Neuromuscular adaptations to plyometric training: depth jump vs. countermovement jump on sand

The aim of the current investigation was to examine the effects of depth jump and countermovement jump training on neuromuscular adaptations using vertical jump and electromyography activity in the muscles. Twenty-seven healthy males (age 20.4 ± 0.3 years; weight 69.8 ± 6.1 kg; height 177.3 ± 6.2 cm) were recruited to participant in the present study and were randomly divided into three groups: depth jump (DJ), countermovement jump (CMJ) and control group. The experimental groups performed either DJ or CMJ training twice weekly for 6 weeks. The training program included five sets of 20 repetitions DJ (from the height of a 45-cm box) or CMJ exercise onto 20-cm dry sand. The electromyography activities in the vastus medialis (VM), and rectus femoris (RF) muscles, and vertical jump (VJ) were measured a week pre and post 6 weeks of training. The results showed significant increases in the integrated electromyography for the VM and RF following DJ and CMJ training on sand, also the DJ and CMJ training on sand induced significant improvement in VJ performance (P < 0.05). In conclusion, the DJ and CMJ training on sand improved electrical activities in the muscle and jump performance, and it can be recommended that, coaches and athletes design plyometrics on sand, because these types of training on sand can be an effective method for improving neuromuscular adaptations.     

The effects of a combined static-dynamic stretching protocol on athletic performance in elite Gaelic footballers: A randomised controlled crossover trial

ObjectivesTo determine the effect of three different static-dynamic stretching protocols on sprint and jump performance in Gaelic footballers.DesignDouble-blind, controlled, crossover trial.SettingSports Institute research environment.ParticipantsSeventeen male elite level Gaelic footballers, aged 18–30 years, completed three stretching protocols.Main Outcome MeasuresAthletic performance was measured by countermovement jump height and power, and timed 10 m, 20 m, and 40 m sprints.ResultsStatic stretching reduced sprint speed by 1.1% over 40 m and 1.0% over 20 m. Static stretching also reduced countermovement jump height by 10.6% and jump power by 6.4%. When static stretching was followed by dynamic stretching, sprint speed improved by 1.0% over 20 m and 0.7% over 40 m (p < 0.05). The static - dynamic stretching protocol also improved countermovement jump height by 8.7% (p < 0.01) and power by 6.7% (p < 0.01).ConclusionsStatic stretching reduces sprint speed and jump performance. Static stretching should be followed by dynamic stretching during warm-up to nullify any performance deficits caused by static stretching.     

A randomized controlled trial of manual therapy and pneumatic compression for recovery from prolonged running – an extended study

Manual therapy (MT) and intermittent pneumatic compression (IPC) are recovery methods used by endurance athletes with little evidence supporting effectiveness. This randomized controlled trial evaluated effectiveness of four daily post-race treatments of a specific MT protocol and IPC compared with supine rest on recovery following an ultramarathon among 56 ultramarathoners. Groups were comparable across all characteristics examined, including post-race plasma creatine kinase concentration. Subject completed timed 400 m runs before the race and on days three, five, seven and 14 post- race, and also provided muscle pain and soreness ratings and fatigue scores immediately before and after treatments, and during the 14 days post- race. Daily subjective measures and 400 m run times were not improved by either treatment, but both treatments reduced (p < .05) muscular fatigue scores acutely after treatment following the race and on post-race day 1, and MT improved (p < .05) muscle pain and soreness acutely following the race.     

Effects of fatigue and surface instability on neuromuscular performance during jumping

It has previously been shown that fatigue and unstable surfaces affect jump performance. However, the combination thereof is unresolved. Thus, the purpose of this study was to examine the effects of fatigue and surface instability on jump performance and leg muscle activity. Twenty elite volleyball players (18 ± 2 years) performed repetitive vertical double‐leg box jumps until failure. Before and after a fatigue protocol, jump performance (i.e., jump height) and electromyographic activity of selected lower limb muscles were recorded during drop jumps (DJs) and countermovement jumps (CMJs) on a force plate on stable and unstable surfaces (i.e., balance pad on top of force plate). Jump performance (3–7%; P < 0.05; 1.14 ≤ d ≤ 2.82), and muscle activity (2–27%; P < 0.05; 0.59 ≤ d ≤ 3.13) were lower following fatigue during DJs and CMJs, and on unstable compared with stable surfaces during DJs only (jump performance: 8%; P < 0.01; d = 1.90; muscle activity: 9–25%; P < 0.05; 1.08 ≤ d ≤ 2.54). No statistically significant interactions of fatigue by surface condition were observed. Our findings revealed that fatigue impairs neuromuscular performance during DJs and CMJs in elite volleyball players, whereas surface instability affects neuromuscular DJ performance only. Absent fatigue × surface interactions indicate that fatigue‐induced changes in jump performance are similar on stable and unstable surfaces in jump‐trained athletes.     

Active versus local vibration warm-up effects on knee extensors stiffness and neuromuscular performance of healthy young males

Objectives

To compare the effects of local-vibration and active warm-up on knee extensors muscle stiffness and neuromuscular performance.

Influence of warm-up duration on physical performance and psychological perceptions in handball players

The purpose of the study was to analyse the effect of two warm-up protocols of different duration on physical performance, perceived load and perception of being ready for a match in handball players. Eighteen handball players were randomly divided into two groups (Wup_34min, warm-up protocol of 34 min, Wup_17min, warm-up protocol of 17 min). Before and after the warm-up protocols, they performed a battery of physical tests and recorded their perception of feeling ready for a match. At the end of the warm-up protocols, all the players evaluated their differentiated perceived effort (dRPE). The results showed that neither of the protocols significantly modified (p > 0.05) the players’ physical performance. However, the Wup_34min group showed higher values in the differentiated warm-up perceived load (dRPE-WL) (p < 0.01, TE = 0.97–1.27, high) than the Wup_17min group. The players with a greater perceived muscular load (RPE_MUSC) experienced a greater decrease in their acceleration capacity (r = 0.48–0.49, p < 0.05). In spite of the fact that neither of the warm-up protocols significantly modified the players’ physical performance, a greater perceived muscular load may cause a greater decrease in acceleration capacity.     

Negative effect of static stretching restored when combined with a sport specific warm-up component

There is substantial evidence that static stretching may inhibit performance in strength and power activities. However, most of this research has involved stretching routines dissimilar to those practiced by athletes. The purpose of this study was to evaluate whether the decline in performance normally associated with static stretching pervades when the static stretching is conducted prior to a sport specific warm-up. Thirteen netball players completed two experimental warm-up conditions. Day 1 warm-up involved a submaximal run followed by 15 min of static stretching and a netball specific skill warm-up. Day 2 followed the same design; however, the static stretching was replaced with a 15 min dynamic warm-up routine to allow for a direct comparison between the static stretching and dynamic warm-up effects. Participants performed a countermovement vertical jump and 20 m sprint after the first warm-up intervention (static or dynamic) and also after the netball specific skill warm-up. The static stretching condition resulted in significantly worse performance than the dynamic warm-up in vertical jump height (?4.2%, 0.40 ES) and 20 m sprint time (1.4%, 0.34 ES) (p < 0.05). However, no significant differences in either performance variable were evident when the skill-based warm-up was preceded by static stretching or a dynamic warm-up routine. This suggests that the practice of a subsequent high-intensity skill based warm-up restored the differences between the two warm-up interventions. Hence, if static stretching is to be included in the warm-up period, it is recommended that a period of high-intensity sport-specific skills based activity is included prior to the on-court/field performance.     

Effects of power and flexibility training on vertical jump technique

PURPOSE: The purpose of this study was to assess the effects of power and flexibility training on countermovement and drop jump techniques. METHOD: All jumps were executed with the goal of attaining maximum height and no restrictions were placed on the magnitude of countermovement or ground contact time. Subjects underwent initial testing followed by random allocation to one of four groups: power training to increase vertical jump height (P), stretching to increase flexibility (S), a combination of power and stretch training (PS), and a control group (C). Training lasted for 10 wk, followed by retesting. Jump height was calculated in addition to the following technique variables: eccentric lower-limb stiffness produced during the countermovement phase, magnitude of countermovement, and in the case of the drop jumps, ground contact time. RESULTS: Groups PS, P, and S all increased countermovement jump (CMJ) height, but only groups PS and P increased drop jump height (DJ30, DJ60, and DJ90 for drop jumps performed from 30-, 60-, and 90-cm drop heights). The technique changes associated with power training were increases in magnitude of countermovement (CMJ, DJ30, DJ60, and DJ90) and increases in ground contact time (DJ30 and DJ60). In addition, the eccentric lower-limb stiffness produced during the countermovement phase of the jumps increased for CMJ and decreased for DJ30, DJ60, and DJ90. Stretching appeared to have no significant effect on CMJ or drop jump technique. CONCLUSION: The results of this study show that when the training goal is maximum jump height alone, it is likely that drop jump technique will change in the direction of a lower eccentric leg stiffness, greater depth of countermovement, and a longer ground contact time, whereas for a countermovement jump eccentric leg stiffness and the depth of countermovement will both increase. It is proposed that these technique changes are a result of attempting to optimize a complex combination of factors involved in jumping (e.g., utilization of elastic energy, Golgi tendon organ inhibition, and contractile component contribution).     

Short duration static stretching preceded by cycling warm-up reduces vertical jump performance in healthy males

Purpose

It has been proposed that warm-up activities including static stretching may have detrimental effects on power performance. While it is well established in the literature that more than 30 s of stretching before exercise induces deficit in force and power production, there are still controversial findings regarding 30 s or less when additional interventions, such as general warm-up, are allied to the stretching. Therefore, the purpose of this study was to evaluate the acute effect of passive static stretching preceded by dynamic warm-up on vertical jump performance.

Methods

Twenty healthy men participated in this study, and attended to one familiarization session and two testing sessions. In the warm-up (WP) condition, participants performed a 5 min warm-up on a cycle ergometer followed by the counter movement jump (CMJ) test. In the warm-up plus static stretching (WP + SS) condition, besides the same previously described warm-up, participants performed 30 s static stretching bouts for calf, hamstrings, gluteus maximus and quadriceps muscles in a randomized order, followed by the CMJ test.

Results

Data distribution was verified by the Shapiro–Wilk test and Paired T-Student test was used to compare jump height between the two conditions. A significant between-condition effect was observed for CMJ height (p < 0.05), such that jump height was significantly lower in WP + SS condition.

Conclusion

The results of the present study demonstrate that a 5 min dynamic warm-up combined to a 30 s of passive static stretch in four muscle groups induce a reduction in lower limb power measured by CMJ height.

     

Effects of cognitive training strategies on muscular force and psychological skills in healthy striking combat sports practitioners

The objective of the present study was to examine the effects of cognitive training strategies on muscular force in healthy combat sports practitioners. Additionally, moderator variable, particularly cognitive training strategies, as well as the potential mediators of self-efficacy and motivation were examined. Forty-four male combat sports practitioners (23.2 ± 3.1 years, 1.74 ± 0.09 m, and 73.4 ± 9.5 kg) participated in the present study. Participants were randomly assigned to three conditions: mental imagery (MI: n = 14), mental training package (MTP: n = 16: combined of motivational self-talk and imagery), or control condition (CG: n = 14: physical training). Thus, self-efficacy, motivation, muscular power in countermovement jump (CMJ) and medicine ball throw (MBT), and strength performance in bench press and half-squat tests were measured before and after 10 weeks of training in each condition. In addition, MTP, MI, and physical training groups performed three times per week (~90-min per session) in alternative days for 10 weeks (30 sessions in total). In fact, MTP had better muscular power (CMJ, p = 0.03; MBT, p < 0.001) and strength performance (bench press, p = 0.04; half-squat, p = 0.02) than physical training (CG). Furthermore, the MBT performance was higher in the MTP condition than in the MI (p = 0.04) after the training period. The results for motivation and self-efficacy were similar, with higher motivation and self-efficacy in MTP after the training period than in other conditions (all, p < 0.05). Significant relationships were identified between changes in motivation and changes in muscular force and between changes in self-efficacy and changes in muscular force (all, p < 0.05). Finally, the results obtained in the present study have confirmed the moderator role of cognitive training strategies. The findings also suggest that motivation and self-efficacy may have a mediator’s role, and provide direction for psyching-up effectiveness.     

Lower extremity variability changes with drop-landing height manipulations

Landing is a common lower extremity injury mechanism in sport, with potential connections to movement control accessed through variability measures. We investigated intra-subject lower extremity variability changes following drop-landing height manipulations using standard deviation (SD) and coefficient of variation (CV) among lower extremity peak sagittal joint angles and moments. Fourteen healthy participants completed five drop-landing trials from five heights 20%, 60%, 100%, 140% and 180% maximum vertical jump height (MVJH). Peak joint angles and moments increased with greater landing height (p < 0.001), highlighting inter-joint differences (Flexion: Knee > Hip > Ankle, p < 0.001; Extensor Moment: Hip > Knee > Ankle, in excess of 60% MVJH, p < 0.05). Kinematic and kinetic SD increased with variable magnitudes, while CV decreased at greater landing heights (p ≤ 0.016). Decreased relative variability under greater task demands may underscore non-contact injury mechanisms from repetitive loading of identical structures.     

Effects of in-season short-term plyometric training on jumping and agility performance of basketball players

The purpose of this investigation was to examine the effects of in-season plyometric training program on power and agility performance in young male basketball players. Twenty intermediate basketball players (age 20.1 ± 1.3 years; height 181.1 ± 8.5 cm; body mass 78.8 ± 5 kg) from Division I province team volunteered to participate in this study and were randomly divided into two groups: plyometric training (PL; n = 10) and control group (CG; n = 10). Plyometric training took place twice weekly for 6 weeks including three sets of 15 repetitions of depth jump (from 45-cm box height), vertical jump, and standing long jump, in addition to regular basketball practice of the team. Vertical jump (VJ), standing long jump (SLJ), 4 × 9-m shuttle run, agility t test (ATT), and Illinois Agility Test (IAT) were measured at pre- and post-training. The PL group showed significant improvement (P < 0.05) in VJ (10.21 ± 2.72 cm), SLJ (21.15 ± 8.10 cm), 4 × 9-m shuttle run (0.62 ± 0.28 s), ATT (1.16 ± 0.57 s), and IAT (1.17 ± 0.65 s) after a 6-week training period and compared to CG. It can be concluded that a 6-week in-season plyometric training program has positive effects for improving power and agility performance in young male basketball players and this study provides support for coaches and basketball players who use this training method during competitive phase.     

No effect on performance tests from a neuromuscular warm-up programme in youth female football: a randomised controlled trial

Purpose

The objective of the present randomised controlled trial was to study the effect of a neuromuscular warm-up programme on performance tests in youth female football.

Methods

Four youth female football teams with players aged 12–16 years were randomised into an intervention group and control group. The intervention was a 15-min neuromuscular warm-up programme carried out twice a week during the 11-week study period. Baseline and follow-up measurements of performance were made indoors and included the star excursion balance test, a countermovement jump test, a triple-hop for distance test, a modified Illinois agility test, and 10- and 20-m sprint tests.

Results

Fifty-two players (intervention 28; control 24) took part in baseline measurements, and after dropout, 41 players (intervention 23; control 18) were included for analysis. Minor positive changes were seen in the control group compared to the intervention group for a sub-score of the star excursion balance test (P < 0.05) and in the modified Illinois agility test (P < 0.05). No improvement was seen in the intervention group from baseline to follow-up.

Conclusions

The study showed that a neuromuscular warm-up programme carried out during 11 weeks did not improve performance in youth female football. This could indicate that the programme does not contain sufficient stimulus to improve performance. A low player attendance at training sessions, and low specificity between exercises in the warm-up programme and the evaluated performance tests may also contribute to the lack of effect.

Level of evidence

I.     

Use of rating of perceived exertion for determining plyometric exercises intensity in physically active men

The purpose of this study was to use rating of perceived exertion (RPE) scale to evaluate popular bilateral plyometric exercise intensities. Fourteen physically active men (age 20.64 ± 1.4 years; height 176.93 ± 6.83 cm; weight 75.28 ± 11.1 kg) volunteered to participate in this study and performed a set of ten repetitions plyometric exercises to depth jump from 35 cm box, 35 cm box jump, depth jump from 60 cm box, 60 cm box jump, pike jump, tuck jump, and squat jump in a session with 5-min rest in between exercises. RPE was measured following the completion of each exercise using 0–10 Borg RPE scale. Data were analyzed using repeated measures ANOVA and the level of significant was set at p <0.05. The results indicated that squat jump was harder than other types of bilateral plyometric exercises such as 35 cm box jump, depth jump from 35 cm box, and tuck jump (p < 0.05). Moreover, the 35 cm box jump was easier than other plyometric exercises (p < 0.05). With regard to the results of this investigation, it can be recommended that athletes and strength and conditioning professionals use these findings to design plyometric training in their training schedule and keep in their mind that plyometric exercises have different intensities, however, the total volume was matched.     

Relationships between swimming style and dry-land strength in breaststroke

In breaststroke, at each arm action corresponds one leg kick; therefore, compared to the other strokes (front crawl, backstroke and butterfly), the contribution of the lower limbs is more important. However, it can be observed that the same distance can be covered at similar velocities with different stroke length (SL) and, as a consequence, stroke rate (SR). Hence, it seems that breaststroke swimmers can use different styles to achieve their goals. Therefore, the assessment of upper and lower limbs strength becomes very important along with the style being used during breaststroke performance. Twenty-four male and twenty female national-level breaststroke swimmers were divided in two groups for each gender, according to their SR (low-SR and high-SR). They performed 100 m breaststroke all-out performance in a 50 m swimming pool. SR, SL and velocity (v) were measured. To assess upper and lower limbs strength, swimmers underwent dry-land chin-up and jump & reach tests. Dry-land tests did not correlate to v (p > 0.05). SL inversely correlated to chin-up and directly correlated to jump & reach (p < 0.01). Regardless to the gender, low-SR had lower chin-up results than high-SR (males 0.19 ± 0.03 vs. 0.24 ± 0.04 nr kg^?1, p < 0.01; females 0.13 ± 0.02 vs. 0.15 ± 0.03 nr kg^?1, p < 0.05) and jumped higher than high-SR (males 31.74 ± 0.50 vs. 25.11 ± 0.55 % height, p < 0.001; females 22.93 ± 0.33 vs. 20.54 ± 0.63 % height, p < 0.01) swimmers. Despite many factors are involved in determining swimming performance, upper and lower limbs strength seems to be linked to a different breaststroke style in our group of swimmers.     

Multimodal approach towards understanding the changes in the autonomic nervous system induced by an ultramarathon

ABSTRACT

Purpose: Running an ultramarathon can be considered as a multifaceted, intense stressor inducing changes within the autonomic nervous system (ANS). The aim of this study was to examine changes within and across ANS modalities in response to an ultramarathon.

Methods: Thirteen runners (44.3 ± 5.9 years) completed a 65 km run. Electrodermal activity (EDA), heart rate (HR), and skin temperature measured at wrist (Temp), were recorded before and after running. Three-minute intervals were analysed. Mean values were compared by t-tests for dependent samples. Joint principal component analysis-canonical correlation analysis (PCA-CCA) and multiset CCA techniques were employed to measure the interactions between either any two or among all modalities.

Results: HR (p < 0.01) and EDA (p < 0.01) increased, while Temp decreased (p < 0.01). PCA-CCA revealed one significant component (p < 0.05) for each modality pair in pre and post measures. Component strength increased from pre (mean = 0.73) to post (mean = 0.92) test. Multiset CCA supported the assumption of increasing strength of correlations across modalities.

Conclusion: Ultramarathon, an intense physical stressor, increases correlations across modalities pointing towards a reorganization of central ANS control to restore dynamic balance after physical load. This characterization of ANS-states might offer new avenues for training control.     

Diurnal variation in long- and short-duration exercise performance and mood states in boys

The aim of the present study was to investigate the effect of time-of-day on long- and short-duration exercise performance and mood states. Twelve prepubertal boys (age 10.7 ± 0.4 years; height 1.47 ± 0.6 m; body-mass 44.8 ± 3.1 kg) performed three test sessions at 08:00, 14:00 and 18:00 h. During each session, they performed the squat jump (SJ), the countermovement jump (CMJ) and the Yo–Yo test. Oral temperature was recorded at the beginning of each test session. Moreover, boys completed the profile of mood states questionnaire before performing the physical tests. The results showed that SJ (p < 0.05), CMJ (p < 0.01) and oral temperature (p < 0.001) were higher at 14:00 and 18:00 h compared to 08:00 h. Maximal aerobic velocity during the Yo–Yo test was higher only at 18:00 h than 08:00 h (p < 0.05). However, mood states were not significantly different between 08:00, 14:00 and 18:00 h. Likewise, we did not observe significant correlations between mood states and physical performances. In conclusion, in boys, both long- and short-duration exercises, performances were better in the afternoon than the morning.     

Caffeine increases strength and power performance in resistance-trained females during early follicular phase

The effects of 4 mg·kg⁻¹caffeine ingestion on strength and power were investigated for the first time, in resistance-trained females during the early follicular phase utilizing a randomized, double-blind, placebo-controlled, crossover design. Fifteen females (29.8 ± 4.0 years, 63.8 ± 5.5 kg [mean ± SD]) ingested caffeine or placebo 60 minutes before completing a test battery separated by 72 hours. One-repetition maximum (1RM), repetitions to failure (RTF) at 60% of 1RM, was assessed in the squat and bench press. Maximal voluntary contraction torque (MVC) and rate of force development (RFD) were measured during isometric knee extensions, while utilizing interpolated twitch technique to measure voluntary muscle activation. Maximal power and jump height were assessed during countermovement jumps (CMJ). Caffeine metabolites were measured in plasma. Adverse effects were registered after each trial. Caffeine significantly improved squat (4.5 ± 1.9%, effect size [ES]: 0.25) and bench press 1RM (3.3 ± 1.4%, ES: 0.20), and squat (15.9 ± 17.9%, ES: 0.31) and bench press RTF (9.8 ± 13.6%, ES: 0.31), compared to placebo. MVC torque (4.6 ± 7.3%, ES: 0.26), CMJ height (7.6 ± 4.0%, ES: 0.50), and power (3.8 ± 2.2%, ES: 0.24) were also significantly increased with caffeine. There were no differences in RFD or muscle activation. Plasma [caffeine] was significantly increased throughout the protocol, and mild side effects of caffeine were experienced by only 3 participants. This study demonstrated that 4 mg·kg⁻¹ caffeine ingestion enhanced maximal strength, power, and muscular endurance in resistance-trained and caffeine-habituated females during the early follicular phase, with few adverse effects. Female strength and power athletes may consider using this dose pre-competition and -training as an effective ergogenic aid.     

The relationship between talent identification testing parameters and performance in elite junior swimmers

Objectives

In elite age-group swimming it is unclear to what degree common assessments of anthropometric, jump performance and front-crawl critical speed (CS) correlate with competition performance.

The influence of youth soccer players’ sprint performance on the different sided games’ external load using GPS devices

ABSTRACT

The aims of this study are 1) to compare sided games’ (SGs) external responses encountered by players according to pitch size and to 2) examine the relationships between sprint performance and SGs’ external physical responses. Twenty soccer players under 15 years of age (U-15) participated in this study. Each player performed a sprinting test (10 m and 30 m sprints) and played a SG on two different pitch sizes (small at 100 [SSG] and large at 200 [LSG] m² per player). Higher external responses (p < 0.01, ES = ?6.41–1.22) were found in LSG in comparison to SSG, except to distance accelerating and decelerating (p > 0.05, ES = ?0.26–0.27). Players who were faster over 10 and 30 m covered higher distances cruising and sprinting (r = ?0.47/-0.66; ± 0.23/± 0.30, respectively, p < 0.05), performed a greater number of sprints, achieved higher maximum velocity (Vel_max) during LSG and covered a greater distance at high-intensity accelerating (r = ?0.50/-0.70; ±0.21/±0.29, respectively, p < 0.05) during both SG. LSG demanded a higher external load in comparison with SSG. In addition, the improved sprint capacity could allow players to perform greater running activities and short-term actions at high-intensities during SG.