Mixed maximal and explosive strength training in recreational endurance runners

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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.

Markers of Low Energy Availability in Overreached Athletes: A Systematic Review and Meta-analysis

BACKGROUND

Overreaching is the transient reduction in performance that occurs following training overload and is driven by an imbalance between stress and recovery. Low energy availability (LEA) may drive underperformance by compounding training stress; however, this has yet to be investigated systematically.

OBJECTIVE

The aim of this study was to quantify changes in markers of LEA in athletes who demonstrated underperformance, and exercise performance in athletes with markers of LEA.

METHODS

Studies using a ≥ 2-week training block with maintained or increased training loads that measured exercise performance and markers of LEA were identified using a systematic search following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Changes from pre- to post-training were analyzed for (1) markers of LEA in underperforming athletes and (2) performance in athletes with ≥ 2 markers of LEA.

RESULTS

From 56 identified studies, 14 separate groups of athletes demonstrated underperformance, with 50% also displaying ≥ 2 markers of LEA post-training. Eleven groups demonstrated ≥ 2 markers of LEA independent of underperformance and 37 had no performance reduction or ≥ 2 markers of LEA. In underperforming athletes, fat mass (d =  - 0.29, 95% confidence interval [CI] - 0.54 to - 0.04; p = 0.02), resting metabolic rate (d =  - 0.63, 95% CI - 1.22 to - 0.05; p = 0.03), and leptin (d =  - 0.72, 95% CI - 1.08 to - 0.35; p < 0.0001) were decreased, whereas body mass (d =  - 0.04, 95% CI - 0.21 to 0.14; p = 0.70), cortisol (d =  - 0.06, 95% CI - 0.35 to 0.23; p = 0.68), insulin (d =  - 0.12, 95% CI - 0.43 to 0.19; p = 0.46), and testosterone (d =  - 0.31, 95% CI - 0.69 to 0.08; p = 0.12) were unaltered. In athletes with ≥ 2 LEA markers, performance was unaffected (d = 0.09, 95% CI - 0.30 to 0.49; p = 0.6), and the high heterogeneity in performance outcomes (I² = 84.86%) could not be explained by the performance tests used or the length of the training block.

CONCLUSION

Underperforming athletes may present with markers of LEA, but overreaching is also observed in the absence of LEA. The lack of a specific effect and high variability of outcomes with LEA on performance suggests that LEA is not obligatory for underperformance.

Effects of Resistance Training on Physical Performance in High-Level 800-Meter Athletes: A Comparison Between High-Speed Resistance Training and Circuit Training

ABSTRACT

Bachero-Mena, B, Pareja-Blanco, F, and González-Badillo, JJ. Effects of resistance training on physical performance in high-level 800-meter athletes: a comparison between high-speed resistance training and circuit training. J Strength Cond Res 35(7): 1905-1915, 2021-This study compared the effects of 2 resistance training programs during 25 weeks on physical performance and hormonal response in high-level 800 m athletes. Thirteen male athletes (800-m personal best: 1:43-1:58 minutes:ss) were divided into 2 groups: high-speed resistance training group (RTG) (n = 6) and circuit training group (CTG) (n = 7). Three tests (T1, T2, and T3) including sprint and 800 m running, strength exercises, and blood hormones samples were performed. Both groups showed improvements in 800 m performance (RTG: likely positive, 80/20/0%; CTG: very likely positive, 98/2/0%); however, RTG showed an additional improvement in 200 m (likely positive, 85/15/0%), countermovement jump (CMJ) (very likely positive, 98/2/0%), and squat (likely positive, 91/9/0%), whereas CTG reached likely positive (88/11/1%) effects in CMJ and unclear/possibly negative effects in the rest of the strength variables analyzed. Concerning hormones, RTG resulted in a likely increase (83/15/3%) in testosterone from T1 to T3, and CTG showed a likely increase (79/17/4%) in cortisol from T2 to T3, remaining the rest of the hormones analyzed unclear. These results suggest that a resistance training characterized by high-speed and low-volume produced better improvements in both strength and running performance than a circuit training, accompanied by little changes in the hormonal response.

Effects of Resistance Circuit-Based Training on Body Composition, Strength and Cardiorespiratory Fitness: A Systematic Review and Meta-Analysis

We assessed the effects of resistance circuit-based training (CT) on strength, cardiorespiratory fitness, and body composition. A systematic review with meta-analysis was conducted in three databases, ending on March, 2020. Meta-analysis and subgroup analysis were used to analyze the effects of pre-post-intervention CT and differences from control groups (CG). Of the 830 studies found, 45 were included in the meta-analysis (58 experimental groups (n = 897) and 34 CG (n = 474)). The CT interventions led to increases in muscle mass (1.9%; p < 0.001) and decreases in fat mass (4.3%; p < 0.001). With regard to cardiorespiratory fitness, CT had a favorable effect on VO2max (6.3%; p < 0.001), maximum aerobic speed or power (0.3%; p = 0.04), and aerobic performance (2.6%; p = 0.006) after training. Concerning strength outcome, the CT increased the strength of the upper and lower extremities. Only the magnitude of strength performance appears to be influenced by the training (number of sessions and frequency) and the training status. Moreover, low and moderate intensities and short rest time between exercise increase the magnitude of change in fat mass loss. Therefore, CT has been shown to be an effective method for improving body composition, cardiorespiratory fitness, and strength of the lower and upper limbs.

Hormonal Contraceptive Use Does Not Affect Strength, Endurance, or Body Composition Adaptations to Combined Strength and Endurance Training in Women

ABSTRACT

Myllyaho, MM, Ihalainen, JK, Hackney, AC, Valtonen, M, Nummela, A, Vaara, E, Häkkinen, K, Kyröläinen, H, and Taipale, RS. Hormonal contraceptive use does not affect strength, endurance, or body composition adaptations to combined strength and endurance training in women. J Strength Cond Res 35(2): 449-457, 2021-This study examined the effects of a 10-week period of high-intensity combined strength and endurance training on strength, endurance, body composition, and serum hormone concentrations in physically active women using hormonal contraceptives (HCs, n = 9) compared with those who had never used hormonal contraceptives (NHCs, n = 9). Training consisted of 2 strength training sessions and 2 high-intensity running interval sessions per week. Maximal bilateral isometric leg press (Isom), maximal bilateral dynamic leg press (one repetition maximum [1RM]), countermovement jump (CMJ), a 3,000-m running test (3,000 m), body composition, and serum hormone levels were measured before and after training between days 1-5 of each subject's menstrual cycle. Both groups increased 1RM and CMJ: HC = 13.2% (p < 0.001) and 9.6% (p < 0.05), and NHC = 8.3% (p < 0.01) and 8.5% (p < 0.001). Hormonal contraceptive improved 3,000 m by 3.5% (p < 0.05) and NHC by 1% (n.s.). Never used hormonal contraceptive increased lean mass by 2.1% (p < 0.001), whereas body fat percentage decreased from 23.9 ± 6.7 to 22.4 ± 6.0 (-6.0%, p < 0.05). No significant changes were observed in body composition in HC. No significant between-group differences were observed in any of the performance variables. Luteinizing hormone concentrations decreased significantly (p < 0.05) over 10 weeks in NHC, whereas other hormone levels remained statistically unaltered in both groups. It seems that the present training is equally appropriate for improving strength, endurance, and body composition in women using HC as those not using HC without disrupting hypothalamic-pituitary-gonadal axis function.

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.

Effect of Strength Training on Biomechanical and Neuromuscular Variables in Distance Runners: A Systematic Review and Meta-Analysis

BACKGROUND

Concurrent strength and endurance (CSE) training improves distance running performance more than endurance training alone, but the mechanisms underpinning this phenomenon are unclear. It has been hypothesised that biomechanical or neuromuscular adaptations are responsible for improvements in running performance; however, evidence on this topic has not been synthesised in a review.

OBJECTIVE

To evaluate the effect of CSE training on biomechanical and neuromuscular variables in distance runners.

METHODS

Seven electronic databases were searched from inception to November 2018 using key terms related to running and strength training. Studies were included if the following criteria were met: (1) population: 'distance' or 'endurance' runners of any training status; (2) intervention: CSE training; (3) comparator: running-only control group; (4) outcomes: at least one biomechanical or neuromuscular variable; and, (5) study design: randomised and non-randomised comparative training studies. Biomechanical and neuromuscular variables of interest included: (1) kinematic, kinetic or electromyography outcome measures captured during running; (2) lower body muscle force, strength or power outcome measures; and (3) lower body muscle-tendon stiffness outcome measures. Methodological quality and risk of bias for each study were assessed using the PEDro scale. The level of evidence for each variable was categorised according to the quantity and PEDro rating of the included studies. Between-group standardised mean differences (SMD) with 95% confidence intervals (95% CI) were calculated for studies and meta-analyses were performed to identify the pooled effect of CSE training on biomechanical and neuromuscular variables.

RESULTS

The search resulted in 1578 potentially relevant articles, of which 25 met the inclusion criteria and were included. There was strong evidence that CSE training significantly increased knee flexion (SMD 0.89 [95% CI 0.48, 1.30], p < 0.001), ankle plantarflexion (SMD 0.74 [95% CI 0.21-1.26], p = 0.006) and squat (SMD 0.63 [95% CI 0.13, 1.12], p = 0.010) strength, but not jump height, more than endurance training alone. Moderate evidence also showed that CSE training significantly increased knee extension strength (SMD 0.69 [95% CI 0.29, 1.09], p < 0.001) more than endurance training alone. There was very limited evidence reporting changes in stride parameters and no studies examined changes in biomechanical and neuromuscular variables during running.

CONCLUSIONS

Concurrent strength and endurance training improves the force-generating capacity of the ankle plantarflexors, quadriceps, hamstrings and gluteal muscles. These muscles support and propel the centre of mass and accelerate the leg during running, but there is no evidence to suggest these adaptations transfer from strength exercises to running. There is a need for research that investigates changes in biomechanical and neuromuscular variables during running to elucidate the effect of CSE training on run performance in distance runners.

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.

Joint-level energetics differentiate isoinertial from speed-power resistance training-a Bayesian analysis

Background

There is convincing evidence for the benefits of resistance training on vertical jump improvements, but little evidence to guide optimal training prescription. The inability to detect small between modality effects may partially reflect the use of ANOVA statistics. This study represents the results of a sub-study from a larger project investigating the effects of two resistance training methods on load carriage running energetics. Bayesian statistics were used to compare the effectiveness of isoinertial resistance against speed-power training to change countermovement jump (CMJ) and squat jump (SJ) height, and joint energetics.

Methods

Active adults were randomly allocated to either a six-week isoinertial (n = 16; calf raises, leg press, and lunge), or a speed-power training program (n = 14; countermovement jumps, hopping, with hip flexor training to target pre-swing running energetics). Primary outcome variables included jump height and joint power. Bayesian mixed modelling and Functional Data Analysis were used, where significance was determined by a non-zero crossing of the 95% Bayesian Credible Interval (CrI).

Results

The gain in CMJ height after isoinertial training was 1.95 cm (95% CrI [0.85–3.04] cm) greater than the gain after speed-power training, but the gain in SJ height was similar between groups. In the CMJ, isoinertial training produced a larger increase in power absorption at the hip by a mean 0.018% (equivalent to 35 W) (95% CrI [0.007–0.03]), knee by 0.014% (equivalent to 27 W) (95% CrI [0.006–0.02]) and foot by 0.011% (equivalent to 21 W) (95% CrI [0.005–0.02]) compared to speed-power training.

Discussion

Short-term isoinertial training improved CMJ height more than speed-power training. The principle adaptive difference between training modalities was at the level of hip, knee and foot power absorption.

Enhanced Strength and Sprint Levels, and Changes in Blood Parameters during a Complete Athletics Season in 800 m High-Level Athletes

The purpose of this study was to analyze changes in sprint, strength, hematological, and hormonal parameters in high-level 800 m athletes during a complete athletics season. Thirteen male athletes of national and international level in 800 m (personal best ranging from 1:43 to 1:58 min:ss) participated in this study. A total of 5 tests were conducted during a complete athletics season. Athletes performed sprint tests (20 and 200 m), countermovement jump (CMJ), jump squat (JS), and full squat (SQ) tests. Blood samples (red and white blood profile) and hormones were collected in test 1 (T1), test 3 (T3), and test 5 (T5). A general increase in the performance of the strength and sprint parameters analyzed (CMJ, JS, SQ, 20 m, and 200 m) during the season was observed, with a significant time effect in CMJ (P < 0.01), SQ (P < 0.01), and 200 m (P < 0.05). This improvement was accompanied by a significant enhancement of the 800 m performance from T3 to T5 (P < 0.01). Significant changes in some hematological variables: hematocrit (Hct) (P < 0.01), mean corpuscular volume (MCV) (P < 0.001), mean corpuscular hemoglobin content (MCHC) (P < 0.001), white blood cells count (WBC) (P < 0.05), neutrophils (P < 0.05), monocytes (P < 0.05), and mean platelet volume (MPV) (P < 0.05) were observed throughout the season. The hormonal response and creatin kinase (CK) did not show significant variations during the season, except for insulin-like growth factor I (IGF-1) (P < 0.05). In conclusion, our results suggest the importance of strength levels in middle-distance athletes. On the other hand, variations in some hematological parameters and a depression of the immune system occurred during the season. Therefore, monitoring of the mechanical, hematological and hormonal response in athletes may help coaches and athletes to optimize the regulation of training contents and may be useful to diagnose states of overreaching or overtraining in athletes throughout the season.

Relationships between Sprint, Jumping and Strength Abilities, and 800 M Performance in Male Athletes of National and International Levels

This study analysed the relationships between sprinting, jumping and strength abilities, with regard to 800 m running performance. Fourteen athletes of national and international levels in 800 m (personal best: 1:43-1:58 min:ss) completed sprint tests (20 m and 200 m), a countermovement jump, jump squat and full squat test as well as an 800 m race. Significant relationships (p < 0.01) were observed between 800 m performance and sprint tests: 20 m (r = 0.72) and 200 m (r = 0.84). Analysing the 200 m run, the magnitude of the relationship between the first to the last 50 m interval times and the 800 m time tended to increase (1st 50 m: r = 0.71; 2nd 50 m: r = 0.72; 3rd 50 m: r = 0.81; 4th 50 m: r = 0.85). Performance in 800 m also correlated significantly (p < 0.01-0.05) with strength variables: the countermovement jump (r = -0.69), jump squat (r = -0.65), and full squat test (r = -0.58). Performance of 800 m in high-level athletes was related to sprint, strength and jumping abilities, with 200 m and the latest 50 m of the 200 m being the variables that most explained the variance of the 800 m performance.

Model approach for stress induced steroidal hormone cascade changes in severe mental diseases

INTRODUCTION

Stress was described by Cushing and Selye as an adaptation to a foreign stressor by the anterior pituitary increasing ACTH, which stimulates the release of glucocorticoid and mineralocorticoid hormones. The question is raised whether stress can induce additional steroidal hormone cascade changes in severe mental diseases (SMD), since stress is the common denominator.

METHODS

A systematic literature review was conducted in PubMed, where the steroidal hormone cascade of patients with SMD was compared to the impact of increasing stress on the steroidal hormone cascade (a) in healthy amateur marathon runners with no overtraining; (b) in healthy well-trained elite soldiers of a ranger training unit in North Norway, who were under extreme physical and mental stress, sleep deprivation, and insufficient calories for 1 week; and, (c) in soldiers suffering from post traumatic stress disorder (PTSD), schizophrenia (SI), and bipolar disorders (BD).

RESULTS

(a) When physical stress is exposed moderately to healthy men and women for 3-5 days, as in the case of amateur marathon runners, only few steroidal hormones are altered. A mild reduction in testosterone, cholesterol and triglycerides is detected in blood and in saliva, but there was no decrease in estradiol. Conversely, there is an increase of the glucocorticoids, aldosterone and cortisol. Cellular immunity, but not specific immunity, is reduced for a short time in these subjects. (b) These changes are also seen in healthy elite soldiers exposed to extreme physical and mental stress but to a somewhat greater extent. For instance, the aldosterone is increased by a factor of three. (c) In SMD, an irreversible effect on the entire steroidal hormone cascade is detected. Hormones at the top of the cascade, such as cholesterol, dehydroepiandrosterone (DHEA), aldosterone and other glucocorticoids, are increased. However, testosterone and estradiol and their metabolites, and other hormones at the lower end of the cascade, seem to be reduced. 1) The rate and extent of reduction of the androgen metabolites may cause a decrease of cellular and specific immunity which can lead to viral and bacterial infections; joint and stomach inflammation; general pain; and allergic reactions. 2) The decrease in testosterone, and estradiol in SMD may have detrimental effects in cell repair as the estradiol metabolite, 2-methoxy-estradiol (2ME2), helps to transforms stem cells into functional cells. As dopamine and 2ME2 are inversely metabolized via various forms of catechol-O-methyl transferase (COMT), well-being and hypertension may be related. 2ME2 is related to vascular endothelial growth factor (VEGF), which regulates blood capillary growth and O2 supply. As reduced O2 is a key marker of stress, the increase of glucocorticoids in all forms of mental and physical stress cannot counterbalance the reduced 2ME2 in cellular and mental stress. The increased cholesterol and triglycerides are related to stroke and infarction, contributing to a reduced life expectancy in SMD between 14 and 20 years. The increase of aldosterone leads to increases in anxiety, edema, and lung infections.

DISCUSSION

Increasing mental and physical stress is related to systematic deviations in the steroidal hormone cascade in the non-psychotic state, which then may cause life threatening co-morbidities in PTSD, SI, and BD.

Predictors of individual adaptation to high-volume or high-intensity endurance training in recreational endurance runners

The aim of this study was to investigate factors that can predict individual adaptation to high-volume or high-intensity endurance training. After the first 8-week preparation period, 37 recreational endurance runners were matched into the high-volume training group (HVT) and high-intensity training group (HIT). During the next 8-week training period, HVT increased their running training volume and HIT increased training intensity. Endurance performance characteristics, heart rate variability (HRV), and serum hormone concentrations were measured before and after the training periods. While HIT improved peak treadmill running speed (RSpeak ) 3.1 ± 2.8% (P < 0.001), no significant changes occurred in HVT (RSpeak : 0.5 ± 1.9%). However, large individual variation was found in the changes of RSpeak in both groups (HVT: -2.8 to 4.1%; HIT: 0-10.2%). A negative relationship was observed between baseline high-frequency power of HRV (HFPnight ) and the individual changes of RSpeak (r = -0.74, P = 0.006) in HVT and a positive relationship (r = 0.63, P = 0.039) in HIT. Individuals with lower HFP showed greater change of RSpeak in HVT, while individuals with higher HFP responded well in HIT. It is concluded that nocturnal HRV can be used to individualize endurance training in recreational runners.

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.