Concurrent criterion validity of a novel portable motion analysis system for assessing the landing error scoring system (LESS) test.

The landing error scoring system (LESS) assesses the quality of a landing after a jump. The quality of the jump is usually evaluated using a three-dimensional (3-D) motion analysis system or a two-dimensional (2-D) video analysis visually rated by a clinician. However, both methods have disadvantages. The aim of this study was to examine the concurrent validity of a novel portable motion analysis system ('PhysiMax System') in assessing the LESS score by comparing it to video analysis. The study population included 48 healthy participants (28.45 ± 5.61 years), each performing the LESS test while two video cameras and the 'PhysiMax' simultaneously recorded the jump. The 'Physimax' system automatically evaluated the LESS. Subsequently, the examiners scored the test by viewing the video recordings, blinded to the 'PhysiMax' results. The mean LESS score, using the video recordings and the 'PhysiMax' was 4.77 (±2.29) and 5.15 (±2.58), respectively, (ICC = 0.80, 95% confidence intervals 0.65-0.87), mean absolute differences 1.13 (95% confidence intervals; 0.79-1.46). The results indicate a high consensus between the methods of measurement. The 'Physimax' system's main advantages are portability, objective evaluation and immediate availability of results. The system can be used by athletic trainers and physiotherapists in the clinic and in the field for jumping assessment.

Reliability and magnitude of mechanical variables assessed from unconstrained and constrained loaded countermovement jumps.

This study aimed to (1) assess the reliability of the force, velocity, and power output variables measured by a force plate and a linear velocity transducer (LVT) for both the unconstrained and constrained loaded countermovement jump (CMJ), and (2) examine the effect of both the CMJ type and the measurement method on the magnitudes of the same variables. Twenty-three men were tested on the free CMJ and the CMJ constrained by a Smith machine. Maximum values of force, velocity, and power were recorded by a force plate and by a LVT attached to a bar loaded by 17, 30, 45, 60, and 75 kg. The reliability of all mechanical variables proved to be high (ICC > 0.70; CV < 10%) and similar for two CMJ types. However, force plate-derived measures displayed greater reliability than the LVT. The LVT also markedly overestimated the magnitudes of the mechanical variables, particularly at lower external loads. Therefore, although both jump types and both methods could be acceptable for routine testing, we recommend the force platform due to a higher reliability and more accurate magnitudes of the obtained variables. The unconstrained loaded CMJ could also be recommended due to the simpler equipment needed.

Efectos del entrenamiento pliométrico acuático vs. seco sobre el salto vertical / Effects of land vs. aquatic plyometric training on vertical jump

El objetivo de este estudio fue comparar los efectos de dos programas de entrenamiento pliométrico (inmersión vs. seco) sobre el salto vertical. 65 hombres físicamente activos fueron asignados aleatoriamente a tres grupos: entrenamiento pliométrico acuático (EPA, n 20), entrenamiento pliométrico (EP, n=20) y grupo control (GC, n=25). Los grupos EPA y EP entrenaron 2 sesiones por semana durante 10 semanas, mientras que GC no realizó entrenamiento alguno. El volumen de entrenamiento fue aumentado desde 10 series de 10 repeticiones en la primera semana hasta 10 series de 55 repeticiones en la última. Tanto EPA como EP aumentaron su rendimiento en CMJ y SJ con respecto al pretest (P≤0,001) sin encontrar diferencias significativas entre grupos, mientras que GC no mostró cambios. Como conclusión, el EPA puede ser un método alternativo a EP ya que ambos producen similares mejoras sobre el salto vertical y el estrés mecánico producido por EPA es menor (AU)

The aim of this study was to compare the effects of two plyometric training program (aquatic vs. land) on vertical jump. 65 male physical education students took part in this study and were randomly assigned to three groups: aquatic plyometric training group (APT, n = 20), plyometric training group (PT, n = 20) and control group (CG, n = 25). The training program was performed for 10 weeks with a frequency of 2 sessions per week. Volume was increased from 10 sets of 10 repetitions to 10 sets of 55 repetitions. Both APT and PT increased the performance in CMJ and SJ with respect to pretest (P ≤ .001), whereas CG remained unaltered. No statistically significant difference was observed between APT and PT. In conclusion, APT may be an alternative method to PT, because both training protocols have produced similar gains in the vertical jump, but APT might cause lower mechanical stress (AU)

A comparison of assisted, resisted, and common plyometric training modes to enhance sprint and agility performance.

BACKGROUND: The purpose of this study was to compare the effect of assisted, resisted and common plyometric training modes to enhance sprint and agility performance. Thirty active young males (age 20.67±1.12, height 174.83±4.69, weight 63.45±7.51) volunteered to participate in this study that 24 completed testing. METHODS: The participants were randomly assigned into different groups: assisted, resisted and common plyometric exercises groups. Plyometric training involved three sessions per week for 4 weeks. The volume load of plyometric training modes was equated between the groups. The posttest was performed after 48 hours of the last training session. Between-group differences were analyzed with the ANCOVA and LSD post-hoc tests, and within-group differences were analyzed by a paired t-test. RESULTS: The findings of the present study indicated that 0-10-m, 20-30-m sprint time and the Illinois Agility Test time significantly decreased in the assisted and resisted plyometrics modes compared to the common plyometric training mode (P≤0.05). Also, the 0-10-m, 0-30-m sprint time and agility T-test time was significantly reduced with resisted plyometrics modes compared to the assisted and common plyometric modes (P≤0.05). There was no significant difference in the 10-20-m sprint time among the three plyometric training modes. CONCLUSIONS: The results of this study demonstrated that assisted and resisted plyometrics modes with elastic bands were effective methods to improve sprint and agility performance than common plyometric training in active males. Also, the resisted plyometrics mode was superior than the assisted plyometrics mode to improving sprint and agility tasks.

Comparison of the force-, velocity-, and power-time curves recorded with a force plate and a linear velocity transducer.

This study aimed to correlate, compare, and determine the reliability of force, velocity, and power values collected with a force plate (FP) and a linear transducer during loaded jumps. Twenty-three swimmers performed an incremental loading test at 25, 50, 75, and 100% of their own body weight on a FP. A linear velocity transducer (LVT) was attached to the bar to assess the peak and the mean values of force, velocity, and power. Both the peak variables (r = 0.94 - 0.99 for peak force, r = 0.83 - 0.91 for peak velocity, and r = 0.90-0.94 for peak power; p < 0.001) and the mean variables (r = 0.96-0.99 for mean force, r = 0.87-0.89 for mean velocity, and r = 0.93-0.96 for mean power; p < 0.001) were strongly correlated between both measurement tools. Differences in the shape of the force-, velocity-, and power-time curves were observed. The LVT data showed a steeper increase in these variables at the beginning of the movement, while the FP recorded larger values in the latter part. Peak values were more reliable than mean values. These results suggest that the LVT is a valid tool for the assessment of loaded squat jump.

Efectos del entrenamiento pliométrico sobre la resistencia cardiorrespiratoria de niños y adolescentes con síndrome de Down / Effects of a circuit training including plyometric jumps on cardiorespiratory fitness of children and adolescents with Down syndrome

Objetivo: Determinar los efectos de 21 semanas de entrenamiento en circuito, incluyendo saltos pliométricos sobre la resistencia cardiorrespiratoria de jóvenes con síndrome de Down (SD). Método: Veintisiete jóvenes con SD de entre 10 y 19 años participaron en este estudio. Los participantes se dividieron en dos grupos: ejercicio (EJE; n= 14) y control (CON; n=13). Antes y después de la realización del programa de entrenamiento se midieron los siguientes parámetros: tiempo de trabajo, valores máximos de consumo de oxígeno, cociente respiratorio, frecuencia cardíaca y ventilación minuto de los participantes mediante una prueba de esfuerzo progresiva en tapiz rodante. Resultados: Los participantes del grupo EJE aumentaron todos los parámetros cardiovasculares en comparación con su valor basal, después del entrenamiento (todos p< 0,05). Además, a pesar de tener unos valores similares antes del entrenamiento, el grupo EJE mostró valores más elevados que el grupo CON después del entrenamiento (todos p<0,05). Conclusión: Se puede concluir que los jóvenes con síndrome de Down pueden conseguir mejoras en diversos parámetros cardiorrespiratorios tras la ejecución de 21 semanas de entrenamiento con ejercicios pliométricos (AU)

Aim: To ascertain the effects of 21 weeks of circuit training, including plyometric jumps, on cardiorespiratory fitness of youths with Down’s syndrome (DS). Methods: Twenty-seven children and adolescent aged 10 to 19 years with DS participated in this study and were divided in two groups: exercise (EXE, n=14) and control (CON, n=13). Work time, peak values of oxygen consumption, respiratory exchange ratio, heart rate and minute ventilation of the participants were measured pre- and post-training with a graded exercise treadmill test. Results: EXE group increased all their cardiorespiratory parameters compared to baseline after 21 weeks of training (all P<.05). Additionally, and despite having similar pre-training values, the EXE group showed higher values than the CON group in all cardiorespiratory parameters after training (all P<.05). Conclusion: It may be concluded that youths with Down syndrome can achieve improvements in several cardiorespiratory parameters when performing 21 weeks of training including plyometric exercises (AU)

Possibility of stretch-shortening cycle movement training using a jump rope.

Although jumping rope has been said to be a typical stretch-shortening cycle movement (SSC) from the dynamic analysis of muscle contraction, there are few research reports that focus on this point. Recently, the function of SSC of the legs with respect to the jumping movement has been evaluated using the rebound jump index (RJ-index). This study aimed to examine the possibility of using rope jumping in SSC training by comparing the RJ-index of the rebound jump (standard value) and the 2 different methods of rope jumping. The subjects included 76 healthy young men. Most subjects were involved in routine sports training 2-3 times per week. They performed the rebound jump (5 consecutive vertical jumps) and both a basic and a double-under jump with the jump rope, according to each participant's individual style (rhythm or timing). The RJ-index was calculated using the ground contact time and the jump height. The reliabilities of the RJ-index in the basic (intraclass correlation coefficient: 0.85) and double-under jump (0.92) were high, and the RJ-index of the latter (1.34 ± 0.24) was significantly higher than that of the former (0.60 ± 0.21). In the case of a group with inferior SSC ability, the RJ-index of the rebound jump only showed a significant correlation with the double-under but not with the basic jump. When using the RJ-index (1.97 ± 0.38) of the rebound jump as a criterion, the double-under-using about 70% of the SSC ability-may be effective for reinforcement of SSC ability.

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

The purpose of this investigation was to determine the concurrent validity of a commonly used electronic switch mat (ESM), or jump mat, compared with force plate (FP) data. The efficiency of collection and accuracy of data are paramount to athlete and player field testing for the strength and conditioning coach who often has access only to a jump mat. Ten subjects from 5 different sporting backgrounds completed 3 squat jumps (SJs), 3 countermovement jumps (CMJs), and 3 drop jumps (DJs). The jumps were performed on an AMTI FP operating at 1,000 Hz with an ESM positioned on top of the platform. All the subjects were experienced with the protocols involved with jump testing. The resulting absolute errors between FP and ESM data were 0.01, 0.02, and 0.01 m for CMJ, SJ, and DJ heights, respectively. However, the coefficient of variation for the DJ contact time (CT) was 57.25%, CMJ (r = 0.996), and SJ (r = 0.958) heights correlated very strongly with force platform data, and DJ data were not as strong (r = 0.683). Confidence interval tests revealed bias toward CMJ and SJ (p < 0.05). The jump mat can accurately calculate the CMJ height, SJ height, and reactive strength index for all the 3 jump protocols. However, the faster CTs and rapid movements involved in a DJ may limit its reliability when giving measures of CT, flight time, and height jumped for DJs. Strength and conditioning coaches can use such a jump mat device with the confidence that it is accurately producing valid measurements of their athlete's performance for CMJ and SJ slow SSC protocols.