Splitting some of his training sessions into sets and repetitions is familiar territory for the track athlete who wants to run faster or boost endurance. Yet it can usefully be adapted for conditioning athletes in any sport. Once you understand the principles, you can tailor your workouts to give yourself the optimum benefit. Even though interval training is far from a new concept, coaches still lack the courage to be imaginative and tend to stick to traditional sessions to boost fitness. These may often be sound in nature, but there is a danger of the athletes becoming bored and stale when the same workouts at the same venues are repeated time after time.
If you are a soccer player, you may already perform high-intensity shuttles separated by short recoveries to improve your speed endurance. This may also have the added benefit of boosting your aerobic system because volumes of research have shown that the best way to lift your VO2 max (an index of aerobic fitness) is to train at an intensity close to, or above, VO2 max. Realistically, this work has to be done in an interval format if the session is going to last any serious length of time-otherwise, after one hard burst for a few minutes you may end up collapsed in a heap of fatigue. This is where the real benefits of interval training become clear: by separating your efforts with short bouts of recovery, you can keep the intensity high, yet extend the volume.
Plan the session first
Our soccer player, however, may be guilty of the cardinal sin of all training: not thinking about and planning the session sensibly beforehand. The very nature of the session working at high intensity leads to the belief that the athlete should be thoroughly exhausted at the end. Yet it is the route to that exhaustion that is often ill-considered how to make the session more than running flat out for as long as possible and then going again on command. The coach should have a clear idea of the physical demands of the sport concerned, particularly the metabolic demands about which energy systems are utilised during the performance. Video analysis of a match can determine typical activity patterns for games players, or heart rates and lactates can be monitored in a race. Armed with such information, you can make sure that the session you are considering is geared to the demands of your sport. Most coaches can gather this information from books and articles about their sport, but measurements on individuals can also help to build up the picture.
Getting the recovery time right
With the demands of the sport in mind, the coach should carefully consider each of three critical aspects of the session: intensity, duration and recovery. Each of these can combine to govern which energy system is utilised to provide the bulk of energy in the muscles used during the mechanical work. If, for example, our soccer player wishes to improve his speed off the mark, he should choose a session with short but explosive activity such as 30m sprints at maximal speed. Here intensity is the critical factor, so High Energy Phosphates (HEP) will be the immediate major source of the ATP (Adenosine Triphosphate) needed to fuel such activity. In such short intensive work, the recovery should be long enough to allow repletion of the HEPs, because if the recovery is too short an alternative energy system will have to be recruited and the quality of the session will be impaired.
Judging the exact recovery time to perfection is not always easy. Research has shown that the depletion of HEPs, after a sprint, starts very quickly and then slows. It takes about 20 seconds for the HEP stores to get back to half of their resting level, but a further 170 seconds to be topped up to normal. Therefore, if our player wants to keep the quality high, the recovery period should be about three minutes. In winter, this may mean putting on and taking off clothing in between the short reps.
Sprinting is only one aspect of soccer, and there may need to be a session dedicated to the ability to repeat high-quality sprints in rapid succession. This will require a different type of interval session because the player is working on the recovery aspect. Here he should cut the recovery between bursts so that the work is repeated before the HEPs are fully back to resting levels. Such activity requires a more significant contribution from glycolysis, a different energy pathway that breaks carbohydrate down, producing ATP very quickly. A series of such sessions may well improve not only lactate tolerance but also the time required to replenish the HEP stores, both of which should enhance soccer fitness.
The type of recovery between efforts is also of paramount importance. Standing around with hands-on-hips, or bent double, is far less effective than walking or, better still, jogging. This active recovery helps to remove and disperse lactate that accumulates in the working muscles during intensive exercise. Indeed, active recovery can almost halve the time that is taken for muscle and blood lactate to return to resting levels after an intense burst and is likely to be even more effective in the aerobically training athlete.
Fartlek for games players
Another type of session can work on both of these aspects as well as on the oxidative system. Although not a structured interval session split into reps and sets like those already described, "fartlek", mixing fast with slow work, can be of immense benefit to those who play field sports. Fartlek comes from the Swedish for "speed play" and has been used by distance runners for years. But for games players, the session should not just use running, but also jogging and walking to fit in with the demands of the sport. After all, no soccer player runs for the whole 90 minutes of a match, the pace is varied. Similarly, the direction of work should not always be straight ahead. This may be important for the track runner who has to cover the ground as quickly as possible in one direction, but the game's player has to go forwards, backwards and from side to side.
This must all be considered if the training session is going to mimic accurately the pattern experienced in a match. Remember, if you are a games player, you are not training to be a better sprinter, you are training to be better at your game. Therefore, sprinting should not just take the form of back and forth shuttles but should make you change direction or even imitate a slalom. This is where the imaginative element comes into play.
Progression is another aspect you need to consider. If you are to improve your condition, there should always be some element of progress in your schedule. With interval training, you have plenty of options to work with. For instance, you can lengthen the distance of your efforts. This is fine if you are a runner, a rower or a cyclist because you can build up the distance closer to your actual race distance. For the games player or sprinter, however, this may not be so appropriate. In field sports, it is rare to have to sprint more than 30m in one go, so it is questionable whether long sprints are a suitable focus in training.
You can improve the intensity, which usually involves performing your reps a little faster. Here you must be careful to keep things specific because if you are, say, a 10K runner it may not be appropriate to be running reps too fast in training. For example, you may be performing aerobic intervals, where the idea of the session is to give an optimal stimulus to the aerobic system. The session might be 5 x 1 mile, where the intention is to be working at your maximum aerobic steady state. You can use heart rate in such sessions to control the intensity and make sure that you are not going too fast.
However, if you are performing quicker, shorter repetitions on the track, heart rate may not be the best guide. In such super-maximal intensities, the heart rate does not entirely reflect the high-intensity encountered, partly because the reps are too short, and the heart rate needs time to reach a steady state. Here it may be more appropriate to use split times to set your goals, with a gradual reduction from session to session to ensure an element of progression.
To improve your endurance, you can cut the recovery time allowed between reps. You can do this systematically - for example, by reducing the recovery time by five seconds each week. If you use a set recovery period, your heart rate before each rep will rise throughout the session. Alternatively, you can use your heart rate to determine your recovery. If you want to maintain quality in a session of 3 x 800m, rather than use a specific time for recovery, you can try waiting for the heart rate to drop to a specific level such as 120 or 100. As individuals vary so enormously in both their resting and maximum heart rates, it is impossible to give a general figure for everyone. Still, trial and error should produce a heart rate that works best for you.
Another way to build endurance is to add to the volume of your session. You can increase the number of reps performed in various sets during the session or even build on the number of sets performed. As long as this is part of a structured plan and conforms to the demands of your sport, it should work well, being a tried and tested method for improving fitness in most sports.
Finally, if you intend to start interval training or rethink your schedule, remember:
The information on this page is adapted from Dunbar (1993) with the kind permission of Electric Word plc.
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