Impact of an incremental running test on jumping kinematics in endurance runners: can jumping kinematic explain the post-activation potentiation phenomenon?

Co-existence of peripheral fatigue of the knee extensors and jump potentiation after an incremental running test to exhaustion in endurance trained male runners

The aim of the present study was to investigate the effect of an incremental running exercise until exhaustion on twitch responses and jump capacity in endurance trained runners. For this purpose, 8 experienced endurance male runners were required to perform neuromuscular function tests before and after a submaximal running bout (control condition -CTR-) or an incremental running test to volitional exhaustion (experimental conditions -EXP-). The twitch interpolation technique was used to assess voluntary activation and muscle contractile properties before and after each condition (CTR and EXP). Countermovement jump was also used to assess the stretch-shortening cycle function before and after both conditions. In addition, rating of perceived exertion, heart rate, blood lactate and skin temperature were also recorded. Only EXP improved jump performance, however, it was also accompanied by a reduction in maximal voluntary contraction and the peak twitch force of the knee extensors evoked by electrical stimulation at 10 Hz (Db10). It is likely that reductions in maximal voluntary contraction may be related to an excitation-contraction coupling failure (i.e. low-frequency fatigue) as suggest the reduction in the Db10. The current results confirm that acute changes in jump performance may not be appropriate to evaluate acute fatigue in endurance trained runners.

Effect of post-activation potentiation using core activation on isometric core strength and countermovement jump variables in university male recreational athletes

Core strengthening exercises have been integrated into the conditioning regimens of sportsmen of all levels. Despite a wealth of evidence, the question of what influence core stability exercises have on jump performance remains unsolved. Only a small percentage of studies have explored effects of standalone core training. The objective of this research was to explore acute changes in countermovement jump (CMJ) performance caused by post-activation potentiation (PAP) adopting core activation exercises. 25 male recreational athletes were recruited as participants. They visited on three occasions-first for familiarisation, following for baseline data using a conventional warmup, and final for repeat data upon inducing PAP. Isometric dynamometer was used to quantify core isometric strength and CMJ variables were evaluated using a Portable performance analysis system with MARS Software. Paired t-test and multivariate analysis were carried out. All core strength metrics reported marked increase at P<0.001 from conventional to PAP warmup. Following CMJ metrics varied significantly: jump height from take-off (P<0.001), jump height from flight (P<0.01), flight time (P<0.01,) and force at free-fall (P<0.001). Core training with PAP is a form of neuromuscular training that has the potential to improve power, agility, and speed by modifying force absorption, active joint stabilisation, and improved movement patterns. These alterations are ascribed to changes in cerebral drive, as well as enhanced motor-unit activation and firing frequency at the muscle level. Before a competition, a core activation warm-up can offer a unique training stimulus and increase performance via an ergogenic response. The core is essential for optimal athletic performance and should not be overlooked.

Effects of an intermittent exercise protocol on ankle control during a single-legged landing

Purpose

To identify the effects of fatigue from an exercise protocol (similar to a soccer match) on ankle motion and forces during single-legged drop landing.

Methods

Seventeen males aged (mean ± SD) 22.2 ± 2.0 years participated in this repeated measures study. A 90-min intermittent exercise protocol with a 15-min rest at halftime was performed. Before, at halftime and after the exercise, participants were tested via a single-legged drop landing task onto a force platform whilst wearing a three-dimensional inertial measurement system (Xsens). Ankle angles (plantarflexion/dorsiflexion and inversion/eversion) were analysed before landing and at peak ground reaction force after landing, and center of pressure was analysed at peak ground reaction force.

Results

No significant differences were found for the outcomes between pre-, halftime and post-exercise (p > 0.05).

Conclusions

Findings suggest that exercises simulating a soccer match (regarding exertion) do not necessarily lead to significant changes in ankle motion or forces around the ankle.

Learning From Human Responses to Deconditioning Environments: Improved Understanding of the "Use It or Lose It" Principle

Physical activity, mobility or patterned mobility (i.e., exercise) is intrinsic to the functioning of Homo sapiens, and required for maintenance of health. Thus, systems such as the musculoskeletal and cardiovascular systems appear to require constant reinforcement or conditioning to maintain integrity. Loss of conditioning or development of chronic deconditioning can have multiple consequences. The study of different types of deconditioning and their prevention or reversal can offer a number of clues to the regulation of these systems and point to how deconditioning poses risk for disease development and progression. From the study of deconditioning associated with spaceflight, a condition not predicted by evolution, prolonged bedrest, protracted sedentary behavior, as well as menopause and obesity and their consequences, provide a background to better understand human heterogeneity and how physical fitness may impact the risks for chronic conditions subsequent to the deconditioning. The effectiveness of optimized physical activity and exercise protocols likely depend on the nature of the deconditioning, the sex and genetics of the individual, whether one is addressing prevention of deconditioning-associated disease or disease-associated progression, and whether it is focused on acute or chronic deconditioning associated with different forms of deconditioning. While considerable research effort has gone into preventing deconditioning, the study of the process of deconditioning and its endpoints can provide clues to the regulation of the affected systems and their contributions to human heterogeneity that have been framed by the boundary conditions of Earth during evolution and the "use it or lose it" principle of regulation. Such information regarding heterogeneity that is elaborated by the study of deconditioning environments could enhance the effectiveness of individualized interventions to prevent deconditions or rescue those who have become deconditioned.

Acute Effects of Aerobic Exercise on Muscle Strength and Power in Trained Male Individuals: A Systematic Review with Meta-analysis

BACKGROUND

Concurrent training can be an effective and time-efficient method to improve both muscle strength and aerobic capacity. A major challenge with concurrent training is how to adequately combine and sequence strength exercise and aerobic exercise to avoid interference effects. This is particularly relevant for athletes.

OBJECTIVE

We aimed to examine the acute effects of aerobic exercise on subsequent measures of muscle strength and power in trained male individuals.

DESIGN

We performed a systematic review with meta-analysis.

DATA SOURCES

Systematic literature searches in the electronic databases PubMed, Web of Science, and Google Scholar were conducted up to July 2021.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Studies were included that applied a within-group repeated-measures design and examined the acute effects of aerobic exercise (i.e., running, cycling exercise) on subsequent measures of lower limb muscle strength (e.g., maximal isometric force of the knee extensors) and/or proxies of lower limb muscle power (e.g., countermovement jump height) in trained individuals.

RESULTS

Fifteen studies met the inclusion criteria. Aerobic exercise resulted in moderate declines in muscle strength (standardized mean difference [SMD] = 0.79; p = 0.003). Low-intensity aerobic exercise did not moderate effects on muscle strength (SMD = 0.65; p = 0.157) while moderate-to-high intensity aerobic exercise resulted in moderate declines in muscle strength (SMD = 0.65; p = 0.020). However, the difference between subgroups was not statistically significant (p = 0.979). Regarding aerobic exercise duration, large declines in muscle strength were found after > 30 min (SMD = 1.02; p = 0.049) while ≤ 30 min of aerobic exercise induced moderate declines in muscle strength (SMD = 0.59; p = 0.013). The subgroup difference was not statistically significant (p = 0.204). Cycling exercise resulted in significantly larger decrements in muscle strength (SMD = 0.79; p = 0.002) compared with running (SMD = 0.28; p = 0.035). The difference between subgroups was statistically significant (p < 0.0001). For muscle power, aerobic exercise did not result in any statistically significant changes (SMD = 0.04; p = 0.846).

CONCLUSIONS

Aerobic exercise induced moderate declines in measures of muscle strength with no statistically significant effects on proxies of muscle power in trained male individuals. It appears that higher compared with lower intensity as well as longer compared with shorter aerobic exercise duration exacerbate acute declines in muscle strength. Our results provide evidence for acute interference effects when aerobic exercies is performed before strength exercises. These findings may help practitioners to better prescribe single training sessions, particularly if environmental and/or infrastructural reasons (e.g., availability of training facilities) do not allow the application of strength training before aerobic exercise.

Caffeine improves performance but not duration of the countermovement jump phases

BACKGROUND

The countermovement jump (CMJ) test is often employed to assess power generated in the lower limbs and has been related to performance in several sports modalities. The objective of this study was to assess the effects of caffeine supplementation on jump height, average power (AP), peak power (PP), maximum velocity (V<inf>max</inf>), force production and duration of the eccentric, isometric and concentric muscle contraction phases of a CMJ.

METHODS

Sixteen resistance-trained men (age: 22.69±2.12 years; height: 1.78±0.06 m; weight: 78.09±10.27 kg) performed a CMJ 60 minutes after having taken an oral supplement containing 6 mg·kg^-1 of caffeine or placebo (sucrose). The study design was randomized, double-blind crossover.

RESULTS

Caffeine ingestion improved jump height (+3.86%, P=0.02), V<inf>max</inf> (+1.49%, P=0.023), AP (+4.83%, P=0.006), and PP (+3.49%, P=0.004).

CONCLUSIONS

Acute caffeine supplementation leads to improved CMJ height, V<inf>max</inf>, AP and PP without significantly affecting the duration of the different test phases. Therefore, caffeine supplementation may be employed as ergogenic aid in sports where CMJ performance has been associated with sport-specific performance enhancements.

Post-Activation Potentiation Increases Recruitment of Fast Twitch Fibers: A Potential Practical Application in Runners

To determine the relationship between fatigue and post-activation potentiation, we examined the effects of sub-maximal continuous running on neuromuscular function tests, as well as on the squat jump and counter movement jump in endurance athletes. The height of the squat jump and counter movement jump and the estimate of the fast twitch fiber recruiting capabilities were assessed in seven male middle distance runners before and after 40 min of continuous running at an intensity corresponding to the individual lactate threshold. The same test was then repeated after three weeks of specific aerobic training. Since the three variables were strongly correlated, only the estimate of the fast twitch fiber was considered for the results. The subjects showed a significant improvement in the fast twitch fiber recruitment percentage after the 40 min run. Our data show that submaximal physical exercise determined a change in fast twitch muscle fiber recruitment patterns observed when subjects performed vertical jumps; however, this recruitment capacity was proportional to the subjects’ individual fast twitch muscle fiber profiles measured before the 40 min run. The results of the jump tests did not change significantly after the three-week training period. These results suggest that pre-fatigue methods, through sub-maximal exercises, could be used to take advantage of explosive capacity in middle-distance runners.

Effects of fatigue on ankle biomechanics during jumps: A systematic review

Fatigue is common during physical activity and can have an effect on ankle biomechanics during different actions, such as a jump. Yet current research on the topic is very heterogeneous and hinders clarity on what changes are actually due to fatigue. Therefore, the aim of this review was to summarise and analyse the current literature that investigates the effects of fatigue on ankle biomechanics during a jump. Searches were conducted in five databases and studies with activities eliciting fatigue and comparing outcomes under a fatigue and non-fatigue conditions were selected. Twelve studies were included, six analysed double legged jumps and six single legged jump. When comparing ankle biomechanics between a fatigued condition and a non-fatigued condition, findings suggested that at initial contact at landing, dorsiflexion increased in single legged jump and plantarflexion increased in double legged jump; at maximum knee flexion after landing, dorsiflexion decreased in double legged jumps and plantarflexion increased at full foot contact in single legged jumps. Also, ankle power (for double legged jump) and ground reaction force (for double and single legged jump) reduced at initial contact to maximum knee flexion at landing after fatigue and ankle power also reduced at takeoff in single legged jumps. The current review shows that fatigue affect ankle biomechanics by reducing dorsiflexion, from initial contact to maximum knee flexion at landing, and power during the jump takeoff. Such information could have implications for injury prevention.

Responsiveness of the Countermovement Jump and Handgrip Strength to an Incremental Running Test in Endurance Athletes: Influence of Sex

The present study analyzed the acute effects of an incremental running test on countermovement jump (CMJ) and handgrip strength performance in endurance athletes, considering the effect of post-exercise recovery time and sex. Thirty-three recreationally trained long-distance runners, 20 men and 13 women, participated voluntarily in this study. The participants performed the Léger test, moreover, the CMJ and handgrip strength tests were carried out before and after the running test and during different stages of recovery (at the 1st min of recovery (posttest1), 5th min of recovery (posttest2), and 10th min of recovery (posttest3)). Two-way analysis of variance revealed a significant improvement in the CMJ (pre-posttest1, p = 0.001) and handgrip strength (pre-posttest2, p = 0.017) during recovery time. The Pearson’s Chi-2 test showed no significant relationship (p ≥ 0.05) between sex and post-activation potentiation (PAP). A linear regression analysis pointed to heart rate recovery as a predictive factor of CMJ improvement (PAP). In conclusion, despite significant fatigue reached during the Léger test, the long-distance runners did not experience an impaired CMJ and handgrip strength performance, either men or women, achieving an improvement (PAP) in posttest conditions. The results obtained showed no significant relationship between sex and PAP. Moreover, significant effect of recovery after running at high intensity on CMJ performance and handgrip strength was found. Finally, the data suggest that PAP condition can be predicted by heart rate recovery in endurance runners.

Post-activation potentiation (PAP) in endurance sports: A review

While there is strong support of the usefulness of post-activation potentiation (PAP) phenomenon in power demanding sports, the role that PAP could play in endurance sports has received less attention. The aim of this review is to present evidence for a better understanding of PAP in endurance athletes; and to discuss the physiological basis and methodological aspects necessary for better practices and designing further studies. A search for relevant articles on PAP and endurance trained athletes was carried out using Medline and ISI Web of Knowledge databases. Twenty-two studies were included in the review. The current evidence suggests the possible influence of PAP for performance enhancement after appropriate conditioning activities during warm up. Evaluation of PAP responses during testing, training and competition may be also important for athletes monitoring. There are many unresolved questions about the optimum load parameters for benefiting from PAP in both training and competition; and the role that PAP may exert for optimal performance while interacting with central and peripheral factors associated with muscle fatigue. Further studies should elucidate the association between PAP responses and long-term adaptations in endurance athletes.