Short term sprint interval vs traditional endurance training
Trying to balance ultra cycling training and a 9-5 job is difficult. Many riders have heard of the benefits of indoor training – intensity, measuring power improvements, strength endurance, etc – hence the reason why dedicated indoor cycling studios like Athlete Lab in Singapore. BUT a lot of cyclists still question its relevance for long endurance rides. I mean how can you possibly improve your slow twitch muscles with short sharp interval sprints?
Well let’s look at the science. In 2006 there was a paper entitled Short-term sprint interval versus traditional endurance training: similar initial adaptations in human skeletal muscle and exercise performance in the Journal of Physiology. It was the first study to directly compare diverse training strategies in a standardized manner and examine changes in exercise capacity for skeletal muscle. The investigation looked at physiological adaptions after low volume spring interval training (SIT) and high volume endurance training (ET) with the training levels consisting of 2 weeks at 2.5h for SIT and 10.5h for ET. The definition of SIT was 30s ‘all out’ cycling at 250% VO2 peak (sound familiar?) 4 to 6 times with recovery of 4minutes and for ET was 90-120 continuous cycling at 65% VO2.
So what did they find? Any bets? Both training methods decreased the time required to complete 50 and 750 kJ time trials with no difference between the two groups. Biopsy samples – you have to do a proper measurement! – were also taken before and after training, and guess what a similar level of increases in muscle oxidative capacity. To detect this the lab rats looked at the maximal activity of cytochrome c oxidase (COX) and COX subunits II & IV protein content which improved alongside muscle buffering capacity & glycogen content. Basically the background to this is that studies have found that even with short periods of endurance training (5-7 days) increases in glycogen availability and a reduction of catabolism is associated with improved endurance capacity. Cytochrome c oxidase or complex IV (seriously 4 years of lectures is flooding back here) is the terminal enzyme in the respiratory electron transport chain of mitochondria – the complex that creates energy in cells. Training induced adaptations leads to an increase in mitochondrial density, leading to increased substrate utilization and detected as changes in the maximal activity. It was generally thought that SIT reduces glycogen and lactate accumulation but increases maximal activity in mitochrondrial enzyme – essentially improves performance on aerobic metabolism. But this study showed that SIT is more effective than ET in improving other determinants of endurance performance – such as muscle buffering capacity.
So science proved that at least in the short term, even with large differences in training volume, sprint interval training was not only a time efficient exercise routine but lead to a comparable level of exercise performance markers (at least in the short term) than high volume endurance training. However I must stress this is not the complete story if you are planning the Race Across America or any stupid long races. Sprint training will improve your fitness levels to the levels seen in endurance training but there are other benefits – time in saddle (I.e. Toughen/strengthen your back & ass), improved fat metabolism when your sugar levels drop off after 1.5hrs and more that I will touch on in later articles. I think it just means you have to double up on your indoor training!
For further reading a background to this study can be found on the Active blog site here
There is also a fantastic, extensive post on aerobic training at Cycling tips