The importance of warm up
Interestingly, despite not being able to give you a conclusive answer as to why, most would be reluctant to give up or alter their warm-up routine. Indeed, most people would indicate that it is not purely a physical benefit, but also psychological readiness to perform. For some, it might also be a chance to check equipment is running smoothly prior to the event.
Just how important IS a warm-up?
The impact of warm-up appears to depend on the event duration – the potential for improvement seems greatest in short term endurance events (up to 10 minutes) and less as event duration increases. A recent study looking at 3km time trialling1 suggests a significant improvement is to be gained, especially in the first 1km of performance, with power output being increased by some 40W. Less, but still meaningful, improvements of ~30s are to be gained for events of ~20 to 30 minutes2.
What is the physiology surrounding the efficacy of warm-up?
The name implies that the majority of the effects observed with prior exercise are attributable to temperature related mechanisms:
- An increased conduction rate of neural impulses
- Greater offloading of oxygen from the blood (haemoglobin) to the muscle
- Speeding of certain metabolic reactions – especially use of the anaerobic energy system
- Improved flexibility around muscle and joint systems
More likely though, performance enhancement may follow on from the metabolic acidity brought about by previous exercise. This has led some researchers to prefer use of the phrase ‘acid-up’3. It is acidity that brings about the following:
- ‘Potentiation’ of muscle fibre recruitment – preparing the fibres for more effective and efficient contraction to do work
- Increased muscle blood flow
- Elevation of oxygen uptake and switching on of the aerobic system
Surely acidity isn’t a good thing?
Most athletes associate acidity with blood lactate build up and subsequent fatigue. However, a lot of research suggests that it is acidity that prepares the body to exercise, especially at race pace intensities.
Research work performed at the University of Brighton4 indicates that exercising at intensities above the lactate threshold, and therefore inducing acidity in the muscle tissues, leads to an elevated oxygen uptake ahead of a second bout of exercise. Therefore, less of the following exercise is performed anaerobically i.e. there is a lower oxygen uptake debt. Initial sparing of the anaerobic capacity may lead to improved performance, as it is a reserve that can then be utilised later on in races.
How the acidity leads to this change isn’t entirely clear yet, but may be related to how oxygen is off-loaded to tissues. Think back to school biology lessons where you may have been introduced to the ‘Bohr effect’. When CO2 and hydrogen ions increase because of exercise, the associated acidity increases the dissociation of oxygen from haemoglobin to the tissue, allowing the tissue to obtain enough oxygen to meet its demands. In a similar way, warm-up exercise affects the degree of oxygen attachment to the haemoglobin– research shows warm-up enables the body an extra ‘reserve’ of O2 early on in exercise.
It is possible that residual acidity in the system changes muscle fibre recruitment patterns. If the acidity of the muscle is decreased, the body may respond with recruitment of more muscle fibres to maintain force development. A further possibility is that muscle blood flow is increased: Acidity leads to increases in bradykinin, a known ‘vasodilator’, which opens up the capillary bed of the exercising muscle tissue.
Intensity of warm-up
If, as suggested, warm-up is more likely to work when resting muscle metabolism is disturbed, the intensity of warm-up is critical to whether it works for an athlete or not. As explained above, research has found a link between the intensity of the warm-up and the oxygen uptake response at the beginning of exercise. Recent work in our laboratories investigated whether performance is actually improved5.
We took a group of cyclists and asked them to perform three types of warm-up: below the lactate threshold (moderate); above the lactate threshold but below the ‘Critical Power’; and above the critical power (severe); and to then enter a performance trial at the CP (this intensity approximates 10 mile time trial pace in most people. We discounted a temperature related effect by equalising the work done across all types of warm-up (so, watts x time was the same for all conditions). We also made sure we used a warm-up that athletes are familiar with i.e. short bursts of activity interspersed with recovery – emulating ‘strides’ or ‘leg openers’.
The effects were quite extraordinary – the ‘heavy’ warm-up not only decreased the oxygen deficit at exercise onset but also improved time to exhaustion by 45s (in a trial lasting ~15 - 20 minutes). The severe warm-up also changed the oxygen uptake response, yet did not give similar changes to performance. In other words, the exercise intensity for the warm-up is crucial: moderate exercise does not enhance the aerobic contribution to subsequent exercise, whereas severe-intensity exercise causes too much disruption for the restoration of resting metabolism and/or removal of fatiguing metabolites.
Take home message
While more ‘aggressive’ methods should be utilised prior to shorter events, with long term performance care must be taken to ensure performance is improved not impaired – to preserve the muscle glycogen stores and to avoid excessive thermoregulatory strain
The key to warm-up is balance – you need to exercise hard and long enough to ‘rev up’ the system, but not so hard that you leave the muscle tissue in a fatigued state.
The problem most athletes have is gauging this balance. Most athletes will hold back on their warm-up in fear of going into the race tired.
It makes sense therefore for athletes and coaches to assess critical power and define the border between heavy and severe exercise. This takes the guess work away, and allows the athlete full confidence in their preparation.
For more information on how to make best use of your warm up see the factsheet "The practicalities of warm up".
1. Hajoglou, A. et al. Med Sci Sports Exerc 2005, 37, 1608-1614.
2. Atkinson, G. et al. J Sports Sci 2005, 23, 321-329.
3. Bishop, D. Sports Med 2003, 33, 439-454.
4. Burnley, M. et al. J Appl Physiol 2000, 89, 1387-1396.
5. Carter, H. et al. Med Sci Sports Exerc 2005, 37, 775-781.