied positively with V̇O2Max in both male (LT1 r=0.54, p=0.003; LT2 r=0.77, p<0.001) and female athletes (LT1 r=0.88, p<0.001; LT2 r=0.92, p<0.001).

Conclusions

The results suggest that, while individuals with low mass and good RE can glide economically as they run, larger individuals can compensate for the negative effects their mass has on RE by increasing their capacity to consume oxygen. The elevated energy expenditure of this low-economy high-energy turnover approach to ER may bring costs associated with energy diversion away from other physiological processes, however.

Triceps Surae Muscle-Tendon Properties as Determinants of the Metabolic Cost in Trained Long-Distance Runners

Purpose: This study aimed to determine whether triceps surae's muscle architecture and Achilles tendon parameters are related to running metabolic cost (C) in trained long-distance runners. Methods: Seventeen trained male recreational long-distance runners (mean age = 34 years) participated in this study. C was measured during submaximal steady-state running (5 min) at 12 and 16 km h-1 on a treadmill. Ultrasound was used to determine the gastrocnemius medialis (GM), gastrocnemius lateralis (GL), and soleus (SO) muscle architecture, including fascicle length (FL) and pennation angle (PA), and the Achilles tendon cross-sectional area (CSA), resting length and elongation as a function of plantar flexion torque during maximal voluntary plantar flexion. Achilles tendon mechanical (force, elongation, and stiffness) and material (stress, strain, and Young's modulus) properties were determined. Stepwise multiple linear regressions were used to determine the relationship between independent variables (tendon resting length, CSA, force, elongation, stiffness, stress, strain, Young's modulus, and FL and PA of triceps surae muscles) and C (J kg-1m-1) at 12 and 16 km h-1. Results: SO PA and Achilles tendon CSA were negatively associated with C (r 2 = 0.69; p < 0.001) at 12 km h-1, whereas SO PA was negatively and Achilles tendon stress was positively associated with C (r 2 = 0.63; p = 0.001) at 16 km h-1, respectively. Our results presented a small power, and the multiple linear regression's cause-effect relation was limited due to the low sample size. Conclusion: For a given muscle length, greater SO PA, probably related to short muscle fibers and to a large physiological cross-sectional area, may be beneficial to C. Larger Achilles tendon CSA may determine a better force distribution per tendon area, thereby reducing tendon stress and C at submaximal speeds (12 and 16 km h-1). Furthermore, Achilles tendon morphological and mechanical properties (CSA, stress, and Young's modulus) and triceps surae muscle architecture (GM PA, GM FL, SO PA, and SO FL) presented large correlations with C.

Reliability of Peak Running Velocity Obtained on the Track Field in Runners of Different Performance Levels

The aim of this study was to verify the reliability of peak running velocity obtained on the track field (V_{peak_TF}) in runners of different performance levels. 39 male endurance runners were divided into two groups: trained runners (TR; n = 22; 10-km time running performance of 35.2 ± 1.7 min), and recreational runners (RR; n = 17; 10-km time running performance of 51.3 ± 4.8 min). They performed three maximal incremental running tests on the official track field (400 m), with an interval of 1 week between trials to determine the reliability of V_{peak_T}. The V_{peak_TF} showed high reliability, presenting an intraclass correlation coefficient and coefficient of variation of 0.97 and 1.28%, and 0.90 and 1.24% for TR and RR, respectively. Both TR and RR showed lowest bias and limits of agreement between test and retest (V_{peak_TF1} and V_{peak_TF2}). In addition, there was no statistical test-retest difference for V_{peak_TF}. In addition, the HR and RPE submaximal values were reliable for both TR and RR. Therefore, the V_{peak_TF} showed high reliability in both TR and RR. These findings reinforce that the protocol for determining V_{peak_TF}, using increments of 1 km h^–1 every 3 min is reliable regardless of the performance level of the runners.

Caffeine Increases Exercise Performance, Maximal Oxygen Uptake, and Oxygen Deficit in Elite Male Endurance Athletes

PURPOSE

The aims of the present study were to test the hypothesis that caffeine increases maximal oxygen uptake (V˙O2max) and to characterize the physiological mechanisms underpinning improved high-intensity endurance capacity.

METHODS

Twenty-three elite endurance-trained male athletes were tested twice with and twice without caffeine (four tests) in a randomized, double-blinded, and placebo-controlled study with crossover design. Caffeine (4.5 mg·kg-1) or placebo was consumed 45 min before standardized warm-up. Time to exhaustion during an incremental test (running 10.5° incline, start speed 10.0 km·h-1, and 0.5 km·h-1 increase in speed every 30 s) determined performance. Oxygen uptake was measured continuously to determine V˙O2max and O2 deficit was calculated.

RESULTS

Caffeine increased time to exhaustion from 355 ± 41 to 375 ± 41 s (Δ19.4 ± 16.5 s; P < 0.001). Importantly, caffeine increased V˙O2max from 75.8 ± 5.6 to 76.7 ± 6.0 mL·kg-1·min-1 (Δ 0.9 ± 1.7 mL·kg-1·min-1; P < 0.003). Caffeine increased maximal heart rate (HRpeak) and ventilation (VEpeak). Caffeine increased O2 deficit from 63.1 ± 18.2 to 69.5 ± 17.5 mL·kg-1 (P < 0.02) and blood lactate compared with placebo. The increase in time to exhaustion after caffeine ingestion was reduced to 11.7 s after adjustment for the increase in V˙O2max. Caffeine did not significantly increase V˙O2max after adjustment for VEpeak and HRpeak. Adjustment for O2 deficit and lactate explained 6.2 s of the caffeine-induced increase in time to exhaustion. The increase in V˙O2max, VE, HR, O2 deficit, and lactate explained 63% of the increased performance after caffeine intake.

CONCLUSION

Caffeine increased V˙O2max in elite athletes, which contributed to improvement in high-intensity endurance performance. Increases in O2 deficit and lactate also contributed to the caffeine-induced improvement in endurance performance.

Peak fat oxidation is positively associated with vastus lateralis CD36 content, fed-state exercise fat oxidation, and endurance performance in trained males

PURPOSE

Whole-body fat oxidation during exercise can be measured non-invasively during athlete profiling. Gaps in understanding exist in the relationships between fat oxidation during incremental fasted exercise and skeletal muscle parameters, endurance performance, and fat oxidation during prolonged fed-state exercise.

METHODS

Seventeen endurance-trained males underwent a (i) fasted, incremental cycling test to assess peak whole-body fat oxidation (PFO), (ii) resting vastus lateralis microbiopsy, and (iii) 30-min maximal-effort cycling time-trial preceded by 2-h of fed-state moderate-intensity cycling to assess endurance performance and fed-state metabolism on separate occasions within one week.

RESULTS

PFO (0.58 ± 0.28 g^.min^-1) was associated with vastus lateralis citrate synthase activity (69.2 ± 26.0 μmol^.min^-1.g^-1 muscle protein, r = 0.84, 95% CI 0.58, 0.95, P < 0.001), CD36 abundance (16.8 ± 12.6 μg^.g^-1 muscle protein, r_s = 0.68, 95% CI 0.31, 1.10, P = 0.01), pre-loaded 30-min time-trial performance (251 ± 51 W, r = 0.76, 95% CI 0.40, 0.91, P = 0.001; 3.2 ± 0.6 W^.kg^-1, r = 0.62, 95% CI 0.16, 0.86, P = 0.01), and fat oxidation during prolonged fed-state cycling (r = 0.83, 95% CI 0.57, 0.94, P < 0.001). Addition of PFO to a traditional model of endurance (peak oxygen uptake, power at 4 mmol^.L^-1 blood lactate concentration, and gross efficiency) explained an additional ~ 2.6% of variation in 30-min time-trial performance (adjusted R² = 0.903 vs. 0.877).

CONCLUSION

These associations suggest non-invasive measures of whole-body fat oxidation during exercise may be useful in the physiological profiling of endurance athletes.

Comprehensive Return to Competitive Distance Running: A Clinical Commentary

Running injuries are very common, and there are well-established protocols for clinicians to manage specific musculoskeletal conditions in runners. However, competitive and elite runners may experience different injuries than the average recreational runner, due to differences in training load, biomechanics, and running experience. Additionally, injury-specific rehabilitation protocols do not consider the broader goal of return to competitive running, including the unique psychosocial and cardiorespiratory fitness needs of elite athletes. This review aims to suggest a guideline for running-specific progression as part of a comprehensive rehabilitation program for injured competitive runners. Tools to evaluate an athlete's psychosocial preparedness to return to competition are presented. Recommendations are also provided for monitoring cardiorespiratory fitness of injured runners, including the nuances of interpreting these data. Finally, a six-phase training paradigm is proposed to guide clinicians as they help competitive runners transition from the early stages of injury through a full return to competition.

Evidence-based Classification in Track Athletics for Athletes with a Vision Impairment: A Delphi Study

SIGNIFICANCE

The Delphi analysis presented here highlights the need for a sport-specific evidence-based classification system for track athletics for athletes with a vision impairment (VI). This system may differ for different race distances. Further research is required to develop a useful test battery of vision tests for classification. The issue of intentional misrepresentation during classification needs particular attention.

PURPOSE

At present, athletes with VI are placed into competition classes developed on the basis of legal definitions of VI. The International Paralympic Committee Athlete Classification Code states that all sports should have their own classification system designed to reflect the (visual) demands of that individual sport. This project gathered expert opinion on the specific requirements for an evidence-based sport-specific classification system for VI track athletics and to identify any particular issues within track athletics that require further research into their impact on sport performance.

METHODS

A three-round Delphi review was conducted with a panel of 17 people with expertise in VI track athletics.

RESULTS

The panel agreed that the current classification system in VI track athletics does not completely minimize the impact of impairment on competition outcome, highlighting the need for improvements. There was clear agreement that the existing measures of vision may fail to adequately reflect the type of vision loss that would impact running performance, with additional measures required. Intentional misrepresentation, where athletes "cheat" on classification tests, remains a serious concern.

CONCLUSIONS

The panel has identified measures of vision and performance that will inform the development of an evidence-based classification system by better understanding the relationship between VI and performance in track athletics. Issues such as the use of guides and whether the current class system was equitable gave rise to differing opinions within the panel, with these varying across the different running distances.

The Importance of 'Durability' in the Physiological Profiling of Endurance Athletes

Profiling physiological attributes is an important role for applied exercise physiologists working with endurance athletes. These attributes are typically assessed in well-rested athletes. However, as has been demonstrated in the literature and supported by field data presented here, the attributes measured during routine physiological-profiling assessments are not static, but change over time during prolonged exercise. If not accounted for, shifts in these physiological attributes during prolonged exercise have implications for the accuracy of their use in intensity regulation during prolonged training sessions or competitions, quantifying training adaptations, training-load programming and monitoring, and the prediction of exercise performance. In this review, we argue that current models used in the routine physiological profiling of endurance athletes do not account for these shifts. Therefore, applied exercise physiologists working with endurance athletes would benefit from development of physiological-profiling models that account for shifts in physiological-profiling variables during prolonged exercise and quantify the 'durability' of individual athletes, here defined as the time of onset and magnitude of deterioration in physiological-profiling characteristics over time during prolonged exercise. We propose directions for future research and applied practice that may enable better understanding of athlete durability.

What are the Benefits and Risks Associated with Changing Foot Strike Pattern During Running? A Systematic Review and Meta-analysis of Injury, Running Economy, and Biomechanics

BACKGROUND

Running participation continues to increase. The ideal strike pattern during running is a controversial topic. Many coaches and therapists promote non-rearfoot strike (NRFS) running with a belief that it can treat and prevent injury, and improve running economy.

OBJECTIVE

The aims of this review were to synthesise the evidence comparing NRFS with rearfoot strike (RFS) running patterns in relation to injury and running economy (primary aim), and biomechanics (secondary aim).

DESIGN

Systematic review and meta-analysis. Consideration was given to within participant, between participant, retrospective, and prospective study designs.

DATA SOURCES

MEDLINE, EMBASE, CINAHL, and SPORTDiscus.

RESULTS

Fifty-three studies were included. Limited evidence indicated that NRFS running is retrospectively associated with lower reported rates of mild (standard mean difference (SMD), 95% CI 3.25, 2.37-4.12), moderate (3.65, 2.71-4.59) and severe (0.93, 0.32-1.55) repetitive stress injury. Studies prospectively comparing injury risk between strike patterns are lacking. Limited evidence indicated that running economy did not differ between habitual RFS and habitual NRFS runners at slow (10.8-11.0 km/h), moderate (12.6-13.5 km/h), and fast (14.0-15.0 km/h) speeds, and was reduced in the immediate term when an NRFS-running pattern was imposed on habitual RFS runners at slow (10.8 km/h; SMD = - 1.67, - 2.82 to - 0.52) and moderate (12.6 km/h; - 1.26, - 2.42 to - 0.10) speeds. Key biomechanical findings, consistently including both comparison between habitual strike patterns and following immediate transition from RFS to NRFS running, indicated that NRFS running was associated with lower average and peak vertical loading rate (limited-moderate evidence; SMDs = 0.72-2.15); lower knee flexion range of motion (moderate-strong evidence; SMDs = 0.76-0.88); reduced patellofemoral joint stress (limited evidence; SMDs = 0.63-0.68); and greater peak internal ankle plantar flexor moment (limited evidence; SMDs = 0.73-1.33).

CONCLUSION

The relationship between strike pattern and injury risk could not be determined, as current evidence is limited to retrospective findings. Considering the lack of evidence to support any improvements in running economy, combined with the associated shift in loading profile (i.e., greater ankle and plantarflexor loading) found in this review, changing strike pattern cannot be recommended for an uninjured RFS runner.

PROSPERO REGISTRATION

CRD42015024523.

Physiological Indicators of Trail Running Performance: A Systematic Review

PURPOSE

To provide a systematic overview of physiological parameters used to determine the training status of a trail runner and how well these parameters correlate with real-world trail running performance.

METHOD

An electronic literature search of the PubMed and Scopus digital databases was performed. Combinations of the terms "trail run" or "trail runner" or "trail running" and "performance" were used as search terms. Seven studies met the inclusion criteria.

RESULTS

Trail running performance most commonly correlated (mean [SD]) with maximal aerobic capacity (71%; r = -.50 [.32]), lactate threshold (57%; r = -.48 [.28]), velocity at maximal aerobic capacity (43%; r = -.68 [.08]), running economy (43%; r = -.31 [.22]), body fat percentage (43%; r = .55 [.21]), and age (43%; r = .52 [.14]). Regression analyses in 2 studies were based on a single variable predicting 48% to 60% of performance variation, whereas 5 studies included multiple variable regression analyses predicting 48% to 99% of performance variation.

CONCLUSIONS

Trail running performance is multifaceted. The classic endurance model shows a weaker association with performance in trail running than in road running. Certain variables associated with trail running research (such as testing procedures, race profiles, and study participants) hinder the execution of comparative studies. Future research should employ trail-specific testing protocols and clear, objective descriptions of both the race profile and participants' training status.

Effect of photobiomodulation therapy on performance and running economy in runners: A randomized double-blinded placebo-controlled trial

The objective of this study was to evaluate effects of photobiomodulation therapy (PBMT) on the 3000 m running performance (primary outcome), running economy (RE), metabolic cost and ratings of perceived exertion during running (secondary outcomes). Twenty male endurance athletes performed 4-min treadmill rectangular test at 12 km.h-1 monitored by a gas analyser. After that, PBMT or placebo in each lower limb was applied, followed performed a maximum test of 3000 m. Immediately after 3000 m test, the athletes repeated the treadmill test. Another application of PBMT/placebo was done after the treadmill test, and athletes went back to the laboratory 24 h later to repeat the treadmill test. After a 72 h interval, athletes repeated all procedures with another treatment intervention (PBMT/placebo). Athletes performed the 3000 m running test ~7s faster when treated with PBMT with similar effort score compared placebo condition. The RE remains unchanged immediately post 3000 m running test, nonetheless RE measured post-24 h improved by 5% with PBMT application without changes in metabolic cost. The PBMT pre- and post-conditioning enhanced the 3000 m running performance and improved RE 24 h following the 3000 m test. However, no changes on ratings of perceived exertion and metabolic cost with the application of PBMT.

Predicting Maximal Oxygen Uptake Using the 3-Minute All-Out Test in High-Intensity Functional Training Athletes

Maximal oxygen uptake (VO2max) and critical speed (CS) are key fatigue-related measurements that demonstrate a relationship to one another and are indicative of athletic endurance performance. This is especially true for those that participate in competitive fitness events. However, the accessibility to a metabolic analyzer to accurately measure VO2max is expensive and time intensive, whereas CS may be measured in the field using a 3 min all-out test (3MT). Therefore, the purpose of this study was to examine the relationship between VO2max and CS in high-intensity functional training (HIFT) athletes. Twenty-five male and female (age: 27.6 ± 4.5 years; height: 174.5 ± 18.3 cm; weight: 77.4 ± 14.8 kg; body fat: 15.7 ± 6.5%) HIFT athletes performed a 3MT as well as a graded exercise test with 48 h between measurements. True VO2max was determined using a square-wave supramaximal verification phase and CS was measured as the average speed of the last 30 s of the 3MT. A statistically significant and positive correlation was observed between relative VO2max and CS values (r = 0.819, p < 0.001). Based on the significant correlation, a linear regression analysis was completed, including sex, in order to develop a VO2max prediction equation (VO2max (mL/kg/min) = 8.449(CS) + 4.387(F = 0, M = 1) + 14.683; standard error of the estimate = 3.34 mL/kg/min). Observed (47.71 ± 6.54 mL/kg/min) and predicted (47.71 ± 5.7 mL/kg/min) VO2max values were compared using a dependent t-test and no significant difference was displayed between the observed and predicted values (p = 1.000). The typical error, coefficient of variation, and intraclass correlation coefficient were 2.26 mL/kg/min, 4.90%, and 0.864, respectively. The positive and significant relationship between VO2max and CS suggests that the 3MT may be a practical alternative to predicting maximal oxygen uptake when time and access to a metabolic analyzer is limited.