Friday, 18 March 2011

Does strength training help distance runners?

Can lifting weights help distance runners run faster or further with no corresponding improvements in aerobic fitness?

Resistance training (RT) takes many forms, including strength training, power training, plyometric training, muscular endurance and hypertrophy (increasing muscle size) work. Most of these forms can aid distance running in some way:

Strength training – enables runners to maintain form when running and be more efficient. Certain exercises are useful in helping prevent injuries;Power training – helps with change of speed and acceleration during races, and with changes in incline during cross-country courses;Plyometric training – helps improve running mechanics (if performed correctly) by improving the reactivity of ankle, foot and pelvic joints whilst running. This can lead to an overall increase in running efficiency and therefore less energy expenditure whilst running;Muscular endurance – where increased local muscular endurance can help with overall endurance by increasing the number and density of mitochondria in the muscles.

The tricky part, of course, is knowing how to balance all the different aspects, without detriment to running training and mechanics.

In terms of muscular coordination, running is an extremely complex activity so care has to be taken to enhance, rather than inhibit it. For example, just using large bounding activities will help use the gastrocnemius and soleus muscles, but will inhibit the smaller foot and ankle muscles that are used to land and react when running. Conversely, wobble board exercises will use the smaller muscle groups, but don't require enough strength in the main muscles to create real improvements in running economy.

Strength improvements and adaptations occur in three ways and generally in the following order:

Intra-muscular coordination

The motor units within each muscle group may not previously have been stimulated adequately. By training the movement patterns you want to optimise with adequate resistance, these motor units can be effectively recruited. By recruiting more motor units within each muscle, more work can be done. Frequent training also enhances the motor units' ability to work in concert with each other and to be recruited simultaneously, rather than one after another.

Inter-muscular coordination

Frequent resistance training will allow more efficient movement patterns because it will decrease the co-contraction of antagonists (opposing muscle groups) when the targeted muscle is required to work. It also develops greater coordination between the targeted and opposing muscles as they become more accustomed to working a certain movement pattern.

Hypertrophy

After an initial training period of around 12 weeks, the muscles may become bigger. This can happen in two ways: hyperplasia (an increase in the number of muscle fibres themselves) and myofibrillar hypertrophy (where the fibre size increases).

For runners, the first two adaptations are important because the correct exercises can enhance running economy and efficiency by allowing better inter-muscular and intra-muscular coordination. Too much hypertrophy on the other hand can be detrimental for two main reasons: firstly, an increase in limb mass will make the levers harder to 'swing' and will either slow the runner down, or will require more energy to maintain the same speed. Second, an increase in muscle mass is associated with a decrease in mitochondrial density, which will decrease aerobic efficiency at the cellular level.

The importance of biarticular muscles

Biarticular muscles pass over more than one joint. These biarticular muscles have more complicated movement patterns than monoarticular muscles (that pass over only one joint) such as the gluteal muscles of the buttocks. They also use elastic strength rather than pure contractile strength in a great deal of the movement(4,5).

There are three main biarticular muscles in the lower limbs which are useful for running: the rectus femoris (frontal thigh), which passes over the front of the knee and hip; the hamstrings, which pass over the back of the knee and hip; and the gastrocnemius (calf), which passes over the ankle and knee. Biarticular muscles use energy efficiently because the counteractive force from one joint is released and used by the other joint. For example, when the hamstring contracts, knee flexion occurs, energy transfer is possible from the knee to the hip, which then helps extend the hip. This occurs very quickly and is difficult to measure – its importance has only recently started to be understood.

This combination of joint movements and energy transfer is important to understand when designing exercises to improve efficiency. If a gluteal muscle is contracted concentrically, the hip will extend. Training a gluteal muscle through strength training in almost any form will have a strong transfer to its use within sport, because it is a simple movement. However, the hamstrings are more difficult to train because of their biarticluar nature. The length of the muscle can be changed by either tilting the pelvis forward or back or by extending or flexing the knee. The nature of the contraction also changes depending on whether the hip or knee is fixed and which part of the running stance is being considered. So, the type of exercise to improve the hamstring function needs to be carefully considered. Simple hamstring curls should be avoided because that's not how this muscle works during running.

What works for runners?

Some form of plyometric activity to work ankle reactivity;Single leg strengthening exercises to improve balance and control in the gluteal area and the knee joint;Hamstring exercises that develop eccentric strength;Some exercises that help develop the core complex around the pelvis that assists in minimising upper body rotation during running.

That exact choice will depend on the individual runner; for example, if a runner has had an injury, or is severely deconditioned then there is a place for general strengthening work in the form of circuit training to establish a sound platform. Jumping too quickly into specific work without an underlying strength base could lead to injury. If a runner has suffered a lower limb injury, the level of coordination will be decreased, so exercises need to be included that re-establish previous motor patterns. Examples of exercises that may be useful can be found below:

Ankle reactivity exercises

All the drills below can improve the foot and ankle's reactivity to changing ground surfaces.

Ankle bounces: The concept behind this exercise to use your calves to propel you off the floor, with as little knee movement as possible. On two feet and keeping the legs almost straight, quickly pull up the toes and jump up off the floor. As you land quickly pull up your toes again and repeat.

Hopping on one leg: In this exercise, you should aim to cover a distance of 15m. The raised foot is used to touch the floor at every hop but with tension held in the foot. Variations on this exercise include:

Making the raised leg perform a high knee action so it has to move rapidly up and down in between hops;Moving the raised leg up and down, but not allowing it to quite touch the floor;The raised leg alternately performs a high knee action with the foot touching the floor, followed by a high knee action where the foot doesn't touch the floor.NB: In all these exercises it is important to keep some tension in the foot – that means keeping it in a neutral position, not pointed up or down. It is also important to minimise the amount of contact time between the foot and the ground.

Leg and core exercisesSingle leg strengthening exercisesSplit squat: Carrying any weighted implement (barbell, dumbbells, sandbag), stand with one foot in front of the other, feet about shoulder width apart. Keep the weight and your shoulders above the hips and bend both knees, to lower the hips. Return to the start position.

One leg hip hitch: Stand with weight on shoulders, one foot on floor, the other resting on a small bench. Lift the foot off the bench and bring the knee up by lifting the hip, the stance leg should be fully extended through hip, knee and ankle and weight should be through the ball of the foot. Hold this position for one second and then return to the start.

A variation to the above is as follows: when the foot comes off the bench, use it to tap the floor by the stance leg then as it returns to the bench, make the stance leg drive forcefully and quickly up until it is fully extended.

Step-ups: With weight on shoulders, stand in front of a small bench or platform that is lower than knee height. As you step up on to the bench with the right leg, drive up quickly with the left leg so it is fully extended. As you transfer weight onto the right leg, bring the left knee quickly forward and up until it is bent at 90 degrees. You are now stood on the bench on your right foot with the left leg bent and raised in front of your body. By varying the weight used, you can vary the speed of movement and change the emphasis of the exercise. Ensure that your head is upright and your back extended throughout.

Core complex exercises

Slow sit up: Lie on the floor with hands behind head, knees bent and feet on floor. Sit up to about 45 degrees and then extend your back by sticking your chest out and pull elbows backwards. As you return to the floor, the back flexes and your elbows return to the front. Variations on the these core exercises include the following:

After sitting up, extend and raise both arms backwards above and behind your head;After sitting up and extending your chest, rotate your upper body and point one elbow in front and the other behind.Medicine ball slams: Hold a medicine ball above your head and reach up as high as you can. Slam it into the ground, catch it and repeat as rapidly as possible.

With all of the above exercises, ensure that you have no existing injuries before starting them. If in doubt on the weight to use, try a very light weight and progress from there. Aim to do five high quality repetitions of each, then rest, then repeat for up to four more sets. The exception is the medicine ball slams where a large number (up to 100) can be performed as a conditioning tool.

Conclusion

Research and anecdotal evidence shows that some form of resistance training is likely to improve your performance as a distance runner. To improve running economy it is important to ensure you have an initial strength base and then move on to working on more specific exercises. Aim to execute strength training twice a week for 20-30 minutes. During the off-season, this could be increased to three times a week for 45 minutes.