Friday, 9 April 2010

The Physiology of Warming Up
Why is it so critical for optimal cycling performance?
By Bruce Ketchum (c/o PEZ)

Pre-event activity, or warm-up, is an integral part of most cyclists’ preparation for competition. Each has his or her own unique routine to follow in order to be mentally and physically prepared for the event. Some find a warm-up essential in order to perform at their very best, while others don’t bother with one and jump into races with seeming ease. Surprisingly, there is only limited scientific investigation into the effects of exercise warm-up. In any case, whether the science is there or not, you will be hard pressed to find a competitive cyclist who will argue that warming up is not important. Physical activity in the minutes leading up to an event, be it light or heavy, will result in a number of physiological changes which are likely to enhance athletic performance. Let’s look a little closer at this.

Stimulate enzyme activity
With the onset of physical activity, muscular contractions will generate more heat than at rest. This increase in muscle temperature has been found to improve the necessary chemical reactions that make a muscle contract. The accelerated metabolic processes within a muscle cell enables the muscle to contract more quickly and with a greater degree of force (4).

One particular mechanism behind this response is greater enzyme activity. Enzymes are small protein molecules that play an important biological role in enhancing the rate of biochemical reactions. It is well known that these reactions are very sensitive to temperature change. In fact, it’s a standard test-tube lesson in high school chemistry class. An increase in temperature equivalent to 10 degrees Celsius will cause a doubling of the rate of enzyme reaction. This is known as the “Q10 effect.”

Be careful, though. You can get too warmed up. Normal body temperature is approximately 37 degrees C. If body temperature exceeds 40 degrees, a decrease in the efficiency of aerobic metabolism can occur since very extreme temperatures can inhibit enzyme activity (1,2). This emphasizes the need for good hydration and other cooling techniques during hot, humid conditions to maximize cycling performance.

Open blood vessels further
Many of the small blood vessels that supply muscle tissues are constricted at rest. Physical activity opens or dilates these vessels, increasing blood flow through the muscles. As most know, this enhanced blood flow increases oxygen and nutrient delivery and improves waste removal.

Timing is important
Exercise performed at a given intensity requires about 10 minutes of continuous activity for a muscle to reach an increased, stable temperature. With that in mind, your warm-up should be a minimum of 10 minutes in duration (1).

Time your warm-up so that you only have to stand around for a few minutes before the start of your event. Having to wait more than five minutes may cause your muscles to cool down too much and allow blood vessels to tighten up again.

Warm up specifically
It’s very important to warm up specifically to your sport to get a proper warm-up. For the cyclist, warming up on the bike is the best way to prepare your muscles for the race. In fact, not warming up specifically may even have a detrimental effect. For example, warming up the wrong muscles while running, let’s say, will shut down the necessary muscles for cycling. The body does this so that more oxygen and nutrients are diverted to the working tissues.

Blood works better when warmed up
Interestingly, as body temperature increases, so does the blood’s ability to deliver oxygen. The altered environment the active muscle cells create around themselves actually causes passing blood in the adjacent vessels to release more oxygen. The muscle cells generate heat, and also decrease the pH (more acidic) by releasing lactic acid and carbon dioxide, which in turn both release hydrogen ions. Increased heat and a higher acidic environment allow more oxygen molecules to dissociate or be released from hemoglobin, the oxygen-transporter protein found in red blood cells (3).

For the same reason, myoglobin, the oxygen-transporter protein found in muscle cells, also is better able to deliver oxygen molecules from the cell’s surface to its engines, the mitochondria, when the muscle is warmed up.

When is a warm-up not necessary?
The shorter a race is, the more important a warm-up is. Any criterium or time-trial will need a proper warm-up. But, very long road race events may not necessitate a good warm-up and may even be detrimental. In long events, a quick and efficient start is not nearly as important. Most long road races typically start out slowly for the first miles. This slow start can replace your warm-up, allowing you to conserve energy - often the limiting factor in the later stages of any long race. Some races may have a controlled start until you pass a more dangerous road section or leave the boundaries of a town. If you know the start is controlled, you may be able to forego your warm-up to save calories. However, make sure there are no serious hills to contend with at the start. A enterprising climber may be very well warmed up and ready to strike in his favourite terrain.

You’ve always known that warming up is important for top cycling performance. Now you know more precisely why it’s so important. Keeping all this in mind as you ready yourself minutes before your next race may even give you a psychological edge over those competitors just sitting there waiting to start cold.

1. Brooks, G. & Fahey, T. Exercise Physiology, Human Bioenergetics and Its Application. Macmillan Publishing Co. 1985.

2. McCardle, W.D. Exercise Physiology, Energy, Nutrition and Human Performance. Lea & Febiger. 1986.

3. Renstrom, P. & Kannus, P. Prevention of injuries in endurance athletes. In Endurance in Sport. Ch.32. pp.325-350, 1992.

4. Safran, M., et al. Warm-up and muscular injury prevention. An update. Sports Med. 8(4): 2239-249, 1989.

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