Studies have shown time and time again that interval training — bursts of harder effort with rest periods in between — is one of the most efficient tools for building cycling fitness, helping you to pedal faster for longer before fatigue sets in.

In the past, however, ‘interval training’ has had a bit of an image problem, often being associated with long, gruelling and monotonous efforts and only relevant to elite athletes.

The good news is that recent research shows that short or even very short work intervals, of around 30 seconds (which are much less demanding to perform than long intervals), can produce excellent gains in endurance. But can such short intervals really produce the same endurance benefits as the more traditional longer interval session?

That’s the question that scientists at the University of Lillehammer in Norway have been attempting to answer in a recently published study, and the findings make fascinating reading.

The science
In the study, a group of 16 cyclists were split into two groups. Both underwent a 10-week interval training programme. However, one group used long intervals of five minutes duration (four in each session) averaging around 324 watts during each interval, whereas the other group performed short intervals with each interval lasting just 30 seconds, at an average of 363 watts.

Importantly, the total workload performed and perceived efforts were the same for each type of training, which meant that the cyclists performing short intervals performed many more per session than those doing long intervals.

Before and again after the 10 weeks of training, all cyclists had fitness tests to see which protocol had proved most effective. In particular, the scientists looked at the cyclists’ maximum oxygen uptake (aerobic power), maximum sustainable power, their power output at second lactate threshold (the point at which lactate rapidly accumulates in the muscles, forcing you to slow down) and how much power they could sustain during a 40-minute all-out time trial.

Before the interval training programme, there were no differences between the two groups. Yet after 10 weeks of training, the short-interval cyclists increased their aerobic power by 8.7 per cent, while those performing long intervals didn’t make any gains. Likewise, when it came to maximum sustainable power, the high-intensity cyclists improved by around 8.5 per cent, whereas the long-interval cyclists made no significant gains.

The long-interval cyclists did make small gains (five per cent) in power output at second lactate threshold, but once again the short-interval trained cyclists came out on top with 12 per cent gains. Short intervals were also more effective at boosting average power output in the 40-minute time trial (12 per cent versus four per cent).

Scand J Med Sci Sports. 2014 Jan 1. doi: 10.1111/sms.12165. [Epub ahead of print]

The bigger picture
Previous studies have demonstrated that short intervals of 30 seconds can be very effective at building aerobic endurance, and are as effective as long intervals (1). This is surprising as you might think that in order to build aerobic endurance you need to perform long aerobic-type workouts.

However, recent research suggests that the intense bursts during interval training are able to stimulate the body’s production of a key molecule called PGC-1, which then acts on ‘endurance genes’ buried in the cell nucleus, boosting their activity (2). As a result, these genes produce more mitochondria in muscle cells with the result that the muscles’ capacity to produce energy aerobically is enhanced.

The short intervals were more effective at building aerobic fitness than the longer intervals, suggesting that they deserve serious consideration by any cyclist wanting to ride faster.

Applying the science
Less fit or novice cyclists: 
Try including at least one session of short intervals into your weekly training programme. Start with four to six bursts of 30 seconds going very hard (but not flat-out), interspersed with one minute of rest time. Build up to eight to 10 bursts.

Fit/accomplished cyclists: Use the protocol above but reduce the rest time to 30 seconds between efforts. Build up to 16 work intervals.

1. Med Sci Sports Exerc 2007; 39:665-671
2. J Physiol 590.5, 2012; 
pp1077–1084