GOOD PRACTICE REFRESHER WARM UP AND STRETCH

Questions are frequently asked by patients about the role and evidence for warming-up and stretching prior to participation in physical activity. The following article attempts to give a brief summary of the effects of a warm-up and we have included, in response to demand, an advice leaflet on the following page which can be handed directly to patients.

While the role of, and evidence for, a warm- up (including stretching) in the prevention of injury is still widely debated, there continues to be clinical, experimental and qualitative observations which do support a link between warm-up and improved performance.

There are two main aims of a warm-up, the first is to increase the core body tempera- ture and the second is to prepare the cardiovascular system for further activity. This is achieved through the repetitive activation of large muscle groups at a low intensity (this will differ across individuals relative to their fitness).

Physiological effects A warm-up affects the musculoskeletal, nervous, and cardiovascular systems and the biochemical processes of many cells which contribute to the functioning of these systems.

1) Musculoskeletal system Increases in temperature of both skeletal muscle as well as connective tissue result in: ● decreased stiffness (1) ● increased extensibility (1)

This leads to increased mechanical effi- ciency of the muscle which results in both more forceful and more rapid contractions of the muscle (2). Research on muscles of rabbits has revealed that a warm-up decreases the stiffness of the musculo- tendinous junction and increases the force and length needed to tear the musculo- tendinous unit when compared with mus-

6 SportEX

cles that had not been warmed up (3). Further research has shown that muscles that have been warmed up through passive methods showed greater extensibility than cold muscle (4).

2) Biochemical activity Increases in core body temperature increase the rate at which several enzyme- related biochemical reactions take place as well as encouraging greater oxygen uptake and release in the blood and muscles respectively. The metabolic rate also increases.

3) Nervous system Increases in core body temperature lead to an increase in the sensitivity of nerve receptors thereby improving the speed of nerve impulse transmission and speeding up reaction times.

4) Cardiovascular system Increases in oxygen requirements by the active muscles triggers an increase in heart rate and stroke volume which together result in increased cardiac output. This increases the delivery of substrates and the rate of removal of metabolic waste.

The goal For most recreational athletes a period of 5-10 minutes of activity such as brisk walking will suffice. The aim is a rise in core temperature of 1-20

C which is best

indicated by an increased heart and respiration rate and mild sweating. If a brisk walk is insufficient try a slow jog or intermittent walking and jogging.

Stretching Range of movement/flexibility is a key component of fitness that is often neglect- ed. However evidence supporting the claim that improving flexibility can actually reduce the risk of injury is again a subject of wide debate due to various difficulties in conducting research. That said, there is still a growing collection of research which does support a correlation between muscle tightness and muscle strains (5,6,7). Loss of flexibility also occurs with age but it can be improved on at any age and becomes an increasingly important factor in maintain- ing the quality of life of older individuals.

References 1. Sapega AA et al. Biophysical factors in range- of-motion exercise. Physician in Sports Medicine 1981;9(12):57-65 2. Bergh U, Ekbolm B. Physical performance and peak aerobic power at different body tempera- tures. Journal of Applied Physiology 1979;46:885-889 3. Safran MR et al. The role of warm-up in mus- cular injury prevention. American Journal of Sports Medicine 1988;16(2):123-129 4. Strickler T et al. The effects of passive warm- ing on muscle injury. American Journal of Sports Medicine 1990;18:141-145 5. Ekstrand et al. Prevention of soccer injuries. Supervision by doctor and physiotherapist. American Journal of Sports Medicine 1989;8:371-384 6. Worrell et al. Comparison of isokinetic strength and flexibility measures between ham- string injured and non-injured athletes. Journal of Orthopaedic Sports Physical Therapy 1991;13:118-125 7. Heiser et al. Prophylaxis and management of hamstring muscle injuries in intercollegiate football players. American Journal of Sports Medicine 1984;12:368-370.

Key stretching points ● Make sure to emphasise the importance of maintaining a good posture while carrying out every stretch ● Encourage the individual to concentrate on breathing slowly and deeply, particular- ly concentrating on exhaling as this may help increase the relaxation of the muscle ● Make sure the stretches are preceded by an active warm-up as outlined above as the tissues will be more flexible ● Hold each stretch for between 15-60 seconds and repeat 3-4 times ● The following leaflet includes stretches for the main muscle groups of the lower limb - it may be beneficial to include additional upper limb and sport-specific stretches