Effects of resistance training on running economy and cross-country performance

Effects of high-intensity interval training and resistance training on physiological parameters and performance of well-trained runners: A randomized controlled trial

This study aimed to verify the effects of 4 weeks of high-intensity interval training (HIIT), heavy (HRT) and explosive (ERT) resistance training on aerobic, anaerobic and neuromuscular parameters and performance of well-trained runners. Twenty-six male athletes were divided into HIIT (n = 10), HRT (n = 7) and ERT (n = 9) groups. Maximal oxygen uptake (V O 2 max ) and the corresponding velocity (vV O 2 max ), anaerobic threshold (AT), running economy (RE), oxygen uptake kinetics, lower-body strength (1RM) and power (CMJ), and the 1500m and 5000m time-trial (TT) were determined. Improvements were observed in vV O 2 max (mean difference (Δ): 2.6%; effect size (ES): 0.63) with HIIT, while AT was incresead in ERT (Δ: 4.3%; ES: 0.73) and HRT (Δ: 6.9%; ES: 0.72) groups. The CMJ performance was increased in ERT (Δ: 13.8%; ES: 1.03), HRT (Δ: 6.9%; ES: 0.55) and HIIT (Δ: 5.4%; ES: 0.34), whereas 1RM increase in HRT (Δ: 38.1%; ES: 1.21) and ERT (Δ: 49.2%; ES: 0.96) groups. HIIT improved the 1500m (Δ: -2.3%; ES: -0.62) and both HRT (Δ: -1.6%; ES: -0.32) and ERT (Δ: -1.7%; ES: -0.31) the 5000m TT. Despite performance adaptations were dependent on the training characteristics, both RT and HIIT model constitute an alternative for training periodization.

Effect of Strength Training Programs in Middle- and Long-Distance Runners' Economy at Different Running Speeds: A Systematic Review with Meta-analysis

BACKGROUND

Running economy is defined as the energy demand at submaximal running speed, a key determinant of overall running performance. Strength training can improve running economy, although the magnitude of its effect may depend on factors such as the strength training method and the speed at which running economy is assessed.

AIM

To compare the effect of different strength training methods (e.g., high loads, plyometric, combined methods) on the running economy in middle- and long-distance runners, over different running speeds, through a systematic review with meta-analysis.

METHODS

A systematic search was conducted across several electronic databases including Web of Science, PubMed, SPORTDiscus, and SCOPUS. Using different keywords and Boolean operators for the search, all articles indexed up to November 2022 were considered for inclusion. In addition, the PICOS criteria were applied: Population: middle- and long-distance runners, without restriction on sex or training/competitive level; Intervention: application of a strength training method for ≥ 3 weeks (i.e., high loads (≥ 80% of one repetition maximum); submaximal loads [40-79% of one repetition maximum); plyometric; isometric; combined methods (i.e., two or more methods); Comparator: control group that performed endurance running training but did not receive strength training or received it with low loads (< 40% of one repetition maximum); Outcome: running economy, measured before and after a strength training intervention programme; Study design: randomized and non-randomized controlled studies. Certainty of evidence was assessed with the GRADE approach. A three-level random-effects meta-analysis and moderator analysis were performed using R software (version 4.2.1).

RESULTS

The certainty of the evidence was found to be moderate for high load training, submaximal load training, plyometric training and isometric training methods and low for combined methods. The studies included 195 moderately trained, 272 well trained, and 185 highly trained athletes. The strength training programmes were between 6 and 24 weeks' duration, with one to four sessions executed per week. The high load and combined methods induced small (ES = - 0.266, p = 0.039) and moderate (ES = - 0.426, p = 0.018) improvements in running economy at speeds from 8.64 to 17.85 km/h and 10.00 to 14.45 km/h, respectively. Plyometric training improved running economy at speeds ≤ 12.00 km/h (small effect, ES = - 0.307, p = 0.028, β1 = 0.470, p = 0.017). Compared to control groups, no improvement in running economy (assessed speed: 10.00 to 15.28 and 9.75 to 16.00 km/h, respectively) was noted after either submaximal or isometric strength training (all, p > 0.131). The moderator analyses showed that running speed (β1 = - 0.117, p = 0.027) and VO2max (β1 = - 0.040, p = 0.020) modulated the effect of high load strength training on running economy (i.e., greater improvements at higher speeds and higher VO2max).

CONCLUSIONS

Compared to a control condition, strength training with high loads, plyometric training, and a combination of strength training methods may improve running economy in middle- and long-distance runners. Other methods such as submaximal load training and isometric strength training seem less effective to improve running economy in this population. Of note, the data derived from this systematic review suggest that although both high load training and plyometric training may improve running economy, plyometric training might be effective at lower speeds (i.e., ≤ 12.00 km/h) and high load strength training might be particularly effective in improving running economy (i) in athletes with a high VO2max, and (ii) at high running speeds.

PROTOCOL REGISTRATION

The original protocol was registered ( https://osf.io/gyeku ) at the Open Science Framework.

Perspectives on Concurrent Strength and Endurance Training in Healthy Adult Females: A Systematic Review

BACKGROUND

Both strength and endurance training are included in global exercise recommendations and are the main components of training programs for competitive sports. While an abundance of research has been published regarding concurrent strength and endurance training, only a small portion of this research has been conducted in females or has addressed their unique physiological circumstances (e.g., hormonal profiles related to menstrual cycle phase, menstrual dysfunction, and hormonal contraceptive use), which may influence training responses and adaptations.

OBJECTIVE

The aim was to complete a systematic review of the scientific literature regarding training adaptations following concurrent strength and endurance training in apparently healthy adult females.

METHODS

A systematic electronic search for articles was performed in July 2021 and again in December 2022 using PubMed and Medline. This review followed, where applicable, the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The quality of the included studies was assessed using a modified Downs and Black checklist. Inclusion criteria were (1) fully published peer-reviewed publications; (2) study published in English; (3) participants were healthy normal weight or overweight females of reproductive age (mean age between > 18 and < 50) or presented as a group (n > 5) in studies including both females and males and where female results were reported separately; (4) participants were randomly assigned to intervention groups, when warranted, and the study included measures of maximal strength and endurance performance; and (5) the duration of the intervention was ≥ 8 weeks to ensure a meaningful training duration.

RESULTS

Fourteen studies met the inclusion criteria (seven combined strength training with running, four with cycling, and three with rowing or cross-country skiing). These studies indicated that concurrent strength and endurance training generally increases parameters associated with strength and endurance performance in female participants, while several other health benefits such as, e.g., improved body composition and blood lipid profile were reported in individual studies. The presence of an "interference effect" in females could not be assessed from the included studies as this was not the focus of any included research and single-mode training groups were not always included alongside concurrent training groups. Importantly, the influence of concurrent training on fast-force production was limited, while the unique circumstances affecting females were not considered/reported in most studies. Overall study quality was low to moderate.

CONCLUSION

Concurrent strength and endurance training appears to be beneficial in increasing strength and endurance capacity in females; however, multiple research paradigms must be explored to better understand the influence of concurrent training modalities in females. Future research should explore the influence of concurrent strength and endurance training on fast-force production, the possible presence of an "interference effect" in athletic populations, and the influence of unique circumstances, such as hormone profile, on training responses and adaptations.

Retrospective and Contemporary Predictors of National Collegiate Athletic Association Division I Cross-Country Performance Are Sex Specific

ABSTRACT

Carder, MJ, Scudamore, EM, Savanna, KN, Pribyslavska, V, Bowling, LR, and O'Neal, EK. Retrospective and contemporary predictors of National Collegiate Athletic Association Division I cross-country performance are sex specific. J Strength Cond Res 37(11): 2267-2272, 2023-The purpose of this study was to identify National Collegiate Athletic Association (NCAA) Division I cross-country (XC) performance potential using laboratory-based and field-based parameters and retrospective high school (HS) personal best (PB) data at various distances of current collegiate XC runners. Fifteen female and 17 male NCAA XC runners provided their PB for 5-km (women) and 8-km (men) distances from the previous season. Bivariate correlation and stepwise and hierarchical regression modeling were used to predict XC performance. Single squat jump height and multijump reactive strength index displayed r < 0.27 for both sexes, suggesting lower-body power is a poor predictor of XC performance or masked by other factors of greater importance. Triceps skinfold thickness approached significance (r = 0.43; p = 0.09) for men but was unrelated to women's performance (r = -0.05; p = 0.86). HS XC PB neared significance (r = 0.55, p = 0.054), but no other single or combination of variables reached significance for female runners. Aerobic capacity displayed a moderate to strong relationship (r = 0.65) for male runners. High school 3,200-m PB for men produced a robust prediction capacity (r = 0.85; p = 0.005, SEE = ± 0.65 minutes), and predicted 8-km PB within 30 seconds for approximately two-thirds of runners. These outcomes suggest when recruiting HS or transfer athletes, male and female XC runners should not be recruited on the same factors. Women's XC PB is more difficult to predict, but skinfold thickness was statistically the least valuable predictor of all factors.

Effects of plyometric vs. strength training on strength, sprint, and functional performance in soccer players: a randomized controlled trial

Plyometric training (PT) has been shown to have numerous benefits and few harmful effects. This study aimed to compare the effects of PT vs. strength training on muscle strength, sprint, and lower limb functional performance in soccer players. Ninety participants (mean age 22.5 years) were equally and randomly divided into three groups: a plyometric training group (PTG; n = 30), a strength training group (STG; n = 30), and a control group (CG; n = 30). In PTG: bounding, hurdling, and drop jumping exercises were performed. In STG: isometric exercises of knee extension (at 60º knee flexion), quadriceps (in supine), hip adductors (in crook lying), and straight leg raise were performed. In CG: no specific training was given. All interventions were performed for eight weeks. Isometric strength (IS), sprint (ST), and single-leg triple hop (SLTH) tests were outcome measures. The wilcoxon signed ranks test was used for with-in-group analysis, and Kruskal Wallis and Mann-Whitney u tests were used for between-group analyses. In PTG: in comparison to a baseline measurement, IS increased by 8.83% (p < 0.05), ST decreased by 20.14% (p < 0.05), and SLTH increased by 7.78% (p < 0.05). In STG: IS increased by 15.76% (p < 0.05), ST decreased by 30.26% (p < 0.05), and SLTH increased by 12.41% (p < 0.05). In CG: IS increased by 5.72% (p < 0.05), ST decreased by 15.54% (p < 0.05), and SLTH increased by 4.41% (p < 0.05). The greatest improvements were observed in STG, followed by PTG and CG. Strength training was found to be more effective than PT in improving muscle strength, sprint, and lower limb functional performance in male soccer players.

Effects of concurrent training sequence on VO2max and lower limb strength performance: A systematic review and meta-analysis

The aim of this study is to compare the effects of concurrent strength and endurance training sequences on VO_2max and lower limb strength performance to provide scientific guidance for training practice. We searched PubMed, EBSCO, Web of Science (WOS), Wanfang, and China National Knowledge Infrastructure (CNKI) databases up to December 2022. The included articles were randomized controlled trials that allowed us to compare the strength-endurance (S-E) sequence and endurance-strength (E-S) sequence on VO_2max, maximum knee extension strength, maximum knee flexion strength, and lower limb power. The Cochrane bias risk tool was used to evaluate the methodological quality of the included literature, and Stata 12.0 was used for the heterogeneity test, subgroup analysis, draw forest map, sensitivity analysis, and publication bias evaluation. The results have been presented as standardized mean differences (SMDs) between treatments with 95% confidence intervals and calculations performed using random effects models. Significance was accepted when p < 0.05. The studies included 19 randomized controlled trials (285 males and 197 females), 242 subjects in S-E sequence, and 240 subjects in E-S sequence in the analyses. No difference changes between S-E and E-S sequences has been observed on VO_2max in the overall analysis (SMD = 0.02, 95% CI: -0.21-0.25, p = 0.859). The S-E sequence shows a greater increase in lower limb strength performance than does the E-S sequence (SMD = 0.19, 95% CI: 0.02-0.37, p = 0.032), which was manifested in the elderly (p = 0.039) and women (p = 0.017); in training periods >8 weeks (p = 0.002) and training frequencies twice a week (p = 0.003); and with maximum knee flexion (p = 0.040) and knee extension strength (p = 0.026), while no difference was found in lower limb power (p = 0.523). In conclusion, the effect of VO_2max will not change with different concurrent training sequences. The S-E sequence improves lower limb strength more significantly, mainly in the improvement of knee flexion and knee extension. This advantage is more related to factors such as age, gender, training period, and training frequency.

Resistance Exercise for Improving Running Economy and Running Biomechanics and Decreasing Running-Related Injury Risk: A Narrative Review

It is well-accepted that at least a certain amount of resistance exercise (RE) is recommended for most endurance athletes. In this review, we aim to summarize the evidence regarding the effects of RE on running economy, running biomechanics, and running-related injury risk in endurance runners. The evidence robustly shows that lower limb RE is effective for improving running economy and performance, with a combination of strength and plyometric training being recommended to improve RE. Isometric training is also emerging as a possible alternative to implement during periods of high overall training load. Lower limb RE may change some aspects of joint kinematics during running; however, the evidence regarding the effects on kinetics is limited. Lower limb RE may help reduce running-related injury risk, but further evidence is needed.

Physiological and Performance Correlates of Squash Physical Performance

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

Outdoor Uphill Exercise Testing for Trail Runners, a More Suitable Method?

There is extensive knowledge about uphill running on a treadmill, although paucity regarding the influence of uphill trail running on exercise capacity in runners. The purpose of this study was to compare an uphill field test with a treadmill test with 1% inclination especially considering cardiopulmonary exercise variables. The difference in those tests between a group of trail runners and a group of road runners was tested for establishing a test specifically for trail runners. Ten male endurance road runners and ten male trail runners performed one maximal incremental treadmill test with 1% inclination and a maximal incremental field test on a hill at 16% inclination which they were instructed to run up four times for three minutes, each time with a higher pace. A mobile cardiopulmonary exercise testing unit was used to measure ventilation. There were no significant differences between trail runners and road runners. The equivalence factor was comparable between both groups. V ˙ O 2 p e a k was comparable for both test protocols. However, there was a significant difference between the two test protocols regarding lactate concentration, the respiratory exchange ratio, running cost, heart rate, Breathing reserve, and O_2pulse. The greater lactate concentration and running cost recorded uphill indicate a higher energy demand during trail running than level road running.

Effects of jump training on physical fitness and athletic performance in endurance runners: A meta-analysis

This systematic review and meta-analysis aimed to assess the effects of jump training (JT) on measures of physical fitness and athletic performances in endurance runners. Controlled studies which involved healthy endurance runners, of any age and sex, were considered. A random-effects model was used to calculate effect sizes (ES; Hedge's g). Means and standard deviations of outcomes were converted to ES with alongside 95% confidence intervals (95%CI). Twenty-one moderate-to-high quality studies were included in the meta-analysis, and these included 511 participants. The main analyses revealed a significant moderate improvement in time-trial performance (i.e. distances between 2.0 and 5.0 km; ES = 0.88), without enhancements in maximal oxygen consumption (VO₂max), velocity at VO₂max, velocity at submaximal lactate levels, heart rate at submaximal velocities, stride rate at submaximal velocities, stiffness, total body mass or maximal strength performance. However, significant small-to-moderate improvements were noted for jump performance, rate of force development, sprint performance, reactive strength, and running economy (ES = 0.36-0.73; p < 0.001 to 0.031; I² = 0.0% to 49.3%). JT is effective in improving physical fitness and athletic performance in endurance runners. Improvements in time-trial performance after JT may be mediated through improvements in force generating capabilities and running economy.

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

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

A 10-Week Block of Combined High-Intensity Endurance and Strength Training Produced Similar Changes in Dynamic Strength, Body Composition, and Serum Hormones in Women and Men

Purpose: To examine the potential sex differences in adaptations to combined endurance and strength training in recreationally endurance trained (eumenorrheic) women (n = 9) and men (n = 10).

Methods: Isometric (ISOM_max) and dynamic bilateral leg press (1RM), countermovement jump (CMJ), running performance (3,000 m time trial), lean mass and body fat % (LEAN and FAT% determined by dual X-ray absorptiometry) as well as serum testosterone and cortisol (TES and COR, respectively, measured using hormone-specific immunoassay kits) were examined before a control period and pre, mid, and post a supervised 10-week combined high-intensity interval endurance training (4 × 4 min intervals and 3 × 3 × 100 m repeated sprints) and mixed maximal and explosive strength training. No more than 2 weeks separated training and testing for either women or men and all women were tested in the early follicular phase of the menstrual cycle to minimize the possible influence of menstrual cycle phase on performance measures.

Results: Absolute and relative changes in 1RM, CMJ, 3,000 m, LEAN, and FAT% were similar between groups. The only statistically significant differences observed between groups were observed at post and included a larger Δ% increase in ISOM_max force in men and a relatively greater Δ% decrease in serum TES in women.

Conclusion: Women and men can achieve similar relative adaptations in dynamic maximal strength and CMJ as well as endurance performance gains and body composition over the same high-intensity 10-week combined program, although relative adaptations in TES may differ.

Wearable Sensors Detect Differences between the Sexes in Lower Limb Electromyographic Activity and Pelvis 3D Kinematics during Running

Each year, 50% of runners suffer from injuries. Consequently, more studies are being published about running biomechanics; these studies identify factors that can help prevent injuries. Scientific evidence suggests that recreational runners should use personalized biomechanical training plans, not only to improve their performance, but also to prevent injuries caused by the inability of amateur athletes to tolerate increased loads, and/or because of poor form. This study provides an overview of the different normative patterns of lower limb muscle activation and articular ranges of the pelvis during running, at self-selected speeds, in men and women.

METHODS

38 healthy runners aged 18 to 49 years were included in this work. We examined eight muscles by applying two wearable superficial electromyography sensors and an inertial sensor for three-dimensional (3D) pelvis kinematics.

RESULTS

the largest differences were obtained for gluteus maximus activation in the first double float phase (p = 0.013) and second stance phase (p = 0.003), as well as in the gluteus medius in the second stance phase (p = 0.028). In both cases, the activation distribution was more homogeneous in men and presented significantly lower values than those obtained for women. In addition, there was a significantly higher percentage of total vastus medialis activation in women throughout the running cycle with the median (25th-75th percentile) for women being 12.50% (9.25-14) and 10% (9-12) for men. Women also had a greater range of pelvis rotation during running at self-selected speeds (p = 0.011).

CONCLUSIONS

understanding the differences between men and women, in terms of muscle activation and pelvic kinematic values, could be especially useful to allow health professionals detect athletes who may be at risk of injury.

Physiological and Race Pace Characteristics of Medium and Low-Level Athens Marathon Runners

This study examined physiological and race pace characteristics of medium- (finish time < 240 min) and low-level (finish time > 240 min) recreational runners who participated in a challenging marathon route with rolling hills, the Athens Authentic Marathon. Fifteen athletes (age: 42 ± 7 years) performed an incremental test, three to nine days before the 2018 Athens Marathon, to determine maximal oxygen uptake (VO2 max), maximal aerobic velocity (MAV), energy cost of running (ECr) and lactate threshold velocity (vLTh), and were analyzed for their pacing during the race. Moderate- (n = 8) compared with low-level (n = 7) runners had higher (p < 0.05) VO2 max (55.6 ± 3.6 vs. 48.9 ± 4.8 mL·kg-1·min-1), MAV (16.5 ± 0.7 vs. 14.4 ± 1.2 km·h-1) and vLTh (11.6 ± 0.8 vs. 9.2 ± 0.7 km·h-1) and lower ECr at 10 km/h (1.137 ± 0.096 vs. 1.232 ± 0.068 kcal·kg-1·km-1). Medium-level runners ran the marathon at a higher percentage of vLTh (105.1 ± 4.7 vs. 93.8 ± 6.2%) and VO2 max (79.7 ± 7.7 vs. 68.8 ± 5.7%). Low-level runners ran at a lower percentage (p < 0.05) of their vLTh in the 21.1-30 km (total ascent/decent: 122 m/5 m) and the 30-42.195 km (total ascent/decent: 32 m/155 m) splits. Moderate-level runners are less affected in their pacing than low-level runners during a marathon route with rolling hills. This could be due to superior physiological characteristics such as VO2 max, ECr, vLTh and fractional utilization of VO2 max. A marathon race pace strategy should be selected individually according to each athlete's level.

Tapering strategies applied to plyometric jump training: a systematic review with meta-analysis of randomized-controlled trials

INTRODUCTION

The purpose of this systematic review was to analyze the effect of plyometric jump training (PJT) applied in conjunction with tapering strategies on the jump performance of team-sport athletes.

EVIDENCE ACQUISITION

The meta-analysis included: 1) randomized-controlled studies that incorporated a PJT program; 2) cohorts of team-sport athletes; 3) jump performance assessments; and 4) studies that incorporated a programmed taper. A systematic search was conducted in distinct electronic databases for relevant studies. Aside from jump performance, the extracted data included characteristics of the participants, PJT, and tapering. Means and standard deviations were used to calculate the effect sizes (ES). To assess the effects of moderator variables, subgroup analyses were performed. The statistical significance level was set as P<0.05.

EVIDENCE SYNTHESIS

From 7020 records initially identified, 14 studies were eligible for meta-analysis. Across all included studies, there was a moderate, significant improvement in jump performance (ES=0.73; P<0.001). Additionally, the subgroup analysis demonstrated that the duration and intensity of the taper and the volume of the PJT induced similar improvements in jump performance (P<0.01).

CONCLUSIONS

In summary, PJT interventions that included a programmed taper induced significant improvements in jump performance in team-sport athletes. These effects were observed after different tapering strategies in terms of volume, taper duration, and the type of PJT prescribed.

Development in Adolescent Middle-Distance Athletes: A Study of Training Loadings, Physical Qualities, and Competition Performance

Jones, TW, Shillabeer, BC, Ryu, JH, and Cardinale, M. Development in adolescent middle-distance athletes: a study of training loadings, physical qualities, and competition performance. J Strength Cond Res XX(X): 000-000, 2019-The purpose of this study was to examine changes in running performance and physical qualities related to middle-distance performance over a training season. The study also examined relationships between training loading and changes in physical qualities as assessed by laboratory and field measures. Relationships between laboratory and field measures were also analyzed. This was a 9-month observational study of 10 highly trained adolescent middle-distance athletes. Training intensity distribution was similar over the observational period, whereas accumulated and mean distance and training time and accumulated load varied monthly. Statistically significant (p < 0.05) and large effect sizes (Cohen's d) (>0.80) were observed for improvements in: body mass (5.6%), 600-m (4.6%), 1,200-m (8.7%), and 1,800-m (6.1%) time trial performance, critical speed (7.1%), V[Combining Dot Above]O2max (5.5%), running economy (10.1%), vertical stiffness (2.6%), reactive index (3.8%), and countermovement jump power output relative to body mass (7.9%). Improvements in 1,800 m TT performance were correlated with increases in V[Combining Dot Above]O2max (r = 0.810, p = 0.015) and critical speed (r = 0.918, p = 0.001). Increases in V[Combining Dot Above]O2max and critical speed were also correlated (r = 0.895, p = 0.003). Data presented here indicate that improvements in critical speed may be reflective of changes in aerobic capacity in adolescent middle-distance athletes.

Optimization of Exercise Countermeasures for Human Space Flight: Operational Considerations for Concurrent Strength and Aerobic Training

The physiological challenges presented by space flight and in microgravity (μG) environments are well documented. μG environments can result in declines muscle mass, contractile strength, and functional capabilities. Previous work has focused on exercise countermeasures designed to attenuate the negative effects of μG on skeletal muscle structure, function, and contractile strength and aerobic fitness parameters. Exposure to μG environments influences both strength and aerobic type physical qualities. As such, the current exercise recommendations for those experiencing μG involve a combination of strength and aerobic training or “concurrent training.” Concurrent training strategies can result in development and maintenance of both strength and aerobic capabilities. However, terrestrial research has indicated that if concurrent training strategies are implemented inappropriately, strength development can be inhibited. Previous work has also demonstrated that the aforementioned inhibition of strength development is dependent on the frequency of aerobic training, modality of aerobic training, the relief period between strength and aerobic training, and the intra-session sequencing of strength and aerobic training. While time constraints and feasibility are important considerations for exercise strategies in μG, certain considerations could be made when prescribing concurrent strength and aerobic training to those experiencing human space flight. If strength and aerobic exercise must be performed in close proximity, strength should precede aerobic stimulus. Eccentric strength training methods should be considered to increase mechanical load and reduce metabolic cost. For aerobic capacity, maintenance cycle and/or rowing-based high-intensity intermittent training (HIIT) should be considered and cycle ergometry and/or rowing may be preferable to treadmill running.

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 Effects of Concurrent Strength and Endurance Training on Physical Fitness and Athletic Performance in Youth: A Systematic Review and Meta-Analysis

Combining training of muscle strength and cardiorespiratory fitness within a training cycle could increase athletic performance more than single-mode training. However, the physiological effects produced by each training modality could also interfere with each other, improving athletic performance less than single-mode training. Because anthropometric, physiological, and biomechanical differences between young and adult athletes can affect the responses to exercise training, young athletes might respond differently to concurrent training (CT) compared with adults. Thus, the aim of the present systematic review with meta-analysis was to determine the effects of concurrent strength and endurance training on selected physical fitness components and athletic performance in youth. A systematic literature search of PubMed and Web of Science identified 886 records. The studies included in the analyses examined children (girls age 6–11 years, boys age 6–13 years) or adolescents (girls age 12–18 years, boys age 14–18 years), compared CT with single-mode endurance (ET) or strength training (ST), and reported at least one strength/power—(e.g., jump height), endurance—(e.g., peak V°O₂, exercise economy), or performance-related (e.g., time trial) outcome. We calculated weighted standardized mean differences (SMDs). CT compared to ET produced small effects in favor of CT on athletic performance (n = 11 studies, SMD = 0.41, p = 0.04) and trivial effects on cardiorespiratory endurance (n = 4 studies, SMD = 0.04, p = 0.86) and exercise economy (n = 5 studies, SMD = 0.16, p = 0.49) in young athletes. A sub-analysis of chronological age revealed a trend toward larger effects of CT vs. ET on athletic performance in adolescents (SMD = 0.52) compared with children (SMD = 0.17). CT compared with ST had small effects in favor of CT on muscle power (n = 4 studies, SMD = 0.23, p = 0.04). In conclusion, CT is more effective than single-mode ET or ST in improving selected measures of physical fitness and athletic performance in youth. Specifically, CT compared with ET improved athletic performance in children and particularly adolescents. Finally, CT was more effective than ST in improving muscle power in youth.

Sequencing Effects of Plyometric Training Applied Before or After Regular Soccer Training on Measures of Physical Fitness in Young Players

Ramirez-Campillo, R, Alvarez, C, Gentil, P, Loturco, I, Sanchez-Sanchez, J, Izquierdo, M, Moran, J, Nakamura, FY, Chaabene, H, and Granacher, U. Sequencing effects of plyometric training applied before or after regular soccer training on measures of physical fitness in young players. J Strength Cond Res 34(7): 1959-1966, 2020-To compare the effects of short-term (i.e., 7 weeks) plyometric jump training applied before (PJT-B) or after (PJT-A) soccer practice on components of physical fitness in young soccer players, a single-blind randomized controlled trial was conducted. Postpubertal boys aged 17.0 ± 0.5 years were allocated to 3 groups: PJT-B (n = 12), PJT-A (n = 14), and control (CON; n = 12). The outcome measures included tests to evaluate 20-m speed, standing long jump (SLJ), squat jump (SJ), countermovement jump (CMJ), and drop jump (DJ), 20-m multistage shuttle run endurance (MSSRT), and Illinois change-of-direction speed (ICODT). Although the CON performed soccer-specific training, the PJT-A and PJT-B groups conducted the same soccer-specific sessions but replaced ∼11% of their time with plyometric training. The PJT-B group performed plyometric exercises after a warm-up program, and the PJT-A group conducted plyometric exercises ∼10 minutes after the completion of soccer training. Analyses of variance were used to detect differences between groups in all variables for pretraining and posttraining tests. Main effects of time (all p < 0.01; d = 0.19-0.79) and group × time interactions (all p ≤ 0.05; d = 0.17-0.76) were observed for all examined variables. Post hoc analyses revealed significant increases in the PJT-B group (SLJ: 9.4%, d = 1.7; CMJ: 11.2%, d = 0.75; 20-m MSSRT: 9.0%, d = 0.77) and the PJT-A group (SLJ: 3.1%, d = 0.7; CMJ: 4.9%, d = 0.27; 20-m MSSRT: 9.0%, d = 0.76). Post hoc analyses also revealed significant increases in the PJT-B group (20-m speed: -7.4%, d = 0.75; 20-cm DJ reactive strength index: 19.1%, d = 1.4; SJ: 6.3%, d = 0.44; ICODT results: -4.2%, d = 1.1). In general, our study revealed that plyometric training is effective in improving measures of physical fitness in young male soccer players when combined with regular soccer training. More specifically, larger training-induced effects on physical fitness were registered if plyometric training was conducted before soccer-specific training.

Assessments of Mechanical Stiffness and Relationships to Performance Determinants in Middle-Distance Runners

PURPOSE

To examine relationships between methods of lower-limb stiffness and their associations with running economy (RE) and maximal velocity (v_max) in middle-distance (MD) runners.

METHODS

Eleven highly trained male MD runners performed a series of mechanical and physiological tests to determine maximal overground sprint speed, RE, and [Formula: see text]. Achilles tendon stiffness (k_T) was estimated using ultrasonography during maximal isometric ankle plantar flexion. Global stiffness qualities were evaluated using a spring-mass model, providing measures of leg (k_leg) and vertical stiffness (k_vert) during running and jumping, respectively.

RESULTS

Very large (r = -.70) and large (r = -.60) negative relationships existed between RE and k_T and k_vert, during plantar flexion and unilateral jumps, respectively. There were large (r = .63) and extremely large (r = -.92) associations between k_vert and k_T and k_leg during sprinting, respectively. Runners' v_max had large positive associations between k_T (r = .52) and k_leg (r = .59) during sprinting.

CONCLUSIONS

In well-trained MD athletes, greater stiffness appears linked to faster and more economical running. Although k_T had the strongest relationship with RE, k_leg while sprinting and k_vert in maximal unilateral jumps may be more practical measures of stiffness. Agreement between global stiffness assessments and k_T highlights the energy contribution of the Achilles tendon to running efficiency and velocity. Further research incorporating these assessment tools could help establish more comprehensive mechanical and metabolic athlete profiles and further our understanding of training adaptations, especially stiffness modification, longitudinally.

Is There an Economical Running Technique? A Review of Modifiable Biomechanical Factors Affecting Running Economy

Running economy (RE) has a strong relationship with running performance, and modifiable running biomechanics are a determining factor of RE. The purposes of this review were to (1) examine the intrinsic and extrinsic modifiable biomechanical factors affecting RE; (2) assess training-induced changes in RE and running biomechanics; (3) evaluate whether an economical running technique can be recommended and; (4) discuss potential areas for future research. Based on current evidence, the intrinsic factors that appeared beneficial for RE were using a preferred stride length range, which allows for stride length deviations up to 3 % shorter than preferred stride length; lower vertical oscillation; greater leg stiffness; low lower limb moment of inertia; less leg extension at toe-off; larger stride angles; alignment of the ground reaction force and leg axis during propulsion; maintaining arm swing; low thigh antagonist–agonist muscular coactivation; and low activation of lower limb muscles during propulsion. Extrinsic factors associated with a better RE were a firm, compliant shoe–surface interaction and being barefoot or wearing lightweight shoes. Several other modifiable biomechanical factors presented inconsistent relationships with RE. Running biomechanics during ground contact appeared to play an important role, specifically those during propulsion. Therefore, this phase has the strongest direct links with RE. Recurring methodological problems exist within the literature, such as cross-comparisons, assessing variables in isolation, and acute to short-term interventions. Therefore, recommending a general economical running technique should be approached with caution. Future work should focus on interdisciplinary longitudinal investigations combining RE, kinematics, kinetics, and neuromuscular and anatomical aspects, as well as applying a synergistic approach to understanding the role of kinetics.

Effects of Heavy Strength Training on Running Performance and Determinants of Running Performance in Female Endurance Athletes

Purpose

The purpose of the current study was to investigate the effects of adding strength training to normal endurance training on running performance and running economy in well-trained female athletes. We hypothesized that the added strength training would improve performance and running economy through altered stiffness of the muscle-tendon complex of leg extensors.

Methods

Nineteen female endurance athletes [maximal oxygen consumption (VO_2max): 53±3 ml∙kg^-1∙min^-1, 5.8 h weekly endurance training] were randomly assigned to either normal endurance training (E, n = 8) or normal endurance training combined with strength training (E+S, n = 11). The strength training consisted of four leg exercises [3 x 4–10 repetition maximum (RM)], twice a week for 11 weeks. Muscle strength, 40 min all-out running distance, running performance determinants and patellar tendon stiffness were measured before and after the intervention.

Results

E+S increased 1RM in leg exercises (40 ± 15%) and maximal jumping height in counter movement jump (6 ± 6%) and squat jump (9 ± 7%, p < 0.05). This was accompanied by increased muscle fiber cross sectional area of both fiber type I (13 ± 7%) and fiber type II (31 ± 20%) in m. vastus lateralis (p < 0.05), with no change in capillary density in m. vastus lateralis or the stiffness of the patellar tendon. Neither E+S nor E changed running economy, fractional utilization of VO_2max or VO_2max. There were also no change in running distance during a 40 min all-out running test in neither of the groups.

Conclusion

Adding heavy strength training to endurance training did not affect 40 min all-out running performance or running economy compared to endurance training only.

Strategies to improve running economy

Running economy (RE) represents a complex interplay of physiological and biomechanical factors that is typically defined as the energy demand for a given velocity of submaximal running and expressed as the submaximal oxygen uptake (VO2) at a given running velocity. This review considered a wide range of acute and chronic interventions that have been investigated with respect to improving economy by augmenting one or more components of the metabolic, cardiorespiratory, biomechanical or neuromuscular systems. Improvements in RE have traditionally been achieved through endurance training. Endurance training in runners leads to a wide range of physiological responses, and it is very likely that these characteristics of running training will influence RE. Training history and training volume have been suggested to be important factors in improving RE, while uphill and level-ground high-intensity interval training represent frequently prescribed forms of training that may elicit further enhancements in economy. More recently, research has demonstrated short-term resistance and plyometric training has resulted in enhanced RE. This improvement in RE has been hypothesized to be a result of enhanced neuromuscular characteristics. Altitude acclimatization results in both central and peripheral adaptations that improve oxygen delivery and utilization, mechanisms that potentially could improve RE. Other strategies, such as stretching should not be discounted as a training modality in order to prevent injuries; however, it appears that there is an optimal degree of flexibility and stiffness required to maximize RE. Several nutritional interventions have also received attention for their effects on reducing oxygen demand during exercise, most notably dietary nitrates and caffeine. It is clear that a range of training and passive interventions may improve RE, and researchers should concentrate their investigative efforts on more fully understanding the types and mechanisms that affect RE and the practicality and extent to which RE can be improved outside the laboratory.

The repeated bout effect of typical lower body strength training sessions on sub-maximal running performance and hormonal response

PURPOSE

This study examined the effects of two typical strength training sessions performed 1 week apart (i.e. repeated bout effect) on sub-maximal running performance and hormonal.

METHODS

Fourteen resistance-untrained men (age 24.0 ± 3.9 years; height 1.83 ± 0.11 m; body mass 77.4 ± 14.0 kg; VOpeak 48.1 ± 6.1 M kg(-1) min(-1)) undertook two bouts of high-intensity strength training sessions (i.e. six-repetition maximum). Creatine kinase (CK), delayed-onset muscle soreness (DOMS), counter-movement jump (CMJ) as well as concentrations of serum testosterone, cortisol and testosterone/cortisol ratio (T/C) were examined prior to and immediately post, 24 (T24) and 48 (T48) h post each strength training bout. Sub-maximal running performance was also conducted at T24 and T48 of each bout.

RESULTS

When measures were compared between bouts at T48, the degree of elevation in CK (-58.4 ± 55.6 %) and DOMS (-31.43 ± 42.9 %) and acute reduction in CMJ measures (4.1 ± 5.4 %) were attenuated (p < 0.05) following the second bout. Cortisol was increased until T24 (p < 0.05) although there were no differences between bouts and no differences were found for testosterone and T/C ratio (p > 0.05). Sub-maximal running performance was impaired until T24, although changes were not attenuated following the second bout.

CONCLUSIONS

The initial bout appeared to provide protection against a number of muscle damage indicators suggesting a greater need for recovery following the initial session of typical lower body resistance exercises in resistance-untrained men although sub-maximal running should be avoided following the first two sessions.

Running economy: measurement, norms, and determining factors

Running economy (RE) is considered an important physiological measure for endurance athletes, especially distance runners. This review considers 1) how RE is defined and measured and 2) physiological and biomechanical factors that determine or influence RE. It is difficult to accurately ascertain what is good, average, and poor RE between athletes and studies due to variation in protocols, gas-analysis systems, and data averaging techniques. However, representative RE values for different caliber of male and female runners can be identified from existing literature with mostly clear delineations in oxygen uptake across a range of speeds in moderately and highly trained and elite runners. Despite being simple to measure and acceptably reliable, it is evident that RE is a complex, multifactorial concept that reflects the integrated composite of a variety of metabolic, cardiorespiratory, biomechanical and neuromuscular characteristics that are unique to the individual. Metabolic efficiency refers to the utilization of available energy to facilitate optimal performance, whereas cardiopulmonary efficiency refers to a reduced work output for the processes related to oxygen transport and utilization. Biomechanical and neuromuscular characteristics refer to the interaction between the neural and musculoskeletal systems and their ability to convert power output into translocation and therefore performance. Of the numerous metabolic, cardiopulmonary, biomechanical and neuromuscular characteristics contributing to RE, many of these are able to adapt through training or other interventions resulting in improved RE.

Warm-up with a weighted vest improves running performance via leg stiffness and running economy

OBJECTIVES

To determine the effects of "strides" with a weighted-vest during a warm-up on endurance performance and its potential neuromuscular and metabolic mediators. A bout of resistance exercise can enhance subsequent high-intensity performance, but little is known about such priming exercise for endurance performance.

DESIGN

A crossover with 5-7 days between an experimental and control trial was performed by 11 well-trained distance runners.

METHODS

Each trial was preceded by a warm-up consisting of a 10-min self-paced jog, a 5-min submaximal run to determine running economy, and six 10-s strides with or without a weighted-vest (20% of body mass). After a 10-min recovery period, runners performed a series of jumps to determine leg stiffness and other neuromuscular characteristics, another 5-min submaximal run, and an incremental treadmill test to determine peak running speed. Clinical and non-clinical forms of magnitude-based inference were used to assess outcomes. Correlations and linear regression were used to assess relationships between performance and underlying measures.

RESULTS

The weighted-vest condition resulted in a very-large enhancement of peak running speed (2.9%; 90% confidence limits ±0.8%), a moderate increase in leg stiffness (20.4%; ±4.2%) and a large improvement in running economy (6.0%; ±1.6%); there were also small-moderate clear reductions in cardiorespiratory measures. Relationships between change scores showed that changes in leg stiffness could explain all the improvements in performance and economy.

CONCLUSIONS

Strides with a weighted-vest have a priming effect on leg stiffness and running economy. It is postulated the associated major effect on peak treadmill running speed will translate into enhancement of competitive endurance performance.

Optimizing strength training for running and cycling endurance performance: A review

Here we report on the effect of combining endurance training with heavy or explosive strength training on endurance performance in endurance-trained runners and cyclists. Running economy is improved by performing combined endurance training with either heavy or explosive strength training. However, heavy strength training is recommended for improving cycling economy. Equivocal findings exist regarding the effects on power output or velocity at the lactate threshold. Concurrent endurance and heavy strength training can increase running speed and power output at VO2max (Vmax and Wmax, respectively) or time to exhaustion at Vmax and Wmax. Combining endurance training with either explosive or heavy strength training can improve running performance, while there is most compelling evidence of an additive effect on cycling performance when heavy strength training is used. It is suggested that the improved endurance performance may relate to delayed activation of less efficient type II fibers, improved neuromuscular efficiency, conversion of fast-twitch type IIX fibers into more fatigue-resistant type IIA fibers, or improved musculo-tendinous stiffness.