B A C K G R O U N D
Past research has investigated the effects of flexibility training on performance during various activities. These studies have focused on long term flexibility programs and their effect on increases in outcome parameters such as vertical jump height or the amount of weight lifted during a bench press. In contrast, very little research has been conducted to investigate the short term effects of warm-up stretching on increases in skills coordination and biomechanics for a given activity. In many cases, the effects have been speculated; however, little quantitative information is available.
The inherent structural elements of muscle resist lengthening. Passive muscle resistance increases as a function of length when the muscle is stretched and can be characterized as stiffness. It has been shown that muscle stiffness increases with inactivity. When inactive, a muscle may develop bonds between actin and myosin filaments increasing its resistive nature.
Stretching can break the bonds or adhesions formed during inactivity and thereby reduce passive muscular stiffness. Stretching as warm-up can also induce other effects which in turn increase muscle elasticity and extendibility. These effects include increases in core temperature, metabolic reactions and muscle blood flow. Static stretching has been shown to be an effective and safe way to warm-up muscles and increase flexibility.
It is defined as a slow stretch of the muscle held for a duration of 6-60 seconds. Passive stretching is an additional classification of stretching defined by no contribution by the individual to generate the muscle lengthening force.
A full golf swing can be characterized
as a ballistic, power generating activity. Power production can be described
as the rate at which muscles produce work and is often directly related
to limited performance in ballistic activities. The ability to produce
power can be enhanced when a muscle is lengthened prior to contraction
(eccentric-concentric contraction). Increased ability to produce positive
work during an eccentric-
concentric contraction is in part attributed
to the storage and use of elastic energy.
It has been shown that warm-up and specifically stretching prior to ballistic activity can increase a muscle's ability to utilize elastic energy to create more efficient power during contraction. However, a majority of the research that has been conducted in this area has concentrated on specific outcome parameters for relatively simple movements as a measure of increased performance. In a more complex motion like the golf swing, groups of muscles work in a finely tuned coordinated effort to create power. The complexity of the motion and the skills involved in performance make a simple measurement of outcome harder to correlate to an increase in power production.
This study will use a specific application of kinetic linking principles (first described by Welch et al, Hitting a Baseball: A Biomechanical Description. JOSPT) to identify increase in skills and biomechanics related to power production. The primary goal will be to investigate the effects of stretching as a warm-up prior to a ballistic activity on biomechanics skills and power production. The secondary goal will be to investigate the comparative effect of two types of stretching (static vs. 'machine assisted' passive) on overall performance.
