Contact Mat Research Articles

The Relationship Between Bat Velocity And Measures Of Strength And Power In Ncaa Division Ii Baseball Players

PURPOSE: This study was designed to examine the relationship between measures of upper and lower-body strength and power components and instantaneous bat velocity in NCAA Division II Collegiate baseball players. METHODS: Ten Division II collegiate baseball players (age: 20.3 ± 1.3 years; mass: 89.6 ± 12.1 kg; average years of experience: 14.9 ± 1.6; 7 right-handed batters) volunteered to participate in this study. Each subject completed two days of testing with a week between test days. Day 1 consisted of 5 repetition maximum bench press, 5 repetition squat, and grip strength. Day 2 consisted of lower body power (vertical jump performed on a contact mat), upper-body power (plyometric pushup performed on a force plate) and instantaneous bat velocity testing. A 3D motion analysis system sampling at 200 Hz was used to record the instantaneous bat velocity with the players hitting a ball from a tee. Spearman rank correlations were performed to establish the magnitude of the relationships between the variables. RESULTS: The magnitude of the relationships between the measures of strength and power and bat velocity ranged from small to large (-0.103 to 0.583) and none were significant (p>0.05). The largest correlation was found between left-hand grip strength and instantaneous bat velocity (0.583). CONCLUSION: Findings from this study suggest the importance of possibly implementing hand grip training to aid in an increase in instantaneous bat velocity. Since the upper-body and lower-body strength components demonstrated only small correlations with bat velocity, training should consist of working on mechanical efficiency of the players swing once muscular strength and power have been developed.

Lower Limb Neuromuscular Asymmetry in Volleyball and Basketball Players.

The primary objective of the present study was to evaluate the agreement between the dominant leg (DL) (determined subjectively) and the stronger leg (SL) (determined via a functional test) in a group of basketball and volleyball players. The secondary objective was to calculate lower limb neuromuscular asymmetry when comparing the DL vs the non-dominant leg (NDL) and the SL vs the weaker (WL) leg in the whole group and when differentiating by sex. Seventy-nine male and female volleyball and basketball players (age: 23.7 ± 4.5 years) performed three single-leg vertical countermovement jumps (SLVCJ) on a contact mat. Vertical jump height and an inter-limb asymmetry index (ASI) were determined. Only 32 (40%) of the subjects had a concordance between the perception of their dominant leg and the limb reaching the highest jump height. Using the DL as the discriminating variable, significant (p<0.05) inter-limb differences were found in the total group of players. When comparing between sexes, significant differences (p<0.05) arose in the female group only. With regard to the WL vs. the SL, significant (p<0.05) differences were noted in the whole group and when stratified into males and females. The mean ASI ranged from 9.31% (males) to 12.84% (females) and from 10.49% (males) to 14.26% (females), when comparing the DL vs. the NDL and the SL vs. the WL, respectively. Subjective expression of leg dominance cannot be used as a predictor of limb jump performance. Vertical jump asymmetry of 10-15% exists and this can be considered as a reference value for male and female basketball and volleyball players.

Explosive power of lower limbs in rhythmic gymnastics athletes in different competitive levels

Abstract The explosive power in Rhythmic Gymnastics shows itself in the great majority of movements and elements performed by the gymnasts, particularly in the jumps, which are essential corporal movements in this sport. The training directed to the development of jumping capacity presents a large quantity of exercises which aim to improve muscular power in the lower limbs and therefore the impulsion capacity. The vertical impulsion is an important measure used to calculate the explosive power of the lower limbs and is directly connected to the success that the gymnast will be able to achieve. Therefore, the aim of this study is to evaluate the height of two jumps in the RG (stag jump and Cossack jump) in contact mat Ergojump, which calculates the jump height in connection with the flight timing, executed by national level junior gymnasts and to compare them to the results of the Junior National Team - in total 30 junior gymnasts with 13.73 ± 0.17 years old. Furthermore, to compare the levels of explosive power of preferred lower limb (PLL) and non-preferred lower limb (NPLL) of all gymnasts in the study, in order to verify eventual functional asymmetries. For the statistical analysis we used Parametric Tests (t Test) and Nonparametric (Mann-Whitney Test and Wilcoxon Test). The gymnasts of the National Team achieved superior marks in 33.3% of the tests and 83.3% of the gymnasts of our sample did not present explosive power asymmetries. We conclude that the gymnasts of the National Team did not show the expected superiority in the tests, and the most of gymnasts presented a harmonious development of explosive power for both lower limbs, since they did not show functional asymmetries.

A New Contact Mat Wireless System for Estimating Vertical Jump Height

Among the different devices available for the assessment of the vertical jump height based on the flight time measurement, the contact mats are surely one of the simplest and portable systems and, for this reason, they are more widely used. This paper deals with the comparative evaluation of the performances of a new contact mat system with respect to a force platform. Some tests have been performed and the relative comparative results will be presented. The study shows a significant concurrent validity of Wi-JumpLe system for the flight and ground contact time measurements. In conclusion, the new contact mat structure together with the electronic measurement system is legitimate to assess vertical jump height and leg extensors muscle power.

IMU- based Determination of Stance Duration During Sprinting

Stride parameters like step length, step rate or stance duration during sprinting represent basic and very useful information for track and field coaches. Contact mats or opto- electronic systems like Optojump allow precise and unobtrusive measurements of theses parameters, but their use is limited in space. Inertial measurement units (IMUs) are not bound to these limitations and therefore offer challenging opportunities for in-field diagnosis, especially if combined with wireless data transmission. IMUs have already been used to detect kinematic parameters in track and field but data analysis can typically only be done offline. In this study, we present an IMU-based wearable measurement system for field-based performance analysis and online monitoring, that allows an accurate detection of step parameters in sprinting. Twelve track and field athletes (10 male, 2 female) performed maximal sprints wearing the IMU attached to both ankles. The OptojumpNext photocell system (Microgate, Bolzano, Italy) was used as reference system. Data acquisition rate for both devices was 1000Hz. Stance durations (tS) during the phase of maximal velocity are extracted onboard from the accelerometer and gyroscope signal and then sent to an external device. Out of 380 contacts, 364 were detected correctly (96%). tS showed a mean difference of -2.5±4.8ms between OptojumpNext and IMU. Bland-Altman plots derive a 95% limit of agreement (LOA) in the range from 6.8 to -11.8ms. Hence, the system enables providing reliable and accurate objective real-time feedback for a group of athletes during a training session or competition.

Accuracy of a Vertical Jump Contact Mat for Determining Jump Height and Flight Time

Several devices are available to measure vertical jump (VJ) height based on flight time, VJ reach height, or ground reaction forces. The purpose of this study was to determine the accuracy of a VJ mat for measuring flight time and VJ height compared with a VJ tester or a force plate. Seventeen men and 18 women (X ± SD; age = 20.9 ± 0.7 years, height = 176.1 ± 0.9 cm, weight = 72.6 ± 13.5 kg) served as subjects. Subjects performed counter-movement vertical jumps while standing on both a force plate (1,000 Hz) and a VJ mat. A Vertec VJ tester was used to measure jump reach. Compared with the force plate, the VJ mat reported greater VJ height (VJ mat = 0.50 ± 0.12 m, force plate = 0.34 ± 0.10 m) and flight time (VJ mat = 0.629 ± 0.078 seconds, force plate = 0.524 ± 0.077 seconds). Comparison of VJ heights from the VJ mat and the Vertec revealed no significant differences (Vertec = 0.48 ± 0.11 m). Regression analyses indicated strong relationships between testing methods and suggested that high VJ performances may be underestimated with the VJ mat. This particular VJ mat compared favorably with the Vertec but not the force plate. It seems that the different flight times derived from the VJ mat may permit the VJ mat to be in closer agreement with VJ heights from the Vertec. Also, the VJ mat may not be an appropriate tool for assessing high VJ performances (i.e., ≥0.70 m; ≈28 inches). Practitioners and researchers using similar VJ mats may not obtain accurate flight times and may underestimate high performers.

Perfil y diferencias antropométricas y físicas de gimnastas de tecnificación de las modalidades de artística y rítmica (Anthropometric and physical differences of the gymnasts from the talent identification program of the artistic and rhythmic specialties

El objetivo del trabajo fue describir y comparar las características físicas y antropométricas de 25 gimnastas pertenecientes al grupo de tecnificación de la Federación Extremeña de Gimnasia. Estas gimnastas fueron clasificadas según modalidad gimnástica: artística femenina (GAF) (n=13) y gimnasia rítmica (GR) (n=12). Las variables dependientes incluyen valoraciones del porcentaje graso, a través de una báscula electrónica de columna con tallímetro (SECA 220cm); perímetros corporales, a través de un plicómetro (Holtain); diámetros y pruebas específicas de flexibilidad, a través de cinta métrica (CM 3m); frecuencia cardíaca, a través del test de Ruffier y uso de pulsómetro (Polar F6); fuerza isométrica del tren inferior, donde se utilizó una célula de carga (SSMAJ 5000N), y la capacidad de salto, a través de una plataforma de contacto (Lafayette CVP A73). Los resultados concluyen que GAF obtiene mejor resultado en las pruebas de flexibilidad (p&lt;.05). Además, el grupo GR cuanto menor porcentaje graso posee mayor capacidad de salto SJ (r=-.774; p&lt;.01) y CMJ (r=-.600; p&lt;.05). En cambio, el grupo GAF cuanto mayor índice de masa corporal menor es su flexibilidad (p&lt;.01). Se concluye que existen diferencias en composición corporal y pruebas físicas entre las modalidades gimnásticas femeninas de artística y rítmica, además de encontrar relaciones entre el rendimiento de dichas pruebas y variables antropométricas. Palabra clave: gimnasia, características antropométricas, flexibilidad, fuerza isométrica, salto.Abstract: The aim of our research was to describe the physical and anthropometric characteristics of 25 gymnasts from the talent identification program of the Extremeña Gymnastics Federation. Subjects were classified according to their specialty: women‘s artistic gymnastic (WAG) and rhythmic gymnastics (RG). The dependent variables include body fat percentage through an electronic scale column with stadiometer (SECA 220cm); body circumferences through a plicometer (Holtain); body diameters and specific tests of flexibility through a tape (CM 3m); a heart rate through Ruffier test and a heart rate monitor (Polar F6); isometric strength of lower extremities through a load cell (SSMAJ 5000N); and jumping ability through a contact mat (Lafayette CVP A73). The results concluded that the WAG group got the best results in flexibility tests (p&lt;.05). Also, the RG group had lower body fat percentage and greater SJ jump ability (r=-.774; p&lt;.01) and CMJ (r=-.600; p&lt;.05). However, the WAG group showed a negative relation between body mass index and flexibility (p&lt;.01). We conclude that there are differences in body composition and physical tests between the specialties/styles of women’s artistic gymnastics and female rhythmic gymnastics; we also found relationships between the performance of such tests and anthropometric variables.Key words: gymnastics, anthropometric characteristics, flexibility, isometric strength, jump.

Concordância e correlação entre três métodos distintos para quantificação da altura do salto vertical

O presente estudo teve como objetivo analisar a correlação e concordância entre três diferentes métodos para quantificação da altura do salto vertical: cinta de Abalakov (AB), tapete de contato (TC) e videogrametria (VG). Treze atletas de vôlei do sexo feminino. Realizaram três saltos verticais máximos com contramovimento sem o auxílio dos membros superiores. Os três métodos mediram a altura do salto simultaneamente. Foram realizados os testes de correlação de Pearson (r) entre cada par de métodos (AB x TC, AB x VG e TC x VG). Por fim, a concordância entre cada par de métodos foi avaliada através da análise gráfica de Bland e Altman. A menor correlação encontrada (r = 0,77; p &lt; 0,01) ocorreu entre os métodos de VG e AB, enquanto que a maior correlação encontrada (r = 0,92; p &lt; 0,01) ocorreu entre os métodos de VG e TC. Não houve concordância satisfatória entre os valores encontrados para os diferentes métodos, sugerindo que profissionais da área tenham cautela na comparação entre resultados de altura do salto vertical obtidos por diferentes métodos.

Comparing Three Devices for Jump Height Measurement in a Heterogeneous Group of Subjects

The purpose of this study was to compare the accuracy of 3 devices for measuring jump heights of subjects with a range of abilities. The methods used were an accelerometer-based technique (KineJump), a contact mat (Newtest Powertimer 300 series), and the Vertec measurement device. The reference method used was a video analysis technique. Data were collected simultaneously with all 4 methods. Of particular interest was to evaluate the accuracy of the accelerometer device (KineJump) because it has not been systematically compared with other methods in the previous literature. Participants (N = 101) varied from well-trained athletes to sedentary individuals and their ages ranging from 18 to 70 years old. From the statistical analysis, it can be concluded that KineJump has accuracy that is at least as good as the accuracy of the Vertec and contact mat, although the overall accuracy of all the methods was disappointing at typically ± 5 cm. The 2 methods that rely on a time-of-flight calculation of the jump height (contact mat and accelerometer) showed systematically lower values than the other 2 methods. None of the physical parameters showed significant correlation with the measurement error made by the methods, with the exception of a slight positive correlation of height, leg length, and foot length to the error of the Vertec method. Linear regression on the Bland-Altman plots did not reveal a significant correlation between the jump height and the error of a method, except for the Vertec. The 3 jump height measurement devices can be used to evaluate performance in a diverse group of people, but considerable deviation from actual jump height is apparent, depending on the method of calculation.

Efeito de diferentes durações do alongamento no desempenho de saltos unipodais

INTRODUÇÃO: A prática de exercícios de alongamento é muito comum como parte do aquecimento em diversas modalidades esportivas, porém, esta prática pode ser negativa para aqueles que desejam o aprimoramento da força e potência muscular, consequentemente, o rendimento dos saltos pode ficar reduzido após exercícios de alongamento, que depende do tempo de duração e intensidade do mesmo.OBJETIVO: Avaliar a influência do tempo de permanência no exercício alongamento sobre o desempenho do drop jump unilateralmente (unipodal).MÉTODOS: A amostra foi composta por 16 adultos jovens hígidos, com larga experiência em saltos. O protocolo de teste consistiu em realizar três drop jumps unipodais máximos a partir de uma plataforma de 15 cm sobre um tapete de salto (Hidrofit(r)), antes e após duas durações (i.e. uma série 3 min. de um lado, e 6 min. para outro, a escolha foi de forma aleatória) de alongamento dos músculos tríceps sural, utilizando uma intensidade entre 70-90% da percepção subjetiva de desconforto. A análise de variância ANOVA (2x2) foi utilizada para verificar diferenças para a altura de salto, tempo de contato e flexibilidade, utilizando um nível de significância de 5%.RESULTADOS: Apresentaram diferenças significativas entre condições pré e pós-alongamento para as durações de 3 e 6 minutos (P=0,002 e P=0,001, respectivamente), com a diminuição na altura máxima do salto. O tempo de contato foi maior apenas para a duração de 6 minutos (P=0,039).CONCLUSÃO: A realização de exercícios de alongamento do músculo tríceps sural por 3 ou 6 minutos de duração resulta na queda do desempenho do drop jumpunipodal, diminuição da altura do salto vertical (para 3 e 6 min. de duração) e tempo de contato (apenas 6' min.), reforçando a necessidade de mais debates na área sobre exercícios de alongamento antes daqueles de potência.

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±4·5years) 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 30·64cm (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.

Effect of Back Squat Depth on Lower-Body Postactivation Potentiation

Postactivation potentiation (PAP) refers to increased muscular force generation after previous muscular activity. Various studies have used different squat variations as a PAP stimulus; however, different squat depths can have different mechanical and physiological demands that could yield different PAP levels and subsequent performance. The study aimed to compare the effects of the parallel (PS) and quarter (QS) squat on PAP. Twenty-seven, semiprofessional, male rugby union players (mean ± SD, 18 ± 2 years, 87.2 ± 5.4 kg, 180.7 ± 5.1 cm) performed a countermovement jump (BL-CMJ) followed by a 10-minute rest. Subsequently, they performed 3 PS or QS, at each squat's respective 3-repetition maximum load, in a randomized counterbalanced order. After a 5-minute rest, another countermovement jump (CMJ) was performed (POST-CMJ). Countermovement jump height (JH), peak power (PP), impulse (I), and flight time (FT) were recorded using a contact mat. BL-CMJ and POST-CMJ pairwise comparisons for all variables were conducted for each squat type to examine performance changes. Delta values were compared to examine whether one squat produced better CMJ results. Both squats induced PAP for all the variables (p < 0.05), although PS produced better results than QS (p < 0.05; JH, 4.6 ± 2 vs. 3.5 ± 2 cm; I, 15 ± 6 vs. 12 ± 5 N&middot;s; PP, 285 ± 109 vs. 215 ± 96 W; FT, 34 ± 23 vs. 26 ± 11 milliseconds for PS vs. QS). This is the first study to demonstrate that different squat types can induce PAP and that PS is more beneficial for subsequent CMJ performance compared with QS. It is suggested that the deeper depth of PS, which increases gluteus maximum activation and work produced, is responsible for the increased CMJ performance.

The Validity of the SmartJump Contact Mat

The aim of this study was to establish the criterion validity of the SmartJump contact mat in assessing vertical jump height (VJH) and peak power (PP). Twenty-three participants (15 men, age = 26 ± 6 years; 8 women, age = 26 ± 9 years) completed a maximal effort vertical jump using 3 different jump types (countermovement jump [CMJ], countermovement with arms [CMJA], and squat jump [SJ]). Data were simultaneously collected on both the contact mat and force platform. Vertical jump height was calculated using the time in air (TIA) method with both force platform (TIA(platform)) and contact mat (TIA(mat)) data and the takeoff velocity (TOV) method using the force platform (TOV(platform)) data. Peak power was calculated using a validated equation. The results showed that VJH and PP calculated using the TIA(mat) method were significantly greater than that calculated from the TIA(platform) and TOV(platform) methods for all jump types (VJH: p < 0.001, PP: p < 0.001). The results from this study show clear discrepancies between apparatus and calculation methods that may have implications for practitioners and should be considered when assessing VJH and PP in the field.

The Type Of Mat (Contact vs. Photocell) Affects Vertical Jump Height Estimated From Flight Time

The purposes of this study were to analyze the validity and reliability of 2 photocell mats and to probe the possible influence of the type of mat (contact vs. photocell) on vertical jump height estimated from flight time. In 2 separate studies, 89 and 92 physical students performed 3 countermovement jumps that were simultaneously registered by a Force Plate (gold standard method), 2 photocell mats (SportJump System Pro and ErgoJump Plus), and a contact mat (SportJump-v1.0). The first study showed that the 2 photocell mats underestimated the vertical jump height (1.3 ± 0.2 cm and 5.9 ± 5.2 cm, respectively), but only SportJump System Pro showed a high correlation with the Force Plate (r = 0.999 and 0.676, respectively) and good intraday reliability (coefficient of variation = 2.98 and 15.94%, intraclass correlation coefficients = 0.95-0.97 and 0.45-0.57, respectively). The second study demonstrated a strong correlation (r = 0.994) between the 2 technologies (contact vs. photocell mats) with differences in vertical jump height of 2.0 ± 0.8 cm (95% confidence interval = 1.9-2.1 cm), which depended on both flight time and subjects' body mass. In conclusion, SportJump System Pro was a valid and reliable device. The new devices to measure vertical jump height from flight time should be validated. The type of mat (contact vs. photocell) affected approximately 6% the vertical jump height (approximately 2 cm in this study), which should be considered in further studies. The use of validated photocell mats instead of the contact mats was recommended.

Does gymnastics practice improve vertical jump reliability from the age of 8 to 10 years?

The objective of this study was to confirm whether gymnastics practice from a young age can induce greater vertical jump reliability. Fifty young female gymnasts (8.84 ± 0.62 years) and 42 females in the control group (8.58 ± 0.92 years) performed the following jump tests on a contact mat: squat jump, countermovement jump, countermovement jump with arm swing and drop jump from heights of 40 and 60 cm. The two testing sessions had three trials each and were separated by one week. A 2 (groups) × 2 (sessions) × 3 (trials) repeated measures analysis of variance (ANOVA) and a test-retest correlation analysis were used to study the reliability. There was no systematic source of error in either group for non-plyometric jumps such as squat jump, countermovement jump, and countermovement jump with arm swing. A significant group per trial interaction revealed a learning effect in gymnasts' drop jumps from 40 cm height. Additionally, the test-retest correlation analysis and the higher minimum detectable error suggest that the quick drop jump technique was not fully consolidated in either group. At an introductory level of gymnastics and between the ages of 8–10 years, the condition of being a gymnast did not lead to conclusively higher reliability, aside from better overall vertical jump performance.

Reliability of Vertical Jump Performance evaluated with contact mat in elderly women

The aim of this study was to evaluate the reliability of the vertical jump (VJ) using a contact mat in elderly women. Thirty-one physically active women aged 69·5 ± 5·6 years participated in this study. Jump performance was evaluated with a contact mat. The first testing session (s1) consisted of four countermovement jumps interspersed with 40 s rest intervals. After a period of 5-7 days, volunteers performed the second session (s2) utilizing the same procedures. The intersession statistical analysis was calculated considering the two highest jumps, one obtained in each section. The intra-session analysis utilized all eight jumps, all four from each section, and the differences between means were calculated by repeated measures ANOVA. Reliability was tested using the intra-class correlation coefficient (ICC) and agreement by the Bland-Altman method. The intra- and inter-subject variation percentage was calculated by the coefficient of variation (CV). The intersession results displayed a high ICC (0·91; P<0·001) and a good agreement verified by the Bland-Altman method. There was a significant difference in the intra-session analysis only in s2 between the jumps 2 and 4. Both in s1 and s2, the ICC was high (0·96; P<0·001; 0·95; P<0·001), and the within session reliability CV was low (10·14% and 9·07%). In physically active elderly women, VJ evaluation using a contact mat is a reliable method and could be used to estimate jump height. Additionally, the results of this study could serve as reference values in similar samples evaluated with the same procedures.

Plyometric Jumping Performances of Male and Female Gymnasts From Different Heights

The objective of this study was to investigate and compare the factors influencing plyometric jumping performance between well-trained gymnasts and a control group. Seventy-six gymnasts and 91 moderately active subjects volunteered to participate in this study. Drop jumps (DJ) were performed from 20-, 40-, 60-, 80-, and 100-cm heights. Flight time (FT) and contact time (CT) were recorded using contact mat. Flight time to contact time (FC) ratio and Bosco expression (BE) were calculated. Male gymnasts scored similar FT to their controls, whereas female gymnasts had significantly longer FT compared with their peers. The gymnasts obtained significantly shorter CT than their control groups, whereas their FC ratios were significantly higher and increased when the height of the drops was close to 60 cm. Moreover, gymnasts' BE was greater in comparison to their respective control groups independent of the drop height. The height of the drop that produced the best FC ratio and BE varied between the groups. The best performances were obtained between 40- and 60-cm drop height for both groups. Female control group showed a trend toward a continuing decline with the increase of the drop height. The best gymnasts (finalists at World Championships) obtained their best performance at 80-cm drop. Flight time is the less discriminating factor distinguishing gymnasts' DJ performances. Considering CT, FC, and BE results all together could better profile the gymnasts rather than taken separately. Bosco expression was shown to be more sensitive to the increase in FT; we suggest BE as the best criteria to assess the appropriate drop height for plyometric training purposes in gymnasts as it has been significantly correlated to FT.

Short report: Recovery of jump performance after a simulated cricket batting innings

The time-course of physical recovery was determined after a 2-h 20-min, simulated cricket batting innings. Several vertical jump measures were assessed before (baseline), immediately after, 24 h after and 48 h after simulated batting. Six, male, academy cricketers (20 ± 2 years) completed a previously developed simulated batting innings (BATEX) at an outdoor net facility. At each assessment point, participants completed countermovement-jumps, squat-jumps and 5-repeated reactive-jumps on a contact mat. Compared with baseline, countermovement flight time was similar immediately after, but decreased 24 h after batting (−3.0 ± 1.8%, p < 0.05, effect size [ES] ± 90% confidence interval [CI]: −1.38 ± 0.52). At 48 h post, countermovement-jump flight time was similar to baseline. A similar pattern occurred in the squat-jump and the decrease in squat-jump flight time 24 h after simulated batting approached significance (p = 0.053, ES ± CI −0.80 ± 0.51). The 5-repeated reactive-jump measures (flight time, contact time and reactive-strength-index) did not decrease after simulated batting (p > 0.05), but there were moderate effect sizes calculated (0.64–0.96). These findings support the continued use of countermovement flight time to assess recovery in cricket, since full recovery of jump performance occurred 48 h after a simulated, prolonged and high intensity-batting century.

Leg Stiffness Changes in Athletes with Achilles Tendinopathy

Overuse injuries of the Achilles tendon cause impairment in lower leg muscle-tendon function. The purpose of this study was to evaluate leg stiffness in patients suffering unilateral Achilles tendinopathy. 51 athletes with unilateral Achilles tendinopathy underwent leg stiffness testing by modeling the vertical ground reaction force in a contact mat, measuring flight and contact time during hopping. Clinical status was estimated with a pain VAS and a validated questionnaire (VISA-A). The 'leg stiffness ratio' (LSR=stiffness of injured leg/stiffness of healthy leg) was calculated to determine the relative patient affectation and for intra-group comparison. 84 percent of subjects showed lower leg stiffness in the affected side during hopping. Leg stiffness was significantly lower in the limb affected by Achilles tendinopathy than in the healthy side (14.07±3.74 kN/m vs. 15.61±4.01 kN/m, p=0.047); overall LSR was 0.90±0.09. Intra-group comparison did not show significant differences related to patients' age, gender, sport level, and site of tendon injury (midportion or insertional). Leg stiffness was significantly reduced in patients with unilateral Achilles tendinopathy probably related to increasing ankle compliance. Regular leg stiffness assessment would be beneficial for athletes suffering Achilles tendon problems in terms of quantifying performance capabilities and providing objective data for a safer return to sport activity.

Predicting Lower Body Power from Vertical Jump Prediction Equations for Loaded Jump Squats at Different Intensities in Men and Women

The purpose of this study was to determine the efficacy of estimating peak lower body power from a maximal jump squat using 3 different vertical jump prediction equations. Sixty physically active college students (30 men, 30 women) performed jump squats with a weighted bar's applied load of 20, 40, and 60% of body mass across the shoulders. Each jump squat was simultaneously monitored using a force plate and a contact mat. Peak power (PP) was calculated using vertical ground reaction force from the force plate data. Commonly used equations requiring body mass and vertical jump height to estimate PP were applied such that the system mass (mass of body + applied load) was substituted for body mass. Jump height was determined from flight time as measured with a contact mat during a maximal jump squat. Estimations of PP (PP(est)) for each load and for each prediction equation were compared with criterion PP values from a force plate (PP(FP)). The PP(est) values had high test-retest reliability and were strongly correlated to PP(FP) in both men and women at all relative loads. However, only the Harman equation accurately predicted PP(FP) at all relative loads. It can therefore be concluded that the Harman equation may be used to estimate PP of a loaded jump squat knowing the system mass and peak jump height when more precise (and expensive) measurement equipment is unavailable. Further, high reliability and correlation with criterion values suggest that serial assessment of power production across training periods could be used for relative assessment of change by either of the prediction equations used in this study.