Factors affecting running economy in trained distance runners

Relationship Between Body Segment Mass and Running Performance in Well-Trained Endurance Runners

This study examined the relationship between body segment mass and running performance in endurance runners. The total (muscle, fat, and bone masses), lean (muscle mass), and fat masses of the leg, arm, and trunk segments in 37 well-trained endurance runners were measured using dual-energy X-ray absorptiometer. The relative segment mass was calculated by normalizing the absolute mass to body mass. There were no significant correlations between absolute total, lean, and fat masses of all 3 segments and personal best 5000-m race time. No significant correlations were also observed between all 3 relative masses of the arm segment and personal best 5000-m race time. In contrast, medium positive correlations were observed between the relative total and lean masses of the leg segment and personal best 5000-m race time (r = .387 and .335, respectively, both P ≤ .031). Furthermore, large negative correlations were observed between the relative total and lean masses of the trunk segment and personal best 5000-m race time (r = -.500 and -.548, respectively, both P ≤ .002). These findings suggest that a mass distribution with smaller leg mass and greater trunk mass may be advantageous for achieving better running performance in endurance runners.

Training-intensity Distribution on Middle- and Long-distance Runners: A Systematic Review

Training-intensity distribution (TID) is considered the key factor to optimize performance in endurance sports. This systematic review aimed to: I) characterize the TID typically used by middle-and long-distance runners; II) compare the effect of different types of TID on endurance performance and its physiological determinants; III) determine the extent to which different TID quantification methods can calculate same TID outcomes from a given training program. The keywords and search strategy identified 20 articles in the research databases. These articles demonstrated differences in the quantification of the different training-intensity zones among quantification methods (i. e. session-rating of perceived exertion, heart rate, blood lactate, race pace, and running speed). The studies that used greater volumes of low-intensity training such as those characterized by pyramidal and polarized TID approaches, reported greater improvements in endurance performance than those which used a threshold TID. Thus, it seems that the combination of high-volume at low-intensity (≥ 70% of overall training volume) and low-volume at threshold and high-intensity interval training (≤ 30%) is necessary to optimize endurance training adaptations in middle-and long-distance runners. Moreover, monitoring training via multiple mechanisms that systematically encompasses objective and subjective TID quantification methods can help coaches/researches to make better decisions.

Comparison and Performance Validation of Calculated and Established Anaerobic Lactate Thresholds in Running

Background and Objectives: This study aimed to compare the calculated running velocity at the anaerobic lactate threshold (cLT_An), determined by a mathematical model for metabolic simulation, with two established threshold concepts (onset of blood lactate accumulation (OBLA; 4 mmol∙L⁻¹) and modified maximal deviation method (mDmax)). Additionally, all threshold concepts were correlated with performance in different endurance running events. Materials and Methods: Ten sub-elite runners performed a 30 s sprint test on a cycle ergometer adjusted to an isokinetic mode set to a cadence of 120 rpm to determine maximal lactate production rate (VLa_max), and a graded exercise test on a treadmill to determine maximal oxygen uptake (VO_2max). Running velocities at OBLA, mDmax, and cLT_An were then compared with each other, and further correlated with running performance over various distances (3000 m, 5000 m, and 10,000 m). Results: The mean difference in cLT_An was −0.13 ± 0.43 m∙s⁻¹ and −0.32 ± 0.39 m∙s⁻¹ compared to mDmax (p = 0.49) and OBLA (p < 0.01), respectively. cLT_An indicated moderate to good concordance with the established threshold concepts (mDmax: ICC = 0.87, OBLA: ICC = 0.74). In comparison with other threshold concepts, cLT_An exhibited comparable correlations with the assessed running performances (cLT_An: r = 0.61–0.76, mDmax: r = 0.69–0.79, OBLA: r = 0.56–0.69). Conclusion: Our data show that cLT_An can be applied for determining endurance performance during running. Due to the consideration of individual physiological profiles, cLT_An offers a physiologically justified approach to assess an athlete’s endurance performance.

Factors correlated with running economy among elite middle- and long-distance runners

Running economy (RE) at a given submaximal running velocity is defined as oxygen consumption per minute per kg body mass. We investigated RE in a group of 12 male elite runners of national class. In addition to RE at 14 and 18 km h-1 we measured the maximal oxygen consumption (VO2max ) and anthropometric measures including the moment arm of the Achilles tendon (LAch ), shank and foot volumes, and muscular fascicle lengths. A 3-D biomechanical movement analysis of treadmill running was also conducted. RE was on average 47.8 and 62.3 ml O2  min-1  kg-1 at 14 and 18 km h-1 . Maximal difference between the individual athletes was 21% at 18 km h-1 . Mechanical work rate was significantly correlated with VO2 measured in L min-1 at both running velocities. However, RE and relative work rate were not significantly correlated. LAch was significantly correlated with RE at 18 km h-1 implying that a short moment arm is advantageous regarding RE. Neither foot volume nor shank volume were significantly correlated to RE. Relative muscle fascicle length of m. soleus was significantly correlated with RE at 18 km h-1 . Whole body stiffness and leg stiffness were significantly correlated with LAch indicating that a short moment arm coincided with high stiffness. It is concluded that a short LAch is correlated with RE. Probably, a short LAch allows for storage of a larger amount of elastic energy in the tendon and influences the force-velocity relation toward a lower contraction velocity.

Relationship between Step Characteristics and Race Performance during 5000-m Race

This study examined the relationship between step characteristics and race time in a 5000-m race. Twenty-one male Japanese endurance runners performed a 5000-m race. Step length, step frequency, contact time, and flight time of two gait cycles (i.e., four consecutive ground contacts) were measured every 400-m by using high-speed video image. Moreover, step length was normalized to body height to minimize the effect of body size. In addition to step characteristics on each lap, the averages of all laps and the per cent change from the first half to the second half were calculated. The average step frequency and step length normalized to body height correlated significantly with the 5000-m race time (r = −0.611, r = −0.575, respectively, p < 0.05 for both). Per cent changes in contact time and step length correlated significantly with the 5000-m race time (r = 0.514, r = −0.486, respectively, p < 0.05 for both). These findings suggest that, in addition to higher step frequency and step length normalized to body height, smaller changes in step length during a given race may be an important step characteristic to achieving superior race performance in endurance runners.

A simplified approach to describe the mean skin temperature variations during prolonged running exercise

Skin blood flow and skin temperature play a fundamental role in the thermoregulatory processes and are expected to largely change in response to a prolonged running exercise. The skin temperature changes have been documented in the literature, mainly through infrared thermographic measurements performed before, after, and, in a limited number of studies, during the exercise. After an initial reduction probably ascribed to skin vasoconstriction, the further skin temperature modifications with time, measured in reference papers during a steady and prolonged run, do not show a common behaviour, probably due to different exercise intensities and environmental conditions reported in these studies. This research aimed to develop a simplified method for describing the skin temperature changes during running exercise through the theoretical solutions of the dynamic energy balance of the human body in the early and late time periods, i.e., close to the onset and the end of exercise. These two asymptotic solutions for the skin temperature, having a largely dissimilar trend, collide at a time instant likely associated with the switch from skin vasoconstriction to vasodilation. Examples of application of the proposed method, based on the intersection of asymptotes, were provided. It was also demonstrated its capability to interpret the experimental skin temperature variations with time for constant-load running exercises reported in the literature under different levels of exercise intensity and environmental conditions.

Relationship between Running Spatiotemporal Kinematics and Muscle Performance in Well-Trained Youth Female Athletes. A Cross-Sectional Study

The purpose of this cross-sectional study was to analyse the relationship of neuromuscular performance and spatiotemporal parameters in 18 adolescent distance athletes (age, 15.5 ± 1.1 years). Using the OptoGait system, the power, rhythm, reactive strength index, jump flying time, and jump height of the squat jump, countermovement jump, and eight maximal hoppings test (HT_8max) and the contact time (CT), flying time (FT), step frequency, stride angle, and step length of running at different speeds were measured. Maturity offset was determined based on anthropometric variables. Analysis of variance (ANOVA) of repeated measurements showed a reduction in CT (p < 0.000) and an increase in step frequency, step length, and stride angle (p < 0.001), as the velocity increased. The HT_8max test showed significant correlations with very large effect sizes between neuromuscular performance variables (reactive strength index, power, jump flying time, jump height, and rhythm) and both step frequency and step length. Multiple linear regression found this relationship after adjusting spatiotemporal parameters with neuromuscular performance variables. Some variables of neuromuscular performance, mainly in reactive tests, were the predictors of spatiotemporal parameters (CT, FT, stride angle, and VO). Rhythm and jump flying time in the HT_8max test and power in the countermovement jump test are parameters that can predict variables associated with running biomechanics, such as VO, CT, FT, and stride angle.

Neither Beetroot Juice Supplementation nor Increased Carbohydrate Oxidation Enhance Economy of Prolonged Exercise in Elite Race Walkers

Given the importance of exercise economy to endurance performance, we implemented two strategies purported to reduce the oxygen cost of exercise within a 4 week training camp in 21 elite male race walkers. Fourteen athletes undertook a crossover investigation with beetroot juice (BRJ) or placebo (PLA) [2 d preload, 2 h pre-exercise + 35 min during exercise] during a 26 km race walking at speeds simulating competitive events. Separately, 19 athletes undertook a parallel group investigation of a multi-pronged strategy (MAX; n = 9) involving chronic (2 w high carbohydrate [CHO] diet + gut training) and acute (CHO loading + 90 g/h CHO during exercise) strategies to promote endogenous and exogenous CHO availability, compared with strategies reflecting lower ranges of current guidelines (CON; n = 10). There were no differences between BRJ and PLA trials for rates of CHO (p = 0.203) or fat (p = 0.818) oxidation or oxygen consumption (p = 0.090). Compared with CON, MAX was associated with higher rates of CHO oxidation during exercise, with increased exogenous CHO use (CON; peak = ~0.45 g/min; MAX: peak = ~1.45 g/min, p < 0.001). High rates of exogenous CHO use were achieved prior to gut training, without further improvement, suggesting that elite athletes already optimise intestinal CHO absorption via habitual practices. No differences in exercise economy were detected despite small differences in substrate use. Future studies should investigate the impact of these strategies on sub-elite athletes’ economy as well as the performance effects in elite groups.

Energetics in elite race walkers

Race walkers must conform to a unique gait pattern with no visible loss of contact with the ground. However, how the gait pattern affects the race walking economy is unclear. We investigated the energy cost (amount of energy spent per distance unit) at different race walking velocities and over a 25 km hybrid walk. Twenty-one international-level male race walkers (V˙O_2peak 63.8 ± 4.3 ml kg^-1 min^-1, age 31 ± 5 y, body mass 68.1 ± 7.0 kg) performed an incremental treadmill test consisting of 4 × 4 min submaximal stages with 1 km h^-1 increments, and a 25 km submaximal hybrid walk (treadmill-overground) on separate days. Energy cost was measured continuously during the submaximal test and at km 0-1, 6-7, 12-13, 18-19, 23-24 of the 25 km hybrid walk. The C_RW was similar across the four submaximal stages where half the athletes completed them at a higher (1 km h^-1) absolute velocity (-0.01-0.15 ± ∼0.65); range of standardised differences ±90% CL, with a tendency for higher performing athletes to have a lower C_RW when this was analysed during absolute race walking velocities of 12, 13 and 14 km^-1 for the entire cohort (0.46-0.49 ± ∼0.67). There was no substantial change in C_RW from the start to the end of the 25 km walk for the entire cohort (0.08 ± 2.2; standardised change ±90% CL). Elite race walkers are characterised by having a similar energy cost among athletes who perform at the same relative exercise intensity, and substantially higher energetics than counterpart elite endurance runners.

The Effect of Static and Dynamic Stretching during Warm-Up on Running Economy and Perception of Effort in Recreational Endurance Runners

This randomized crossover counterbalanced study investigated, in recreational runners, the acute effects of pre-exercise stretching on physiological and metabolic responses, endurance performance, and perception of effort. Eight male endurance runners (age 36 ± 11 years) performed three running-until-exhaustion tests, preceded by three warm-ups, including the following different stretching protocols: static (SS), dynamic (DS), and no-stretching (NS). During the SS and DS sessions, the warm-up consisted of 10 min of running plus 5 min of SS or DS, respectively, while during the NS session, the warm-up consisted of 15 min of running. Physiological and metabolic responses, and endurance running performance parameters, were evaluated. The perception of effort was derived from the rating of perceived exertion (RPE). Running economy significantly improved after SS (p < 0.05) and DS (p < 0.01), and RPE values were significantly lower in SS (p < 0.05) and DS (p < 0.01), compared to NS. No differences in physiological and metabolic responses among the sessions were found. This study showed that including SS and DS within the warm-up ameliorated running economy and decreased the perception of effort during a running-until-exhaustion test, highlighting the benefits of stretching on endurance performance. These results should encourage recreational runners to insert stretching during warm-up, to optimize the running energy costs, reducing the perception of effort and making the training sessions more enjoyable.

Observational vs coaching feedback on non-dominant whole-body motor skill performance - application to technique training

We studied the effect of peer- and self-observational feedback versus coaching feedback during technique training on performance in competitive adolescent cross-country skiers. Fifty-four skiers (14.3 ± 0.6 years) were divided into a control group and three intervention groups (dyad practice, video, or coaching feedback), which practiced in the asymmetrical uphill sub-technique G2 on one side (non-dominant side), but not the other (dominant side) for 6 × 30 min over a 5 weeks period, on roller skis outdoors. High-speed performance and skiing economy were assessed on a roller ski treadmill before and after the intervention, and a questionnaire was answered post-intervention. The video feedback (p = .025, d = .65) and coaching feedback (p = .007, d = .89) groups improved high-speed performance during the intervention and an ANCOVA showed a tendency for different change scores between interventions (F_3,49  = 2.5, p = .068, η p 2  = .134), with a difference between the coaching feedback and dyad practice (p = .05). No change was seen in skiing economy in any group. Coaching feedback ranked higher on enjoyment compared with dyad practice (p < .001) and led to higher self-perception of improved technique compared with the control group (p = .038). Overall, feedback from a competent coach seems better than observation for improving performance in young athletes, although self-observation through video with attentional cues seems a promising tool for increasing individual feedback when coaching large groups.

Association between patellar tendon moment arm and running performance in endurance runners

A shorter joint moment arm (MA) may help maintain the necessary muscle force when muscle contractions are repeated. This beneficial effect may contribute to reducing the energy cost during running. In this study, we examined the correlation between patellar tendon MA and running performance in endurance runners. The patellar tendon MA and quadriceps femoris muscle volume (MV) in 42 male endurance runners and 14 body size-matched male untrained participants were measured using a 1.5-T magnetic resonance system. The patellar tendon MA was significantly shorter in endurance runners than in untrained participants (p = 0.034, d = 0.65). In endurance runners, shorter patellar tendon MA correlated significantly with better personal best 5000-m race rime (r = 0.322, p = 0.034). A trend toward such a significant correlation was obtained between quadriceps femoris MV and personal best 5000-m race time (r = 0.303, p = 0.051). Although the correlation between patellar tendon MA and personal best 5000-m race time did not remain significant after adjusting for the quadriceps femoris MV (partial r = 0.247, p = 0.120), a stepwise multiple regression analysis (conducted with body height, body mass, patellar tendon MA, and quadriceps femoris MV) selected the patellar tendon MA (β = 0.322) as only a predictive variable for the personal best 5000-m race time (adjusted R2  = 0.081, p = 0.038). These findings suggest that the shorter patellar tendon MA, partially accorded with the smaller quadriceps femoris size, may be a favorable morphological variable for better running performance in endurance runners.

Effects of Plyometric Training on Soft and Hard Surfaces for Improving Running Economy

The present study investigated the effects of plyometric jump training on hard and soft surfaces on running economy (RE), maximal oxygen uptake (VO_2max), running performance and the rate of force development in orienteers. Nineteen orienteers (11 women and 8 men, body mass 61.1 ± 7.3 kg, age 21 ± 5.8 yrs) were randomly stratified based on sex, age, VO_2max and RE to plyometric jumping training (8 sessions over 4 weeks) on either a hard or a soft surface. RE, VO_2max and running performance were assessed on a treadmill and outdoor on- and off-trail loops. Moreover, ground reaction forces and force development were assessed during a one leg drop-jump test. The training intervention led to an overall 2-7% improvement in treadmill and off-trail RE, independent of the jumping surface and running velocity assessed. These improvements were not explained by force development during drop jump tests, which remained unchanged following the intervention. The changes in time-trial performance were associated with changes in RE. Plyometric training improved RE with no difference between the hard or the soft training surface and improved RE was also independent of the running speed assessed. Furthermore, improved running performance was associated with changes in RE after the intervention.

Limitations of Foot-Worn Sensors for Assessing Running Power

Running power as measured by foot-worn sensors is considered to be associated with the metabolic cost of running. In this study, we show that running economy needs to be taken into account when deriving metabolic cost from accelerometer data. We administered an experiment in which 32 experienced participants (age = 28 ± 7 years, weekly running distance = 51 ± 24 km) ran at a constant speed with modified spatiotemporal gait characteristics (stride length, ground contact time, use of arms). We recorded both their metabolic costs of transportation, as well as running power, as measured by a Stryd sensor. Purposely varying the running style impacts the running economy and leads to significant differences in the metabolic cost of running (p < 0.01). At the same time, the expected rise in running power does not follow this change, and there is a significant difference in the relation between metabolic cost and power (p < 0.001). These results stand in contrast to the previously reported link between metabolic and mechanical running characteristics estimated by foot-worn sensors. This casts doubt on the feasibility of measuring running power in the field, as well as using it as a training signal.

Level, Uphill, and Downhill Running Economy Values Are Correlated Except on Steep Slopes

The aim of this study was first to determine if level, uphill, and downhill energy cost of running (ECR) values were correlated at different slopes and for different running speeds, and second, to determine the influence of lower limb strength on ECR. Twenty-nine healthy subjects completed a randomized series of 4-min running bouts on an instrumented treadmill to determine their cardiorespiratory and mechanical (i.e., ground reaction forces) responses at different constant speeds (8, 10, 12, and 14 km·h⁻¹) and different slopes (−20, −10, −5, 0, +5, +10, +15, and +20%). The subjects also performed a knee extensor (KE) strength assessment. Oxygen and energy costs of running values were correlated between all slopes by pooling all running speeds (all r² ≥ 0.27; p ≤ 0.021), except between the steepest uphill vs. level and the steepest downhill slope (i.e., +20% vs. 0% and −20% slopes; both p ≥ 0.214). When pooled across all running speeds, the ECR was inversely correlated with KE isometric maximal torque for the level and downhill running conditions (all r² ≥ 0.24; p ≤ 0.049) except for the steepest downhill slope (−20%), but not for any uphill slopes. The optimal downhill grade (i.e., lowest oxygen cost) varied between running speeds and ranged from −14% and −20% (all p < 0.001). The present results suggest that compared to level and shallow slopes, on steep slopes ~±20%, running energetics are determined by different factors (i.e., reduced bouncing mechanism, greater muscle strength for negative slopes, and cardiopulmonary fitness for positive slopes). On shallow negative slopes and during level running, ECR is related to KE strength.

Running into Fatigue: The Effects of Footwear on Kinematics, Kinetics, and Energetics

PURPOSE

Recent studies identified a redistribution of positive mechanical work from distal to proximal joints during prolonged runs, which might partly explain the reduced running economy observed with running-induced fatigue. Higher mechanical demand of plantar flexor muscle-tendon units, for example, through minimal footwear, can lead to an earlier onset of fatigue, which might affect the redistribution of lower extremity joint work during prolonged runs. Therefore, the purpose of this study was to examine the effects of a racing flat and cushioned running shoe on the joint-specific contributions to lower extremity joint work during a prolonged fatiguing run.

METHODS

On different days, 18 runners performed two 10-km runs with near-maximal effort in a racing flat and a cushioned shoe on an instrumented treadmill synchronized with a motion capture system. Joint kinetics and kinematics were calculated at 13 predetermined distances throughout the run. The effects of shoes, distance, and their interaction were analyzed using a two-factor repeated-measures ANOVA.

RESULTS

For both shoes, we found a redistribution of positive joint work from the ankle (-6%) to the knee (+3%) and the hip (+3%) throughout the entire run. Negative ankle joint work was higher (P < 0.01) with the racing flat compared with the cushioned shoe. Initial differences in foot strike patterns between shoes disappeared after 2 km of running distance.

CONCLUSIONS

Irrespective of the shoe design, alterations in the running mechanics occurred in the first 2 km of the run, which might be attributed to the existence of a habituation rather than fatigue effect. Although we did not find a difference between shoes in the fatigue-related redistribution of joint work from distal to more proximal joints, more systematical studies are needed to explore the effects of specific footwear design features.

The effect of probiotic supplementation on performance, inflammatory markers and gastro-intestinal symptoms in elite road cyclists

Background

Elite athletes may suffer from impaired immune function and gastro-intestinal (GI) symptoms, which may affect their health and may impede their performance. These symptoms may be reduced by multi-strain probiotic supplementation. Therefore, the aim of the current study is to examine the effects of probiotic supplementation on aerobic fitness characteristics, inflammatory markers and incidence and severity of GI symptoms in elite cyclists.

Methods

Twenty-seven male cyclists, ranked elite or category 1 level competitions, were randomly assigned to a multi-strain probiotic-supplemented group (E, n = 11) or placebo group (C, n = 16). All participants visited the laboratory at the beginning of the study and following 90 d of supplementation/placebo. Prior to testing, all participants completed a GI symptoms questionnaire and underwent physical and medical examination, and anthropometric measurements. Venous blood was drawn for inflammatory markers analysis. The cyclists then underwent maximal oxygen consumption (VO₂max) test and time-to-fatigue (TTF) test at 85 % of maximal power, 3 h following the VO₂max test. All testing procedures were repeated after 90 d of probiotic / placebo treatment (double blind design).

Results

Lower incidence of nausea, belching, and vomiting (P < 0.05) at rest, and decreased incidence of GI symptoms during training were found in E group vs. C Group, respectively (∆GI -0.27 ± 0.47 % vs. 0.08 ± 0.29 %, P = 0.03), no significant changes were observed in the incidence of total overall GI symptoms (∆GI -5.6 ± 14.7 % vs. 2.6 ± 11.6 %, P = 0.602) Mean rate of perceived exertion (RPE) values during the TTF were lower in E group (∆RPE: -0.3 ± 0.9 vs. 0.8 ± 1.5, P = 0.04). No significant changes were measured between and within groups in VO₂max and TTF values, mean levels of C-reactive protein (CRP), IL-6-and tumor necrosis factor alpha (TNFα) values following treatment.

Conclusions

Probiotics supplementation may have beneficial effects on GI symptoms in elite cyclists. Future studies, using higher doses and during different training seasons, might help understanding the effects of probiotic supplementation on elite athletes’ health and performance.

Trial registration

NIH clinicaltrial.gov#NCT02756221 Registered 25 April 2016.

Body Mass and Body Composition Changes over 7 Years in a Male Professional Rugby Union Team

The purpose of this study was to investigate longitudinal body mass and body composition changes in one professional rugby union team (n=123), (i) according to position [forwards (n=58) versus backs (n=65)], analysis of players with 6 consecutive seasons of DXA scans (n=21) and, (iii) to examine differences by playing status [academy and international], over 7 years. Players [mean age: 26.8 y, body mass index: 28.9+kg.m²] received DXA scans at fourtime points within each year. A modest (but non-significant) increase in mean total mass (0.8 kg) for professional players was reflected by increased lean mass and reduced body fat mass. At all-time points, forwards had a significantly greater total mass, lean mass and body fat percentage compared to backs (p<0.05). Academy players demonstrated increased total and lean mass and decreased body fat percentage over the first 3 years of senior rugby, although this was not significant. Senior and academy international players had greater lean mass and lower body fat percentage (p<0.05) than non-international counterparts. Despite modest increases in total mass; reflected by increased lean mass and reduced fat mass, no significant changes in body mass or body composition, irrespective of playing position were apparent over 7 years.

Aerodynamic effects and performance improvements of running in drafting formations

Drafting as a process to reduce drag and to benefit from the presence of other competitors is applied in various sports with several recent examples of competitive running in formations. In this study, the aerodynamics of a realistic model of a female runner is calculated by computational fluid dynamics (CFD) simulations at four running speeds of 15 km h^-1, 18 km h^-1, 21 km h^-1, and 36 km h^-1. Aerodynamic power fractions of the total energy expenditure are found to be in the range of 2.6%-8.5%. Additionally, four exemplary formations are analysed with respect to their drafting potential and resulting drag values are compared for the main runner and her pacers. The best of the formations achieves a total drag reduction on the main runner of 75.6%. Moreover, there are large variations in the drag reduction between the considered formations of up to 42% with respect to the baseline single-runner case. We conclude that major drag reduction of more than 70% can already be achieved with fairly simple formations, while certain factors, such as runners on the sides, can have a detrimental effect on drag reduction due to local acceleration of the passing flow. Using an empirical model for mechanical power output during running, gains of metabolic power and performance predictions are evaluated for all considered formations. Improvements in running economy are up to 3.5% for the best formation, leading to velocity gains of 2.3%. This translates to 154 s (≈2.6 min) saved over a marathon distance. Consequently, direct conclusions are drawn from the obtained data for ideal drafting of long-distance running in highly packed formations.

Is Motorized Treadmill Running Biomechanically Comparable to Overground Running? A Systematic Review and Meta-Analysis of Cross-Over Studies

BACKGROUND

Treadmills are often used in research, clinical practice, and training. Biomechanical investigations comparing treadmill and overground running report inconsistent findings.

OBJECTIVE

This study aimed at comparing biomechanical outcomes between motorized treadmill and overground running.

METHODS

Four databases were searched until June 2019. Crossover design studies comparing lower limb biomechanics during non-inclined, non-cushioned, quasi-constant-velocity motorized treadmill running with overground running in healthy humans (18-65 years) and written in English were included. Meta-analyses and meta-regressions were performed where possible.

RESULTS

33 studies (n = 494 participants) were included. Most outcomes did not differ between running conditions. However, during treadmill running, sagittal foot-ground angle at footstrike (mean difference (MD) - 9.8° [95% confidence interval: - 13.1 to - 6.6]; low GRADE evidence), knee flexion range of motion from footstrike to peak during stance (MD 6.3° [4.5 to 8.2]; low), vertical displacement center of mass/pelvis (MD - 1.5 cm [- 2.7 to - 0.8]; low), and peak propulsive force (MD - 0.04 body weights [- 0.06 to - 0.02]; very low) were lower, while contact time (MD 5.0 ms [0.5 to 9.5]; low), knee flexion at footstrike (MD - 2.3° [- 3.6 to - 1.1]; low), and ankle sagittal plane internal joint moment (MD - 0.4 Nm/kg [- 0.7 to - 0.2]; low) were longer/higher, when pooled across overground surfaces. Conflicting findings were reported for amplitude of muscle activity.

CONCLUSIONS

Spatiotemporal, kinematic, kinetic, muscle activity, and muscle-tendon outcome measures are largely comparable between motorized treadmill and overground running. Considerations should, however, particularly be given to sagittal plane kinematic differences at footstrike when extrapolating treadmill running biomechanics to overground running. Protocol registration CRD42018083906 (PROSPERO International Prospective Register of Systematic Reviews).

The Relationship between VO2max, Power Management, and Increased Running Speed: Towards Gait Pattern Recognition through Clustering Analysis

Triathlon has become increasingly popular in recent years. In this discipline, maximum oxygen consumption (VO₂max) is considered the gold standard for determining competition cardiovascular capacity. However, the emergence of wearable sensors (as Stryd) has drastically changed training and races, allowing for the more precise evaluation of athletes and study of many more potential determining variables. Thus, in order to discover factors associated with improved running efficiency, we studied which variables are correlated with increased speed. We then developed a methodology to identify associated running patterns that could allow each individual athlete to improve their performance. To achieve this, we developed a correlation matrix, implemented regression models, and created a heat map using hierarchical cluster analysis. This highlighted relationships between running patterns in groups of young triathlon athletes and several different variables. Among the most important conclusions, we found that high VO₂max did not seem to be significantly correlated with faster speed. However, faster individuals did have higher power per kg, horizontal power, stride length, and running effectiveness, and lower ground contact time and form power ratio. VO₂max appeared to strongly correlate with power per kg and this seemed to indicate that to run faster, athletes must also correctly manage their power.

Effect of Achilles Tendon Mechanics on the Running Economy of Elite Endurance Athletes

The Achilles tendon stores and releases strain energy, influencing running economy. The present study aims to verify the influence of the Achilles tendon tangent modulus, as a material property, on running economy by comparing two groups of elite endurance-performance athletes undergoing different running training volumes. Twelve athletes, six long-distance runners and six pentathletes, were studied. Long-distance runners had a higher weekly running training volume (116.7±13.7 vs. 58.3±20.4 km, p<0.05) and a better running economy (204.3±12.0 vs. 222.0±8.7 O₂ mL ∙ kg^-1 ∙ km^-1, p<0.05) evaluated in a treadmill at 16 km·h^-1, 1% inclination. Both groups presented similar VO_2max (68.5±3.8 vs. 65.7±5.0 mL ∙ min^-1 ∙ kg^-1, p>0.05). Achilles tendon tangent modulus was estimated from ultrasound-measured deformations, with the ankle passively mobilized by a dynamometer. True stress was calculated from the measured torque. The long-distance runners had a higher maximum tangent modulus (380.6±92.2 vs. 236.2±82.6 MPa, p<0.05) and maximum true stress than pentathletes (24.2±5.1 vs. 16.0±3.5 MPa, p<0.05). The correlation coefficient between tangent modulus at larger deformations was R=-0.7447 (p<0.05). Quantifying tendon tissue adaptations associated with different running training volumes will support subject and modality-specific workouts prescription of elite endurance athletes.

Lower extremity compression garments use by athletes: why, how often, and perceived benefit

Background

Studies on the benefits of lower extremity compression garments (CGs) have focused on their effects on post-exercise recovery and performance improvement. Less is known about why athletes actually use CGs, the frequency with which they use them, and perceived benefits from using CGs. The purpose of this study was to investigate which athletes use CGs, why athletes use CGs, when CGs are worn by athletes, and, in case of an injury or injury prevention, for which injuries CGs are used.

Methods

This cross-sectional study involved 512 athletes who used lower extremity CGs. Athletes completed a questionnaire on the type of CGs they used, and when and why they used them. They also reported their sports participation, past and current sports injuries, and the perceived benefits of using CGs.

Results

88.1% (n=451) of the athletes were endurance athletes and 11.9% (n=61) were non-endurance athletes. Endurance and non-endurance athletes reported running (84.7%, n=382) and obstacle course racing (24.6%, n=15) the most frequently as primary sports, respectively. The most-used CG was the compression sock (59.2%, n=303). In total, 47.5% (n=246) of the athletes used a CG primarily to prevent re-injury and 14.5% (n=74) to reduce symptoms of a current sports injury. Other primary reported aims were primary prevention (13.6%), post-exercise recovery (14.3%), sports performance improvement (8.8%), and to look good (0.2%). The point prevalence of past and current sports injuries among all athletes was 84.2 and 20.2%, respectively. The most common current sports injuries were shin and calf injuries. Many athletes “always” or “often” used their CGs during training (56.8%, n=279) and competitions (72.9%, n=264). Furthermore, almost 90% of the athletes that aimed to prevent re-injury by using CGs reported that CGs contributed to secondary injury prevention.

Conclusion

88% of the CG-users were endurance athletes, of which 85% were runners. All athletes mainly used CGs to prevent injury recurrence, but also to reduce symptoms of a current sports injury. A majority of the athletes reported positive perceived effects from the CGs. CGs were used more during than after sports participation.

Footwear designed to enhance energy return improves running economy compared to a minimalist footwear: does it matter for running performance?

The present study compared the effects of a footwear designed to enhance energy return (thermoplastic polyurethane, TPU) vs minimalist shoes on running economy (RE) and endurance performance. In this counterbalanced and crossover design study, 11 recreational male runners performed two submaximal constant-speed running tests and two 3-km time-trials with the two shoe models. Oxygen uptake was measured during submaximal constant-speed running tests in order to determine the RE at 12 km/h and oxygen cost of running (CTO2) at individual average speed sustained during the 3-km running time-trials wearing either of the two shoes. Our results revealed that RE was improved (2.4%) with TPU shoes compared with minimalist shoes (P=0.01). However, there was no significant difference for CTO2 (P=0.61) and running performance (P=0.52) comparing the TPU (710±60 s) and the minimalist (718±63 s) shoe models. These novel findings demonstrate that shoes with enhanced mechanical energy return (i.e. TPU) produced a lower energy cost of running at low (i.e., 12 km/h) but not at high speeds (i.e., average speed sustained during the 3-km running time-trial, ∼15 km/h), ultimately resulting in similar running performance compared to the minimalist shoe.

Performance determinants, running energetics and spatiotemporal gait parameters during a treadmill ultramarathon

Purpose

The objective of this study was to investigate the changes in metabolic variables, running energetics and spatiotemporal gait parameters during an 80.5 km treadmill ultramarathon and establish which key predictive variables best determine ultramarathon performance.

Methods

Twelve participants (9 male and 3 female, age 34 ± 7 years, and maximal oxygen uptake (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}V˙O_2max) 60.4 ± 5.8 ml·kg⁻¹·min⁻¹) completed an 80.5 km time trial on a motorised treadmill in the fastest possible time. Metabolic variables: oxygen consumption (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}V˙O₂), carbon dioxide production (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}V˙CO₂) and pulmonary ventilation (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}V˙_E) were measured via indirect calorimetry every 16.1 km at a controlled speed of 8 km·h⁻¹ and used to calculate respiratory exchange ratio (RER), the energy cost of running (Cr) and fractional utilisation of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}V˙O_2max (F). Spatiotemporal gait parameters: stride length (SL) and cadence (SPM) were calculated via tri-axial accelerometery.

Results

Trial completion time was 09:00:18 ± 01:14:07 (hh:mm:ss). There were significant increases in \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}V˙O₂, Cr, F, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}V˙_E and heart rate (HR) (p < 0.01); a significant decrease in RER (p < 0.01) and no change in SL and SPM (p > 0.05) across the measured timepoints. F and Cr accounted for 61% of the variance in elapsed finish time (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$R_{{{\text{adj}}}}^{{2}}$$\end{document}Radj2 = 0.607, p < 0.01).

Conclusion

A treadmill ultramarathon elicits significant changes in metabolic variables, running energetics and spatiotemporal gait parameters. With F and Cr explaining 61% of variance in finish time. Therefore, those able to maintain a higher F, while adopting strategies to minimise an increase in Cr may be best placed to maximise ultramarathon performance.

Effect of Foot Orthoses on Running Economy and Foot Longitudinal Arch Motion in Runners With Flat-Arched Feet

PURPOSE

To determine the effect of manipulating foot longitudinal arch motion with different-stiffness foot orthoses on running economy (RE) in runners with flat-arched feet and if changes in arch deformation and recoil were associated with changes in RE.

METHODS

Twenty-three recreational distance runners performed 5-minute submaximal treadmill runs at 12 km·h-1, in the following 3 conditions in a randomized order: (1) footwear only, (2) flexible orthoses (reduced arch thickness), and (3) standard orthoses. The RE (submaximal steady-state oxygen consumption [VO2submax]) and sagittal arch range of motion were compared among conditions using a repeated-measures analysis of variance and effect sizes (Cohen d). Pearson correlation coefficients were used to determine the association between the change in the sagittal arch range of motion and VO2submax.

RESULTS

Compared with standard orthoses, the mean VO2submax was significantly lower in both the flexible orthoses (-0.8 mL·kg-1·min-1, P < .001, d = 0.35) and footwear-only conditions (-1.2 mL·kg-1·min-1, P < .001, d = 0.49). The change in VO2submax between the flexible orthoses and footwear-only conditions was significantly positively correlated with the change in sagittal arch range of motion (r = .591, P = .005).

CONCLUSION

Conventional foot orthoses were associated with poorer RE compared with flexible orthoses and footwear alone. Changes in arch deformation were positively correlated to changes in oxygen consumption, indicating that foot orthoses that limit arch deformation and recoil degrade RE. Foot orthoses that facilitate energy storage and release in the foot longitudinal arch may be advisable for athletes prescribed these devices for clinical purposes to maintain optimal running performance.

Effect of Resistance Training of Psoas Major in Combination With Regular Running Training on Performance in Long-Distance Runners

PURPOSE

The study determined whether the increase in the cross-sectional area (CSA) of psoas major, which is known as a hip-flexion muscle, by resistance training combined with running training improves the performance of long-distance runners.

METHODS

Subjects were 8 well-trained male long-distance runners. The personal best time in a 5000-m race was 15:10.0 (0:20.5) (mean [SD]). Each subject performed resistance training twice per week with running training for 12 weeks. The authors used 3 resistance training regimens that would train the hip flexor muscles. Training intensity was a maximum of 10 repetitions. The training amount was 3 sets × 10 times during the first 4 weeks followed by 4 sets × 10 times during the last 8 weeks. The authors measured the CSA of psoas major using magnetic resonance imaging and the performance of long-distance runners using a constant velocity running test before (pre) and after (post) the training term.

RESULTS

The combination training significantly (P < .01, d = 0.34) increased the CSA of psoas major (pre: 16.2 [1.5] cm2, post: 16.7 [1.4] cm2) and significantly (P < .01, d = 1.41) improved the duration of the constant velocity running test (pre: 500 [108] s, post: 715 [186] s). Moreover, multiple regression analysis showed that the pre to post change in the duration of the constant velocity exercise was significantly correlated with the change in CSA of the psoas major.

CONCLUSION

The authors suggest that resistance training of psoas major with running training is correlated with an improvement in the performance of long-distance runners.

V[Combining Dot Above]O2peak Comparison of a Treadmill Vs. Cycling Protocol in Elite Teenage Competitive Runners, Cyclists, and Swimmers

ABSTRACT

Marko, D, Bahenský, P, Snarr, RL, and Malátová, R. V[Combining Dot Above]O2peak Comparison of a treadmill vs. cycling protocol in elite teenage competitive runners, cyclists, and swimmers. J Strength Cond Res XX(X): 000-000, 2021-The purpose of this study was to compare the cardiorespiratory and metabolic responses of a maximal graded exercise test (GXT) on a treadmill and cycle ergometer in elite-level, youth competitive athletes. Thirty-one athletes (11 distance runners, 11 mountain-bike cyclists, and 9 long-distance swimmers) were randomly selected to complete either a running or cycling GXT on the first day, followed by the alternative 72 hours apart. The initial work rate for each GXT was set at 50% of the individuals' previously established V[Combining Dot Above]O2peak to elicit fatigue within 8-12 minutes. For the treadmill protocol, speed was increased by 1 km·h-1 each minute, with a constant 5% grade, until volitional fatigue. Cycle ergometer work rate was increased by 30 W every minute until volitional fatigue or the inability to maintain proper cadence (i.e., 100 ± 5 rev·min-1). Throughout both testing sessions, V[Combining Dot Above]O2peak, heart rate [HR] peak, breathing frequency (BF), tidal volume (VT), and minute ventilation (VE) were assessed and used to compare within-sport differences. Runners displayed a higher V[Combining Dot Above]O2peak (∼7%; d = 0.92), HRpeak (4%; d = 0.77), VE (6%; d = 0.66), and BF (12%; d = 0.62) on the treadmill vs. cycle. However, the cycling group demonstrated a greater V[Combining Dot Above]O2peak (∼8%; d = 0.92), VT (∼14%; d = 0.99), and VE (∼9%; d = 0.78) on the cycle, despite no change in HRpeak. For swimmers, the treadmill GXT elicited higher values in V[Combining Dot Above]O2peak (∼5%; d = 0.75), BF (∼11.5%; d = 0.78), and HRpeak (3%; d = 0.69). Collectively, these findings indicate that exercise mode may greatly affect physiological outcome variables and should be considered before exercise prescription and athletic monitoring.

Muscle Tone and Body Weight Predict Uphill Race Time in Amateur Trail Runners

Background: Vertical kilometer is an emerging sport where athletes continuously run uphill. The aims of this study were to assess changes in vertical impacts caused by uphill running (UR) and the relation between the anthropometric and lower limb muscular characteristics with speed. Methods: Ten male experienced runners (35 ± 7 years old) participated in this study. In the racetrack (4.2 km long, 565 m high), seven sections were stablished. Mean speed and impact value of sections with similar slope (≈21%) were calculated. The gastrocnemius stiffness (GS) and tone (GT); and the vastus lateralis stiffness (VS) and tone (VT) were assessed before the race. Results: Pearson’s correlation showed a linear relationship between vs. and VT (r = 0.829; p = 0.000), GT and GS (r = 0.792; p = 0.001). Mean speed is correlated with weight (r = −0.619; p = 0.024) and GT (r = 0.739; p = 0.004). Multiple linear regressions showed a model with weight and GT as dependent variables of mean speed. Mean impacts decreased significantly between sections along the race. Conclusions: The vertical impacts during UR were attenuated during the race. Moreover, body weight and GT were associated with the time-to-finish, which supports that low weight alone could not be enough to be faster, and strength training of plantar flexors may be a determinant in UR.

Effects of adding post-workout microcurrent in males cross country athletes

Post-exercise microcurrent based treatments have shown to optimise exercise-induced adaptations in athletes. We compared the effects of endurance training in combination with either, a microcurrent or a sham treatment, on endurance performance. Additionally, changes in body composition, post-exercise lactate kinetics and perceived delayed onset of muscle soreness (DOMS) were determined. Eighteen males (32.8 ± 6.3 years) completed an 8-week endurance training programme involving 5 to 6 workouts per week wearing a microcurrent (MIC, n=9) or a sham (SH, n=9) device for 3-h post-workout or in the morning during non-training days. Measurements were conducted at pre- and post-intervention. Compared to baseline, both groups increased (P < 0.01) maximal aerobic speed (MIC, pre = 17.6 ± 1.3 to post=18.3 ± 1.0; SH, pre=17.8 ± 1.5 to post = 18.3 ± 1.3 km^.h^-1) with no changes in V˙O_2peak. No interaction effect per group and time was observed (P=0.193). Although both groups increased (P < 0.05) trunk lean mass (MIC, pre=23.2 ± 2.7 to post=24.2 ± 2.0; SH, pre=23.4 ± 1.7 to post=24.3 ± 1.6 kg) only MIC decreased (pre=4.8 ± 1.5 to post=4.5 ± 1.5, p=0.029) lower body fat. At post-intervention, no main differences between groups were observed for lactate kinetics over the 5 min recovery period. Only MIC decreased (P<0.05) DOMS at 24-h and 48-h, showing a significant average lower DOMS score over 72-h after the completion of the exercise-induced muscle soreness protocol. In conclusion, a 3-h daily application of microcurrent over an 8-week endurance training programme produced no further benefits on performance in endurance-trained males. Nonetheless, the post-workout microcurrent application promoted more desirable changes in body composition and attenuated the perception of DOMS over 72-h post-exercise.

Reliability of Change-of-Direction Economy in Soccer Players

Purpose: To evaluate the reliability of new change-of-direction-economy tests (assessing energetic efficiency when performing continuous shuttle runs) compared with common running-economy tests in soccer players Methods: Sixteen subelite, male soccer players were recruited to perform a testing battery involving running economy (RE), 10-m shuttle-running economy (SRE10), and 20-m shuttle-running economy (SRE20) at 8.4 km·h−1 mean speed on 2 different days within 48 hours. SRE10 and SRE20 consisted of continuous shuttle runs interspersed with 180° directional changes. During the RE, SRE20, and SRE10 tests, respiratory exchange ratio and oxygen uptake were collected and used to calculate the movement-economy values over any running condition as oxygen cost and energetic cost. The secondary variables (carbon dioxide production, heart rate, minute ventilation, and blood lactate) were also monitored during all tests. Results: Depending on expression (oxygen cost or energetic cost), reliability was established for RE (CV: 5.5%–5.8%; ICC = .77–.88), SRE10 (CV: 3.5%–3.8%; ICC = .78–.96), and SRE20 (CV: 3.5%–3.8%; ICC = .66–.94). All secondary physiological variables reported good reliability (CV < 10%), except for blood lactate (CV < 35.8). The RE, SRE10, and SRE20 tests show good reliability in soccer players, whereas blood lactate has the highest variability among physiological variables during the economy tests. Conclusion: The assessment of change-of-direction economy through performing 20- and 10-m shuttle runs is reliable and can be applied to evaluate soccer players’ energetic movement efficiency under more soccer-specific running conditions.

Influence of Biomechanical Parameters on Performance in Elite Triathletes along 29 Weeks of Training

The purpose of the study was to assess how the modification of biomechanical parameters influences the performance of elite triathletes. Four elite international triathletes participated in this study. The anthropometric method ISAK was used to estimate the triathlete’s body composition. For the physiological and biomechanical parameters, a running test (RT) was performed on an outdoor track, with the participants wearing the Stryd Summit Footpod (Stryd, Boulder, CO, USA). The pre-test took place in the last week of an adaptation mesocycle; then, after 29 weeks of training, the triathletes performed the post-test. A within-subject repeated measures design was used to assess changes in the anthropometric, physiological and biomechanical parameters. Pearson correlations (r) were applied to determine the relationship between the performance at different intensities (VT1, VT2 and MAS) and the biomechanical parameters. Concerning the anthropometric characteristics, significant differences were found in the summation (Σ) of skinfold (8.1 cm); as a consequence, the % fat mass was reduced (1.2%). Significant differences were found in the physiological values (VO2 and % VO2max), speed and biomechanical parameters, such as step length normalized, to the specific physiological intensity of the short-distance triathlon, the VT2. Therefore, performance improvement in the running segment could not only be explained by physiological changes, but also by biomechanical parameters changes.

Predictors of Athlete's Performance in Ultra-Endurance Mountain Races

Background: In previous studies, ultra-endurance performance has been associated with training and psychological variables. However, performance under extreme conditions is understudied, mainly due to difficulties in making field measures. Aim: The aim of this study was to analyze the role of training, hydration, nutrition, oral health status, and stress-related psychological factors in athletes’ performance in ultra-endurance mountain events. Methods: We analyzed the variables of race time and training, hydration state, nutrition, oral health status, and stress-related psychological factors in 448 ultra-endurance mountain race finishers divided into three groups according to race length (less than 45 km, 45–90 km, and greater than 90 km), using a questionnaire. Results: Higher performance in ultra-endurance mountain races was associated with better oral health status and higher accumulative altitude covered per week as well as higher positive accumulative change of altitude per week during training. In longer distance races, experience, a larger volume of training, and better hydration/nutrition prior to the competition were associated with better performance. Conclusions: Ultra-endurance mountain athletes competing in longer races (>90 km) have more experience and follow harder training schedules compared with athletes competing in shorter distances. In longer races, a larger fluid intake before the competition was the single best predictor of performance. For races between 45 and 90 km, training intensity and volume were key predictors of performance, and for races below 45 km, oral health status was a key predictor of performance. Psychological factors previously reported as ultra-endurance mountain race performance predictors were inconsistent or failed to predict the performance of athletes in the present research.

The Impact of a Single Stretching Session on Running Performance and Running Economy: A Scoping Review

One determining factor for running performance is running economy (RE), which can be quantified as the steady-state oxygen consumption at a given running speed. Stretching is frequently applied in sports practice and has been widely investigated in recent years. However, the effect of stretching on RE and performance is not clear. Thus, the purpose of this scoping review is to investigate the effects of a single bout of stretching on RE and running performance in athletes (e.g., recreational and elites) and non-athletes. The online search was performed in PubMed, Scopus, and Web of Science databases. Only studies that explored the acute effects of stretching on RE (or similar variables) and/or running performance variables with healthy and adult participants, independent of activity level, were included in this review. Eleven studies met the inclusion criteria with a total of 44 parameters (14 performance-related/30 metabolic parameters) and 111 participants. Regardless of the stretching technique, there was an improvement both in performance variables (21.4%) and metabolic variables (13.3%) following an acute bout of stretching. However, detrimental effects in performance variables (28.5%) and metabolic variables (6.6%) were also reported, though the results were influenced by the stretching duration and technique. Although it was observed that a single static stretching exercise with a duration of up to 90 s per muscle group can lead to small improvements in RE (1.0%; 95% CI: -1.04 to 2.22), negative effects were reported in running performance (-1.4%; 95% CI: -3.07 to -0.17). It was also observed that a single bout of dynamic stretching only resulted in a negligible change in RE -0.79% (95% CI: -0.95 to 4.18) but a large increase in running performance (9.8%; 95% CI: -3.28 to 16.78), with an overall stretch duration (including all muscles) between 217 and 900 s. Therefore, if stretching is applied without additional warm-up, the results suggest applying dynamic stretching (for a short overall stretching duration of ≤220 s) rather than static stretching if the goal is to increase running performance. In general, only short static stretching durations of ≤60 s per muscle-tendon unit are advisable. One study reported that less flexible runners have greater benefits from stretching than athletes with normal flexibility. In addition, it can be suggested that less flexible runners should aim for an optimum amount of flexibility, which would likely result in a more economical run.

Longer Achilles tendon moment arm results in better running economy

Based on the current literature, the link between Achilles tendon moment arm length and running economy is not well understood. Therefore, the aim of this study was to further investigate the connection between Achilles tendon moment arm and running economy and the influence of Achilles tendon moment arm on the function of the plantarflexor muscle-tendon unit during running.Ten male competitive marathon runners volunteered for this study. The participants ran on a treadmill at two running speeds: 3 and 3.5 m s-1. During running the oxygen consumption, lower leg kinematics, electrical activity of plantar flexor muscles, and fascicle behavior of the lateral gastrocnemius were measured simultaneously. On the second occasion, an MRI scan of the right leg was taken and used to estimate the Achilles tendon moment arm length.There was a negative correlation between running economy and the body height normalized moment arm length at both selected speeds (r = -0.68, P = 0.014 and r = -0.70, P = 0.01). In addition, Achilles tendon moment arm length correlated with the amplitude of the ankle flexion at both speeds (r = -0.59, P = 0.03 and r = -0.60, P = 0.03) and with the electrical activity of the medial gastrocnemius muscle at 3 m s-1 speed (r = -0.62, P = 0.02). Our finding supports the concept that a longer moment arm could be beneficial for distance runners.

Is individual day-to-day variation of arterial stiffness associated with variation of maximal aerobic performance?

Background

Maximal aerobic capacity, e.g. maximal oxygen uptake (V̇O₂max), is not constant, and it has a time-dependent variation based on the condition of individual. On the other hand, arterial properties play an important role in determining aerobic performance, and lower arterial stiffness is associated with higher cardiorespiratory fitness levels. This study examined whether individual variations in maximal aerobic performance are associated with arterial stiffness.

Methods

Twenty-four (mean age, 19.8 ± 0.2 y) and 10 (mean age, 21.2 ± 0.2 y) recreationally active young men and women participated in Experiment 1 (Ex1) and in Experiment 2 (Ex2), respectively. Aerobic performance was assessed using a graded power test (Ex1) or a 1500-m time trial (Ex2). Simultaneously, brachial-ankle pulse wave velocity (baPWV) was measured as an index of arterial stiffness in both Ex1 and Ex2 before the exercise trials. In both experiments, subjects returned for measurement of baPWV and V̇O₂max or 1500-m time trial at 1 month after first measurements.

Results

No significant differences in mean baPWV, V̇O₂max or 1500-m run time were seen between first and second visits. Mean baPWV was significantly lower on days when participants showed higher V̇O₂max or better 1500-m run time (P = 0.001 each) than on days when participants showed lower V̇O₂max or worse 1500-m run time. In addition, a significant relationship was seen between individual changes in baPWV from first to second visits and changes in V̇O₂max (P=0.0001) or 1500-m run time (P=0.04).

Conclusion

These findings suggest that individual day-to-day variations in maximal aerobic performance are associated with variations in arterial stiffness.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13102-021-00231-1.

Physiological Adaptations to High-Intensity Interval and Continuous Training in Kayak Athletes

Papandreou, A, Philippou, A, Zacharogiannis, E, and Maridaki, M. Physiological adaptations to high-intensity interval and continuous training in kayak athletes. J Strength Cond Res 34(8): 2258-2266, 2020-High-intensity interval training (HIIT) seems to be more effective than continuous training (CT) for the improvement of physical condition and sports performance. This study compared physiological adaptations with HIIT and CT in flat water kayak athletes. Twenty-four national-class kayakists were divided into 3 groups (n = 8 per group), 2 of which participated in an 8-week CT or HIIT program, whereas the third one served as control (C). An incremental maximum oxygen uptake (V[Combining Dot Above]O2max), a maximal anaerobic Wingate-type, as well as 1,000-m (T1,000 m) and 200-m (T200 m) time test were performed before and after the training period on a kayak ergometer, to determine changes in V[Combining Dot Above]O2max, peak blood lactate ([La]peak), paddling speed at V[Combining Dot Above]O2max ((Equation is included in full-text article.)), heart rate at V[Combining Dot Above]O2max (HRpeak), paddling economy speed (PEs; speed at 75% of V[Combining Dot Above]O2max), paddling speed at anaerobic ventilatory threshold (PSVT2), maximal paddling speed (PSpeak), and reduction of PSpeak (PSR). V[Combining Dot Above]O2max, [La]peak, HRpeak, and PSR did not change after the 8-week training compared with baseline in either training group (p > 0.05). However, significant changes were found in PSVT2 and T200 m (HIIT), (Equation is included in full-text article.), PEs, PSpeak, and T1,000 m (CT and HIIT) (p < 0.05-0.0001) as compared to baseline. Moreover, percent changes were different between the training groups in PEs, and between control and training groups in PSpeak and (Equation is included in full-text article.)(p < 0.05-0.01). Both training programs improved physiological and performance variables; however, HIIT resulted in significant changes of PSVT2 and T200 m and higher improvement of PEs with 15 times less training time compared with CT. Thus, HIIT seems more time-efficient than CT for improving paddling economy of kayaking performance.

The use of a running power-meter for performance analysis in five-a-side football

BACKGROUND

Power output considers all movement aspects of the game of football and could have meaningful impact for teams.

PURPOSE & METHODS

To assess inter-reliability of ten power meters designed for running; and as a descriptor of individual and team performance during a five-a-side football match. The work aimed to assess inter-device reliability of running power-meters combined with data analysis from intermittent running, along with descriptives of player work rate, gait and team performance during a small-sided game of football.

METHODS

10 different running power meters inter-reliability were on a treadmill at 8, 10, 12, and 16 km h^-1 for 60 s in a random order. Football players (N = 10) performed the Yo-Yo ET1 with the running power meters to determine participants' endurance capability, while assessing the ability to record metrics of gait and power output during intermittent running. Following a period of 7-days participants took part in a 20 min small-sided game of football wearing the running power meters to provide descriptors of work and gait.

RESULTS

Good inter-device reliability for the power meters (CV 1.67, range 1.51-1.94 %) during continuous treadmill running were found. Overall mean ± SD results for Yo-Yo ET1 power output 263 ± 36W, power:weight 3.59 ± 0.34W∙kg^-1 significantly (p < 0.05) increased with successive stages, while ground-contact time 234 ± 17 ms, and vertical oscillation 90.7 ± 27 mm did not change (p > 0.05). Descriptive analysis of the small-sided game presented mean ± SD absolute and relative power outputs of 148 ± 44W and 1.98 ± 0.53W∙kg^-1, equating to 54 ± 21 %W_max and 74 ± 5%HR_max. Characteristics of gait included cadence 125 ± 22 rpm, ground contact time 266 ± 19 ms, and vertical oscillation 76.7 ± 7 mm. The winning team worked relatively harder than the losing team (53.3 ± 0.7 %W_max vs 46.7 ± 0.4 %W_max, p < 0.0001) with more time (398 s vs 141 s) spent above 70 %W_max.

SIGNIFICANCE

As such, the use of a running power-meter is a useful tool for comparing work rate and aspects of gait between team members while more research is required to investigate relative work rate (%W_max) within the field.

Energetics of Swimming With Hand Paddles of Different Surface Areas

ABSTRACT

Crocker, GH, Moon, JF, Nessler, JA, and Newcomer, SC. Energetics of swimming with hand paddles of different surface areas. J Strength Cond Res 35(1): 205-211, 2021-Hand paddles are one of the most common training aids used by the competitive swimmer, yet little is known regarding how hand paddle surface area affects the metabolic cost of transport (COT) while swimming. The purpose of this study was to determine how altering hand paddle size affects energy use during submaximal, front-crawl (i.e., freestyle) swimming. Twenty-six proficient, adult swimmers (13 men and 13 women) completed six 3-minute trials in a flume at a constant pace (102 cm·s-1; 1:38 per 100 m). Trials were performed in random order, using 1 of 5 pairs of hand paddles of different sizes or no paddles at all. Paddle surface areas were 201, 256, 310, 358, and 391 cm2 per hand. Without paddles, COT, arm cadence, and distance per stroke were 7.87 ± 1.32 J·kg-1·m-1, 29.4 ± 4.9 min-1, and 2.13 ± 0.34 m, which corresponded to a rate of oxygen consumption (V̇o2) of 23.3 ± 3.7 ml·kg-1·min-1 and a heart rate (HR) of 118 ± 17 b·min-1. The use of larger hand paddles decreased COT, cadence, V̇o2, and HR and increased distance traveled per stroke (all p < 0.001). However, the magnitude of the change of COT decreased as paddle size increased, indicating diminishing marginal return with increasing paddle surface area. The largest sized paddles increased COT per stroke compared with swimming without paddles (p = 0.001). Therefore, results from this study suggest that an optimal hand paddle size exists (210-358 cm2) for proficient, adult swimmers, which reduces COT without increasing COT per stroke.

Downhill Running: What Are The Effects and How Can We Adapt? A Narrative Review

Downhill running (DR) is a whole-body exercise model that is used to investigate the physiological consequences of eccentric muscle actions and/or exercise-induced muscle damage (EIMD). In a sporting context, DR sections can be part of running disciplines (off-road and road running) and can accentuate EIMD, leading to a reduction in performance. The purpose of this narrative review is to: (1) better inform on the acute and delayed physiological effects of DR; (2) identify and discuss, using a comprehensive approach, the DR characteristics that affect the physiological responses to DR and their potential interactions; (3) provide the current state of evidence on preventive and in-situ strategies to better adapt to DR. Key findings of this review show that DR may have an impact on exercise performance by altering muscle structure and function due to EIMD. In the majority of studies, EIMD are assessed through isometric maximal voluntary contraction, blood creatine kinase and delayed onset muscle soreness, with DR characteristics (slope, exercise duration, and running speed) acting as the main influencing factors. In previous studies, the median (25th percentile, Q1; 75th percentile, Q3) slope, exercise duration, and running speed were - 12% (- 15%; - 10%), 40 min (30 min; 45 min) and 11.3 km h-1 (9.8 km h-1; 12.9 km h-1), respectively. Regardless of DR characteristics, people the least accustomed to DR generally experienced the most EIMD. There is growing evidence to suggest that preventive strategies that consist of prior exposure to DR are the most effective to better tolerate DR. The effectiveness of in-situ strategies such as lower limb compression garments and specific footwear remains to be confirmed. Our review finally highlights important discrepancies between studies in the assessment of EIMD, DR protocols and populations, which prevent drawing firm conclusions on factors that most influence the response to DR, and adaptive strategies to DR.

Effects of compression garments on surface EMG and physiological responses during and after distance running

BACKGROUND

The few previous studies that focused on the effects of compression garments (CG) on distance running performance have simultaneously measured electromyogram, physiological, and perceptual parameters. Therefore, this study investigated the effects of CG on muscle activation and median frequency during and after distance running, as well as blood-lactate concentration and rating of perceived exertion (RPE) during distance running.

METHODS

Eight healthy male recreational runners were recruited to randomly perform two 40 min treadmill running trials, one with CG, and the other with control garment made of normal cloth. The RPE and the surface electromyography (EMG) of 5 lower extremity muscles including gluteus maximus (GM), rectus femoris (RF), semitendinosus (ST), tibialis anterior (TA), and gastrocnemius (GAS) were measured during the running trial. The blood-lactate levels before and after the running trial were measured.

RESULTS

Wearing CG led to significant lower muscle activation (p  <  0.05) in the GM (decreased 7.40%-14.31%), RF (decreased 4.39%-4.76%), and ST (decreased 3.42%-7.20%) muscles; moreover, significant higher median frequency (p< 0.05) in the GM (increased 5.57%) and ST (increased 10.58%) muscles. Wearing CG did not alter the RPE values or the blood-lactate levels (p > 0.05).

CONCLUSION

Wearing CG was associated with significantly lower muscle activation and higher median frequency in the running-related key muscles during distance running. This finding suggested that wearing CG may improve muscle function, which might enhance running performance and prevent muscle fatigue.

Metabolic and Cardiorespiratory Responses of Semiprofessional Football Players in Repeated Ajax Shuttle Tests and Curved Sprint Tests, and Their Relationship with Football Match Play

In this study, the Ajax Shuttle Test (AST) and the Curved Sprint Test (CST) were conducted on semiprofessional football players to evaluate (1) their test performance, (2) the extent of anaerobic glycolysis by measuring blood lactate, (3) performance decrement and onset of fatigue, and (4) the correlation between selected physiological variables and test performance. Thirty-two semiprofessional Polish football players participated in this study. Both AST and CST were conducted on an outdoor football ground and were conducted in two sets; each set had six repetitions. In the case of AST, the total duration for 6 repetitions of the exercise in Sets 1 and 2 were 90.63 ± 3.71 and 91.65 ± 4.24 s, respectively, whereas, in the case of CST, the respective values were 46.8 ± 0.56 and 47.2 ± 0.66 s. Peak blood lactate concentration [La] after Sets 1 and 2 of AST were 14.47 ± 3.77 and 15.00 ± 1.85 mmol/L, and in the case of CST, the values were 8.17 ± 1.32 and 9.78 ± 1.35 mmol/L, respectively. Performance decrement in AST was more than in CST, both after Set 1 (4.32 ± 1.43 and 3.31 ± 0.96 in AST and CST, respectively) and Set 2 (7.95 ± 3.24 and 3.71 ± 1.02 in AST and CST, respectively). Only in a few of the repetitions, pulmonary ventilation (V_E) and oxygen uptake (VO₂) were found to be significantly correlated with the performance of the volunteers in both AST and CST. Respiratory exchange ratio (RER) was significantly correlated with most of the repetitions of AST, but not with CST. The study concludes that (1) AST shows more dependence on the anaerobic glycolytic system than shorter repetitive sprints (as in CST), (2) there is more performance decrement and fatigue in AST than in CST, and (3) early decrease in performance and fatigue in the semiprofessional football players in AST and CST may be due to the insufficiency of their aerobic energy system.

Why does strength training improve endurance performance?

OBJECTIVE

The specificity of training principle holds that adaptations to exercise training closely match capacity to the specific demands of the stimulus. Improvements in endurance sport performance gained through strength training are a notable exception to this principle. While the proximate mechanisms for how strength training produces muscular adaptations beneficial to endurance sports are increasingly well understood, the ultimate causes of this phenomenon remain unexplored.

METHODS

Using a holistic approach tying together exercise physiology and evolution, I argue that we can reconcile the apparent "endurance training specificity paradox."

RESULTS AND CONCLUSIONS

Competing selective pressures, inherited mammalian biology, and millennia of living in energy-scarce environments constrained our evolution as endurance athletes, but also imparted high muscular plasticity which can be exploited to improve endurance performance beyond what was useful in our evolutionary past.

Assessing body composition in rugby players: agreement between different methods and association with physical performance

BACKGROUND

This study investigated the comparability between air displacement plethysmography (ADP), dual-energy X-ray absorptiometry (DXA), and bioelectrical impedance analysis (BIA) methods for body composition assessment and their correlations with physical performance in rugby players.

METHODS

Nineteen male elite players participated in the study. ADP, DXA, and BIA were used to assess fat-mass and fat-free mass. Physical performance was assessed by means of Carminatti's test of peak velocity (PVTCAR), countermovement jump (CMJ), sprint speed (10 and 30-m), and match performance analyses (sprinting, distance covered, and high-intensity running).

RESULTS

BIA overestimated fat-mass (13±41%; r2=0.60) and underestimated fat-free mass (-1±7%; r2=0.66) compared to ADP (P=0.001). BIA underestimated fat-mass (-28±3%; r2=0.92) and overestimated fat-free mass (10±5%; r2=0.87) compared to DXA (P<0.001). ADP underestimated fat-mass (-36±37%; r2=0.69) and overestimated fat-free mass (11±8%; r2=0.52) compared to DXA (P<0.001). Fat-mass measured by ADP, DXA, and BIA negatively correlated with PVTCAR (r2≥0.49), height and peak power from CMJ (r2≥0.30), sprinting ability (r2≥0.65), and match performance variables (r2≥0.30).

CONCLUSIONS

As long as one considers that ADP and BIA underestimated fat-mass and overestimated fat-free mass compared to DXA, the methods can be used to estimate body composition, particularly to track body fat-mass changes, which negatively influence several physical capacities determinant to rugby performance. The limitations of the methods should be borne in mind when assessing the body composition of rugby athletes.

Concurrent complex and endurance training for recreational marathon runners: Effects on neuromuscular and running performance

Marathon performance is influenced by factors such as aerobic capacity and those related to neuromuscular function. Complex training (CPX) is a multicomponent training method, wherein heavy strength and plyometric exercises alternate within a single session and is an effective method to improve neuromuscular adaptations. This study compared the effects of CPX, heavy strength training (HST) and endurance-strength (EST) combined with running endurance training on neuromuscular adaptations and running performance in 38 recreational marathoners (age:31.4 ± 3.8 years, VO_2max:57.6 ± 6.8 ml·kg^-1·min^-1). Athletes were allocated in 3 groups: CPX, HST and EST and were tested for one maximum repetition strength (1RM), squat jump and countermovement jumps (SJ, CMJ), leg press (LP) concentric and eccentric strength, running economy (RE) and velocity at VO_2max (vVO_2max) before and after the 6-week intervention. CPX and HST were performed 2 times per week in conjunction with the running endurance training. RE and vVO_2max improved in CPX and HST groups (p < 0.01, RE: -5% to -6.4%, vVO2max: 5.7% and 4.2%, respectively) with no change in EST. Similarly, all neuromuscular performance indicators improved in CPX and HST (p < 0.0167, 1RM strength:19.7% to 25.1%, SJ and CMJ: 5.3% to 11.6%, LP concentric and eccentric strength: 5.5% to 18.0%). In summary, 6-week of concurrent CPX or HST and endurance training resulted in similar improvement in maximum strength, RE, and vVO_2max. Importantly, both CPX and HST training resulted in greater improvements in eccentric strength and RE compared to EST that performed concurrent endurance-strength and endurance training.

Influence of Shoe Mass on Performance and Running Economy in Trained Runners

Purpose

The aim of this study was to assess the effects of adding shoe mass on running economy (RE), gait characteristics, neuromuscular variables and performance in a group of trained runners.

Methods

Eleven trained runners (6 men and 5 women) completed four evaluation sessions separated by at least 7 days. The first session consisted of a maximal incremental test where the second ventilatory threshold (VT₂) and the speed associated to the VO_2max (vVO_2max) were calculated. In the next sessions, RE at 75, 85, and 95% of the VT₂ and the time to exhaustion (TTE) at vVO_2max were assessed in three different shoe mass conditions (control, +50 g and +100 g) in a randomized, counterbalanced crossover design. Biomechanical and neuromuscular variables, blood lactate and energy expenditure were measured during the TTE test.

Results

RE worsened with the increment of shoe mass (Control vs. 100 g) at 85% (7.40%, 4.409 ± 0.29 and 4.735 ± 0.27 kJ⋅kg⁻¹⋅km⁻¹, p = 0.021) and 95% (10.21%, 4.298 ± 0.24 and 4.737 ± 0.45 kJ⋅kg⁻¹⋅km⁻¹, p = 0.005) of VT₂. HR significantly increased with the addition of mass (50 g) at 75% of VT₂ (p = 0.01) and at 75, 85, and 95% of VT₂ (p = 0.035, 0.03, and 0.03, respectively) with the addition of 100 g. TTE was significantly longer (∼22%, ∼42 s, p = 0.002, ES = 0.149) in the Control condition vs. 100 g condition, but not between Control vs. 50 g (∼24 s, p = 0.094, ES = 0.068).

Conclusion

Overall, our findings suggest that adding 100 g per shoe impairs running economy and performance in trained runners without changes in gait characteristics or neuromuscular variables. These findings further support the use of light footwear to optimize running performance.

Visual classification of running economy by distance running coaches

AbstractObjectives: This study assessed the ability of coaches to rank-order distance runners on running economy (RE) through visual assessment. Methods: Running economy was measured in five trained recreational distance runners at a speed of 3.57 m_·s^-1, with a minimum VO₂ difference of 2-mL.kg^-1.min^-1 between adjacent runners. Following measurement of RE, participants were filmed from the front, side, and rear while running on a treadmill. Endurance coaches from high school to international level (N = 121) viewed each video and ranked the runners on a scale from 1 (most economical) to 5 (least economical). Coaches also completed a demographic questionnaire and listed running style biomechanical observations they used in determining each ranking. A cumulative odds ordinal logistic regression with proportional odds was run to determine the effect of coaching level, years of coaching experience, years of training experience, competition level, certification status, and education level, on the ability of distance running coaching to accurately rank RE among a group of runners. Results: No coaching characteristic was a significant predictor of ranking accuracy, χ² = 3.566, p = .735. Conclusions: Visual assessment of effort, based on RE, is a difficult task, even for the trained eye and could be related to difficulty in understanding the interaction effect of various RE factors or the translation of scientific-based knowledge to the field of play. Practically, coaches should be cautious when recommending biomechanical adjustments without considering the interconnected factors related to such changes.