Running: a guide to healthy interval training

Interval training is one of the most strenuous types of training for runners: the sudden upping of the tempo puts a big strain on their cardiovascular system, muscles, tendons and ligaments. You need a certain degree of running experience and underlying stamina, as well as sound health, before starting interval training – if you’re not sure, it’s better to check first with a doctor to see whether this sort of training is suitable for you.

Interval training involves alternating periods of exertion and recovery. You incorporate a certain number of fast-paced runs into your normal running routine. In between, you jog slowly or powerwalk. The key thing is not to put yourself under pressure: do not push yourself to the limit at the outset. “This means you don’t sprint during the fast sections, you just run faster than usual,” explains Joy Marxer, health advisor at Helsana. “Interval training can also comprise three minutes of jogging and five minutes of brisk walking. The important thing is just to alternate the pace.”

Essentially, this form of training is suitable for everyone, including beginners, once they possess a certain basic level of stamina. Beginners must be careful not to get too ambitious. In other words, less is more. “Start with one interval run per week,” advises Joy Marxer, adding: “Give your body at least one day’s rest after each interval training session, no matter how fit and experienced you are.” Otherwise you risk overtraining.

During the fast segments, your pulse rate increases and your maximum oxygen uptake is enhanced. This provides your muscles with more oxygen for energy supply – your body can work out longer and more intensively. The change of pace means your body has to constantly adapt and suffers, especially at the beginning, from a lack of oxygen. Your body responds by trying to optimise your metabolism and learns, with regular training, to adapt to the faster pace.

This “oxygen boost” increases the size and number of mitochondria in your muscle cells. Mitochondria are also described as the powerhouse of the cell. Their job is to produce energy. The more functioning mitochondria we have in our body, the better our health and endurance level. 

Interval training also increases the anaerobic threshold. The aerobic-anaerobic threshold denotes the exertion range within which the supply and consumption of oxygen within the body’s cells is just about balanced, or at which the formation and breakdown of lactate is still in equilibrium. Lactate is produced in the muscles when there is no longer enough oxygen to produce energy during intense, fast exercise. Glucose is then converted into lactic acid in the body.

Excessive lactate makes your legs heavy and tired, which is why recovery after a hard workout is very important. Otherwise, performance decreases – and the risk of injury increases.

Regeneration is the crucial thing. The body needs a minimum of 24 hours’ rest after interval training to recover. It is also important when you start with interval training that you do it on routes that are familiar to you – ideally on flat terrain. “So, at the beginning, it’s better to stay off any narrow trails,” stresses Joy Marxer. “The risk of you tripping and getting injured is much greater on these routes.” Also, start off your interval training gently. A solid running technique is also important and can be easily developed.

Sports medicine defines this as a response to chronic overload. It is usually triggered by repeated workouts that are too intense or too long. Overtraining shows itself when performance suddenly drops despite regular training – caused by the body not having enough time to regenerate. Possible symptoms include:

• very painful, long-lasting muscle ache
• sudden drop in performance
• muscle loss despite training
• loss of appetite
• disturbed sleep
• greater susceptibility to infections
• extreme tiredness
• mood swings, including feelings of depression
• inner restlessness and nervousness

The basics

• Warm-up phase: this lowers the risk of injury and prepares your body for physical exertion. Take ten to fifteen minutes to warm up with some light jogging.
• Training location: start interval training on level ground. Standard running tracks or tartan tracks are ideal. The inside lanes are 400 metres long and ideal for following set workouts.
• Frequency: beginners and newcomers should start with one interval training session per week. If you already jog regularly, several times a week, doing one or two interval training sessions per week is also a possibility – but you must always take a day’s break in between.
• Duration: no more than 30 minutes, in general.

Interval routine

If you train on a running track, then intervals of 8 x 400 metres are a good idea. You do one lap of fast-paced running – at the beginning it’s better to run medium-fast instead of fast – and then do a lap of slow, easy jogging.

If you don’t have a running track nearby, you can set a time limit, for example:

• 2 minutes medium-fast to fast running – 3 minutes slow jogging break
• 1 minute high-speed running – 2 minutes slow jogging break

Try out different intervals. The recovery phase should be longer than the intensive training phase.

Please note: adapt the speed and intervals to your fitness level. Pay attention to your body and give yourself sufficient breaks where you just jog slowly.

Jogging in interval sessions has another benefit: this intensive training burns more calories. Although there are recovery breaks during interval running workouts, your body’s reserves are not completely replenished during this short time – so you’re burning fat at full throttle.