Efectos del entrenamiento con movimientos de halterofilia en el rendimiento de esprint, salto y cambio de dirección en deportistas: Una revisión sistemática (Effects of weightlifting training on sprint, jump and change of direction performance in athlete

La capacidad de generar máxima potencia neuromuscular es el factor más importante y determinante en el rendimiento atlético. Debido a esto, el entrenamiento con movimientos de Halterofilia (EMH) y sus derivados es uno de los métodos más usados, ya que la evidencia muestra que genera adaptaciones de fuerza-potencia superiores comparadas con el entrenamiento de fuerza tradicional, de salto y de kettlebells. Objetivo: Identificar los efectos del EMH en la capacidad de salto, esprint y cambio de dirección (COD) en población deportista. Método: Se realizó una búsqueda exhaustiva en diferentes bases de datos, como PUBMED, Sportdiscus (EBSCO), Scopus y Web of Science (WOS) bajo modelo PRISMA. Los trabajos revisados fueron experimentales con y sin grupo de control, entre los años 2000 y 2020. Resultados: El EMH produce mejoras significativas en las capacidades de salto, de esprint y de COD en población deportista. Conclusión: El EMH genera mejoras significativas en el rendimiento de salto, carreras y cambio de dirección bajo distintos protocolos. Existe evidencia que sustenta la aplicación de EMH, recomendando sus derivados centrados en el segundo tirón y aquellos que utilicen el ciclo de estiramiento-acortamiento en sus variantes colgantes. Abstract: The ability to generate maximum power is the most important and determining neuromuscular function in sports performance. Therefore, weightlifting training (WT) and its derivatives is one of the most widely used methods, generating superior strength-power adaptations compared to traditional strength training, jumping and kettlebell training. Objective: To identify the effects of WT on the ability to jump, sprint and change of direction (COD) in athletes. Method: An exhaustive search was carried out in different databases, such as PUBMED, Sportdiscus (EBSCO), Scopus and Web of Science (WOS) under the PRISMA model. The reviewed papers were experimental with and without a control group, between the years 2000 and 2020. Results: The WT produces significant improvements in jump, sprint and in change of direction capacities in the sport population. Conclusion: WT generates significant improvements in jumping, running and change of direction performance under different protocols. There is evidence supporting the use of WT, suggesting its derivatives focused on the second pull and those that use the stretch-shortening cycle in their hanging variants.

Interrelationship between specific high-intensity intermittent efforts ability with aerobic capacity and slow stretch-shortening cycle utilization in taekwondo athletes

BACKGROUND: Repeat high-intensity intermittent efforts is a taekwondo-specific ability but the influence of aerobic capacity and dynamic strength characteristics on this ability has received relatively little attention in the literature. OBJECTIVE: To examine the relationship between specific high-intensity intermittent efforts with aerobic capacity and slow stretch-shortening cycle utilization in taekwondo athletes. METHODS: Nineteen taekwondo male athletes were assessed by squat jump (SJ), countermovement jump (CMJ), 20-meter shuttle run (20MSR), and frequency speed of kick test multiple (FSKTMULT). From the FSKTMULT, total kicks and kick decrement index [KDI] were calculated. Additionally, from both jump tests, the slow stretch-shortening cycle utilization (Slow SSC Utilization) was determined from the eccentric utilization ratio [EUR], pre-stretch augmentation [PSA], and reactive strength index [RSI]. RESULTS: There were positive and significant correlations between total kicks with 20MSR (r= 0.85; p= 0.00) and SJ (r= 0.66; p< 0.05). The multiple regression model demonstrated that total kicks where significantly influenced by 20MSR (R2= 71%; p= 0.00). Additionally, only EUR and RSI explained total kicks performance to a greater proportion (R2= 76%). CONCLUSIONS: The FSKTMULT total kicks performance is positively correlated and influenced by aerobic capacity and slow SSC utilization.

Acute Effects of Different Plyometric and Strength Exercises on Balance Performance in Youth Weightlifters

Background: High-intensity muscle actions have the potential to temporarily improve the performance which has been denoted as postactivation performance enhancement.Objectives: This study determined the acute effects of different stretch-shortening (fast vs. low) and strength (dynamic vs. isometric) exercises executed during one training session on subsequent balance performance in youth weightlifters.Materials and Methods: Sixteen male and female young weightlifters, aged 11.3±0.6years, performed four strength exercise conditions in randomized order, including dynamic strength (DYN; 3 sets of 3 repetitions of 10 RM) and isometric strength exercises (ISOM; 3 sets of maintaining 3s of 10 RM of back-squat), as well as fast (FSSC; 3 sets of 3 repetitions of 20-cm drop-jumps) and slow (SSSC; 3 sets of 3 hurdle jumps over a 20-cm obstacle) stretch-shortening cycle protocols. Balance performance was tested before and after each of the four exercise conditions in bipedal stance on an unstable surface (i.e., BOSU ball with flat side facing up) using two dependent variables, i.e., center of pressure surface area (CoP SA) and velocity (CoP V).Results: There was a significant effect of time on CoP SA and CoP V [F(1,60)=54.37, d=1.88, p&lt;0.0001; F(1,60)=9.07, d=0.77, p=0.003]. In addition, a statistically significant effect of condition on CoP SA and CoP V [F(3,60)=11.81, d=1.53, p&lt;0.0001; F(3,60)=7.36, d=1.21, p=0.0003] was observed. Statistically significant condition-by-time interactions were found for the balance parameters CoP SA (p&lt;0.003, d=0.54) and CoP V (p&lt;0.002, d=0.70). Specific to contrast analysis, all specified hypotheses were tested and demonstrated that FSSC yielded significantly greater improvements than all other conditions in CoP SA and CoP V [p&lt;0.0001 (d=1.55); p=0.0004 (d=1.19), respectively]. In addition, FSSC yielded significantly greater improvements compared with the two conditions for both balance parameters [p&lt;0.0001 (d=2.03); p&lt;0.0001 (d=1.45)].Conclusion: Fast stretch-shortening cycle exercises appear to be more effective to improve short-term balance performance in young weightlifters. Due to the importance of balance for overall competitive achievement in weightlifting, it is recommended that young weightlifters implement dynamic plyometric exercises in the fast stretch-shortening cycle during the warm-up to improve their balance performance.

Substantial Achilles adaptation following strength training has no impact on tendon function during walking

Tendons are responsive to mechanical loading and their properties are often the target of intervention programs. The tendon’s mechanical properties, particularly stiffness, also govern its function, therefore changes to these properties could have substantial influence on energy-saving mechanisms during activities utilizing the stretch-shortening cycle. We investigated Achilles tendon (AT) function in vivo during walking with respect to a training intervention that elicited significant increases in AT stiffness. 14 men and women completed 12-weeks of isometric plantarflexor strength training that increased AT stiffness, measured during isometric MVC, by ~31%. Before and after the intervention, participants walked shod at their preferred velocity on a fully-instrumented treadmill. Movement kinematics, kinetics and displacement of the gastrocnemius medialis muscle-tendon junction were captured synchronously using 3D motion capture and ultrasound imaging, respectively. A MANOVA test was used to examine changes in AT force, stress, strain, stiffness, Young’s modulus, hysteresis and strain energy, measured during walking, before and following strength training. All were non-significant for a main effect of time, therefore no follow-up statistical tests were conducted. Changes in joint kinematics, tendon strain, velocity, work and power and muscle activity during the stance phase were assessed with 1D statistical parametric mapping, all of which also demonstrated a lack of change in response to the intervention. This in vivo examination of tendon function in walking provides an important foundation for investigating the functional consequences of training adaptations. We found substantial increases in AT stiffness did not impact on tendon function during walking. AT stiffness measured during walking, however, was unchanged with training, which suggests that increases in stiffness may not be evident across the whole force-elongation relation, a finding which may help explain previously mixed intervention results and guide future investigations in the functional implications of tendon adaptation.

The effect of stretch–shortening magnitude and muscle–tendon unit length on performance enhancement in a stretch–shortening cycle

Stretch-induced residual force enhancement (rFE) is associated with increased performance in a stretch–shortening cycle (SSC). Although the influence of different range of motions and muscle–tendon unit lengths has been investigated in pure stretch-hold experiments in vivo, the contribution to a SSC movement in human muscles remains unclear. In two sessions, 25 healthy participants performed isometric reference (ISO), shortening hold (SHO) and SSC contractions on an isokinetic dynamometer. We measured the net knee-joint torque, rotational mechanical work, knee kinematics and fascicle behavior (m. vastus lateralis) of the upper right leg. In session 1 the SHO- and SSC-magnitude was changed respectively (SHO: 50°–20°, 80°–20° and 110°–20°; SSC: 20°–50°–20°, 20°–80°–20° and 20°–110°–20°) and in session 2 the muscle–tendon unit length (SHO: 50°–20°, 80°–50° and 110°–80°; SSC: 20°–50°–20°, 50°–80°–50° and 80°–110°–80°; straight leg = 0°). In both sessions, rotational work was significantly (p < 0.05) increased in the SSC compared to the SHO contractions (in the range of 8.1–17.9%). No significant difference of joint torque was found in the steady-state for all SSC-magnitudes compared to the corresponding SHO contractions in session 1. In session 2, we found only significantly (p < 0.05) less depressed joint torque in the SSC at the longest muscle–tendon unit length compared to the corresponding SHO condition, without any differences in knee kinematics and fascicle behavior. Therefore, the physiological relevance of rFE might be particularly important for movements at greater muscle–tendon unit lengths.

Stretch-shortening cycle exercises can efficiently optimize gait-symmetry and balance capabilities in children with unilateral cerebral palsy: A randomized controlled trial

BACKGROUND: Children with unilateral cerebral palsy (UCP) experience an asymmetrical gait pattern and poor balance capabilities. Effective interventions, therefore, are needed to facilitate remediation of these functional issues. OBJECTIVE: This study was set out to investigate the emerging role of stretch-shortening cycle (SSC) exercises on gait-symmetry and balance in children with UCP. METHODS: In this randomized controlled trial, 42 children with UCP (age; 8 –12 years) were enrolled and received either standard physical rehabilitation (control group; n = 21) or the SSC exercise program plus physical rehabilitation (SSC group; n = 21). Spatial- and temporal-gait symmetry index (GSI) and specific balance capabilities [reactive balance, directional control, movement synchronization, and sensory organization] were assessed before and after 16 sessions that were carried out twice/week over non-sequential days in an 8-week program. RESULTS: Using the pre-treatment scores as covariates, the post-treatment spatial- (P = 0.006; η p 2 = 0.17) and temporal- GSI (P < .001; η p 2 = 0.46) scores reduced significantly in the SSC group as compared to the control group, suggesting favorable improvement of gait symmetry. Also, all measures of balance (P < 0.05; η p 2 ranged between 0.10 and 0.29) improved remarkably, post-treatment, in SSC group in comparison with the control group. CONCLUSION: The evidence from this study suggests that SSC exercises besides standard physical rehabilitation appear to be effective for improving gait symmetry and boosting balance capabilities in children with UCP.