INTERVAL TRAINING FOR COMPETITIVE ATHLETES
The first workout type in a high performance program is intervals. Intervals add variety both in your training and in your training benefits, adaptations, so you can most efficiently improve your fitness level. If you are not doing interval training as part of your schedule now, it’s me to start.
“Interval” can be a somewhat muddled term. By definition, interval training is a type of workout which consists of a period of high intensity exercise followed by a period of rest – complete or incomplete rest. Several intervals are called a repetition (reps). Several repetitions are called a set. Following each exercise interval is a recovery me (rest) which allows for recuperations.
Intervals are written in a standard way, a coach’s shorthand. Seems confusing at first. Go to your master’s swim workout and you’ll see this coach’s shorthand posted on a workout board.
The interval training system has been supported by a tremendous amount of research to validate the premise that by raising and lowering your heart rate or workloads during a single workout, multiple zone benefits occur. Among the most basic of these benefits are:
- Increased endurance ability or aerobic capacity, which is measured by the amount of oxygen that you can use (VO2 max).
- Increased total number of calories burned if you increase your intensity.
- Increased fun, because you add variety to your workout.
- Increased focus on your training because of the need to watch for me and intensity variations, which seems to make the me go by faster.
But, there is even more benefit to you depending on the type of interval training that you might do.
There are four different types of intervals, defined by their duration: short or sprint intervals, middle-distance intervals, long intervals, and endurance intervals. The four different interval types each affect different energy systems. Energy systems are the means by which the body transports and converts various fuels into energy. That’s the primary point of doing intervals: to train the energy systems to both utilize specific fuels and deliver nutrients to your muscles more efficiently and to improve lactate tolerance. You are actually training your fuel system as much if not more than the specific muscles.
To understand the different types of intervals, here’s a more complete explanation.
Sprint and Middle-Distance Intervals benefits:
- Increased anaerobic enzyme activity • Increased lactate tolerance (pH levels) • Increased specific muscle strength in the specific muscles used • Increased power of fast-twitch muscle fibers (Type II) • Increased phosphagen utilization (ATP-PC)
Long and Endurance Intervals benefits:
- Increased anaerobic threshold heart rate • Increased amount of me spent at higher percentages of VO max
- Increased lactate threshold and tolerance • Increased number of mitochondria (density of mitochondria)
- Increased oxygen transport to and through the membranes • Increased amount of oxidative enzyme activity
- Increased glycogen sparing ability
There are four more important pieces to high performance interval- based training:
1) how many reps or total number of intervals,
2) how much me for rest between intervals,
3) the type of rest in-between reps, and
4) the work-to-rest ratio in each interval. When you have these pieces you can create a variety of interval workouts to match your goals. The table below illustrates the typical characteristics of the respective types of intervals.
There are two types of rest: complete and active. After the interval is over, you take a break or rest interval to allow time for your heart rate to drop to a lower zone. This is called a “recovery period” or recovery interval, and it allows your body to recover from the intensity of the interval, to shuttle away some lac c acid, and to resupply the muscles with fuel. Complete rest means that you slow to a stop, while active rest means that you slow down but you continue to move – that would be a walk or jog if you were running. Active rest for a cyclist means to shift down to lower gears and spin easy. Active rest to a swimmer means to continue to swim but using a different stroke for recovery and slow.
Here’s an example. Let’s say you want to do a long interval workout day. You are a swimmer and usually you like to swim continuously for the amount of me you have – say 30 minutes. You’re ready for a change and want to exercise a different energy system with high performance heart zones intervals. Today you want to take that same amount of me, 30 minutes, but this me you are going to break it into five different parts. Your first five minutes is a warm-up of mixed strokes. You then start four sets of five-minute intervals by increasing the intensity of your pace by about 5-10 beats per minute, with a 3-minute active rest during the break between the two intervals. After completing the second of the two high-intensity intervals you take your warm-down swim.
You might ask what additional benefit you gain for the trade-off in complexity with long interval training. The great news is that you are getting new benefits with each of the heart rate zones you’re now exercising in. The new zones challenge different energy systems and, sure enough, the body responds to your new regimen with adaptation – the specific energy system or muscle fibers involved change and improve their fuel utilization, becoming stronger and more efficient to meet the workload imposed upon them. In other words, you can train at higher workloads and perform better, and you can race faster.
Looking at each of the four different intervals respectively, here’s what you are trying to accomplish:
- Endurance Intervals. These are the very long repeat workouts at lower percentages of your maximum heart rate. A good example would be cross-country ski intervals – loop format. If your loop is 1–2 km, then your cardio-interval might be 5 sets at 80%-85% of maximum heart rate with a 2-4-minute active rest recovery between loops. This workout simulates racing conditions and results in improvement in your oxygen uptake. If you are a marathoner, this is key interval workout for you if you want to improve your me. The table below schematically illustrates endurance intervals.
- Long Intervals. These are long intervals at slightly faster pace than your race pace or at heart rates about 5 bpm above your low threshold heart rate. The purpose is to challenge your mitochondria, the energy factories in your muscle cells, to continue to produce energy at very high rates of demand. Typically, the effort interval is between a minute and five minutes and the rest interval 1-3 minutes. Because the intensity of the interval is slightly above your first threshold heart rate, you are working in an oxygen debt condition and must allow enough rest to repay this oxygen loan. If you are a 10K athlete, this will probably be your most important interval session. The table below demonstrates interval training sessions.
- Middle Intervals. These are the intervals for the middle-distance sprint athletes like the 100-meter swimmers and the 400-meter runners. The reason that these intervals are specific to these athletes is that they have the greatest need to improve their anaerobic glycolytic energy system – their ability to tolerate high levels of lactic acid. To develop this ability, middle intervals are a must. Middle distance athletes’ training must be event specific, and their intervals can last from 10 seconds to one minute, with the recovery interval twice the length of the effort interval. This is a fast interval and you might well see your maximum heart rate on your heart rate monitor in the last few seconds. Because heart rate monitors work by averaging heart rates every 3-5 seconds depending on the model, your heart rate is actually faster than the monitor reads because of the lag time involved. The active recovery period is important. Continuing to move during the recovery helps with the removal of the lactic acid from the muscle tissues. This lactic acid is transported from the working muscles to the liver and other organs. At the liver, it is resynthesized into glucose, which reenters the blood stream and is transported back to the working muscles for fuel. This is called the “Cori cycle” and provides a benefit to middle-distance athletes who rely primarily on glucose for their energy. The following table shows you the pattern of a middle interval.
- Short Intervals. For sprint-distance athletes, the primary adaptation that needs to occur is to enhance their bodies’ abilities to provide immediate bursts of quick energy derived from the creatine phosphate (CP) system (anaerobic phosphagen). You only have enough CP stored for about 10 seconds of high intensity exercise. Therefore, for these interval sets, all the effort intervals need to be no more than 10 seconds in length with about three times that amount of time for recovery. Recovery needs to be complete rest, with little to no movement, to allow for the resynthesis of intramuscular phosphates (such as ATP and creatine phosphate). This system recovers quicker when you stop, typically requiring about 30 seconds. These are all out sprint intervals – throw your heart rate monitor to the winds. In a 10-second interval you are totally driving sport-specific muscles and not your heart. However, remember that your heart is a “work now/pay now” muscle, so it is probably reaching close to maximum even though your heart rate monitor may not be presenting the data this way. Your goal is to build up to 20-25 repeats of this interval but start with about 10. It is extremely taxing and not for those just starting to learn interval training.
For the newly-converted interval trainers, start with the long or endurance intervals. They are more enjoyable and cover much lower heart rate numbers. You might even begin with a “fartlek,” because they are as much for fun as for changing heart rate intensity. “Fartlek” is a Scandinavian term for “speed play,” and it is just that: it playfully increases and decreases your heart’s and your body’s speed to obtain some of the benefits of intervals but with more fun attached.
A good example of a fartlek workout is the telephone pole fartlek. After you warm up, do a 10-20 bpm pick-up to the next pole and then slow back down to the following pole for recovery and repeat. If you don’t have telephone poles, then use mailboxes, fence posts, or sign posts. As you get more accustomed to intervals, try the shorter ones and feel the differences. Each of the four intervals taxes a different energy system. Remember that, and you’ll feel the experience accordingly.
Intervals can be helpful for almost all individuals who are training. For those who are part of a special population such as the physically challenged or rehabilitation patients, interval exercise can help raise your aerobic fitness levels without the stress on your systems of steady-state high intensity. The latest research shows that several, shorter intervals can result in some of the same adaptations as fewer, longer intervals. You don’t even have to do them back-to-back. It’s been shown that five minutes a day, three to six times a day is as good a work- out as one session of 15-30 minutes.
If a single workout or a string of them is missed, don’t go back and try to make any of them up. If you miss some, and we all do, it’s okay. You may need to rework your training schedule because, if it doesn’t fit your time and your lifestyle schedule, it won’t work for you. Busy people all struggle to juggle their limited time, but it can fit if you will make it fit. You can wake early and work out during eating periods and eat during working periods; you can even have a personal life by inviting your partner to train with you. It’s that simple – make your training tree a part of your lifestyle.