Factors affecting running economy in trained distance runners

Level Versus Uphill Economy and Mechanical Responses in Elite Ultra-Trail Runners

AIM

The purpose of this brief report was to examine the net oxygen cost, oxygen kinetics, and kinematics of level and uphill running in elite ultra-trail runners.

METHODS

Twelve top-level ultra-distance trail runners performed two 5-minute stages of treadmill running (level, 0%, men 15 km·h^-1, women 13 km·h^-1; and uphill, 12%, men 10 km·h^-1, women 9 km·h^-1). Gas exchanges were measured to obtain the net oxygen cost and assess oxygen kinetics. Additionally, running kinematics were recorded with inertial measurement unit motion sensors on the wrist, head, belt, and foot.

RESULTS

Relationships resulted between level and uphill running regarding oxygen uptake, respiratory exchange ratio, net energy and oxygen cost, as well as oxygen kinetics parameters of amplitude and time delay of the primary phase, and time to reach V̇O₂ steady state. Of interest, net oxygen cost demonstrated a significant correlation between level and uphill conditions (r=0.826, p<0.01). Kinematics parameters demonstrated relationships between level and uphill running as well (including contact time, aerial time, stride frequency, and stiffness; all p<0.01).

CONCLUSION

This study indicated strong relationships between level and uphill values of net oxygen cost, the time constant of the primary phase of oxygen kinetics, and biomechanical parameters of contact and aerial time, stride frequency, and stiffness in elite mountain ultra-trail runners. These results show that these top-level athletes are specially trained for uphill locomotion at the expense of their level running performance and suggest that uphill running is of utmost importance for success in mountain ultra-trail races.

Positive Work Contribution Shifts from Distal to Proximal Joints during a Prolonged Run

PURPOSE

To investigate the joint-specific contributions to the total lower-extremity joint work during a prolonged fatiguing run.

METHODS

Recreational long-distance runners (n = 13) and competitive long-distance runners (n = 12) performed a 10-km treadmill run with near-maximal effort. A three-dimensional motion capture system synchronized with a force-instrumented treadmill was used to calculate joint kinetics and kinematics of the lower extremity in the sagittal plane during the stance phase at 13 distance points over the 10-km run.

RESULTS

A significant (P < 0.05) decrease of positive ankle joint work as well as an increase of positive knee and hip joint work was found. These findings were associated with a redistribution of the individual contributions to total lower-extremity work away from the ankle toward the knee and hip joint which was more distinctive in the recreational runner group than in the competitive runner group. This redistribution was accomplished by significant (P < 0.05) reductions of the external ground-reaction force lever arm and joint torque at the ankle and by the significant (P < 0.05) increase of the external ground-reaction force lever arm and joint torque at the knee and hip.

CONCLUSIONS

The redistribution of joint work from the ankle to more proximal joints might be a biomechanical mechanism that could partly explain the decreased running economy in a prolonged fatiguing run. This might be because muscle-tendon units crossing proximal joints are less equipped for energy storage and return compared with ankle plantar flexors and require greater muscle volume activation for a given force. To improve running performance, long-distance runners may benefit from an exercise-induced enhancement of ankle plantar flexor muscle-tendon unit capacities.

The benefits of nutritional counselling for improving sport performance

BACKGROUND

It is well known that the synergy between physical activity and healthy eating habits is an important combination for the achievement of different objectives. However, recent studies in the literature focused mainly on the effect of this synergy on weight loss or different non communicable diseases. In this study, we aimed to investigate the effect of healthy eating, based on the Mediterranean diet, on physical performance of kickboxers and runners.

METHODS

Forty athletes were recruited from the University Sports Center of Bergamo. Twenty participants practiced kickboxing, an High Energy Expenditure Rate sport, whereas twenty subjects practiced half marathon, a typical High Energy Expenditure Volume sport. Kickboxers and runners were randomly divided into two sub-groups of ten subjects each: one was the control group (CG) and one the nutritional counselling group (NCG), in which subjects were instructed to follow a nutritional counselling.

RESULTS

At the baseline, runners started with greater VO2max and lower resting metabolic rate compared to kickboxers. After three months of controlled diet and training, kickboxers in NCG improved their results in Counter Movement Jump (CMJ) Test (P=0.015) and squat (P=0.012). Moreover, athletes had a decrease in body fat percentage (P=0.008). Runners in NCG, had a significant VO2max (P=0.007) increase and a reduction in body fat percentage (P=0.002). They also showed an increase of squat (P=0.012) and CMJ test (P=0.024).

CONCLUSIONS

Significant benefits were achieved in all groups of athletes, but results were maximized by training plus nutritional counselling.

A New Method to Improve Running Economy and Maximal Aerobic Power in Athletes: Endurance Training With Periodic Carbon Monoxide Inhalation

Background

Altitude training stimulates erythropoietin hormone (EPO) release and increases blood hemoglobin (Hb) mass, which may result in improved oxygen (O₂) transport capacity. It was hypothesized in the present study that periodic inhalation of carbon monoxide (CO) might elicit similar physiological adaptations compared to altitude training.

Methods

Twelve male college student athletes, who were well-trained soccer players, participated. They performed a 4-week treadmill-training program, five times a week. Participants were randomly assigned into an experimental group with inhaling CO (INCO) (1 mL/kg body weight for 2 min) in O₂ (4 L) before all training sessions and a control group without inhaling CO (NOCO). CO and EPO concentrations in venous blood were first measured acutely at the 1st, 2nd, 4th, 6th, and 8th hour after INCO, and total hemoglobin mass (tHb), running economy and VO₂max were measured before and after the 4 weeks training intervention.

Results

HbCO% increased from 0.7 to 4.4% (P < 0.05) after 1 h of CO inhalation and EPO increased from 1.9 to 2.7 mIU/mL after 4 h post CO inhalation (P < 0.05) acutely before the intervention. After the training, the tHb and VO₂max in the INCO group increased significantly by 3.7 and 2.7%, respectively, while no significant differences were observed in the NOCO condition. O₂ uptake at given submaximal speeds declined by approximately 4% in the INCO group.

Conclusion

Acutely, EPO increased sharply post CO inhalation, peaking at 4 h post inhalation. 4-weeks of training with CO inhalation before exercise sessions improved tHb and VO₂max as well as running economy, suggesting that moderate CO inhalation could be a new method to improve the endurance performance in athletes.

Nitrate Supplementation Combined with a Running Training Program Improved Time-Trial Performance in Recreationally Trained Runners

Our purpose was to verify the effects of inorganic nitrate combined to a short training program on 10-km running time-trial (TT) performance, maximum and average power on a Wingate test, and lactate concentration ([La⁻]) in recreational runners. Sixteen healthy participants were divided randomly into two groups: Nitrate (n = 8) and placebo (n = 8). The experimental group ingested 750 mg/day (~12 mmol) of nitrate plus 5 g of resistant starch, and the control group ingested 6 g of resistant starch, for 30 days. All variables were assessed at baseline and weekly over 30 days. Training took place 3x/week. The time on a 10-km TT decreased significantly (p < 0.001) in all timepoints compared to baseline in both groups, but only the nitrate group was faster in week 2 compared to 1. There was a significant group × time interaction (p < 0.001) with lower [La] in the nitrate group at week 2 (p = 0.032), week 3 (p = 0.002), and week 4 (p = 0.003). There was a significant group time interaction (p = 0.028) for Wingate average power and a main effect of time for maximum power (p < 0.001) and [La⁻] for the 60-s Wingate test. In conclusion, nitrate ingestion during a four-week running program improved 10-km TT performance and kept blood [La⁻] steady when compared to placebo in recreational runners.

Years of running experience influences stride-to-stride fluctuations and adaptive response during step frequency perturbations in healthy distance runners

RESEARCH QUESTION

The current study investigated stride-to-stride fluctuations of step rate and contact time in response to enforced step frequency perturbations as well as adaptation and de-adaptation behavior.

METHODS

Forty distance runners ran at a self-selected speed and were asked to match five different enforced step frequencies (150, 160, 170, 180, and 190 beats per min). The influence of experience was explored, because running is a skill that presumably gets better with practice, and increased years of running experience is protective against injury. Detrended fluctuation analysis was used to determine the strength of long-range correlations in gait fluctuations at baseline, during the perturbation, and post-perturbation. Adaptive response was measured by the ability to match, rate of matching, and aftereffect of step frequency perturbations.

RESULTS

The structure of stride-to-stride fluctuations for step rate and contact time did not change during the perturbation or post-perturbation compared to baseline. However, fluctuations in step rate were affected by the level of perturbation. Runners with the most experience had a less persistent structural gait pattern for both step rate and contact time at baseline. Highly experienced runners also demonstrated the best adaptive response. They better matched the enforced step frequency, reached the enforced step frequency sooner, and returned to preferred step frequency more quickly following removal of the perturbation.

SIGNIFICANCE

These findings indicate baseline locomotor flexibility may be beneficial to achieve task demands and return to a stable state once the task is complete. Increased locomotor flexibility may also be a contributing factor for reduced injury risk in experienced runners.

Effects of complex training versus heavy resistance training on neuromuscular adaptation, running economy and 5-km performance in well-trained distance runners

Background

Recently, much attention has been paid to the role of neuromuscular function in long-distance running performance. Complex Training (CT) is a combination training method that alternates between performing heavy resistance exercises and plyometric exercises within one single session, resulting in great improvement in neuromuscular adaptation. The purpose of this study was to compare the effect of CT vs. heavy resistance training (HRT) on strength and power indicators, running economy (RE), and 5-km performance in well-trained male distance runners.

Methods

Twenty-eight well-trained male distance runners (19–23 years old, VO_2max:65.78 ± 4.99 ml.kg⁻¹.min⁻¹) performed one pre-test consisting of: maximum strength (1RM), counter movement jump (CMJ) height, peak power, a drop jump (DJ), and RE assessments, and blood lactate concentration (BLa) measurement at the speeds from 12–16 km.h⁻¹, a 50-m sprint, and a 5-km running performance test. They were then divided into 3 groups: complex training group (CT, n = 10), that performed complex training and endurance training; heavy resistance training group (HRT, n = 9) that performed heavy strength training and endurance training; and control group (CON, n = 9) that performed strength-endurance training and endurance training. After the 8 weeks training intervention, all participants completed a post-test to investigate the training effects on the parameters measured.

Results

After training intervention, both the CT and HRT groups had improvements in: 1RM strength (16.88%, p < 0.001; 18.80%, p < 0.001, respectively), CMJ height (11.28%, p < 0.001; 8.96%, p < 0.001, respectively), 14 km.h⁻¹RE (−7.68%, p < 0.001; −4.89%, p = 0.009, respectively), 50-m sprints (−2.26%, p = 0.003; −2.14%, p = 0.007, respectively) and 5-km running performance (−2.80%, p < 0.001; −2.09%, p < 0.001, respectively). The CON group did not show these improvements. All three training groups showed improvement in the 12 km.h⁻¹RE (p ≤ 0.01). Only the CT group exhibited increases in DJ height (12.94%, p < 0.001), reactive strength index (19.99%, p < 0.001), 16 km.h⁻¹ RE (−7.38%, p < 0.001), and a reduction of BLa concentrations at the speed of 16 km.h⁻¹ (−40.80%, p < 0.001) between pre- and post-tests.

Conclusion

This study demonstrated that CT can enhance 1RM strength, CMJ height, 12 and 14 km.h⁻¹REs, 50-m sprints and 5-km running performances in well-trained male distance runners and may be superior to HRT for the development of reactive strength and 16 km.h⁻¹RE, and reduction of BLa concentrations at speed of 16 km.h⁻¹. Young male distance runners could integrate CT into their programs to improve the running performance.

Contemporary Nutrition Strategies to Optimize Performance in Distance Runners and Race Walkers

Distance events in Athletics include cross country, 10,000-m track race, half-marathon and marathon road races, and 20- and 50-km race walking events over different terrain and environmental conditions. Race times for elite performers span ∼26 min to >4 hr, with key factors for success being a high aerobic power, the ability to exercise at a large fraction of this power, and high running/walking economy. Nutrition-related contributors include body mass and anthropometry, capacity to use fuels, particularly carbohydrate (CHO) to produce adenosine triphosphate economically over the duration of the event, and maintenance of reasonable hydration status in the face of sweat losses induced by exercise intensity and the environment. Race nutrition strategies include CHO-rich eating in the hours per days prior to the event to store glycogen in amounts sufficient for event fuel needs, and in some cases, in-race consumption of CHO and fluid to offset event losses. Beneficial CHO intakes range from small amounts, including mouth rinsing, in the case of shorter events to high rates of intake (75-90 g/hr) in the longest races. A personalized and practiced race nutrition plan should balance the benefits of fluid and CHO consumed within practical opportunities, against the time, cost, and risk of gut discomfort. In hot environments, prerace hyperhydration or cooling strategies may provide a small but useful offset to the accrued thermal challenge and fluid deficit. Sports foods (drinks, gels, etc.) may assist in meeting training/race nutrition plans, with caffeine, and, perhaps nitrate being used as evidence-based performance supplements.

Effects of Strength Training on Postpubertal Adolescent Distance Runners

PURPOSE

Strength training activities have consistently been shown to improve running economy (RE) and neuromuscular characteristics, such as force-producing ability and maximal speed, in adult distance runners. However, the effects on adolescent (<18 yr) runners remains elusive. This randomized control trial aimed to examine the effect of strength training on several important physiological and neuromuscular qualities associated with distance running performance.

METHODS

Participants (n = 25, 13 female, 17.2 ± 1.2 yr) were paired according to their sex and RE and randomly assigned to a 10-wk strength training group (STG) or a control group who continued their regular training. The STG performed twice weekly sessions of plyometric, sprint, and resistance training in addition to their normal running. Outcome measures included body mass, maximal oxygen uptake (V˙O2max), speed at V˙O2max, RE (quantified as energy cost), speed at fixed blood lactate concentrations, 20-m sprint, and maximal voluntary contraction during an isometric quarter-squat.

RESULTS

Eighteen participants (STG: n = 9, 16.1 ± 1.1 yr; control group: n = 9, 17.6 ± 1.2 yr) completed the study. The STG displayed small improvements (3.2%-3.7%; effect size (ES), 0.31-0.51) in RE that were inferred as "possibly beneficial" for an average of three submaximal speeds. Trivial or small changes were observed for body composition variables, V˙O2max and speed at V˙O2max; however, the training period provided likely benefits to speed at fixed blood lactate concentrations in both groups. Strength training elicited a very likely benefit and a possible benefit to sprint time (ES, 0.32) and maximal voluntary contraction (ES, 0.86), respectively.

CONCLUSIONS

Ten weeks of strength training added to the program of a postpubertal distance runner was highly likely to improve maximal speed and enhances RE by a small extent, without deleterious effects on body composition or other aerobic parameters.

Physical exercise training for type 3 spinal muscular atrophy

BACKGROUND

Physical exercise training might improve muscle and cardiorespiratory function in spinal muscular atrophy (SMA). Optimization of aerobic capacity or other resources in residual muscle tissue through exercise may counteract the muscle deterioration that occurs secondary to motor neuron loss and inactivity in SMA. There is currently no evidence synthesis available on physical exercise training in people with SMA type 3.

OBJECTIVES

To assess the effects of physical exercise training on functional performance in people with SMA type 3, and to identify any adverse effects.

SEARCH METHODS

On 8 May 2018, we searched the Cochrane Neuromuscular Specialised Register, Cochrane Central Register of Controlled Trials, MEDLINE, Embase, CINAHL, AMED, and LILACS. On 25 April 2018 we searched NHSEED, DARE, and ClinicalTrials.gov and WHO ICTRP for ongoing trials.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) or quasi-RCTs lasting at least 12 weeks that compared physical exercise training (strength training, aerobic exercise training, or both) to placebo, standard or usual care, or another type of non-physical intervention for SMA type 3. Participants were adults and children from the age of five years with a diagnosis of SMA type 3 (Kugelberg-Welander syndrome), confirmed by genetic analysis.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methodological procedures.

MAIN RESULTS

We included one RCT that studied the effects of a six-month, home-based, combined muscle strength and recumbent cycle ergometry training program versus usual care in 14 ambulatory people with SMA. The age range of the participants was between 10 years and 48 years. The study was evaluator-blinded, but personnel and participants could not be blinded to the intervention, which placed the results at a high risk of bias. Participants performed strength training as prescribed, but 50% of the participants did not achieve the intended aerobic exercise training regimen. The trial used change in walking distance on the six-minute walk test as a measure of function; a minimal detectable change is 24.0 m. The change from baseline to six months' follow-up in the training group (9.4 m) was not detectably different from the change in the usual care group (-0.14 m) (mean difference (MD) 9.54 m, 95% confidence interval (CI) -83.04 to 102.12; N = 12). Cardiopulmonary exercise capacity, assessed by the change from baseline to six months' follow-up in peak oxygen uptake (VO2max) was similar in the training group (-0.12 mL/kg/min) and the usual care group (-1.34 mL/kg/min) (MD 1.22 mL/kg/min, 95% CI -2.16 to 4.6; N = 12). A clinically meaningful increase in VO2max is 3.5 mL/kg/min.The trial assessed function on the Hammersmith Functional Motor Scale - Expanded (HFMSE), which has a range of possible scores from 0 to 66, with an increase of 3 or more points indicating clinically meaningful improvement. The HFMSE score in the training group increased by 2 points from baseline to six months' follow-up, with no change in the usual care group (MD 2.00, 95% CI -2.06 to 6.06; N = 12). The training group showed a slight improvement in muscle strength, expressed as the manual muscle testing (MMT) total score, which ranges from 28 (weakest) to 280 (strongest). The change from baseline in MMT total score was 6.8 in the training group compared to -5.14 in the usual care group (MD 11.94, 95% CI -3.44 to 27.32; N = 12).The trial stated that training had no statistically significant effects on fatigue and quality of life. The certainty of evidence for all outcomes was very low because of study limitations and imprecision. The study did not assess the effects of physical exercise training on physical activity levels. No study-related serious adverse events or adverse events leading to withdrawal occurred, but we cannot draw wider conclusions from this very low-certainty evidence.

AUTHORS' CONCLUSIONS

It is uncertain whether combined strength and aerobic exercise training is beneficial or harmful in people with SMA type 3, as the quality of evidence is very low. We need well-designed and adequately powered studies using protocols that meet international standards for the development of training interventions, in order to improve our understanding of the exercise response in people with SMA type 3 and eventually develop exercise guidelines for this condition.

Are changes in running economy associated with changes in performance in runners? A systematic review and meta-analysis

Improvements in running economy (RE) are thought to lead to improvements in running performance (P). Multiple interventions have been designed with the aim of improving RE in middle and long-distance runners. The aim of this study was to assess the effect of interventions of at least 2-weeks' duration on RE and P and to determine whether there is a relationship between changes in RE (ΔRE) and changes in running performance (ΔP). A database search was carried out in Web of Science, Scopus and SPORTDiscus. In accordance with a PRISMA checklist 10 studies reporting 12 comparisons between interventions and controls were included in the review. There was no correlation between percentage ΔRE and percentage ΔP (r = 0.46, P = 0.936, 12 comparisons). There was a low risk of reporting bias but an unclear risk of bias for other items. Meta-analyses found no statistically significant differences between interventions and controls for RE (SMD (95% CI) = -0.37 (-1.43, 0.69), 204 participants, p = 0.49) or for P (SMD (95% CI) = -0.65 (-26.02, 24.72, 204 participants, p = 0.99). There is a need for studies of greater statistical power, methodological quality, duration and homogeneity of intervention and population. Standardised measures of performance and greater control over non-intervention training are also required.

Extrapolating Metabolic Savings in Running: Implications for Performance Predictions

Training, footwear, nutrition, and racing strategies (i.e., drafting) have all been shown to reduce the metabolic cost of distance running (i.e., improve running economy). However, how these improvements in running economy (RE) quantitatively translate into faster running performance is less established. Here, we quantify how metabolic savings translate into faster running performance, considering both the inherent rate of oxygen uptake-velocity relation and the additional cost of overcoming air resistance when running overground. We collate and compare five existing equations for oxygen uptake-velocity relations across wide velocity ranges. Because the oxygen uptake vs. velocity relation is non-linear, for velocities slower than ∼3 m/s, the predicted percent improvement in velocity is slightly greater than the percent improvement in RE. For velocities faster than ∼3 m/s, the predicted percent improvement in velocity is less than the percent improvements in RE. At 5.5 m/s, i.e., world-class marathon pace, the predicted percent improvement in velocity is ∼2/3rds of the percent improvement in RE. For example, at 2:04 marathon pace, a 3% improvement in RE translates to a 1.97% faster velocity or 2:01:36, almost exactly equal to the recently set world record.

A time to exhaustion model during prolonged running based on wearable accelerometers

Defining relationships between running mechanisms and fatigue can be a major asset for optimising training. This article proposes a biomechanical model of time to exhaustion according to indicators derived from accelerometry data collected from the body. Ten volunteers were recruited for this study. The participants were equipped with 3 accelerometers: on the right foot, at the tibia and at the L4-L5 lumbar spine. A running test was performed on a treadmill at 13.5 km/h until exhaustion. Thirty-one variables were deployed during the test. Multiple linear regressions were calculated to explain the time to exhaustion from the indicators calculated on the lumbar, tibia and foot individually and simultaneously. Time to exhaustion was predicted for simultaneous measurement points with r 2 = 0.792 and 21 indicators; for the lumbar with r 2 = 0.568 and 11 indicators; for the tibia with r 2 = 558 and 11 indicators; and for the foot with r 2 = 0.626 and 12 indicators. This study allows the accurate modelling of the time to exhaustion during a running-based test using indicators from accelerometer measurements. The individual models highlight that the location of the measurement point is important and that each location provides different information. Future studies should focus on homogeneous populations to improve predictions and errors.

Whole-Body High-Intensity Interval Training Induce Similar Cardiorespiratory Adaptations Compared With Traditional High-Intensity Interval Training and Moderate-Intensity Continuous Training in Healthy Men

Schaun, GZ, Pinto, SS, Silva, MR, Dolinski, DB, and Alberton, CL. Sixteen weeks of whole-body high-intensity interval training induce similar cardiorespiratory responses compared with traditional high-intensity interval training and moderate-intensity continuous training in healthy men. J Strength Cond Res 32(10): 2730-2742, 2018-Low-volume high-intensity interval training (HIIT) protocols that use the body weight as resistance could be an interesting and inexpensive alternative to traditional ergometer-based high-intensity interval training (HIIT-T) and moderate-intensity continuous training (MICT). Therefore, our aim was to compare the effects of 16 weeks of whole-body HIIT (HIIT-WB), HIIT-T, and MICT on maximal oxygen uptake (V[Combining Dot Above]O2max), second ventilatory threshold (VT2), and running economy (RE) outcomes. Fifty-five healthy men (23.7 ± 0.7 years, 1.79 ± 0.01 m, 78.5 ± 1.7 kg) were randomized into 3 training groups (HIIT-T = 17; HIIT-WB = 19; MICT = 19) for 16 weeks (3× per week). The HIIT-T group performed eight 20-second bouts at 130% of the velocity associated to V[Combining Dot Above]O2max (vV[Combining Dot Above]O2max) interspersed by 10-second passive recovery on a treadmill, whereas HIIT-WB group performed the same protocol but used calisthenics exercises at an all-out intensity instead of treadmill running. Finally, MICT group exercised for 30 minutes at 90-95% of the heart rate (HR) associated to VT2. After the intervention, all groups improved V[Combining Dot Above]O2max, vV[Combining Dot Above]O2max, time to exhaustion (Tmax), VT2, velocity associated with VT2 (vVT2), and time to reach VT2 (tVT2) significantly (p < 0.05). Moreover, Tmax, vVT2, and tVT2 were greater after HIIT-T compared with HIIT-WB (p < 0.05), whereas oxygen uptake increased and HR decreased during the RE test in all groups (p < 0.05). Our results demonstrate that HIIT-WB can be as effective as traditional HIIT while also being time-efficient compared with MICT to improve health-related outcomes after 16 weeks of training. However, HIIT-T and MICT seem preferable to enhance performance-related outcomes compared with HIIT-WB.

Photobiomodulation Therapy on Physiological and Performance Parameters During Running Tests: Dose-Response Effects

Dellagrana, RA, Rossato, M, Sakugawa, RL, Baroni, BM, and Diefenthaeler, F. Photobiomodulation therapy on physiological and performance parameters during running tests: Dose-response effects. J Strength Cond Res 32(10): 2807-2815, 2018-This study was aimed at verifying effects of photobiomodulation therapy (PBMT) with different energy doses (15, 30, and 60 J per site) on physiological and performance parameters during running tests. Fifteen male recreational runners participated in a crossover, randomized, double-blind, and placebo-controlled trial. They performed testing protocol in 5 sessions with different treatments: control, placebo, and PBMT with 15, 30, or 60 J per site (14 sites in each lower limb). Physiological and performance variables were assessed during submaximal (at 8 and 9 km·h) and maximal running tests. Photobiomodulation therapy with 30 J significantly improved running economy (RE) at 8 and 9 km·h (3.01%, p=0.008 and 3.03%, p=0.009, respectively), rate of perceived exertion (RPE) at 8 km/h21 (7.86%, p=0.033), velocity at V[Combining Dot Above]O2max (3.07%, p= 0.029), peak of velocity (PV) (1.49%, p=0.035), and total time to exhaustion (TTE) (3.41%, p=0.036) compared with placebo. Photobiomodulation therapy with 15 J improved running economy at 9 km/h21 (2.98%, p=0.025), rate of perceived exertion at 8 km/h21 (4.80%, p=0.010), PV (1.33%, p=0.008), total time to exhaustion (3.06%, p=0.008), and total distance (4.01%, p=0.011) compared with the placebo; whereas PBMT with 60 J only increased RE at 9 km/h21 (3.87%, p=0.024) compared with placebo. All PBMT doses positively affected physiological and/or performance parameters; however, magnitude-based inference reported that PBMT applied with 30 J led to more beneficial effects than 15 and 60 J.

Running Performance, VO2max, and Running Economy: The Widespread Issue of Endogenous Selection Bias

Studies in sport and exercise medicine routinely use samples of highly trained individuals in order to understand what characterizes elite endurance performance, such as running economy and maximal oxygen uptake VO_2max. However, it is not well understood in the literature that using such samples most certainly leads to biased findings and accordingly potentially erroneous conclusions because of endogenous selection bias. In this paper, I review the current literature on running economy and VO_2max, and discuss the literature in light of endogenous selection bias. I demonstrate that the results in a large part of the literature may be misleading, and provide some practical suggestions as to how future studies may alleviate endogenous selection bias.

Effects of Strength Training on the Physiological Determinants of Middle- and Long-Distance Running Performance: A Systematic Review

Background

Middle- and long-distance running performance is constrained by several important aerobic and anaerobic parameters. The efficacy of strength training (ST) for distance runners has received considerable attention in the literature. However, to date, the results of these studies have not been fully synthesized in a review on the topic.

Objectives

This systematic review aimed to provide a comprehensive critical commentary on the current literature that has examined the effects of ST modalities on the physiological determinants and performance of middle- and long-distance runners, and offer recommendations for best practice.

Methods

Electronic databases were searched using a variety of key words relating to ST exercise and distance running. This search was supplemented with citation tracking. To be eligible for inclusion, a study was required to meet the following criteria: participants were middle- or long-distance runners with ≥ 6 months experience, a ST intervention (heavy resistance training, explosive resistance training, or plyometric training) lasting ≥ 4 weeks was applied, a running only control group was used, data on one or more physiological variables was reported. Two independent assessors deemed that 24 studies fully met the criteria for inclusion. Methodological rigor was assessed for each study using the PEDro scale.

Results

PEDro scores revealed internal validity of 4, 5, or 6 for the studies reviewed. Running economy (RE) was measured in 20 of the studies and generally showed improvements (2–8%) compared to a control group, although this was not always the case. Time trial (TT) performance (1.5–10 km) and anaerobic speed qualities also tended to improve following ST. Other parameters [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}$$\dot{V}{\text{O}}_{{2{ \hbox{max} }}}$$\end{document}V˙O2max), velocity at \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}{\text{O}}_{{2{ \hbox{max} }}}$$\end{document}V˙O2max, blood lactate, body composition] were typically unaffected by ST.

Conclusion

Whilst there was good evidence that ST improves RE, TT, and sprint performance, this was not a consistent finding across all works that were reviewed. Several important methodological differences and limitations are highlighted, which may explain the discrepancies in findings and should be considered in future investigations in this area. Importantly for the distance runner, measures relating to body composition are not negatively impacted by a ST intervention. The addition of two to three ST sessions per week, which include a variety of ST modalities are likely to provide benefits to the performance of middle- and long-distance runners.

The Relationship between Running Power and Running Economy in Well-Trained Distance Runners

A novel running wearable called the Stryd Summit footpod fastens to a runner’s shoe and estimates running power. The footpod separates power output into two components, Stryd power and form power. The purpose of this study was to measure the correlations between running economy and power and form power at lactate threshold pace. Seventeen well-trained distance runners, 9 male and 8 female, completed a running protocol. Participants ran two four-minute trials: one with a self-selected cadence, and one with a target cadence lowered by 10%. The mean running economy expressed in terms of oxygen cost at self-selected cadence was 201.6 ± 12.8 mL·kg⁻¹·km⁻¹, and at lowered cadence was 204.5 ± 11.5 mL·kg⁻¹·km⁻¹. Ventilation rate and rating of perceived exertion (RPE) were not significantly different between cadence conditions with one-tailed paired t-test analysis (ventilation, p = 0.77, RPE, p = 0.07). Respiratory exchange ratio and caloric unit cost were significantly greater with lower cadence condition (respiratory exchange ratio, p = 0.03, caloric unit cost, p = 0.03). Mean power at self-selected cadence was 4.4 ± 0.5 W·kg⁻¹, and at lowered cadence was 4.4 ± 0.5 W·kg⁻¹. Mean form power at self-selected cadence was 1.1 ± 0.1 W·kg⁻¹, and at lowered cadence was 1.1 ± 0.1 W·kg⁻¹. There were positive, linear correlations between running economy and power (self-selected cadence and lower cadence, r = 0.6; the 90% confidence interval was 0.2 to 0.8); running economy and form power (self-selected cadence and lower cadence r = 0.5; the 90% confidence interval was 0.1 to 0.8). The findings suggest running economy is positively correlated with Stryd’s power and form power measures yet the footpod may not be sufficiently accurate to estimate differences in the running economy of competitive runners.

A systematic review on small-sided games in football players: Acute and chronic adaptations

Small-sided games (SSG) are played on a small pitch, often using modified rules and involving a smaller number of players. This article aimed to critically analyse the literature to determine how small-sided games affect the performance of football players in the short- and long term. Electronic databases were searched for literature dating from January 2000 to July 2018. The methodological quality of the studies was evaluated using the modified Downs and Black Quality Index (cross-sectional studies) and the Physiotherapy Evidence Database (PEDro) scale (intervention studies). Fifty-three studies, 44 cross-sectional and 9 intervention studies, met the inclusionary criteria for review. Most of the cross-sectional studies focused on describing the differences between SSG protocols, whereas 4 studies focused on making a comparison between "interval" and "continuous" SSG training regimes. On the other hand, intervention studies focused on making a comparison between SSG-based protocols and high-intensity intermittent training (HIIT)-based running protocols, in addition to determine the effect of a SSG-based training programme alone. SSG-based football plans (2 to 4 SSG sessions per week) show athletic performance improvements in football players by improving sprint, repeated sprint ability (RSA) and change of direction (COD) along with muscular and physiological adaptation.

Effect of different loading conditions on running mechanics at different velocities

Weighted vests are widely used to improve running economy and performance. However, it is not well-studied how running mechanics are adapted to counteract the higher peak vertical ground reaction forces (Fpeak) while running with such a device. Therefore, the present study aimed to investigate the effects of different loading conditions on running mechanics at different velocities. Thirteen subjects participated in two separate sessions one week apart. In the first session, maximal aerobic speed (MAS) was determined through a maximal incremental running test while in the second session, they were instructed to run during one minute under different loading (0%, +10% and +20% of body mass [BM]) and velocity (60%, 80% and 100% of MAS) conditions in a random order. Spatiotemporal data were recorded and then running mechanics modelled using the spring-mass model. The main results indicated that vertical and leg stiffness (Kvert and Kleg, respectively) were increased (P < .001) as velocity increased but remained unaltered (P > .05) when load was changed. At the same time, alterations of the running kinematics were observed such as longer contact times, reduced flight times, stride frequencies and step lengths, as well as an increase of the centre of mass dynamics. Based on these results it is assumed that runners maintain a certain stiffness level for each velocity despite different loading conditions. As a consequence, Fpeak increases and this probably causes spatiotemporal adjustments in the movement kinematics.

Movement Economy in Soccer: Current Data and Limitations

Soccer is an intermittent team-sport, where performance is determined by a myriad of psychological, technical, tactical, and physical factors. Among the physical factors, endurance appears to play a key role into counteracting the fatigue-related reduction in running performance observed during soccer matches. One physiological determinant of endurance is movement economy, which represents the aerobic energy cost to exercise at a given submaximal velocity. While the role of movement economy has been extensively examined in endurance athletes, it has received little attention in soccer players, but may be an important factor, given the prolonged demands of match play. For this reason, the current review discusses the nature, impact, and trainability of movement economy specific to soccer players. A summary of current knowledge and limitations of movement economy in soccer is provided, with an insight into future research directions, to make this important parameter more valuable when assessing and training soccer players’ running performance.

Effects of upper and lower body wearable resistance on spatio-temporal and kinetic parameters during running

Wearable resistance training involves added load attached directly to the body during sporting movements. The effects of load position during running are not yet fully established. Therefore, the purpose of this research was to determine spatio-temporal and kinetic characteristics during submaximal running using upper, lower and whole-body wearable resistance (1-10% body mass (BM)). Twelve trained male runners completed eight 2-min treadmill running bouts at 3.9 m/s with and without wearable resistance. The first and last bouts were unloaded, while the middle 6 were randomised wearable resistance conditions: upper body (UB) 5% BM, lower body (LB) 1%, 3%, 5% BM and whole body (WB) 5%, 10% BM. Wearable resistance of 1-10% BM resulted in a significant increase in heart rate (5.40-8.84%), but minimal impact on spatio-temporal variables. Loads of 5% BM and greater caused changes in vertical stiffness, vertical and horizontal force, and impulse. Functional and effective propulsive force (2.95%, 2.88%) and impulse (3.40%, 3.38%) were significantly (p < 0.05) greater with LB5% than UB5%. Wearable resistance may be used to increase muscular kinetics during running without negatively impacting spatio-temporal variables. The application of these findings will vary depending on athlete goals. Future longitudinal studies are required to validate training contentions.

Reproducibility of the Evolution of Stride Biomechanics During Exhaustive Runs

Running biomechanics and its evolution that occurs over intensive trials are widely studied, but few studies have focused on the reproducibility of stride evolution in these runs. The purpose of this investigation was to assess the reproducibility of changes in eight biomechanical variables during exhaustive runs, using three-dimensional analysis. Ten male athletes (age: 23 ± 4 years; maximal oxygen uptake: 57.5 ± 4.4 ml0₂·min^-1·kg^-1; maximal aerobic speed: 19.3 ± 0.8 km·h^-1) performed a maximal treadmill test. Between 3 to 10 days later, they started a series of three time-to-exhaustion trials at 90% of the individual maximal aerobic speed, seven days apart. During these trials eight biomechanical variables were recorded over a 20-s period every 4 min until exhaustion. The evolution of a variable over a trial was represented as the slope of the linear regression of these variables over time. Reproducibility was assessed with intraclass correlation coefficients and variability was quantified as standard error of measurement. Changes in five variables (swing duration, stride frequency, step length, centre of gravity vertical and lateral amplitude) showed moderate to good reproducibility (0.48 ≤ ICC ≤ 0.72), while changes in stance duration, reactivity and foot orientation showed poor reproducibility (-0.71 ≤ ICC ≤ 0.04). Fatigue-induced changes in stride biomechanics do not follow a reproducible course across the board; however, several variables do show satisfactory stability: swing duration, stride frequency, step length and centre of gravity shift.

Accuracy of training recommendations based on a treadmill multistage incremental exercise test

Competitive runners will occasionally undergo exercise in a laboratory setting to obtain predictive and prescriptive information regarding their performance. The present research aimed to assess whether the physiological demands of lab-based treadmill running (TM) can simulate that of over-ground (OG) running using a commonly used protocol. Fifteen healthy volunteers with a weekly mileage of ≥ 20 km over the past 6 months and treadmill experience participated in this cross-sectional study. Two stepwise incremental tests until volitional exhaustion was performed in a fixed order within one week in an Outpatient Clinic research laboratory and outdoor athletic track. Running velocity (IATspeed), heart rate (IATHR) and lactate concentration at the individual anaerobic threshold (IATbLa) were primary endpoints. Additionally, distance covered (DIST), maximal heart rate (HRmax), maximal blood lactate concentration (bLamax) and rate of perceived exertion (RPE) at IATspeed were analyzed. IATspeed, DIST and HRmax were not statistically significantly different between conditions, whereas bLamax and RPE at IATspeed showed statistical significance (p < 0.05). Apart from RPE at IATspeed, IATspeed, DIST, HRmax and bLamax strongly correlate between conditions (r = 0.815-0.988). High reliability between conditions provides strong evidence to suggest that running on a treadmill are physiologically comparable to that of OG and that training recommendations and be made with assurance.

Effects of Plyometric Training on Explosive and Endurance Performance at Sea Level and at High Altitude

Plyometric training performed at sea level enhance explosive and endurance performance at sea level. However, its effects on explosive and endurance performance at high altitude had not been studied. Therefore, the aim of this study was to determine the effects of a sea level short-term (i.e., 4-week) plyometric training program on explosive and endurance performance at sea level and at high altitude (i.e., 3,270 m above sea level). Participants were randomly assigned to a control group (n = 12) and a plyometric training group (n = 11). Neuromuscular (reactive strength index – RSI) and endurance (2-km time-trial; running economy [RE]; maximal oxygen uptake - VO₂max) measurements were performed at sea level before, at sea level after intervention (SL +4 week), and at high altitude 24-h post SL +4 week. The ANOVA revealed that at SL +4 week the VO₂max was not significantly changed in any group, although RE, RSI and 2-km time trial were significantly (p < 0.05) improved in the plyometric training group. After training, when both groups were exposed to high altitude, participants from the plyometric training group showed a greater RSI (p < 0.05) and were able to maintain their 2-km time trial (11.3 ± 0.5 min vs. 10.7 ± 0.6 min) compared to their pre-training sea level performance. In contrast, the control group showed no improvement in RSI, with a worse 2-km time trial performance (10.3 ± 0.8 min vs. 9.02 ± 0.64 min; p < 0.05; ES = 0.13). Moreover, after training, both at sea level and at high altitude the plyometric training group demonstrated a greater (p < 0.05) RSI and 2-km time trial performance compared to the control group. The oxygen saturation was significantly decreased after acute exposure to high altitude in the two groups (p < 0.05). These results confirm the beneficial effects of sea level short-term plyometric training on explosive and endurance performance at sea level. Moreover, current results indicates that plyometric training may also be of value for endurance athletes performing after an acute exposure to high altitude.

The Effects of a Compression Garment on Lower Body Kinematics and Kinetics During a Drop Vertical Jump in Female Collegiate Athletes

Background

The use of compression garments has spread rapidly among athletes, largely because of marketing and perceived benefits. Upon review, it is unclear whether compression garments have a significant effect on performance and recovery, although they have been found to enhance proprioception. Further, it is reported that compression of the knee joint improves both dynamic and static balance. However, there is currently a paucity of data demonstrating the effects of compression garments on the biomechanical risk factors of knee-related injuries in female athletes.

Purpose

To evaluate the ability of a directional compression garment to alter hip and knee kinematics and kinetics during a drop vertical jump (DVJ) in healthy college-aged female athletes.

Study Design

Controlled laboratory study.

Methods

A sample of 23 healthy female collegiate athletes (mean age, 19.6 ± 1.3 years) participating in jumping sports (volleyball, basketball, and soccer) was included in this analysis. Each athlete performed 2 sets of 3 DVJs with and without a directional compression garment. Three-dimensional hip and knee kinematics and kinetics were collected using a standard Helen-Hayes 29-marker set, which was removed and reapplied after the garment was fitted, as well as 8 visible-red cameras and 2 force platforms. Each participant was tested in a single session.

Results

Hip abduction range of motion was significantly reduced from 12.6° ± 5.5° to 10.2° ± 4.6° (P = .002) while performing DVJs without and with the compression garment, respectively. No statistically significant differences between conditions were found in peak hip abduction, knee valgus range of motion, peak valgus, peak hip abduction moment, and peak knee valgus moment.

Conclusion

The results of this study show that wearing compression garments does have minimal effects on lower body mechanics during landing from a DVJ, partially supporting the idea that compression garments could acutely alter movement patterns associated with the knee injury risk. However, further research should focus on muscle activation patterns and adaptations over time.

Clinical Relevance

The use of specifically designed compression garments could aid in the prevention of knee injuries by inducing changes in jumping mechanics.

Hip muscular strength balance is associated with running economy in recreationally-trained endurance runners

Background

The percentage of sustained maximal oxygen uptake and the running economy are important factors that determine the running success of endurance athletes. Running economy is defined as the oxygen uptake required to run at a given speed and depends on metabolic, cardiorespiratory, biomechanical, neuromuscular, and anthropometric factors. With regard to anthropometric characteristics, total body mass seems to be a crucial factor for the running economy. Moreover, neuromuscular components, especially knee muscular strength and the strength balance ratio, also seem to be critical for the running economy. In addition to knee muscle strength, hip muscle strength is also an important contributor to running performance on level or hilly ground. However, the relationship between running economy and the hip muscles is unknown. Thus the aim of the present study was to verify whether hip flexor and extensor isokinetic peak torque, the isokinetic strength balance ratio, total body mass and fat free mass were associated with running economy in both sexes and to compare sex differences in physical fitness and isokinetic strength characteristics.

Methods

A total of 24 male (31.0 ± 7.7 years, 176.2 ± 7.3 cm, and 70.4 ± 8.4 kg) and 15 female (31.3 ± 6.7 years, 162.9 ± 3.9 cm, and 56.0 ± 5.3 kg) recreationally-trained endurance runners were recruited. Maximal oxygen uptake, running economy, conventional (concentric flexors-to-concentric extensors) and functional (concentric flexors-to-eccentric extensors) hip isokinetic strength balance ratios, peak torque of the hip flexor and extensor muscles, total body mass, and fat-free mass were measured. Running economy was assessed on two separate days by means of the energy running cost (E_c) using a motorized treadmill at 10.0 and 12.0 km h⁻¹ (3% gradient) and 11.0 and 14.0 km h⁻¹ (1% gradient).

Results

The functional balance ratio was significantly and negatively associated with E_c at 11.0 (r =  − 0.43, P = 0.04) and 12.0 km h⁻¹ (r =  − 0.65, P = 0.04) when using a 3% gradient in male runners. Considering muscular strength, male runners only showed a significant relationship between E_c (assessed at 12 km h⁻¹ and a 3% gradient) and peak torque for extensor muscle eccentric action (r = 0.72, P = 0.04). For female runners, only peak torque relative to total body mass for extensor muscles (180° s⁻¹) was positively associated with E_c when assessed at 10 km h⁻¹ using a 3% gradient (r = 0.59, P = 0.03). No significant relationships were found between E_c and total body mass or fat-free mass.

Discussion

Given that the functional balance ratio was associated with a better E_c, coaches and athletes should consider implementing a specific strengthening program for hip flexor muscles to increase the functional ratio.

A 3-minute test of cardiorespiratory fitness for use in primary care clinics

BACKGROUND

Cardiorespiratory fitness (CRF) is the only major risk factor that is not routinely assessed in the clinical setting, for preventive medicine. A valid and practical CRF test is needed for use in the clinics. The objective of this study is to demonstrate the validity of a 3-minute squat test to assess CRF in primary care.

METHODS

A cross-sectional study in which the participants performed both the Ruffier squat test and the Balke maximal treadmill test. The study was conducted in a clinical setting from September 2016 to March 2017. We recruited a convenient sample of 40 adults between 18 and 64 years from the general U.S. population. Participants completed 30 squats in 45 seconds, paced by a metronome. Heart rate was measured at rest (P1), immediately after the test (P2), one minute after the test (P3). [Formula: see text] was measured using the Balke maximal treadmill fitness test.

RESULTS

Of the 40 participants, there were 18 men and 22 women. Mean age was 31.2 years (SD = 9.9). We found that the best [Formula: see text] predictors were HR features P1/height and (P2-P3)/age3. Our best-performing model using these two features predicted individuals' CRF levels with an adjusted R2 of 0.637, sensitivity of 0.79, and specificity of 0.56.

CONCLUSIONS

The study provided strong evidence for the validity of the squat test in the clinical setting. Further, the equation of our model along with [Formula: see text] normative tables provides an efficient and easy way to assess CRF in a primary care setting.

The exercise sex gap and the impact of the estrous cycle on exercise performance in mice

Exercise physiology is different in males and females. Females are poorly studied due to the complexity of the estrous cycle and this bias has created an exercise sex gap. Here, we evaluated the impact of sexual dimorphism and of the estrous cycle on muscle strength and running power of C57BL/6 mice. Like men, male mice were stronger and more powerful than females. Exercise-induced increase of O₂ consumption (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{{\bf{V}}}$$\end{document}V˙O₂) and CO₂ production (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{{\bf{V}}}$$\end{document}V˙CO₂) were equal between sexes, indicating that running economy was higher in males. Thermoregulation was also more efficient in males. In females, proestrus increased exercise \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{{\bf{V}}}$$\end{document}V˙O₂ and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{{\bf{V}}}$$\end{document}V˙CO₂ at low running speeds (30–35% female \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{{\bf{V}}}$$\end{document}V˙O_2max) and estrus worsened thermoregulation. These differences translated into different absolute and relative workloads on the treadmill, even at equal submaximal \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{{\bf{V}}}$$\end{document}V˙O₂ and belt speeds. In summary, our results demonstrate the better muscle strength, running power and economy, and exercise-induced thermoregulation of males compared to females. Proestrus and estrus still undermined the running economy and exercise-induced thermoregulation of females, respectively. These results demonstrate an important exercise sex gap in mice.

The effects of beetroot juice supplementation on exercise economy, rating of perceived exertion and running mechanics in elite distance runners: A double-blinded, randomized study

Purpose

Nitrate-rich beetroot juice supplementation has been extensively used to increase exercise economy in different populations. However, its use in elite distance runners, and its potential effects on biomechanical aspects of running have not been properly investigated. This study aims to analyze the potential effects of 15 days of beetroot juice supplementation on physiological, psychological and biomechanical variables in elite runners.

Methods

Twelve elite middle and long-distance runners (age = 26.3 ± 5.1yrs, VO₂Max = 71.8±5.2 ml*kg^-1*min^-1) completed an incremental running test to exhaustion on a treadmill before and after a 15-days supplementation period, in which half of the group (EG) consumed a daily nitrate-rich beetroot juice and the other group (PG) consumed a placebo drink. Time to exhaustion (TEx), running economy, vastus lateralis oxygen saturation (SmO₂), leg stiffness and rate of perceived exertion (RPE) were measured at 15, 17.1 and 20 km/h during the incremental test.

Results

Likely to very likely improvements in EG were observed for the RPE (Standardized mean difference (SMD) = -2.17, 90%CI = -3.23, -1.1), SmO₂ (SMD = 0.72, 90%CI = 0.03, 1.41) and TEx (SMD = 1.18, 90%CI = -0.14, 2.5) in comparison with PG. No other physiological or biomechanical variable showed substantial improvements after the supplementation period.

Conclusions

Fifteen days of nitrate-rich beetroot juice supplementation produced substantial improvements in the time to exhaustion in elite runners; however, it didn’t produce meaningful improvements in running economy, VO₂Max or mechanical parameters.

Computational and Complex Network Modeling for Analysis of Sprinter Athletes' Performance in Track Field Tests

Sports and exercise today are popular for both amateurs and athletes. However, we continue to seek the best ways to analyze best athlete performances and develop specific tools that may help scientists and people in general to analyze athletic achievement. Standard statistics and cause-and-effect research, when applied in isolation, typically do not answer most scientific questions. The human body is a complex holistic system exchanging data during activities, as has been shown in the emerging field of network physiology. However, the literature lacks studies regarding sports performance, running, exercise, and more specifically, sprinter athletes analyzed mathematically through complex network modeling. Here, we propose complex models to jointly analyze distinct tests and variables from track sprinter athletes in an untargeted manner. Through complex propositions, we have incorporated mathematical and computational modeling to analyze anthropometric, biomechanics, and physiological interactions in running exercise conditions. Exercise testing associated with complex network and mathematical outputs make it possible to identify which responses may be critical during running. The physiological basis, aerobic, and biomechanics variables together may play a crucial role in performance. Coaches, trainers, and runners can focus on improving specific outputs that together help toward individuals' goals. Moreover, our type of analysis can inspire the study and analysis of other complex sport scenarios.

Genetic selection of athletic success in sport-hunting dogs

We found that hundreds of years of selection by humans have produced sport-hunting breeds of superior speed and athleticism through strong selection on multiple genes relating to cardiovascular, muscle, and neuronal functions. We further substantiated these findings by showing that genes under selection significantly enhanced athleticism, as measured by racing speed and obstacle course success, using standardized measures from dogs competing in national competitions. Overall these results reveal both the evolutionary processes and the genetic pathways putatively involved in athletic success.

Modern dogs are distinguished among domesticated species by the vast breadth of phenotypic variation produced by strong and consistent human-driven selective pressure. The resulting breeds reflect the development of closed populations with well-defined physical and behavioral attributes. The sport-hunting dog group has long been employed in assistance to hunters, reflecting strong behavioral pressures to locate and pursue quarry over great distances and variable terrain. Comparison of whole-genome sequence data between sport-hunting and terrier breeds, groups at the ends of a continuum in both form and function, reveals that genes underlying cardiovascular, muscular, and neuronal functions are under strong selection in sport-hunting breeds, including ADRB1, TRPM3, RYR3, UTRN, ASIC3, and ROBO1. We also identified an allele of TRPM3 that was significantly associated with increased racing speed in Whippets, accounting for 11.6% of the total variance in racing performance. Finally, we observed a significant association of ROBO1 with breed-specific accomplishments in competitive obstacle course events. These results provide strong evidence that sport-hunting breeds have been adapted to their occupations by improved endurance, cardiac function, blood flow, and cognitive performance, demonstrating how strong behavioral selection alters physiology to create breeds with distinct capabilities.

The Age-Related Performance Decline in Ironman Triathlon Starts Earlier in Swimming Than in Cycling and Running

Käch, I, Rüst, CA, Nikolaidis, PT, Rosemann, T, and Knechtle, B. The age-related performance decline in Ironman triathlon starts earlier in swimming than in cycling and running. J Strength Cond Res 32(2): 379-395, 2018-In Ironman triathlon, the number of overall male and female finishers increased in the past 30 years, while an improvement in performance has been reported. Studies concluding these numbers only analyzed the top 10 athletes per age group instead of all finishers; therefore, a selection bias might have occurred. The aim of this study was to investigate participation, performance, and the age-related performance decline of all pro- and age-group triathletes ranked in all Ironman triathlons held worldwide between 2002 and 2015. Split and overall race times of 329,066 (80%) male and 81,815 (20%) female athletes competing in 253 different Ironman triathlon races were analyzed. The number of finishers increased in all age groups with the exception of women in age group 75-79 years. In pro athletes, performance improved in all disciplines. In age-group athletes, performance improved in younger age groups for running (from 18-24 to 40-44 years) and older age groups for swimming (from 50-54 to 65-69 years) and cycling (from 35-39 to 55-59 years), whereas it impaired in younger age groups for swimming (from 18-24 to 45-49 years) and cycling (from 18-24 to 30-34 years), and older age groups in running (from 45-49 to 70-74 years). The age-related performance decline started in women in age group 25-29 years in swimming and in age group 30-34 years in cycling, running, and overall race time, whereas it started in men in age group 25-29 years in swimming and in age group 35-39 years in cycling, running, and overall race time. For athletes and coaches, performance improved in younger age groups for running and older age groups for swimming and cycling, and the age-related decline in performance started earlier in swimming than in cycling and running. In summary, women should start competing in Ironman triathlon before the age of 30 years and men before the age of 35 years to achieve their personal best Ironman race time.

Functional Exercise Training and Undulating Periodization Enhances the Effect of Whole-Body Electromyostimulation Training on Running Performance

The popularity of whole-body electromyostimulation is growing during the last years, but there is a shortage of studies that evaluate its effects on physical fitness and sport performance. In this study, we compared the effects of a periodized and functional whole-body-electromyostimulation training on maximum oxygen uptake (VO₂max), ventilatory thresholds (VT1 and VT2), running economy (RE), and lower-body muscle strength in runners, vs. a traditional whole-body-electromyostimulation training. A total of 12 male recreational runners, who had been running 2–3 times per week (90–180 min/week) for at least the previous year and had no previous experience on WB-EMS training, were enrolled in the current study. They were randomly assigned to a periodized and functional whole-body-electromyostimulation training group (PFG) (n = 6; 27.0 ± 7.5 years; 70.1 ± 11.1 kg; 1.75 ± 0.05 m) whose training program involved several specific exercises for runners, or a traditional whole-body-electromyostimulation training group (TG) (n = 6; 25.8 ± 7.4 years; 73.8 ± 9.8 kg; 1.73 ± 0.07 m), whose sessions were characterized by circuit training with 10 dynamic and general exercises without external load. The training programs consisted of one whole-body electromyostimulation session and one 20-min running session per week, during 6 weeks. The PFG followed an undulating periodization model and a selection of functional exercises, whereas the TG followed a traditional session structure used in previous studies. Both groups were instructed to stop their habitual running training program. VO₂max, VT1, VT2, RE, and lower body muscle strength (vertical jump) were measured before and after the intervention. The PFG obtained significantly higher improvements when compared with the TG in terms of VO₂max (2.75 ± 0.89 vs. 1.03 ± 1.01 ml/kg/min, P = 0.011), VT2 (2.95 ± 1.45 vs. 0.35 ± 0.85 ml/kg/min, P = 0.005), VO₂max percentage at VT2 (5.13 ± 2.41 vs. 0.63 ± 1.61%), RE at VT1 (−7.70 ± 2.86 vs. −3.50 ± 2.16 ml/kg/km, P = 0.048), RE at 90% of VT2 (−15.38 ± 4.73 vs. −3.38 ± 4.11 ml/kg/km, P = 0.005), and vertical jump in Abalakov modality (2.95 ± 0.94 vs. 0.52 ± 1.49 cm, P = 0.008). Therefore, we conclude that running performance improvements were better after a 6-week program following an undulating periodization and consisting on functional exercises when compared with a 6-week traditional WB-EMS program.

Adaptations to Endurance and Strength Training

The capacity for human exercise performance can be enhanced with prolonged exercise training, whether it is endurance- or strength-based. The ability to adapt through exercise training allows individuals to perform at the height of their sporting event and/or maintain peak physical condition throughout the life span. Our continued drive to understand how to prescribe exercise to maximize health and/or performance outcomes means that our knowledge of the adaptations that occur as a result of exercise continues to evolve. This review will focus on current and new insights into endurance and strength-training adaptations and will highlight important questions that remain as far as how we adapt to training.

Current Soccer Footwear, Its Role in Injuries and Potential for Improvement

Soccer is the most popular sport in the world and generates great financial revenue. It is also a sport whose practice has evolved considerably in terms of intensity and commitment, and in which the intrinsic risk of injury (not directly related to an interaction with the environment) is particularly high. In this context, the cleated shoe as a major component of soccer equipment may play a key role in the overexposure to injury. Soccer shoe evolution is all the more challenging, because design and mechanical structure differ in many points compared to other modern shoes developed for sports such as running, tennis and basketball. This critical review aims to elucidate the characteristics of modern soccer footwear and their possible link to soccer-specific injuries, focusing on the following areas: (1) ergonomics, comfort and proprioception; (2) shoe mechanical characteristics; (3) field surfaces and shoe design.

Theoretical considerations for muscle-energy savings during distance running

We have recently demonstrated that the triceps surae muscles energy cost (EC_TS) represents a substantial portion of the total metabolic cost of running (E_run). Therefore, it seems relevant to evaluate the factors which dictate EC_TS, namely the amount and velocity of shortening, since it is likely these factors will dictate E_run. E_run and triceps surae morphological and AT mechanical properties were obtained in 46 trained and elite male and female distance runners using ultrasonography and dynamometry. EC_TS (J·stride^-1) at the speed of lactate threshold (sLT) was estimated from AT force and crossbridge mechanics and energetics. To estimate the relative impact of these factors on EC_TS, mean values for running speed, body mass, resting fascicle length (L_f), Achilles tendon stiffness and moment arm and maximum isometric plantarflexion torque were obtained. EC_TS was calculated across a range (mean ± 1 sd) of values for each independent factor. Average sLT was 233 m·min^-1. At this speed, EC_TS was 255 J·stride^-1. Estimated fascicle shortening velocity was 0.08 V_max and the level of muscle activation was 84.7% of maximum isometric torque. Compared to the EC_TS calculated from the lowest range of values obtained for each independent factor, higher AT stiffness was associated with a 39% reduction in EC_TS, 81% reduction in fascicle shortening velocity and a 31% reduction in muscle activation. Longer AT moment arms and elevated body masses were associated with an increase in EC_TS of 18% and 23%, respectively. These results demonstrate that a low EC_TS is achieved primarily from a high AT stiffness and low body mass, which is exemplified in elite distance runners.

Isometric pre-conditioning blunts exercise-induced muscle damage but does not attenuate changes in running economy following downhill running

Running economy (RE) is impaired following unaccustomed eccentric-biased exercises that induce muscle damage. It is also known that muscle damage is reduced when maximal voluntary isometric contractions (MVIC) are performed at a long muscle length 2-4 days prior to maximal eccentric exercise with the same muscle, a phenomenon that can be described as isometric pre-conditioning (IPC). We tested the hypothesis that IPC could attenuate muscle damage and changes in RE following downhill running. Thirty untrained men were randomly assigned into experimental or control groups and ran downhill on a treadmill (-15%) for 30 min. Participants in the experimental group completed 10 MVIC in a leg press machine two days prior to downhill running, while participants in the control group did not perform IPC. The magnitude of changes in muscle soreness determined 48 h after downhill running was greater for the control group (122 ± 28 mm) than for the experimental group (92 ± 38 mm). Isometric peak torque recovered faster in the experimental group compared with the control group (3 days vs. no full recovery, respectively). No significant effect of IPC was found for countermovement jump height, serum creatine kinase activity or any parameters associated with RE. These results supported the hypothesis that IPC attenuates changes in markers of muscle damage. The hypothesis that IPC attenuates changes in RE was not supported by our data. It appears that the mechanisms involved in changes in markers of muscle damage and parameters associated with RE following downhill running are not completely shared.

Female PFP patients present alterations in eccentric muscle activity but not the temporal order of activation of the vastus lateralis muscle during the single leg triple hop test

This study aimed to compare the concentric and eccentric activity and the temporal order of peak activity of the hip and knee muscles between women with patellofemoral pain (PFP) and healthy women during the single leg triple hop test (SLTHT). Electromyographic (EMG) and Kinematic data were collected from 14 healthy women (CG) and 14 women diagnosed with PFP (PFG) during a single session of the single leg triple hop test. Integral surface electromyography (iEMG) data of the hip and knee muscles in eccentric and concentric phases and the length of time that each muscle needed to reach the maximal peak of muscle activity were calculated. The iEMG in the eccentric phase was significantly higher (p < 0.05) than the concentric phase, for the gluteus maximus and gluteus medius muscles (CG and PFG) and for the vastus lateralis muscle (PFG). The vastus lateralis muscle was the first muscle to reach the highest peak of activity in the PFG, and the third to reach this peak in the CG. In the present study, the activity of the vastus lateralis muscle during the eccentric phase of the jump was greater than concentric phase, as a temporal anticipation of its peak in activity among women with PFP.

Keto-adaptation enhances exercise performance and body composition responses to training in endurance athletes

BACKGROUND

Low-carbohydrate diets have recently grown in popularity among endurance athletes, yet little is known about the long-term (>4wk) performance implications of consuming a low-carbohydrate high fat ketogenic diet (LCKD) in well-trained athletes.

METHODS

Twenty male endurance-trained athletes (age 33±11y, body mass 80±11kg; BMI 24.7±3.1kg/m²) who habitually consumed a carbohydrate-based diet, self-selected into a high-carbohydrate (HC) group (n=11, %carbohydrate:protein:fat=65:14:20), or a LCKD group (n=9, 6:17:77). Both groups performed the same training intervention (endurance, strength and high intensity interval training (HIIT)). Prior to and following successful completion of 12-weeks of diet and training, participants had their body composition assessed, and completed a 100km time trial (TT), six second (SS) sprint, and a critical power test (CPT). During post-intervention testing the HC group consumed 30-60g/h carbohydrate, whereas the LCKD group consumed water, and electrolytes.

RESULTS

The LCKD group experienced a significantly greater decrease in body mass (HC -0.8kg, LCKD -5.9kg; P=0.006, effect size (ES): 0.338) and percentage body fat percentage (HC -0.7%, LCKD -5.2%; P=0.008, ES: 0.346). Fasting serum beta-hydroxybutyrate (βHB) significantly increased from 0.1 at baseline to 0.5mmol/L in the LCKD group (P=0.011, ES: 0.403) in week 12. There was no significant change in performance of the 100km TT between groups (HC -1.13min·s, LCKD -4.07min·s, P=0.057, ES: 0.196). SS sprint peak power increased by 0.8 watts per kilogram bodyweight (w/kg) in the LCKD group, versus a -0.1w/kg reduction in the HC group (P=0.025, ES: 0.263). CPT peak power decreased by -0.7w/kg in the HC group, and increased by 1.4w/kg in the LCKD group (P=0.047, ES: 0.212). Fat oxidation in the LCKD group was significantly greater throughout the 100km TT.

CONCLUSIONS

Compared to a HC comparison group, a 12-week period of keto-adaptation and exercise training, enhanced body composition, fat oxidation during exercise, and specific measures of performance relevant to competitive endurance athletes.

Pilates training improves 5-km run performance by changing metabolic cost and muscle activity in trained runners

Purpose

Strength training improves distance running economy and performance. This finding is based predominantly on maximal and explosive strength programmes applied to locomotor muscles, particularly on the lower limbs. It is not certain whether a minimization of metabolic cost (C_met) and an improvement in running performance is feasible with strength training of the postural and trunk muscles.

Methods

Using kinematic, neuromuscular and metabolic measurements of running at two different speeds before and after a 12-week Pilates training programme, we tested the hypothesis that core training might improve the running C_met and performance of trained runners. Thirty-two individuals were randomly assigned to the control group (CG, n = 16) or the Pilates group (PG, n = 16).

Results

Confirming our hypothesis, a significant improvement (p<0.05) was observed for running performance in the PG (pre: 25.65±0.4 min; post: 23.23±0.4 min) compared to the CG (pre: 25.33±0.58 min; post: 24.61±0.52 min). Similarly, the PG (4.33±0.07 J.kg^-1.m^-1) had better responses than the CG (4.71±0.11 J.kg^-1.m^-1) during post-training for C_met. These findings were accompanied by decreased electromyographic activity of the postural muscles at submaximal running intensities in the PG.

Conclusions

Overall, these results provide a rationale for selecting strength training strategies that target adaptations on specific postural and locomotor muscles for trained distance runners.

Executive control processes are associated with individual fitness outcomes following regular exercise training: blood lactate profile curves and neuroimaging findings

Cardiovascular training has been associated with neuroimaging correlates of executive control functions (ECF) in seniors and children/adolescents, while complementary studies in middle-aged populations are lacking. Ascribing a prominent role to cardiorespiratory fitness improvements, most studies concentrated on training-induced gains in maximal oxygen uptake (VO₂max), although other fitness indices may provide complementary information. Here, we investigated the impact of long-term sub-maximal exercise training on interference control, considering individual training-induced shifts in blood lactate profile curves (BLC) and VO₂max. Twenty-three middle-aged sedentary males (M = 49 years) underwent a six-month exercise program (intervention group, IG). Additionally, 14 individuals without exercise training were recruited (control group, CG, M = 52 years). Interference control was assessed before and after the intervention, using a functional magnetic resonance imaging (fMRI) flanker paradigm. Task performance and brain activations showed no significant group-by-time interactions. However, regression analyses in the IG revealed significant associations between individual fitness gains and brain activation changes in frontal regions, which were not evident for VO₂max, but for BLC. In conclusion, training-induced plasticity of ECF-related brain activity can be observed in late middle adulthood, but depends on individual fitness gains. For moderate training intensities, BLC shifts may provide sensitive markers for training-induced adaptations linked to ECF-related brain function.