Can you overdo interval training?

Worried about doing too much interval training? Joe Beer explains the amount you should do, and how to tell if you're overdoing it.

Triathlete checking run watch during a session of interval training

Absolutely yes! However, we must qualify what intervals are, how to do them and the symptoms of overdoing them.


Intervals are pre-defined periods of effort within a session plan; these range from longer aerobic (70-80%HRmax), tempo to threshold (82-87%) and high-intensity (87-92% HRmax) to short power sprints (e.g. 8secs peak effort). They should be planned and not just dropped in because you feel good, bored or want to beat Strava.

Interval sessions should account for around 10% of weekly volume, but I often see athletes who actually do 10-20% of their week as random speed work when their zone-1 sessions go off plan – this may be the biggest single reason why interval sessions fail to work or cause burn out.

The signs of over stretching yourself are disturbed sleep, loss of appetite, sense of humour failure, reduced libido, disturbed HRV (heart-rate variability) scores and reduced ability in high-intensity sessions.


An example of a good interval plan: over a month, Bentley and co-workers (2017) found two sessions of intervals a week (7 x 5mins @85% HRmax), complemented by all other training in zone 1 (55-80%HRmax), improved performance. Interestingly, just doing cycling intervals helped both run and bike performance.

Best heart rate training zones for cycling

Best heart rate zones for running

Explained – when to train low, when to train high