Validation of an electronic jump mat to assess stretch-shortening cycle function

Isometric Shoulder and Hip Strength Impact on Throwing Velocity and Reactive Strength

The aim of the study is to examine relationships between shoulder extension-flexion and internal-external rotation strength of professional male handball players with throwing velocity, and the hip extension-flexion strength with horizontal and vertical reactive strength index. Fifteen professional male handball players participating in 1st League matches took part in the study. The results showed that isometric shoulder flexion and extension strength significantly predicted stable throwing velocity (r2=between 0.27-0.73) and dynamic throwing velocity (r2=between 0.30-0.62). In addition, isometric internal and external rotation strength significantly predicted stable throwing velocity (r2=between 0.32-0.54) and dynamic throwing velocity (r2=between 0.31-0.44). Moreover, isometric hip extension and flexion strength significantly predicted vertical reactive strength index (r2=between 0.31-0.45) and horizontal reactive strength index (r2=between 0.26-0.42). In conclusion, it was observed that shoulder strength has an enhancing effect on handball players' throwing velocity, while hip strength is a determining factor for the reactive strength index. In this context, it is assumed that shoulder weakness during throwing will affect the accuracy and velocity of throwing by disrupting the angular momentum, while weakness in the hip during the jump phase of the throwing motion will negatively affect the explosive power by limiting stabilization during landing.

Jumping Asymmetries and Risk of Injuries in Preprofessional Ballet

BACKGROUND

Preprofessional ballet dancers are exposed to the risk of injuries, primarily in the lower extremities, with most injuries occurring during jumping and landing activities. Interlimb asymmetry during jumping and landing activities has been associated with the injury risk in adolescent athletes, but this has not been examined in dancers.

PURPOSE

To investigate associations between interlimb asymmetry during a double-leg countermovement jump (DL-CMJ) and single-leg jump (SLJ) and the injury risk in adolescent preprofessional ballet dancers.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

Adolescent preprofessional ballet dancers (N = 255) performed 3 DL-CMJs and 3 SLJs on force plates during annual screening. Absolute and directional (separate values for left and right limb dominance) asymmetries in a set of kinetic variables during a DL-CMJ and in jump height during an SLJ were calculated. Each variable was characterized as having "high" or "normal" asymmetry according to the percentage of asymmetry (greater than or less than or equal to, respectively, the mean ± 0.5 SD) based on the present sample. Risk ratios (RRs) and 95% CIs were calculated based on the injury incidence in the subsequent academic year.

RESULTS

Of the 242 dancers that satisfied the inclusion criteria, 128 injuries were observed in the subsequent academic year. In the whole sample, 3 absolute, 7 left limb-dominant, and 1 right limb-dominant kinetic asymmetry in the eccentric, concentric, and landing phases of the DL-CMJ as well as left limb-dominant jump height asymmetry in the SLJ were associated with a significant (P < .001) increase in the injury risk (RR, 1.28-1.69 [95% CI, 1.02-2.37]). Separating by sex, asymmetries in the eccentric and landing phase of the DL-CMJ were not significant in boys, while in girls, RRs for asymmetries in the eccentric and landing phase of the DL-CMJ increased, and SLJ jump height asymmetry was not significant.

CONCLUSION

Higher asymmetries in certain kinetic variables during the DL-CMJ and in jump height during the SLJ were associated with an elevated risk of injuries in elite preprofessional ballet dancers with some sex-specific differences. Associations were mainly identified for high left limb-dominant asymmetry in the takeoff phase, suggesting that the injury risk may be specific to a relative right limb deficit.

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.

Reactive strength index during single-limb vertical continuous jumps after anterior cruciate ligament reconstruction: cross-sectional study

BACKGROUND

The association of the reactive strength index (RSI) during single-limb vertical continuous jumps (SVCJs) with single-limb hop tests in athletes after anterior cruciate ligament reconstruction (ACLR) is unclear. Thus, this study aimed to confirm the measurement properties of the RSI during SVCJs in athletes with ACLR at the phase of determining the timing of their return to sport.

METHODS

RSI during SVCJs and single-limb hop (single, triple, and crossover) tests were measured for post-ACLR and healthy athletes. The limb symmetry index (LSI) was calculated using the measurements of each parameter. For each test, patients were divided into two subgroups according to their LSI score (≥ 90%, satisfactory; < 90%, unsatisfactory). Fisher's exact test was used to examine the association of single-limb hop tests with RSI during the SVCJs.

RESULTS

A total of 21 post-ACLR and 17 healthy athletes completed all the tests. RSI during SVCJs was significantly lower on the involved limb than on the uninvolved limb in post-ACLR athletes (P < 0.001). The LSI of RSI during SVCJs of post-ACLR athletes was significantly lower than that of the healthy athletes (P < 0.01). Among the post-ACLR athletes, < 30% of those with LSIs > 90% in the single-limb hop tests had an LSI > 90% of the RSI during SVCJs.

CONCLUSIONS

RSI during SVCJs of post-ACLR athletes was significantly lower on the involved limb than on the uninvolved limb, and the asymmetry was more remarkable in the SVCJs than in the single-limb hop tests.

Acute effects of vibration foam rolling and local vibration during warm-up on athletic performance in tennis players

Athletes are currently fond of vibration foam rollers (VFRs) and commercial portable vibration percussion devices (PVPDs). It is still unknown whether using these devices during warm-up has an immediate impact on athletic performance. A randomized block design was used in this study. The acute effects of VFR and PVPD on tennis players’ athletic performance during warm-up were compared. For the countermovement jump (CMJ), reactive strength index (RSI), and hexagon test (HT), the difference in performance between all interventions was significant (p = 0.007–0.034, η²_p = 0.266–0.364). Only those who received VFR had significantly different CMJ and HT results when compared to the control group (CMJ height = 53.18 ±4.49 cm, p = 0.03, d = 1.26; HT time = 10.73 ±0.4 s, p = 0.03, d = 1.12). Participants’ RSI values were significantly different after VFR (RSI = 2.01 ±0.11 cm·mm^–1, p = 0.012, d = 1.76) and PVPD (RSI = 1.99 ±0.11 cm·mm^–1, p = 0.025, d = 1.52) compared to the control group. Therefore, when using VFR and PVPD as part of warm-up protocols for tennis players of varying skill levels, VFR could have an immediate positive effect on power, reactive strength, and change of direction performance, while PVPD could immediately improve reactive strength performance.

Single-Leg Vertical Hop Test Detects Greater Limb Asymmetries Than Horizontal Hop Tests After Anterior Cruciate Ligament Reconstruction in NCAA Division 1 Collegiate Athletes

BACKGROUND

Knee function deficits may persist after anterior cruciate ligament reconstruction (ACLR). Return to sport (RTS) testing batteries assess recovery after ACLR and can guide RTS progression, but the ideal test components are debatable. The single leg vertical hop for height (SLVH) test using a commercially available jump mat may provide a valuable assessment of knee function.

HYPOTHESIS/PURPOSE

The purpose of this study was to compare the limb symmetry index (LSI) of SLVH to horizontal hop testing in a cohort of National Collegiate Athletic Association (NCAA) Division 1 collegiate athletes after ACLR. The hypothesis was the SLVH would elicit significantly lower LSI than horizontal hop tests.

STUDY DESIGN

Cross-Sectional Study.

METHODS

Eighteen National Collegiate Athletic Association (NCAA) Division 1 collegiate athletes (7 males, 11 females) at 7.33 ± 2.05 months after ACLR were included in this retrospective study. LSI was calculated for single hop for distance (SHD), triple hop for distance (THD), cross-over hop for distance (CHD), timed 6-meter hop (T6H), and SLVH. A repeated measures ANOVA was performed to identify differences in LSI for each test. Spearman's Rho correlation coefficient was calculated to examine the relationship between LSIs for each test.

RESULTS

The LSI for SLVH (84.48% ± 11.41%) was significantly lower than LSI for SHD (95.48 ± 8.02%, p = 0.003), THD (94.40 ± 3.70%, p = 0.002), CHD (95.85 ± 7.00, p = 0.007), and T6H (97.69 ± 6.60%, p = 0.001). The correlation of LSI between SLVH and the horizontal hop tests was weak and non-significant for SHD (rs = 0.166, p = 0.509), CHD (rs = 0.199, p = 0.428), and T6H (rs = 0.211, p = 0.401) and moderate and non-significant for THD (rs = 0.405, p = 0.096).

CONCLUSIONS

Individuals after ACLR had lower LSI on the SLVH than on horizontal hop tests and weak to moderate correlations between the tests suggest SLVH detects performance deficits not identified by the horizontal hop tests.

LEVEL OF EVIDENCE

3.

Protective and Recovery Effects of Resveratrol Supplementation on Exercise Performance and Muscle Damage following Acute Plyometric Exercise

Plyometric exercise (PE) is an effective training method to increase muscle mass and strength. However, excessive or inappropriate conditions might cause exercise-induced muscle damage (EIMD). Resveratrol (RES) is a natural polyphenol plant antitoxin, which improves exercise performance, and exhibits anti-oxidation, anti-inflammatory, and anti-cancer effects. Therefore, this study investigated the effect of RES supplementation on the recovery of muscle damage, inflammation, soreness, muscle power, and anaerobic performance following plyometric-exercise-induced muscle damage (PEIMD). The present study was a double-blind, placebo-controlled research trial. Thirty-six young, untrained males were enrolled into the placebo (n = 12), RES-500 (500 mg RES/day, n = 12), or RES-1000 (1000 mg RES/day, n = 12) group by a jumping height-counterbalanced grouping design. At baseline, to pre-PEIMD, supplements were pre-loaded 7 days before they conducted PEIMD, and the exercise performance, delayed-onset muscle soreness (DOMS) and muscle damage biomarkers were measured over the experimental period at baseline, pre-PEIMD, and post-PEIMD at 2, 24, 48, and 72 h. As a result, we found that, at 72 h post-EIMD, the force peak (FP) and rate of force development (RFD) of the counter movement jump (CMJ) in RES groups showed no significant difference compared to that at baseline but was significantly greater than the placebo group. In the Wingate anaerobic test (WAnT), supplementation in the RES group had a better recovery effect on the relative peak power (RPP), relative mean power (RMP) and fatigue index (FI) (p < 0.05), especially in the high-dose group. For the detection of muscle pain after PEIMD, the RES supplement group was significantly better than the placebo group (p < 0.05). In addition, for muscle damage indexes, such as creatine kinase (CK) and lactate dehydrogenase (LDH), after PEIMD, supplementation with RES could significantly reduce and accelerate recovery (p < 0.05). In addition, the blood biochemical indicators of blood count, liver function, and kidney function showed that RES will not cause adverse risks to the human body. Our results suggest that replenishing RES in advance could effectively reduce muscle pain, increase exercise performance, and decrease muscle damage indicators caused by PEIMD, and the recovery was faster. Therefore, plyometric exercises combined with suitable RES supplementation could be an effective candidate for controlling muscle damage, improving physical adaption, and recovering anaerobic capacity.

Comparison of Different Functional Tests for Leg Power and Normative Bilateral Asymmetry Index in Healthy Collegiate Athletes

Background

Bilateral leg power is being increasingly investigated as a proxy for the recovery of muscle performance after injury. Functional tests like the single leg hop for distance (SLHD) and single leg vertical jump (SLVJ) are often used to determine symmetry and return to play (RTP) readiness. As an injury predictor, leg power is accurately measured with the Keiser Air420 seated leg press.

Purpose

To measure and analyze lower leg asymmetry in healthy collegiate athletes across each test battery.

Methods

Eighty-eight healthy student-athletes (44 males, 44 females) across 14 varsity teams at Wake Forest University performed the SLHD, SLVJ, and the Keiser. Horizontal and vertical displacement were measured via the SLHD and SLVJ, respectively. Peak power was recorded via the Keiser Air420 leg press. Pearson correlations and repeated measures ANOVA were used to calculate associations and compare bilateral asymmetry indices (BAI) and raw scores.

Results

There was a significant effect on each test’s raw BAI (P < 0.01). The mean absolute BAI were 5.42 ± 4.9%, 6.64 ± 4.9% and 5.36 ± 4.7% for the SLHD, SLVJ and Keiser, respectively. The SLVJ and Keiser (dominant leg r = 0.832, nondominant leg r = 0.826) were more highly correlated than the SLHD and Keiser (dominant leg r = 0.645, nondominant leg r = 0.687), all of which were statistically significant (P < 0.01).

Conclusion

At the 90th percentile, healthy collegiate athletes attained <15% BAI. We recommend the implementation of a battery of tests to determine normative lower limb asymmetry. A battery of functional tests may present different asymmetry indices as opposed the 10% reference asymmetry.

Long-term effects of school barefoot running program on sprinting biomechanics in children: A case-control study

BACKGROUND

The acute changes of running biomechanics in habitually shod children when running barefoot have been demonstrated. However, the long-term effects of barefoot running on sprinting biomechanics in children is not well understood.

RESEARCH QUESTION

How does four years of participation in a daily school barefoot running program influence sprint biomechanics and stretch-shortening cycle jump ability in children?

METHODS

One hundred and one children from barefoot education school (age, 11.2 ± 0.7 years-old) and 93 children from a control school (age, 11.1 ± 0.7 years-old) performed 50 m maximal shod and barefoot sprints and counter movement jump and five repeated-rebound jumping. To analyse sprint kinematics, a high-speed camera (240 fps) was used. In addition, foot strike patterns were evaluated by using three high-speed cameras (300 fps). Jump heights for both jump types and the contact times for the rebound jump were measured using a contact mat system. Two-way mixed ANOVA was used to examine the effect of school factor (barefoot education school vs control school) and footwear factor (barefoot vs shod) on the sprinting biomechanics.

RESULTS

Sprinting biomechanics in barefoot education school children was characterised by significantly shorter contact times (p = 0.003) and longer flight times (p = 0.005) compared to control school children regardless of footwear condition. In shod sprinting, a greater proportion of barefoot education school children sprinted with a fore-foot or mid-foot strike compared to control school children (p < 0.001). Barefoot education school children also had a significantly higher rebound jump height (p = 0.002) and shorter contact time than control school children (p = 0.001).

SIGNIFICANCE

The results suggest that school-based barefoot running programs may improve aspects of sprint biomechanics and develop the fast stretch-shortening cycle ability in children. In order to confirm this viewpoint, adequately powered randomised controlled trials should be conducted.

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.

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.

Reliability and validity of the Chronojump open-source jump mat system

Vertical jump performance is a commonly used test to measure lower-limb muscle power that is carried out with several types of equipment. The aim of this study was to validate an open-source jump mat (Chronojump Boscosystems) against a proprietary jump mat (Globus Ergo Tester). Sixty-three active sportsmen (age 23.3 ± 2.4 years) completed 8 maximal-effort countermovement jumps (CMJ). The heights of the 504 CMJ were measured from the two jump mats simultaneously. Reliability was examined with intra-class correlation coefficients (ICC), paired samples t-tests, coefficient of variation (CV) and Cronbach’s α. Bivariate Pearson’s correlation coefficient (r) was used to examine validity. Effects were evaluated using non-clinical magnitude-based inference. There was almost perfect agreement between instruments (ICC = 0.999−1.000, most likely positive 100/0/0). Paired t-test showed a mean difference of 0.03 ± 0.21 cm (90% CI -0.04 − -0.01) between instruments (most likely trivial 0/100/0). Both instruments showed very good stability (α = 1.00, CV = 4.28±1.95%). The smallest worthwhile change and typical error values were 1.3 and 0.29 cm, respectively and therefore, the signal-to-noise ratio of both instruments was large: 4.5. Finally, almost perfect correlation between instruments was observed (r = 0.999, most likely positive 100/0/0). Chronojump can be regarded as a sensitive instrument to detect changes in jump height performance over the possible noise around the measure. The results supported the open-source jump mat to be a useful, valid and reliable, low-cost testing device to monitor variations in vertical jumping performance.

Aerobic fitness, upper-body strength and agility predict performance on an occupational physical ability test among police officers while wearing personal protective equipment

BACKGROUND

Police institutions often use Occupational Physical Ability Tests (OPATs) as a measure of occupational performance. These tests are utilized to mimic the daily and essential tasks performed by the police officers, but few are performed with load carriage (LC). The purpose of this study was to examine the physical performance predictors of an OPAT performed without (NPPE) and with (WPPE) LC.

METHODS

Thirteen federal highway police officers (age: 36.8±3.7 years, body mass: 89±10.7 kg, height: 180±5.6 cm) volunteered to complete a battery of physical fitness tests (aerobic power and capacity, muscular endurance, lower limb power, upper limb strength, agility and anaerobic power) and anthropometrics. Occupational performance was measured by the total OPAT time consisting of 7 sequential police tasks. All subjects randomly completed the tests on both LC conditions.

RESULTS

Agility (P<0.01), lower limb power and height (P<0.05) were significantly related to performance in the NPPE OPAT. In the WPPE condition, aerobic power (absolute and relative) (P<0.01), lower limb power and agility (P<0.05). The best predictors for OPAT performance were agility (R2=0.45, P<0.01) in the NPPE condition, as well as relative aerobic power, upper limb strength and agility in the WPPE condition (R2=0.81, P<0.01).

CONCLUSIONS

Different conditions of LC have distinct occupational performance predictors. Thus, considering LC, physical exercise programs aimed at improving police occupational performance should aim at improving agility, upper limb strength and aerobic fitness.

Beneficial effects of a negative ion patch on eccentric exercise-induced muscle damage, inflammation, and exercise performance in badminton athletes

Complementary and alternative medicines (CAMs) are widely applied and accepted for therapeutic purposes because of their numerous benefits. Negative ion treatment belongs to one of the critical categories defined by the National Center for CAM, with such treatment capable of air purification and ameliorating emotional disorders (e.g., depression and seasonal affective disorder). Negative ions can be produced naturally and also by a material with activated energy. Exercise-induced muscle damage (EIMD) often occurs due to inadequate warm up, high-intensity exercise, overload, and inappropriate posture, especially for high-intensive competition. Few studies have investigated the effects of negative ion treatment on muscular injury in the sports science field. In the current study, we enrolled badminton athletes and induced muscle damage in them through eccentric exercise in the form of a high-intensity squat program. We evaluated the effects of negative ion patches of different intensities at three points (preexercise, postexercise, and recovery) by analyzing physiological indexes (tumor necrosis factor [TNF]-α, interleukin [IL]-6, IL-10, creatine kinase [CK], and lactate dehydrogenase [LDH] levels) and performing a functional assessment (a countermovement jump [CMJ] test). We found that a high-intensity negative ion patch could significantly reduce the levels of TNF-α, an injury-associated inflammatory cytokine, and related markers (CK and LDH). In addition, muscular overload-caused fatigue could be also ameliorated, as indicated by the functional CMJ test result, and related muscular characteristics (tone and stiffness) could be effectively improved. Thus, the negative ion treatment could effectively improve physiological adaption and muscular fatigue recovery after EIMD in the current study. The negative ion patch treatment can be further integrated into a taping system to synergistically fulfill exercise-induced damage protection and functional elevation. However, the effects of this treatment require further experimental validation.

Effect of Landing Posture on Jump Height Calculated from Flight Time

Flight time is widely used to calculate jump height because of its simple and inexpensive application. However, this method is known to give different results than the calculation from vertical velocity at takeoff. The purpose of this study is to quantify the effect of postural changes between takeoff and landing on the jump height from flight time. Twenty-seven participants performed three vertical jumps with arm swing. Three-dimensional coordinates of anatomical landmarks and the ground reaction force were analyzed. Two methods of calculating jump height were used: (1) the vertical velocity of the whole-body center of mass (COMwb) at takeoff and (2) flight time. The jump height from flight time was overestimated by 0.025 m compared to the jump height from the takeoff velocity (p < 0.05) due to the lower COMwb height at landing by −0.053 m (p < 0.05). The postural changes in foot, shank, and arm segments mainly contributed to decreasing the COMwb height (−0.025, −0.014, and −0.017 m, respectively). The flight time method is reliable and had low intra-participant variability, but it cannot be recommended for a vertical jump when comparing with others (such as at tryouts) because of the potential “cheating” effect of differences in landing posture.

Combined Effects of Self-Myofascial Release and Dynamic Stretching on Range of Motion, Jump, Sprint, and Agility Performance

Richman, ED, Tyo, BM, and Nicks, CR. Combined effects of self-myofascial release and dynamic stretching on range of motion, jump, sprint, and agility performance. J Strength Cond Res 33(7): 1795-1803, 2019-Massage has been used as both a pre- and post-exercise modality with purported benefits to flexibility and athletic performance. This study was designed to determine the effect of a 6-minute protocol of self massage known as self-myofascial release (SMR) using a foam rolling device in conjunction with a general warm-up and sport-specific dynamic stretching (DS) session on flexibility and explosive athletic performance in a sample of 14 female collegiate athletes. After familiarization, participants completed 2 testing sessions that began with 5 minutes of jogging at a self-selected pace, followed by either a 6-minute foam rolling session (SMR) or 6 minutes of light walking (LW) and a subsequent 6-minute period of sport-specific DS. Sit-and-reach (SR) was measured after a general warm-up, the SMR, or LW session, and following DS, after which participants performed 3 trials each of squat jump (SJ), countermovement jump (CMJ), and drop jump (DJ). Two additional tests, the agility T-Test (TT) and a 10-yd short sprint (SP), were then performed. The change in SR after SMR was significantly greater than the change seen in SR after LW, although the total changes seen in each condition were not statistically different after the addition of DS. Squat jump and CMJ improved by 1.72 ± 2.47 cm and 2.63 ± 3.74 cm (p = 0.070, p = 0.070), with no significant change to DJ, SP, and TT. Self-myofascial release in the form of foam rolling after a general warm-up and preceding a DS session seems to improve SJ and CMJ with no detriment to flexibility, DJ, sprint, and agility performance in comparison with LW and DS.

Effects of Personal Protective Equipment on the Performance of Federal Highway Policemen in Physical Fitness Tests

Marins, EF, Cabistany, L, Bartel, C, Dawes, J, and Del Vecchio, FB. Effects of personal protective equipment on the performance of Federal Highway Policemen in physical fitness tests. J Strength Cond Res 34(1): 11-19, 2020-Personal protective equipment (PPE), worn by police officers, provides protection and can modify physiological and performance responses during physical efforts. Physiological, perceptual, and physical responses were compared with PPE (WPPE) and without PPE (NPPE) among the Brazilian Federal Highway Policemen (FHP). Nineteen (n = 19) FHP completed 2 experimental trials: NPPE and WPPE (load = 8.3 kg). Tests of aerobic and anaerobic power, muscular strength and endurance, as well as change of direction speed (CODS) were performed under both conditions. Heart rate reductions were shown at the second ventilatory threshold (1.4%) and maximal exercise (1.5%) WPPE. In comparison with NPPE, physical performance in the WPPE condition showed decreases in the following: treadmill time at maximal exercise (21%, p < 0.001); time in the isometric trunk test (28.9%, p < 0.001); vertical jump height (11.6 and 10.5%, p < 0.001); standing long jump distance (7.3%, p < 0.001); bar hang time (14.8%, p < 0.05); and CODS (2.6%, p < 0.05). Results indicate that PPE use reduces physical performance of FHP in cardiorespiratory, strength, power, and CODS tests.

Validity and Reliability of an Electronic Contact Mat for Drop Jump Assessment in Physically Active Adults

The aim of the present study was to investigate the concurrent validity and the test–retest reliability of an electronic contact mat for drop jump assessment in physically active adults. Seventy-nine young, physically active adults participated in the validity study, and 49 subjects were recruited for the reliability study. The motor task required subjects to perform two-legged drop jumps using drop heights of 24, 43, and 62 cm as well as one-legged drop jumps with the left and right leg using a drop height of 24 cm. Ground contact times were simultaneously quantified with an electronic contact mat, a force plate (i.e., gold standard), and a light-barrier system (another criterion device). Concurrent validity was assessed using intraclass correlation coefficient (ICC), systematic bias, limits of agreement, and linear regression analysis. Test–retest reliability (one week apart) was determined by calculating the ICC, the standard error of measurement (SEM), the coefficient of variation (CV), and Lin´s concordance correlation coefficient (р_c). Further, we determined the minimal detectable change (MDC_95%). Irrespective of drop height and jump condition, good agreements between testing devices (ICC ≥ 0.95) were shown. Compared to the force plate (−0.6 to 3.1 ms) but not to the light-barrier system (31.4 to 41.7 ms), the contact mat showed low systematic bias values. In terms of test–retest reliability, our analyses showed that the measuring devices are in agreement (ICC: 0.70–0.92; SEM: 8.5–18.4 ms; CV: 3.6–6.4%). Depending on the measurement device, drop height, and jump condition, a MDC_95% value ranging from 23.6 to 50.9 ms represents the minimum amount of change needed to identify practical relevant effects in repeated measurements of drop jump performance. Our findings indicate that the electronic contact mat is a valid and reliable testing device for drop jump assessment from different drop heights in young physically active adults.

Jump height as performance indicator for the selection of youth football players to national teams

BACKGROUND

Different jump tests such as the Countermovement Jump (CMJ), Abalakov Jump (AJ) and Standing Long Jump (SLJ) are often used in practice to evaluate muscular power and functional performance in football. These tests are also used in different selection processes and talent identification, but the significance of the tests for the selection of youth players to national teams are relatively unknown. The aim of this study was to compare jump ability between youth football players selected or not selected for the national team.

METHODS

In this cross-sectional study, 22 players (aged 17±2 years), 11 national players (NP) and 11 non-national players (NNP) were evaluated in three different jump tests; CMJ, AJ and SLJ. Mean scores for the tests were analyzed and compared.

RESULTS

Significant differences were found between the groups regarding jump height in favor of the NP group in both the CMJ (NP 39.9±5.0 cm vs. NNP 34.2±4.9 cm, P=0.013) and the AJ (NP 47.1±5.4 vs. NNP 40.9±4.7, P=0.010). No group difference was found regarding jump length in SLJ (NP 246.2±17.9 vs. NNP 232.9±16.5, P=0.084).

CONCLUSIONS

The results suggest that tests, measuring jump height, could be used as a performance indicator and part of the selection process of youth football players to national teams, whereas the use of jump length could be questioned.

Assessing Reactive Strength Measures in Jumping and Hopping Using the Optojump™ System

The aim of this study was to assess the concurrent validity of the Optojump™ system (Microgate, Bolzano, Italy) versus a force platform in the estimation of temporal and reactive strength measures. In two separate investigations, twenty physically active males performed double-leg and single-leg drop jumps from a box height of 0.3 m and a 10 s vertical bilateral hopping test. Contact time, flight time and total time (the sum of contact and flight time) were concurrently assessed during single and double-leg drop jumps and during hopping. Jump height, the reactive strength index and the reactive strength ratio were also calculated from contact time and flight time. Despite intraclass correlation coefficients (ICCs) for all variables being close to 1 (ICC > 0.975), a significant overestimation was found in contact time (0.005 ± 0.002 s) and underestimations in flight time (0.005 ± 0.003 s), the reactive strength index (0.04 ± 0.02 m·s-1) and the reactive strength ratio (0.07 ± 0.04). Overestimations in contact time and underestimations in flight time were attributed to the physical design of the Optojump™ system as the transmitter and receiver units were positioned 0.003 m above the floor level. The Optojump™ demonstrated excellent overall temporal validity with no differences found between systems for total time. Coaches are advised to be consistent with the instrumentation used to assess athletes, however, in the case of comparison between reactive strength values collected with the Optojump™ and values collected with a force platform, regression equations are provided.

Validity and intra-rater reliability of MyJump app on iPhone 6s in jump performance

OBJECTIVES

Smartphone applications are increasingly used by researchers, coaches, athletes and clinicians. The aim of this study was to examine the concurrent validity and intra-rater reliability of the smartphone-based application, MyJump, against laboratory-based force plate measurements.

DESIGN

Cross sectional study.

METHODS

Participants completed counter-movement jumps (CMJ) (n=29) and 30cm drop jumps (DJ) (n=27) on a force plate which were simultaneously recorded using MyJump. To assess concurrent validity, jump height, derived from flight time acquired from each device, was compared for each jump type. Intra-rater reliability was determined by replicating data analysis of MyJump recordings on two occasions separated by seven days.

RESULTS

CMJ and DJ heights derived from MyJump showed excellent agreement with the force plate (ICC values range from 0.991 for CMJ to 0.993) However mean DJ height from the force plate was significantly higher than MyJump (mean difference: 0.87cm, 95% CI: 0.69-1.04cm). Intra-rater reliability of MyJump for both CMJ and DJ was almost perfect (ICC values range from 0.997 for CMJ to 0.998 for DJ); however, mean CMJ and DJ jump height for Day 1 was significantly higher than Day 2 (CMJ: 0.43cm, 95% CI: 0.23-0.62cm); (DJ: 0.38cm, 95% CI: 0.23-0.53cm).

CONCLUSION

The present study finds MyJump to be a valid and highly reliable tool for researchers, coaches, athletes and clinicians; however, systematic bias should be considered when comparing MyJump outputs to other testing devices.

Validity Study of a Jump Mat Compared to the Reference Standard Force Plate

Background:

In the field of vertical jump diagnostics, force plates (FP) are the reference standard. Recently, despite a lack of evidence, jump mats have been used increasingly. Important factors in favor of jumping mats are their low cost and portability.

Objectives:

This validity study compared the Haynl-Elektronik jump mat (HE jump mat) with the reference standard force plate.

Materials and Methods:

Ten healthy volunteers participated and each participant completed three series of five drop jumps (DJ). The parameters ground contact time (GCT) and vertical jump height (VJH) from the HE jump mat and the FP were used to evaluate the concurrent validity. The following statistical calculations were performed: Pearson's correlation (r), Bland-Altman plots (standard and for adjusted trend), and regression equations.

Results:

The Bland-Altman plots suggest that the HE jump mat measures shorter contact times and higher jump heights than the FP. The trend-adjusted Bland-Altman plot shows higher mean differences and wider wing-spreads of confidence limits during longer GCT. During the VJH the mean differences and the wing-spreads of the confidence limits throughout the range present as relatively constant. The following regression equations were created, as close as possible to the true value: GCT = 5.920385 + 1.072293 × [value HE jump mat] and VJH = -1.73777 + 1.011156 × [value HE jump mat].

Conclusions:

The HE jump mat can be recommended in relation to the validity of constraints. In this study, only a part of the quality criteria were examined. For the final recommendation it is advised to examine the HE jump mat on the other quality criteria (test-retest reliability, sensitivity change).

Comparison and analysis of three different methods to evaluate vertical jump height

The purpose of this study was to compare three methods to assess vertical jump height, to determine their limitations and to propose solutions to mitigate their effects. The chosen methods were the contact mat, the optical system and the Sargent jump. The testing environment was designed such that all three systems simultaneously measured the vertical jump height. A total of 41 kinesiology students (18 women, 23 men, mean age 23·2 ± 4·5 years) participated in this study. Data show that the contact mat and the optical system essentially provide similar results (P = 0·912) and that the correlation coefficient between the two systems was 0·972 (r(2)  = 0·944). However, it was found that the Sargent jump has a tendency to overestimate the height, providing a measurement that is significantly different from the other two methods as the jumps are higher than 30·64 cm (P = 0·044). Through the design of the experiment, several sources of errors were identified and mathematically modelled. These sources include optical sensor placement, flat-footed landing and hip/knee bend. Whenever possible, the errors were quantified and solutions were proposed.