Validity and Usability of a New System for Measuring and Monitoring Variations in Vertical Jump Performance

Correlation Between Propulsive Velocity, Maximum Velocity, and Power and the 2D:4D Ratio in Paralympic Powerlifting Athletes

Background: Among the strength sports we have Paralympic powerlifting, and the factors that influence strength have been investigated; among them is the relationship between strength and the ratio of the size of the second and fourth fingers of the hand (2D:4D). Objectives: The study is aimed at evaluating the relationship between the 2D:4D finger length ratio and the dynamic strength indicators, mean propulsive velocity (MPV), maximum velocity (Vmax), and power, with loads of 45% and 80% of one repetition maximum (1RM), in Paralympic powerlifting. Methodology: Sixteen elite Paralympic powerlifting athletes were evaluated for dynamic strength indicators, MPV, Vmax, and power, with loads of 45% and 80% 1RM. The 2D:4D proportions and correlations between the indicators were evaluated of 2D:2D ratios and dynamic strength indicators. Results: Moderate correlations were found between MPV 45% and 4D (r = 0.551, p = 0.027), between MPV 45% and R-L 2D:4D diff. (r = -0.595, p = 0.015), between power 80% and L2 (r = 0.542, p = 0.030), and between MPV 45% and R-L 2D:4D (r = -0.585, p = 0.017). There was also a moderate correlation between power 80% left 2D (r = -0.542, p = 0.030). However, no correlation was found between the 2D:4D ratios and dynamic strength indicators in Paralympic powerlifting. Conclusion: The 2D:4D ratio presents a moderate correlation with dynamic strength indicators in Paralympic powerlifting athletes, where the ratios with the velocity of 45 of 1RM can be used as a predictor but with caution.

Comparison between Warm-Up Protocols in Post-Activation Potentiation Enhancement (PAPE) of Sprint and Vertical Jump Performance in a Female Futsal Team

The aim of this study was to examine the influence of three warm-up protocols, with and without post-activation performance enhancement (PAPE), on sprint and vertical jump performance in female athletes. Twenty-five university futsal athletes were randomly assigned to three protocols: i) Traditional Warm-Up (TWU), involving cardiovascular, coordination exercises, and dynamic stretching; ii) Drop Jump Warm-Up (DJWU), consisting of drop jumps from heights of 30 and 40 cm; and iii) Maximum Isometric Warm-Up (MIWU), with high-intensity isometric contractions held for 10 seconds in a squat position at approximately 130-135 degrees of knee flexion. Tests included the countermovement vertical jump (CMVJ) and a 20-meter sprint (S20). The CMVJ showed a significant increase across all three groups (F(1,72) = 125.312; p < .0001; ηp2 = 0.635), while S20 displayed a significant time reduction only for MIWU (p = .002). Although no significant differences were found between groups, individual analysis revealed significant CMVJ differences for TWU, DJWU, and MIWU (p < .0001). We conclude that PAPE effectiveness varies according to protocol and individual athlete characteristics; however, maximum isometric exercises appear to have a more pronounced effect on PAPE production in sprint performance.

Effects of weighing phase duration on vertical force-time analyses and repeatability

Force plate analyses of various activities sometimes require the average (WPav) and standard deviation (WPsd) of force across the Weighing Phase (i.e., quiet period) to calculate kinetic, temporal and kinematic metrics. Yet, the influence of weighing phase duration on these analyses has been scarcely investigated. This study investigated the effects of weighing phase duration on the agreement between vertical force-time variables and the repeatability of WPav and WPsd. Durations of 0.5, 1.0 and 1.5 s were compared to 2.0 s. Limits of agreement (LOA) for system weight, onset threshold, onset time, net impulse, take-off velocity and take-off displacement were calculated for 137 counter-movement, squat and single leg jumps. Repeatability coefficients for WPav and WPsd estimated the consistency between repeated trials. Shorter weighing phase durations produced small differences in WPav (LOA < ±0.25%), which accumulated during integration, affecting net impulse, take-off velocity (LOA ±2%) and take-off displacement (LOA ±23%). Differences were substantial using 5xWPsd as the onset threshold (LOA approximately ±25% to ±72%), consequently influencing onset time (LOA approximately ±6% to ±18%). WPav repeatability was high but the within-trial differences could augment with integration, requiring weighing phases longer than 2 s. WPsd had poor repeatability and its use requires further investigation.

Concurrent Validity and Reliability of a Free Smartphone Application for Evaluation of Jump Height

Background/Objectives: Jump test assessment is commonly used for physical tests, with different type of devices used for its evaluation. The purpose of the present study was to examine the validity and reliability of a freely accessible mobile application (VertVision, version 2.0.5) for measuring jump performance. Methods: With that intent, thirty-eight college age recreationally active subjects underwent test assessment after a specific warm-up, performing countermovement jumps (CMJs) and squat jumps (SJs) on a contact platform while being recorded with a smartphone camera. Jump height was the criterion variable, with the same formula being used for both methods. Data analysis was performed by two experienced observers. Results: The results showed strong correlations with the contact platform (ICC > 0.9) for both jumps. Furthermore, between-observer reliability was also high (ICC > 0.9; CV ≤ 2.19), with lower values for smallest worthwhile change (≤0.23) and typical error of measurement (≤0.14). Estimation error varied when accounting for both observers, with the SJ accounting for bigger differences (4.1-6.03%), when compared to the CMJ (0.73-3.09%). Conclusions: The study suggests that VertVision is a suitable and handy method for evaluating jump performance. However, it presents a slight estimation error when compared to the contact platform.

Effects of Inertial Flywheel Training vs. Accentuated Eccentric Loading Training on Strength, Power, and Speed in Well-Trained Male College Sprinters

This study aimed to evaluate and compare the effects of inertial flywheel training and accentuated eccentric loading training on the neuromuscular performance of well-trained male college sprinters. Fourteen sprinters were recruited and randomly assigned to either the flywheel training (FWT, n = 7) group or the accentuated eccentric loading training (AELT, n = 7) group. The FWT group completed four sets of 2 + 7 repetitions of flywheel squats, whereas the AELT group performed four sets of seven repetitions of barbell squats (concentric/eccentric: 80%/120% 1RM). Both groups underwent an eight-week squat training program, with two sessions per week. A two-way repeated ANOVA analysis was used to find differences between the two groups and between the two testing times (pre-test vs. post-test). The results indicated significant improvements in all measured variables for the FWT group: 1RM (5.0%, ES = 1.28), CMJ (13.3%, ES = 5.42), SJ (6.0%, ES = 2.94), EUR (6.5%, ES = 4.42), SLJ (2.9%, ES = 1.77), and 30 m sprint (-3.4%, ES = -2.80); and for the AELT group: 1RM (6.3%, ES = 2.53), CMJ (7.4%, ES = 3.44), SJ (6.4%, ES = 2.21), SLJ (2.2%, ES = 1.20), and 30 m sprint (-3.0%, ES = -1.84), with the exception of EUR (0.9%, ES = 0.63, p = 0.134), showing no significant difference. In addition, no significant interaction effects between group and time were observed for 1RM back squat, SJ, SLJ, and 30 m sprint (p > 0.05). Conversely, a significant interaction effect between group and time was observed for both CMJ and EUR (p < 0.001); post hoc analysis revealed that the improvements in CMJ and EUR were significantly greater in the FWT group compared to the AELT group (p < 0.001). These findings indicate that both FWT and AELT are effective at enhancing lower-body strength, power, and speed in well-trained male college sprinters, with FWT being particularly more effective in promoting elastic energy storage and the full utilization of the stretch-shortening cycle.

Concurrent validity of countermovement and squat jump height assessed with a contact mat and force platform in professional soccer players

Purpose

The aim of this study was to assess the concurrent validity of a contact mat against force plates to measure jump height in countermovement jump (CMJ) and squat jump (SJ) in professional soccer players.

Methods

23 male professional soccer players performed the CMJ and SJ, which were concurrently recorded using a portable contact mat (SmartJump) and a portable dual force plate system (ForceDecks). Equivalence testing between both systems (contact mat vs. force plate) and the two methods (impulse-momentum vs. flight-time and flight-time vs. flight-time) was performed compared to equivalence bounds of ±1.1 cm for the CMJ and ±1.6 cm for the SJ. Additionally, 95% Limits of Agreement (LoA) and intraclass correlation coefficients (ICC) were computed.

Results

Mean differences for the impulse-momentum vs. flight-time comparison for CMJ [3.2 cm, 95% CI (2.3-4.1)] and SJ [2.7 cm, (1.8-3.6)] were non-equivalent between both systems. LoA were larger than the equivalence bunds for CMJ and SJ, while ICCs were good [CMJ, 0.89, (0.76-0.95)] and excellent [SJ, 0.91, (0.79-0.96)]. As for the flight-time vs. flight-time comparison, mean differences were non-equivalent for the CMJ [1.0 cm (0.8 to 1.2 cm)] and equivalent for the SJ [0.9 cm (0.7-1.1 cm)]. LoA were narrower than the equivalence bounds for CMJ and SJ, while ICCs were excellent [CMJ, 0.995, 95% CI (0.989-0.998); SJ, 0.997, 95% CI (0.993-0.997)].

Conclusion

Our findings indicate that the SmartJump contact mat cannot be used interchangeably with the ForceDecks force platform to measure jump height for the CMJ and SJ.

Monitoring Bar Velocity to Quantify Fatigue in Resistance Training

We analyzed the effects of load magnitude and bar velocity variables on sensitivity to fatigue. Seventeen resistance-trained men (age=25.7±4.9 years; height=177.0±7.2 cm; body mass=77.7±12.3 kg; back-squat 1RM=145.0±33.9 kg; 1RM/body mass=1.86) participated in the study. Pre- and post-exercise changes in the mean propulsive velocity (MPV) and peak velocity (PV) in the back-squat at different intensities were compared with variations in the countermovement jump (CMJ). CMJ height decreased significantly from pre- to post-exercise (∆%=-7.5 to -10.4; p<0.01; ES=0.37 to 0.60). Bar velocity (MPV and PV) decreased across all loads (∆%=-4.0 to -12.5; p<0.01; ES=0.32 to 0.66). The decrease in performance was similar between the CMJ, MPV (40% and 80% 1RM; p=1.00), and PV (80% 1RM; p=1.00). The magnitude of reduction in CMJ performance was greater than MPV (60% 1RM; p=0.05) and PV (40% and 60% 1RM; p<0.01) at the post-exercise moment. Low systematic bias and acceptable levels of agreement were only found between CMJ and MPV at 40% and 80% 1RM (bias=0.35 to 1.59; ICC=0.51 to 0.71; CV=5.1% to 8.5%). These findings suggest that the back-squat at 40% or 80% 1RM using MPV provides optimal sensitivity to monitor fatigue through changes in bar velocity.

Effects of Ischemic Preconditioning on Sport-Specific Performance in Highly Trained Taekwondo Athletes

Ischemic preconditioning (IPC), which involves episodes of blood flow restriction followed by reperfusion, has uncertain effects on athletes. Additionally, employing sports-specific tests that are highly familiar to athletes can enhance methodological rigor in determining IPC's effects on taekwondo performance. This study aimed to investigate IPC's influence on taekwondo athletes' performance through two studies. To induce occlusion in both studies, the cuff was inflated to an individualized occlusion pressure established for each athlete's lower limb, with four cycles of occlusion lasting five minutes each, alternated with five-minute reperfusion intervals. Both traditional frequentist statistics and Bayesian analysis were employed. In the first study, eleven high-level athletes were subjected to either IPC or a placebo (SHAM) procedure on both legs, followed by performing countermovement jumps (CMJs) and a specific taekwondo endurance test. However, no significant differences were observed in taekwondo endurance performance or CMJ between the IPC and SHAM conditions. The second study involved fourteen elite athletes who underwent the same IPC or SHAM conditions, performing CMJ and three bouts of the Multiple Frequency Speed of Kick test (FSKTmult) in three blocks, each separated by approximately thirty minutes. Again, the results indicated no significant differences in FSKTmult measures or CMJ performance between the two conditions. In conclusion, IPC did not significantly affect neuromuscular (in both studies), endurance (in the first study), or anaerobic (in the second study) performance in these taekwondo athletes.

The acute effects of brace use on lower extremity performance in individuals with adolescent idiopathic scoliosis

BACKGROUND

Braces have been a popular treatment option for scoliosis among healthcare professionals for many years. However, the effect of braces on scoliosis treatment remains a subject of ongoing debate and research.

AIMS

Our study aimed to evaluate the effects of wearing a spinal brace on vertical jump, postural control, reach distance, and fall risk in patients with Adolescent Idiopathic Scoliosis (AIS).

METHODS

We included 33 patients with AIS aged between 10 to 18 years old in our cross-sectional study. Patients were randomly subjected to vertical jump test, standing long jump test, timed up and go test, postural control, and forward reach test, while wearing and not wearing the scoliosis brace, respectively.

RESULTS

Our findings revealed that patients wearing scoliosis braces had significantly lower vertical jumps (p = .001), standing long jumps (p < .001), and forward reach distances with their dominant (p = .002) and non-dominant limbs (p = .007) compared to those who did not wear the brace. However, there was no significant difference in postural control and timed up and go test between the two groups (p > .05).

CONCLUSIONS

Our study suggests that wearing a scoliosis brace may negatively affect an individual's vertical and standing long jumps, and forward reach distances. However, wearing or not wearing the brace had no significant effect on postural control and timed stand-up test. Long-term follow-up studies are needed to evaluate the overall effectiveness of scoliosis braces in treating AIS.

Using Physiological Laboratory Tests and Neuromuscular Functions to Predict Extreme Ultratriathlon Performance

Purpose: This study aims to investigate the relationship between split disciplines and overall extreme ultra-triathlon (EUT) performance and verify the relationship among physiological and neuromuscular measurements with both fractional and total EUT performance while checking which variables could predict partial and overall EUT race time. Methods: Eleven volunteers (37 ± 6 years; 176.9 ± 6.1 cm; 77.9 ± 10.9 kg) performed two maximal graded tests (cycling and running) for physiological measurements and muscle strength/power tests to assess neuromuscular functions. Results: The correlation of swimming split times to predict overall EUT race times was lower than for cycling and running split times (r2 = 0.005; p > .05; r2 = 0.949; p < .001 and r2 = 0.925; p < .001, respectively). VO2peak obtained during running test (VO2peakrun) and VT power output assessed during cycling test (VTPO) were the highest predictors of cycling performance (r2 = 0.92; p = .017), whereas VO2peakrun and peakpower output in the cycling test (PPO) were the highest predictors of running performance (r2 = 0.94; p = .008). Conclusion: VO2peakrun and VTPO, associated to jump height assessed during countermovement jump (CMJ) test were the highest correlated variables to predict total EUT performance (r2 = 0.99; p = .007). In practical terms, coaches should include the assessment of VO2peakrun, VTPO, and CMJ to evaluate the athletes' status and monitor their performance throughout the season. Future studies should test how the improvement of these variables would affect EUT performance during official races.

Analysis of the accuracy and reliability of vertical jump evaluation using a low-cost acquisition system

BACKGROUND

The vertical jump can be analyzed based on the flight time achieved by the individual. This measurement can be obtained using a force platform or a three-dimensional infrared camera system, but such equipment is expensive and requires training for data collection and processing. Thus, this study aimed to evaluate the accuracy and reliability of using a smartphone and the Kinovea software compared with a force platform as a method of vertical jump analysis.

METHODS

For this purpose, two independent evaluators analyzed videos of bipodal and unipodal vertical jumps by counting the variables among participants. The participants performed three consecutive jumps in bipodal and unipodal conditions with the dominant and non-dominant legs.

RESULTS

The intra-rater analysis for bipodal jumps was found to have excellent reproducibility (ICC = 0.903 to 0.934), whereas for unipodal jumps, the reproducibility was moderate to excellent (ICC = 0.713 to 0.902). The inter-rater analysis showed that for bipodal jumps, the reproducibility is substantial to excellent (ICC = 0.823 to 0.926), while for unipodal jumps, it is moderate (ICC = 0.554 to 0.702).

CONCLUSIONS

Therefore, it can be concluded that the vertical jump evaluation can be performed using the smartphone-Kinovea system. However, the same evaluator should carry out the evaluation to maintain reliable indices.

Sprint and Jump Training on Sand vs. Grass Surfaces: Effects on the Physical Performance of Young Soccer Players

ABSTRACT

Pereira, LA, Freitas, TT, Zabaloy, S, Ferreira, RCA, Silva, ML, Azevedo, PHSM, and Loturco, I. Sprint and jump training on sand versus grass surfaces: effects on the physical performance of young soccer players. J Strength Cond Res 37(9): 1828-1833, 2023-The aims of this study were to (a) examine the effects of a 6-week sand training program including both sprint and jump exercises on the speed-related and vertical jump performance of elite young soccer players and (b) compare the changes induced by a sand training scheme with those induced by a similar training program (in volume, intensity, and exercise types) performed on grass. Twenty-four under-20 soccer players were randomly allocated to 2 training groups, as follows: "sand" ( n = 12) or "grass" ( n = 12) groups. Athletes performed squat and countermovement jumps, linear sprints, and Zigzag change-of-direction speed tests at pre-, mid- (after 6 training sessions), and postintervention (after 12 training sessions). Both groups exhibited similar increases in the vertical jump and Zigzag performance after the 6-week training period ( p values ranging from 0.0001 to 0.025; effect size ranging from 1.05 to 3.78, for main effect of time). No significant changes were detected for the linear sprint velocity for both the groups ( p values ranging from 0.079 to 1.00; effect size ranging from 0.07 to 0.65, for main effect of time). In summary, training on sand or grass surfaces resulted in similar improvements in the physical performance of elite young soccer players. This study confirms the current evidence on the effectiveness of both soft and harder training surfaces in improving the sprint and jump performance of team-sport athletes.

The profiles of single leg countermovement jump kinetics and sprinting in female soccer athletes

The purposes were to evaluate kinetics in lower limbs using single leg countermovement jump (SLCMJ) and to identify the differences in SLCMJ kinetics between sprinting fast players and sprinting slow players in elite university female soccer players. Seventeen participants at the national tournament level completed the survey. SLCMJ and 30 m sprinting tests were performed. A force-plate was used to collect the data of the SLCMJ test. Significant differences of concentric maximum rate of force development (RFD), concentric RFD, concentric RFD/body weight (BW), peak net takeoff force/BW, peak power, and peak power/BW existed between both legs during the SLCMJ among all the participants. For further analysis, the participants were divided into fast group and slow group based on sprinting performance. Significant differences existed between the two groups in concentric peak velocity (nondominant, p = 0.028) and vertical velocity at takeoff (nondominant, p = 0.021). Concentric maximum RFD (p = 0.036) was significantly different between both legs in the slow group. Among elite university female soccer players, the players who presented more increased asymmetry of kinetic characteristics of jumping, also showed weak sprinting performance. Moreover, the players presented the best performance in velocity of the jumping variables and also had the best sprinting performance. Coaches and players should focus on keeping inter-limb balance and developing jumping velocity to improve sports performance. In future, the cause-and-effect relationship between jumping and sprinting should be identified.

Association among inflammaging, body composition, physical activity, and physical function tests in physically active women

BACKGROUND

Inflammaging is a phenomenon that has been associated with the development and progression of sarcopenia and frailty syndrome. According to the literature, on the one side, the increase in body fat is associated with a systemic pro-inflammatory status, which consequently favors inflammaging, and on the other side, the regular practice of physical exercise can mitigate the development of this scenario. Therefore, here, we aimed to evaluate the association between inflammaging and physical factors, both body and functional, in a group of physically active older women.

METHODS

Seventy older women (mean age 72.66 ± 6.17 years) participated in this observational cross-sectional and were separated into the eutrophic, overweight, and obese groups. It was assessed: by bioimpedance-body fat percentage (Fat%) and total (Fat kg), skeletal muscle mass (muscle), and free fat mass both in percentage (FFM%) and total (FFMkg); by the International Physical Activity Questionnaire (IPAQ)-the time of moderate-intensity physical activity per week; by physical tests-handgrip (HG), sit-up-stand-on-the-chair in 5 repetitions (Sit-up) and vertical squat jump test (SJ); in addition to the determination of serum cytokine concentration (IL-6, TNF-α, IL-10, and IL-8), and also body mass index (BMI) and calf circumference (Calf).

RESULTS

Higher FFM% and lower body fat (both kg and %) were found in the eutrophic group than in the other groups. The eutrophic group also performed more weekly physical activity, jumped higher, and presented not only higher serum IL-6 concentration but also an increased ratio of IL-10/IL-6, IL-10/TNF-α, IL-10/IL-8 as compared to the values found in the overweight group. The obese group presented higher body fat (kg and %) and lower FFM% than the other groups and also higher serum IL-6 concentration than the overweight group. Interestingly, several significant negative and positive correlations between body composition, physical tests, and serum cytokine concentrations were found in the eutrophic and obese groups.

CONCLUSION

While the eutrophic older women group showed a remarkable regulation of the systemic inflammatory status with positive associations in the physical parameters assessed, the overweight and obese groups presented impairment regulations of the inflammaging, which could be related to less weekly physical activity and higher body fat.

The validity and reliability of counter movement jump height measured with the Polar Vantage V2 sports watch

The purpose of the present study was to assess the validity and reliability of the jump height measured by the Polar Vantage V2 sports watch in comparison to a gold-standard force plate measurement. Fifteen healthy adults, seven female, age 20-42 years participated in the study and performed six sets of three CMJs, on two consecutive days. The participants wore the Polar Vantage V2 sports watch (Polar Electro Oy, Kempele, Finland) whilst performing the jumps on two force plates (AMTI, Watertown, Massachusetts, United States). Jump height was on the one hand extracted directly from the watch ("leg recovery test") and on the other hand calculated by the flight time method with the force plate data. To assess validity, we calculated the mean absolute error, constructed Bland-Altman plots and applied an ordinary least squares regression analysis. To test for left-to-right and day-to-day reliability, we calculated Pearson and intraclass correlations. We found a mean error of ≈5% and a high correlation (r = 0.96; p < 0.001) for the jump height measured by the Polar Vantage V2 sports watch compared to the force plate measurement. The Bland-Altmann plot together with the ordinary least squares regression analysis showed no systematic bias between the methods with a minimal difference at a jump height of 30 cm. For reliability of left-to-right and day-to-day measurements, we found high Pearson and ICC correlations and no indications for systematic bias by Bland-Altmann analysis. The present study has demonstrated that the "leg recovery test" of the Polar Vantage V2 sports watch provide a valid and reliable measurement of the mean vertical jump height of three consecutive CMJs. For the first time the jump height of a CMJ can be measured solely by a sports watch without the need to attach additional sensors or measurement devices. Thus, the "leg recovery test" is an easy to administer, valid and reliable test, that can be used in future studies to measure CMJ-height in the field when lab-based assessments are unavailable or inconvenient. This opens new avenues for cross-sectional and longitudinal assessments of neuromuscular power of the lower extremities in a large number of participants.

Reliability of My Jump 2 Derived from Crouching and Standing Observation Heights

The crouching or prone-on-the-ground observation heights suggested by the My Jump app are not practical in some settings, so users usually hold smartphones in a standing posture. This study aimed to analyze the reliability of My Jump 2 from the standardized and standing positions. Two identical smartphones recorded 195 countermovement jump executions from 39 active adult athletes at heights 30 and 90 cm, which were randomly assessed by three experienced observers. The between-observer reliability was high for both observation heights separately (ICC~0.99; SEM~0.6 cm; CV~1.3%) with low systematic (0.1 cm) and random (±1.7 cm) errors. The within-observer reliability for the three observers comparing the standardized and standing positions was high (ICC~0.99; SEM~0.7 cm; CV~1.4%), showing errors of 0.3 ± 1.9 cm. Observer 2 was the least accurate out of the three, although reliability remained similar to the levels of agreement found in the literature. The reliability of the mean observations in each height also revealed high reliability (ICC = 0.993; SEM = 0.51 cm; CV = 1.05%, error 0.32 ± 1.4 cm). Therefore, the reliability in the standing position did not change with respect to the standardized position, so it can be regarded as an alternative method to using My Jump 2 with practical added benefits.

Differences in Strength, Speed, and Power Performance Between Visually Impaired Paralympic and Olympic Sprinters

PURPOSE

To compare the strength, speed, and power performance of elite sprinters with and without visual impairment.

METHODS

Twelve elite able-bodied sprinters and 15 Paralympic sprinters with visual impairment took part in this study. Sprinters from both groups performed the following tests: squat and countermovement jumps, maximum bar-power output in the half-squat and jump-squat exercises, and 60-m sprint. The differences between groups in all variables examined were analyzed using the independent t test.

RESULTS

Olympic sprinters revealed better performances in all tests when compared with Paralympic sprinters with visual impairment (effect sizes ranging from 1.29 to 9.04; P < .001). Differences of ∼32% and ∼20% were found for the half-squat and loaded and unloaded vertical jumps, respectively. Smaller differences (from ∼8% to ∼11%) were obtained in linear sprint performance.

CONCLUSIONS

Between-groups differences peaked at low-velocity exercises (eg, ∼32% in the half-squat) and decreased as movement velocity and specificity increased (eg, ∼8% at 60-m sprint). Thus, the greatest differences between Olympic and Paralympic sprinters seem to be related to their ability to apply force at low movement velocities. Coaches are encouraged to work on all sprinting phases and across the entire force-velocity spectrum, bearing in mind that improvements in strength capacity will possibly lead to increased sprint performance in Paralympic sprinters with visual impairment, especially in the acceleration phase of sprinting.

Variations in Internal and External Training Load Measures and Neuromuscular Performance of Professional Soccer Players During a Preseason Training Period

We described the internal and external training loads (TLs) experienced by soccer players over a 4-week preseason, examined their effects on vertical jump (VJ) performance, and investigated the relationships between different TL variables. Eighteen professional soccer players performed 17 training sessions and 1 friendly-match (FM) over the preseason. The internal TL was obtained using the session-rating of perceived exertion method. The external TL variables collected were total and high-intensity distances, body-load, and high-metabolic power distance via the GPS system. VJ performance was assessed 13 times throughout the study. Moreover, total quality recovery and delayed onset muscle soreness were assessed before every training session as a measure of recovery status. Players were divided, using a median split analysis, into two groups, according to their VJ performance (i.e., “lower” and “higher” VJ). External TL variables displayed similar variations across training sessions and were significantly interrelated (r ranging from 0.48 to 0.88). In periods where higher internal TLs were detected, impaired recovery status was noticed. Notably, the higher VJ group exhibited decreased jump performance at post-test and higher internal and external TLs across the entire preseason (compared to the lower VJ group). From our results it is suggested that professional soccer players with higher VJ performance are potentially more susceptible to concurrent training effects.

Pre-season in soccer: a paradox between a high volume of technical/tactical training and improvement in the neuromuscular performance of elite women soccer players

BACKGROUND

there is a paradox between the development of strength-power abilities and the high volume of technical/tactical training in elite soccer players during the pre-season. This concurrent effect between aerobic and neuromuscular training regimes induce impairment in power performance.

METHODS

this study aimed to investigate the effect of an equalized program of strength-power training (4-5 sessions/week) and soccer training (4-6 sessions/week) in power and aerobic performance during 8-weeks of pre-season in elite women soccer players. Vertical jumps [squat jump (SJ); countermovement jump (CMJ)] and Yo-Yo intermittent recovery level 1 test (YOYO-R1) were assessed pre- and post pre-season. A paired sample t-test was used to compare differences between pre and post pre-season (Δ%). The level of significance was established at p ≤ 0.05.

RESULTS

the women soccer players improved the SJ (p<0.001; Δ%=12), CMJ (p<0.001; Δ%=8.5), and YOYO-R1 (p<0.001; Δ% =28.5). There was a body recomposition observed, lower body fat (p = 0.004; Δ%=15), higher fat free mass (p = 0.001; Δ%=5).

CONCLUSIONS

our results demonstrated that it is possible to develop aerobic and power abilities of elite women soccer players during pre-season using an equalized ratio of soccer training and strength-power training schedules.

A Novel Approach for Athlete Profiling: The Unilateral Dynamic Strength Index

ABSTRACT

Bishop, C, Read, P, Lake, J, Loturco, I, and Turner, A. A novel approach for athlete profiling: The unilateral dynamic strength index. J Strength Cond Res 35(4): 1023-1029, 2021-The Dynamic Strength Index (DSI) provides a ratio of the peak force an athlete can produce in both isometric and ballistic tasks. Although the DSI measured during bilateral tests has been examined, unilateral DSI scores have not been reported to date and thus was the aim of the present study. Twenty-eight recreational sport athletes performed 3 trials of a unilateral isometric squat and countermovement jump (CMJ) to measure peak force in each task across 2 separate test sessions. The unilateral DSI was calculated using both left vs. right and dominant vs. nondominant limbs. Good to excellent reliability was shown in the isometric squat (intraclass correlation coefficient [ICC] = 0.86-0.96; coefficient of variation [CV] ≤ 5.7%) and the CMJ (ICC = 0.83-0.93; CV ≤ 5.8%) on both limbs. The DSI showed moderate to good reliability (ICC = 0.71-0.79; CV = 7.54-11.9%). Dynamic Strength Index scores of 0.52-0.55 and 0.55-0.59 were reported on the left and right limbs, respectively, with no significant differences reported between limbs. A significant difference (p = 0.04) was seen for the CMJ between left and right during the second test session only. The dominant and nondominant limbs reported mean DSI scores of 0.53-0.57, and significant differences were evident between limbs in both the isometric squat and CMJ (p < 0.01). This study provides normative data for the unilateral DSI and indicates acceptable levels of reliability, whereas the consistency of individual measures of peak force can be considered good when quantified unilaterally.

Reliability and Validity of the Polar V800 Sports Watch for Estimating Vertical Jump Height

This study aimed to assess the reliability and validity of the Polar V800 to measure vertical jump height. Twenty-two physically active healthy men (age: 22.89 ± 4.23 years; body mass: 70.74 ± 8.04 kg; height: 1.74 ± 0.76 m) were recruited for the study. The reliability was evaluated by comparing measurements acquired by the Polar V800 in two identical testing sessions one week apart. Validity was assessed by comparing measurements simultaneously obtained using a force platform (gold standard), high-speed camera and the Polar V800 during squat jump (SJ) and countermovement jump (CMJ) tests. In the test-retest reliability, high intraclass correlation coefficients (ICCs) were observed (mean: 0.90, SJ and CMJ) in the Polar V800. There was no significant systematic bias ± random errors (p > 0.05) between test-retest. Low coefficients of variation (<5%) were detected in both jumps in the Polar V800. In the validity assessment, similar jump height was detected among devices (p > 0.05). There was almost perfect agreement between the Polar V800 compared to a force platform for the SJ and CMJ tests (Mean ICCs = 0.95; no systematic bias ± random errors in SJ mean: -0.38 ± 2.10 cm, p > 0.05). Mean ICC between the Polar V800 versus high-speed camera was 0.91 for the SJ and CMJ tests, however, a significant systematic bias ± random error (0.97 ± 2.60 cm; p = 0.01) was detected in CMJ test. The Polar V800 offers valid, compared to force platform, and reliable information about vertical jump height performance in physically active healthy young men.

Curve Sprint in Elite Female Soccer Players: Relationship with Linear Sprint and Jump Performance

The aim of this study was to examine the associations between linear sprint, curve sprint (CS), change of direction (COD) speed, and jump performance in a sample of 17 professional female soccer players. All athletes performed squat and countermovement jumps, single leg horizontal triple jumps, 17 m linear sprints, CS tests, and a 17 m Zigzag COD test. A Pearson product–moment test was performed to determine the relationships among the assessed variables. The significance level was set at p < 0.05. Nearly perfect associations (r > 0.9) were found between linear and CS velocities. Players faster in linear sprints and CS exhibited greater COD deficits. No significant associations were found between COD deficit and either body mass or sprint momentum. Jumping ability was significantly correlated with linear sprint and CS performance, but not to COD performance. These findings may be used by coaches and practitioners to guide testing and training prescriptions in this population. The associations observed here suggest that training methods designed to improve linear sprint and CS velocities may benefit from the implementation of vertically and horizontally oriented plyometric exercises.

The single-leg vertical hop provides unique asymmetry information in individuals after anterior cruciate ligament reconstruction

BACKGROUND

Traditional testing to identify asymmetries after anterior cruciate ligament reconstruction include four similar horizontal hopping tests. The purpose of this study was to determine whether a single-leg vertical hopping test can identify performance and biomechanical asymmetries, and whether performance asymmetries provide unique information compared to traditional tests.

METHODS

Twelve women with history of anterior cruciate ligament reconstruction [age: 21.1 years (SD 3.2), height: 165.8 cm (SD 6.0), mass: 68.3 kg (SD 8.8)] completed traditional horizontal hop testing. Participants also performed a single-leg vertical hop for maximal height while instrumented for three-dimensional motion analysis. Paired t-tests were performed to identify side-to-side differences in performance variables and Spearman's rank correlations were performed of limb symmetry indices to identify whether the single-leg vertical hop test provides unique information. Repeated measures MANOVAs were performed to identify single-leg vertical hop biomechanical asymmetries.

FINDINGS

Participants exhibited significant side-to-side performance differences during the single-leg vertical hop [mean difference = 0.02 m (SD 0.03), P = .04]. Only weak to moderate relationships were identified between limb symmetry indices of the single-leg vertical hop and other horizontal hopping tests. The vertical hop elicited significant asymmetries of joint kinematics (P = .04) and angular impulse (P = .04). Specifically, the involved limb showed lower peak ankle dorsiflexion (P = .004) and knee abduction (P = .02) angles, lower sagittal plane impulse at the knee (P = .02) and greater sagittal plane impulse at the hip (P = .03).

INTERPRETATION

The single-leg vertical hop can identify performance and biomechanical asymmetries in individuals after anterior cruciate ligament reconstruction, potentially providing complementary information to standard horizontal hopping tests.

Autoregulation in Resistance Training: Addressing the Inconsistencies

Autoregulation is a process that is used to manipulate training based primarily on the measurement of an individual's performance or their perceived capability to perform. Despite being established as a training framework since the 1940s, there has been limited systematic research investigating its broad utility. Instead, researchers have focused on disparate practices that can be considered specific examples of the broader autoregulation training framework. A primary limitation of previous research includes inconsistent use of key terminology (e.g., adaptation, readiness, fatigue, and response) and associated ambiguity of how to implement different autoregulation strategies. Crucially, this ambiguity in terminology and failure to provide a holistic overview of autoregulation limits the synthesis of existing research findings and their dissemination to practitioners working in both performance and health contexts. Therefore, the purpose of the current review was threefold: first, we provide a broad overview of various autoregulation strategies and their development in both research and practice whilst highlighting the inconsistencies in definitions and terminology that currently exist. Second, we present an overarching conceptual framework that can be used to generate operational definitions and contextualise autoregulation within broader training theory. Finally, we show how previous definitions of autoregulation fit within the proposed framework and provide specific examples of how common practices may be viewed, highlighting their individual subtleties.

Bipedal hopping as a new measure to detect subtle sensorimotor impairment in people with multiple sclerosis

BACKGROUND

Bipedal hopping has the potential to detect subtle multiple sclerosis (MS)-related impairments, especially among patients who "pass" typical movement tests. In this narrative review, we outline the biomechanics of bipedal hopping and propose its usefulness as a novel outcome measure for people with MS having mild disability.

METHODS

We summarize articles that (1) examined the biomechanics of jumping or hopping and (2) tested the validity and/or reliability of hopping tests. We consolidated consistencies and gaps in research and opportunities for future development of the bipedal hop test.

RESULTS

Bipedal hopping requires immense power, coordination, balance, and ability to reduce co-contraction; movement components typically affected by MS. These impairments can be measured and differentiated by examining specific variables, such as hop length (power), symmetry (coordination), center of pressure (balance), and coefficient of variability (co-contraction/spasticity). Bipedal hopping challenges these aspects of movement and exposes sensorimotor impairments that may not have been apparent during walking.

CONCLUSIONS

Testing of bipedal hopping on an instrumented walkway may detect and monitor sensorimotor control in people with MS who do not currently present with clinical deficits. Early measurement is imperative for precise rehabilitation prescription to slow disability progression prior to onset of measurable gait impairment.Implications for rehabilitationJumping and hopping tests detect lower limb and balance impairments in children, athletes, and older adults.Bipedal hop test measures multiple domains: power, coordination, balance, and muscle timing.Bipedal hop test may expose subtle sensorimotor impairments in people with multiple sclerosis.Multiple variables measured can discern type of sensorimotor impairment to direct personalized rehabilitation programs.

Effects of Six Weeks of High-Intensity Functional Training on Physical Performance in Participants with Different Training Volumes and Frequencies

High-intensity functional training (HIFT) is characterized by presenting high volumes and training intensities with constantly varied exercises. The aim of this study was to analyze the internal training load and the effects of high-intensity functional training on physical performance in subjects with different training volumes and frequencies. A total of 31 volunteers involved in high-intensity functional training (14 men and 17 women) were divided according to their training volumes and frequencies (high training-volume and frequency-HTVF; (n = 17) (nine women and eight men; age: 31.0 ± 6.3 years; height: 168.8 ± 8.1 cm, body weight: 73.6 ± 11.9 kg; BMI: 25.96 kg/m²) and moderate training volume and frequency-MTVF; (n = 14) (eight women and six men; age: 26.6 ± 4.7 years; height: 167.2 ± 8.6 cm, body weight: 75.8 ± 18.0 kg; BMI: 27.33 kg/m²)). The internal training load was determined using the session-rating of perceived exertion method. The monotony index (MI) and training strain (TS) were used to determine training variability during the training weeks. Countermovement vertical jump height, 20-m sprinting and handgrip strength were assessed at baseline and after six weeks of training. There was a time effect for MI ((F_{(5, 145)} = 5.942; p = 0.0001)), TS ((F_{(5, 145)} = 5.734; p = 0.0001)), weekly internal training load ((F_{(4.006, 116.87)} = 4.188; p = 0.003)) and mean weekly internal training load ((F_{(4.006, 116.87)} = 4.188; p = 0.003)). There was no increase in performance in either group for countermovement vertical jump height ((F_(1,29) = 6.081; p = 0.050)), sprinting ((F_(1,29) = 1.014; p = 0.322)), right handgrip strength ((F_(1,29) = 2.522; p = 0.123)) or left handgrip strength ((F_(1,29) = 2.550; p = 0.121)). The current findings suggest that six weeks of high-intensity functional training was not able to increase performance in either group. Therefore, different volumes and frequencies do not seem to influence the increase in physical performance of HIFT practitioners.

Validity, reliability and usefulness of smartphone and kinovea motion analysis software for direct measurement of vertical jump height

Jumping is a simple exercise determined by several biomechanical and physiological factors. Measures of vertical jump height are common and easy to administer tests of lower limb muscle power that are carried out with several types of equipment. This study aimed to validate and address the usefulness of the combination of smartphone and computer-based applications (Smartphone-Kinovea) against a laboratory-based Motion Capture System. One hundred and twelve healthy adults performed three maximal-effort countermovement jumps each. Both instruments measured the heights of the 336 trials concurrently while tracking the excursion of the body center of gravity. The vertical velocity at take-off v_to and the impulse J were computed with jump height h measures. Intraclass correlation coefficient (ICC) results indicated very high agreement for h and v_to (0.985) and almost perfect agreement for J (0.997), and Cronbach's α=0.99. Low mean differences were observed between instruments for h: -0.22 ± 1.15 cm, v_to: -0.01 ± 0.04 m/s, and J: -0.56 ± 2.92 Ns, all p<0.01. The smallest worthwhile change (SWC) and the typical error of measurement (SEM) were 1.34 cm, 0.81 cm for h; 1.15 m/s, 0.03 m/s for v_to, and 2.93 Ns, 2.25 Ns for J, so the usefulness of the method is established (SWC/SEM>1). Bland-Altman plots showed very low mean systematic bias ± random errors (-0.22 ± 2.25 cm; -0.01 ± 0.08 m/s; -0.56 ± 5.73 Ns), without association between their magnitudes (r²=0.005, r²=0.005, r²=0.001). Finally, very high to practically perfect correlation between isntruments were observed (r = 0.985; r = 0.986; r = 0.997). Our results suggest that the Smartphone-Kinovea method is a valid and reliable, low-cost instrument to monitor changes in jump performance in a healthy, active population diverse in gender and physical condition.

Curve sprinting in soccer: relationship with linear sprints and vertical jump performance

We examined the relationships among linear speed, vertical jumping ability and curve sprint (CS) performance. Moreover, the correlations between linear and curvilinear sprint velocities and CS deficit were tested. Twenty-eight under-20 soccer players performed squat and countermovement jumps, 17-m linear sprint (with split times at 5 and 10 m), and a CS test for both sides. For the first time, the new proposed CS deficit was calculated as the difference between 17-m velocity and CS test velocity. Pearson’s product moment of correlation was performed to determine the relationships among the distinct variables tested. Significance level was set at P < 0.05. Large to very large relationships between linear sprint speed and CS performance were observed, on both the “good” and “weak” sides. In addition, moderate to large correlations between linear and curve sprint abilities and vertical jumps were found. Finally, the CS deficit was negatively associated with the CS good side performance. Linear sprint and CS velocities for both good and weak sides were closely related. The CS deficit was only related to the CS weak side performance, and the vertical jumping ability was significantly associated with both linear and curvilinear sprint velocities. The present results suggest that training methods capable of improving linear sprint and vertical jumping abilities may also improve CS performance.

Is Tensiomyography-Derived Velocity of Contraction a Sensitive Marker to Detect Acute Performance Changes in Elite Team-Sport Athletes?

PURPOSE

To examine the variations in the velocity of contraction (Vc) assessed using tensiomyography, vertical jumping ability, and sprinting speed induced by 4 different exercise protocols (ie, strength, sprint, plyometric, and technical training sessions) in 14 male national-team rugby players (age 21.8 [2.6] y, weight 83.6 [8.5] kg, and height 177.4 [6.7] cm).

METHODS

Physical tests were conducted immediately before and after 4 distinct workouts in the following order: tensiomyography in the rectus femoris and biceps femoris muscles, squat and countermovement jumps, and 30-m sprint velocity. To analyze the differences in the assessed variables before and after each training session, the differences based on magnitudes were calculated.

RESULTS

After strength and plyometric workouts, the players presented possible to almost certain impairments in sprint and jump performance and in the Vc of the rectus femoris (effect sizes 0.26-0.64). After the sprint-training session, possible to very likely decreases were observed in the squat jump, 30-m sprint, and Vc of the biceps femoris (effect sizes 0.21-0.44). By contrast, after the technical training, athletes demonstrated a possible increase in the squat jump and Vc in both muscles examined (effect sizes 0.13-0.20).

CONCLUSIONS

The main finding of this research is that, for the vast majority of results, the direction of changes observed in Vc were the same as those observed in performance assessments. This suggests that Vc might be used as a sensitive marker of acute variations in speed and power performance of elite team-sport athletes.

Differences in Change of Direction Speed and Deficit Between Male and Female National Rugby Sevens Players

Freitas, TT, Alcaraz, PE, Calleja-González, J, Arruda, AFS, Guerriero, A, Kobal, R, Reis, VP, Pereira, LA, and Loturco, I. Differences in change of direction speed and deficit between male and female national rugby sevens players. J Strength Cond Res XX(X): 000-000, 2019-The aims of this study were to assess the change of direction (COD) deficit in different tasks and to investigate the differences in COD ability and COD deficit between male and female rugby sevens players. Thirty-six elite rugby players from the Brazilian National senior sevens teams (18 males and 18 females) completed the following physical assessments: squat and countermovement jumps; drop jump from a 45-cm height; horizontal single and triple jumps; 40-m linear sprint; Pro-agility, L-drill, and Zig-zag COD tests; and 1 repetition maximum test in the squat exercise. The differences between male and female performances were determined using magnitude-based inferences, an independent t test, and effect sizes (ES). Pearson's product-moment correlations were performed to determine the relationships among the different COD velocities and COD deficits. Men demonstrated likely to almost certainly significantly higher performances than women in all speed-power assessments and COD tasks (ES ranging from 0.61 to 2.09; p < 0.05), with the exception of the Zig-zag drill (ES = 0.24; p > 0.05). Furthermore, males displayed significantly greater COD deficits in all tests and higher sprint momentum (ES ranging from 0.78 to 2.95; p < 0.05). Large significant relationships among COD velocities (r ranging from 0.71 to 0.88; p < 0.05) and almost perfect significant correlations among all COD deficits (r ranging from 0.90 to 0.95; p < 0.05) were obtained in both sexes. The present results indicate that male rugby players are less efficient at changing direction, relative to their maximum sprint velocity. In addition, the correlations between the different COD deficits and COD speeds suggest that elite rugby players demonstrate similar ability to change direction, independently of the angle of directional change. From a practical perspective, this implies that a more comprehensive training strategy including eccentric exercises, acceleration-deceleration drills, and directional change technique is warranted to improve the COD ability (and reduce the COD deficit) of faster and more powerful rugby sevens players.

Long-Term Analysis of Elite Basketball Players' Game-Related Statistics Throughout Their Careers

The aim of the present study was to analyze the changes of game-related statistics in expert players across their whole sports careers. From an initial sample including 252 professional basketball players competing in Spanish first division basketball league (ACB) in the 2017-2018 season, 22 met the inclusion criteria. The following game-related statistics were studied: average points, assist, rebounds (all normalized by minute played), 3-point field goals percentage, 2-point field goals percentage, and free throws percentage per season. Each variable was individually investigated with a customized excel spreadsheet assessing individual variations and career trends were calculated. The results showed a positive trend in most of the investigated players in assists (91% of cases) and free throw percentages (73% of cases). Similar percentages of positive and negative trends were observed for all the other game-related statistics (range: 41-59% for negative and positive, respectively). In conclusion, an increase in assist and free throw performance was shown in the investigated players across their playing career. This information is essential for basketball coaches suggesting the use of most experienced players in the final moments of the game.

Change-of-direction, speed and jump performance in soccer players: a comparison across different age-categories

This study examined the age-specific development of vertical jump height, straight and change-of-direction (COD) speed, and COD deficit in one-hundred and eighty-two elite soccer players from different age-categories (U15, U17, U20, and Senior). All participants were players of two distinct clubs and were undertaking different training routines, as planned by their technical staff members. For this purpose, the soccer players performed: (1) squat and countermovement jumps; (2) a maximal 20-m linear sprint speed test, and (3) the Zigzag COD test. The magnitude-based inference approach and standardized differences were used to compare the age-groups. Sprint speed at longer distances (20-m) increased progressively across the age-ranges. In contrast, speed and acceleration performances at shorter distances (5-m) were better in U15 than in the other age-categories. The COD speed did not change throughout the younger categories but presented a meaningful decrease in the Senior category. Surprisingly, despite the progressive increase in volume and intensity of neuromuscular training from younger to older categories, the COD deficit presented a gradual increase across the age-groups. It is possible that simple modulation of the strength-power training program during the maturation process is not sufficient to produce faster adult players with enhanced ability to change direction. Therefore, coaches are strongly encouraged to implement specific COD training practices to tolerate braking at increasing running speeds and appropriate volume and intensity of soccer specific training throughout the players' specialization process.

One-Repetition-Maximum Measures or Maximum Bar-Power Output: Which Is More Related to Sport Performance?

PURPOSE

To compare the associations between optimum power loads and 1-repetition-maximum (1RM) values (assessed in half-squat and jump-squat exercises) and multiple performance measures in elite athletes.

METHODS

Sixty-one elite athletes (15 Olympians) from 4 different sports (track and field [sprinters and jumpers], rugby sevens, bobsled, and soccer) performed squat and countermovement jumps, half-squat exercise (to assess 1RM), half-squat and jump-squat exercises (to assess bar-power output), and sprint tests (60 m for sprinters and jumpers and 40 m for the other athletes). Pearson product-moment correlation test was used to determine relationships between 1RM and bar-power outputs with vertical jumps and sprint times in both exercises.

RESULTS

Overall, both measurements were moderately to near perfectly related to speed performance (r values varying from -.35 to -.69 for correlations between 1RM and sprint times, and from -.36 to -.91 for correlations between bar-power outputs and sprint times; P < .05). However, on average, the magnitude of these correlations was stronger for power-related variables, and only the bar-power outputs were significantly related to vertical jump height.

CONCLUSIONS

The bar-power outputs were more strongly associated with sprint-speed and power performance than the 1RM measures. Therefore, coaches and researchers can use the bar-power approach for athlete testing and monitoring. Due to the strong correlations presented, it is possible to infer that meaningful variations in bar-power production may also represent substantial changes in actual sport performance.

Change of Direction Deficit in National Team Rugby Union Players: Is There an Influence of Playing Position?

The aim of this study was to investigate the change of direction (COD) ability and deficits of elite rugby union players, discriminating between position (backs and forwards), and between “faster and slower players”, in multiple COD tasks. Twenty-four male rugby union players from the Brazilian senior National team completed the following assessments: Squat and countermovement jumps; drop jump; standing long jump, horizontal triple jumps; 40-m linear sprint; Pro-agility, L-Drill, and Zig-zag COD tests; and squat 1-repetition maximum. The differences between backs and forwards and between faster and slower performers were examined using magnitude-based inferences. Backs were faster (in both linear and COD speed tests) and jumped higher than forwards. Moreover, they generated an inferior sprint momentum. No differences were found in COD deficit between playing positions. However, when dividing the sample by median split, faster players outperformed their slower counterparts in all power–speed variables and presented higher COD deficits. These results suggest that separating rugby players by playing position might not discriminate players with different COD skills and that the median split analysis is more sensitive to identifying these differences. Furthermore, the present data indicate that faster rugby players are less efficient at changing direction and tolerating higher approach velocities in COD maneuvers.

Selective Influences of Maximum Dynamic Strength and Bar-Power Output on Team Sports Performance: A Comprehensive Study of Four Different Disciplines

This study examined the selective influences of one-repetition maximum (1RM) values [assessed in the half-squat (HS)] and bar-power production [assessed in both HS and jump squat (JS) exercises] on the physical performance of male and female team sport athletes from four different sports. Three-hundred and three elite players (31 Olympians) from four different disciplines (47 male soccer players, 58 female soccer players, 28 male handball players, 58 female handball players, 49 male rugby players, and 63 male futsal players) participated in this study. The physical tests were performed over 2 consecutive days for soccer and rugby players, and in 1 day for the remaining athletes. On the first day, rugby and soccer athletes performed squat jumps (SJ), countermovement jumps (CMJ), and HS 1RM. On the second day, they executed HS and JS tests (to assess the maximum bar-power output) and the linear and change-of-direction (COD) speed tests. For the other players, the sequence of the measurements was the same; however, they did not perform the HS exercise. Athletes were separated, using a median split analysis, into two distinct groups, according to their bar-power output in both JS and HS exercises and their performance in HS 1RM. The magnitude-based inferences method was used to examine the differences between "higher" and "lower" performance groups. Overall, the bar-power outputs were better connected to improved acceleration, speed, and jump performance than the 1RM measures. From these findings, it is possible to infer that players able to produce higher bar-power outputs are likely to sprint faster and jump higher. Therefore, coaches involved in team sports are strongly encouraged to use the bar-power method to evaluate the athletic performance of their players.

Vertically and horizontally directed muscle power exercises: Relationships with top-level sprint performance

The capacity to rapidly generate and apply a great amount of force seems to play a key role in sprint running. However, it has recently been shown that, for sprinters, the technical ability to effectively orient the force onto the ground is more important than its total amount. The force-vector theory has been proposed to guide coaches in selecting the most adequate exercises to comprehensively develop the neuromechanical qualities related to the distinct phases of sprinting. This study aimed to compare the relationships between vertically-directed (loaded and unloaded vertical jumps, and half-squat) and horizontally-directed (hip-thrust) exercises and the sprint performance of top-level track and field athletes. Sixteen sprinters and jumpers (including three Olympic athletes) executed vertical jumps, loaded jump squats and hip-thrusts, and sprinting speed tests at 10-, 20-, 40-, 60-, 100-, and 150-m. Results indicated that the hip-thrust is more associated with the maximum acceleration phase (i.e., from zero to 10-m; r = 0.93), whereas the loaded and unloaded vertical jumps seem to be more related to top-speed phases (i.e., distances superior to 40-m; r varying from 0.88 to 0.96). These findings reinforce the mechanical concepts supporting the force-vector theory, and provide coaches and sport scientists with valuable information about the potential use and benefits of using vertically- or horizontally-based training exercises.

Perceived training load and jumping responses following nine weeks of a competitive period in young female basketball players

The aims of this study were to describe the session rating of perceived exertion (sRPE), total quality recovery (TQR), and variations in countermovement jump (CMJ) height throughout nine weeks of a competitive period in young female basketball players. In total, 10 young female basketball players (17.2 ± 0.4 years; 71.8 ± 15.0 kg; 177.2 ± 9.5 cm) participated in this study. The sRPE and TQR were assessed in each training session, whereas the CMJ height was assessed prior to the first weekly training session. The magnitude-based inferences method was used to compare the sRPE, TQR, and CMJ height across the nine weeks of training. The training loads accumulated in weeks 1, 2, and 3 were likely to almost certainly be higher than in the following weeks (ES varying from 0.67 to 2.55). The CMJ height in week 1 was very likely to be lower than in weeks 2, 5, 7, and 8 (ES varying from 0.24 to 0.34), while the CMJ height of the 9th week was likely to almost certainly be higher than all previous weeks of training (ES varying from 0.70 to 1.10). Accordingly, it was observed that when higher training loads were accumulated, both CMJ and TQR presented lower values than those presented during periods with lower internal training loads. These results highlight the importance of using a comprehensive and multivariate approach to effectively monitor the physical performance of young athletes.

Mixed Training Methods: Effects of Combining Resisted Sprints or Plyometrics with Optimum Power Loads on Sprint and Agility Performance in Professional Soccer Players

The aim of this study was to compare the effects of two different mixed training programs (optimum power load [OPL] + resisted sprints [RS] and OPL + vertical/horizontal plyometrics [PL]) on neuromuscular performance of elite soccer players during a short-term training preseason. Eighteen male professional soccer players took part in this study. The athletes were pair-matched in two training groups: OPL + RS and OPL + PL. Unloaded and resisted sprinting speeds at 5-, 10-, 20-, and 30-m, change of direction (COD) speed, and performance in the squat jump (SJ), countermovement jump (CMJ), and horizontal jump (HJ) were assessed pre- and post- a 5-week training period. Magnitude based inference with the effect sizes were used for data analysis. A possible increase in the SJ and CMJ heights and a likely increase in the HJ distance were observed in the OPL + PL group. Meaningful improvements were observed in the COD speed test for both training groups comparing pre- and post-measures. In both unloaded and resisted sprints, meaningful decreases were observed in the sprinting times for all distances tested. This study shows that a mixed training approach which comprises exercises and workloads able to produce positive adaptations in different phases of sprinting can be a very effective strategy in professional soccer players. Moreover, the possibility of combining optimum power loads with resisted sprints and plyometrics emerges as a novel and suitable option for coaches and sport scientists, due to the applicability and efficiency of this strength-power training approach.

Effects of Unloaded vs. Loaded Plyometrics on Speed and Power Performance of Elite Young Soccer Players

The purpose of this study was to investigate the effects of loaded and unloaded plyometric training strategies on speed and power performance of elite young soccer players. Twenty-three under-17 male soccer players (age: 15.9 ± 1.2 years, height: 178.3 ± 8.1 cm, body-mass (BM): 68.1 ± 9.3 kg) from the same club took part in this study. The athletes were pair-matched in two training groups: loaded vertical and horizontal jumps using an haltere type handheld with a load of 8% of the athletes' body mass (LJ; n = 12) and unloaded vertical and horizontal plyometrics (UJ; n = 11). Sprinting speeds at 5-, 10-, and 20-m, mean propulsive power (MPP) relative to the players' BM in the jump squat exercise, and performance in the squat jump (SJ) and countermovement jump (CMJ) were assessed pre- and post-training period. During the experimental period, soccer players performed 12 plyometric training sessions across a 6-week preseason period. Magnitude based inferences and standardized differences were used for statistical analysis. A very likely increase in the vertical jumps was observed for the LJ group (99/01/00 and 98/02/00 for SJ and CMJ, respectively). In the UJ group a likely increase was observed for both vertical jumps (83/16/01 and 90/10/00, for SJ and CMJ, respectively). An almost certainly decrease in the sprinting velocities along the 20-m course were found in the LJ group (00/00/100 for all split distances tested). Meanwhile, in the UJ likely to very likely decreases were observed for all sprinting velocities tested (03/18/79, 01/13/86, and 00/04/96, for velocities in 5-, 10-, and 20-m, respectively). No meaningful differences were observed for the MPP in either training group (11/85/04 and 37/55/08 for LJ and UJ, respectively). In summary, under-17 professional soccer players increased jumping ability after a 6-week preseason training program, using loaded or unloaded jumps. Despite these positive adaptations, both plyometric strategies failed to produce worthwhile improvements in maximal speed and power performances, which is possible related to the interference of concurrent training effects. New training strategies should be developed to ensure adequate balance between power and endurance loads throughout short (and high-volume) soccer preseasons.