Browsing Sport and physical activity by Publisher "NSCA National Strength and Conditioning Association"
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Determinants of club head speed in PGA professional golfersTurner, AN. Determinants of club head speed in PGA professional golfers. J Strength Cond Res 30(8): 2266-2270, 2016 - Club head speed (CHS) has been significantly correlated with golf performance, but only in amateurs. The purpose of this study therefore, was to investigate the relationship between field-based measures of strength and power with CHS in Professional Golfers Association (PGA) professional golfers, and further determine differences between age groups. A correlation design was used to test relationships between squat jump (SJ), seated medicine ball throw (SMBT), rotational medicine ball throw (RMBT), and CHS. Twenty participants volunteered to take part in the study (age, 31.95 ± 8.7 years; height, 182.75 ± 6.88 cm; mass, 90.47 ± 15.6 kg). Intraclass correlation coefficients reported high reliability for performance variables (r 0.85-0.95). Significant correlations (p < 0.01) were found between CHS and SJ (r 0.817) and SMBT (r 0.706), but not RMBT (r 0.572). A stepwise linear regression analysis identified that SJ and SMBT explained 74% of the variance in CHS. When dividing the sample based on age, professionals <30 years (n 10; 25.6 ± 2.9 years) displayed significantly (p ≤ 0.05) higher CHS and SJ height compared with professionals >30 (n 10; 39.7 ± 5.5 years). Correlations to CHS for <30 were significant for SJ (r 0.801) and SMBT (r 0.643), but nonsignificant for RMBT. Those >30 had significant correlations to CHS not only in SMBT (r 0.881) and SJ (r 0.729), but also in RMBT (r 0.642). The results of this study suggest that SJ and SMBT have the largest contribution to CHS in PGA professional golfers. When comparing age groups, it appears that younger golfers (<30 years) utilize more leg strength whereas older golfers (>30 years) utilize more upper body strength. Results suggest that strength-based leg exercises and power-based chest exercises may improve CHS in professional golfers.
Effects of concurrent activation potentiation on countermovement jump performanceThe purpose of this study was to assess the effects of concurrent activation potentiation (CAP) on countermovement jump (CMJ) performance. Twenty-four resistance-trained males (mean ± SD; age: 25 ± 4 years, body mass: 78.7 ± 10.3 kg) performed a CMJ on a force plate under 4 different conditions: (a) a control condition where the CMJ was performed with hands on hips and lips pursed, thus preventing jaw or fist contraction from occurring, (b) a jaw condition where the CMJ was performed with maximal contraction of the jaw, (c) a fist condition where the CMJ was performed with maximal contraction of the fists, and (d) a combined condition where the CMJ was performed with maximal contraction of both jaw and fists. Jump height (JH), peak force (PF), rate of force development (RFD), and time to peak force (TTPF) were calculated from the vertical force trace. There was no significant difference in PF (p 0.88), TTPF (p 0.96), JH (p 0.45), or RFD (p 0.06) between the 4 conditions. Effect size (ES) comparisons suggest a potential for CMJ with fist and jaw contraction (BOTH condition) to augment both PF (2.4%; ES: 0.62) and RFD (9.9%; ES: 0.94) over a normal CMJ (NORM condition). It is concluded that CAP by singular and combined contractions has no significant impact on CMJ performance; however, substantial interindividual variation in response to CAP was observed, and such techniques may therefore warrant consideration on an individual basis.
Lower extremity stiffness: considerations for testing, performance enhancement, and injury riskBrazier, J, Maloney, S, Bishop, C, Read, PJ, and Turner, AN. Lower extremity stiffness: considerations for testing, performance enhancement, and injury risk. J Strength Cond Res 33(4): 1156-1166, 2019 - Force-deformation characteristics of the lower limb have been associated with athletic performance and may modulate the risk of injury. Despite these known associations, measurements of lower extremity stiffness are not commonly administered by strength and conditioning coaches. This review provides an overview of the available literature pertaining to the effects of lower extremity stiffness on physical performance and injury risk. Practical methods of monitoring and training stiffness are also discussed. The cumulative body of evidence indicates that increases in lower extremity stiffness are associated with heightened performance in athletic tasks such as hopping, jumping, throwing, endurance running, sprinting, and changing direction. Relationships with injury are less conclusive because both excessive and insufficient limb stiffness have been postulated to increase risk. Thus, the optimal level of stiffness seems to be dependent on the anthropometry and physical capabilities of the athlete, in addition to sport-specific activity demands. Training interventions can positively enhance lower extremity stiffness, including isometric, eccentric, and isotonic strength training and plyometrics. Complex training also seems to provide a potent stimulus and may be more effective than the use of singular training modes. For plyometric activities, it is recommended that coaches use a developmental sequence of exercises with increasing eccentric demand to provide an appropriate stimulus based on the training age and technical competency of the athlete.
Postactivation potentiation and change of direction speed in elite academy rugby playersThis study investigated the effect of preceding proagility sprints with maximal isometric squats to determine if postactivation potentiation (PAP) could be harnessed in change of direction speed. Sixteen elite under-17 rugby union players (age: 16 6 0.41 years; body mass: 88.7 6 12.1 kg; height: 1.83 6 0.07 m) from an Aviva Premiership rugby club were tested. Subjects performed a change of direction specific warm-up, followed by 2 baseline proagility tests. After 10-minute recovery, 3 3 3-second maximal isometric squats with a 2-minute recovery between sets were completed as a conditioning activity (CA) on a force plate where peak force and mean rate of force development over 300 milliseconds were measured. The proagility test was repeated at set time intervals of 1, 3, 5, and 7 minutes after the CA. Overall proagility times were significantly slower (p, 0.05) at 1 minute post-CA compared with the baseline (3.3%), with no significant differences occurring at 3, 5, or 7 minutes post-CA. Therefore, it appears that performing multiple sets of maximal isometric squats do not enhance proagility performance.