Date of Award

2009

Document Type

Thesis - ECU Access Only

Publisher

Edith Cowan University

Degree Name

Master of Science (Sports Science)

School

School of Exercise, Biomedical and Health Science

Faculty

Faculty of Computing, Health and Science

First Supervisor

Michael McGuigan

Second Supervisor

Michael Newton

Abstract

Postactivation potentiation (PAP) has been recognised as an improvement in muscle-twitch force following conditioning contractile activity. The phosphorylation of myosin regulatory light chains has been identified as the principal mechanism underlying PAP. Contractile activity has been shown to produce both PAP and fatigue, and it is the balance between the two that determines whether the response is enhanced, suppressed or unaffected. To date, the optimum time period between the heavy-resistance exercise and subsequent power performance remains to be elucidated. Similarly, many studies have been conducted on the effects of whole-body vibration (WBV) in relation to PAP with inconclusive results. The use of WBV with elite athletes has been limited, and there are no published studies focussing on WBV and its possible use in activating PAP. The purpose of the present study was to determine whether an acute enhancement of power (PAP) differs between WBV training and a heavy set of resistance exercise, and to investigate the time-course changes at 1, 3 and 5 minutes post WBV and heavy resistance exercise interventions. Fifteen male professional rugby union players (age 20.4±2.6 yrs) were recruited as participants. Using a cross-over design where participants performed all interventions, the heavy-resistance intervention consisted of a 3RM back squat, while the WBV intervention consisted of participants performing full dynamic squats whilst exposed to a vibration treatment (40 Hz, 4 mm displacement) on a VibroGym Professional vibration platform. A control condition consisting of body-weight squats only was also employed. All interventions were performed after a standardised squat warm-up. Peak power and peak displacement were measured by means of a countermovement jump. Comparison between interventions showed no statistically significant differences in peak power or peak displacement at any time point, but ES calculations indicated that moderate to large changes occurred in peak displacement (WBV - 5.9%, ES=0.60; 3RM - 10.9%, ES=1.09; Control - 8.2%, ES=1.05). The results also showed that a large effect (ES=1.16) was evident 3-5 minutes post-intervention. The results from the present study suggest that in professional rugby union players, PAP may be elicited from both WBV and heavy-resistance exercise. The large effects found post-intervention have implications for both strength and conditioning coaches and athletes in understanding potential outcomes when trying to elicit PAP using WBV or heavy-resistance exercise. Further study in this area will need to focus on the underlying mechanisms and their effects on an elite or high-performance population.

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