WARM-UP STRATEGIES AND THEIR EFFECT ON PERFORMANCE: PART 2 – THE PHYSIOLOGICAL MECHANISMS
Although emerging evidence is proving valuable insight into the effectiveness, or lack thereof, of various warm-up strategies, it is important to ask why are some more effective than others? Which mechanisms are responsible at a physiological level? We will cover some of the proposed mechanisms, but it is important to note that further research is required.
Passively or actively elevating muscle temperature can markedly influence exercise performance. This is thought to be the result of effects on:
- Muscle metabolism: Elevating muscle temperature has been linked with faster adenosine triphosphate (ATP) turnover, which can increase power production particularly in the first 2 minutes of exercise.
- Muscle fibre performance: Passive warming strategies result in greater PCr and ATP utilisation in type 2 fibres during high frequency contraction tasks, and in type 1 fibres during low frequency tasks.
- Muscle fibre conduction velocity: The MFCV in muscles both actively and passively involved in the warm-up has also been reported to increase (5 % in the hand and 8.5 % in the leg) following a moderate-intensity running-based warm-up. Similarly, different types of active warm-up modalities, running or back squat-based, produced 12 % increases in MFCV. This was associated with a 3 °C augmentation in muscle temperature and reported to elicit a measurable increase in both MFCV and power.
Warming up can stimulate changes in the mechanisms underlying both anaerobic and aerobic metabolism.Studies have shown that completion of a priming exercise bout which elicits a degree of lactic acidosis, can increase the amplitude of the primary VO2 response and a reduction in the VO2 slow component. This may preserve anaerobic energy stores for the sprint to the line! Despite the precise physiological mechanisms for this response remaining unclear, these changes in metabolic function can also improve exercise tolerance and Increase power output.
PAP is a phenomenon where muscular performance is acutely enhanced when preceded by maximal or near-maximal neuromuscular activation exercises. Mechanisms through which PAP may improve subsequent physical performance include:
- Enhanced central output to motor neurons
- Increased reflex electrical activity in the spinal cord
- Phosphorylation of myosin regulatory light chains
- Increased concentration of sarcoplasmic Ca2, which, in turn, can increase actin–myosin cross-bridge cycling (improved muscle contraction power and frequency)
Most commonly a heavy resistance, low repetition back squat has been utilised to achieve improved performance in the lower limb musculature during sprinting and jumping tasks. Finding the perfect balance between fatigue and PAP is the greatest challenge to implement such a warm up successfully and consistently.
Typical strategies include visualization, saying of cue words, attentional focus and preparatory arousal (‘psyching-up’). These strategies are designed to narrow an individual’s attention and build their self-confidence. Examples include a sprinter listening for the starters gun and thinking ‘drive hard out of the blocks’ in preparation, or a golfer focusing on his weight transfer or visualising the line of the club swing. You may have even seen athletes with certain cue words written on their wrists to draw their attention to certain aspects of their performance. It is also important to simply come out of a warm up feeling good, and feeling confident in your body.
5. Muscle/tendon tissue mechanisms
There a number of mechanisms proposed for the the effects various warm up strategies have on muscle/tendon tissue properties.
- Acute muscle stretching has been hypothesized as reducing tendon stiffness, forcing the muscle to work at shorter and weaker (according to its force–length relationship) lengths. In addition, potential reductions in muscle length would not affect, or may even increase, force production in muscles working at optimum length or on the descending limb of their force–length relation. Given our current understanding, changes in muscle length are unlikely to be an important mechanism influencing the force reduction after SS
- Mechanical stretch imposed on the muscle–tendon unit could cause damage within the muscle itself, thus reducing contractile force capacity
- Muscle stretching may also reduce blood flow and tissue oxygen availability, causing an accumulation of metabolic end products and/or reactive oxygen and nitrogen species