The research in physical preparation for elite level soccer players highlights that repeated high-intensity performance ability is one of the most sensitive measures of match performance. The Yo-Yo Intermittent Recovery Test is the standard test in soccer for determining repeated high-intensity performance ability i.e. the better the result on a Yo-Yo test, the greater distance a player can cover on the pitch at high intensity.
A new study scheduled for publication appears in Medicine and Science in Sports and Exercise looked at the effect of performing one additional speed-endurance training session per week on a number of soccer performance indicators including Yo-Yo test, 10 & 30m sprint test and agility test. The subjects (n = 13) were put through a 5-week training programme of 6-9 repetitions * 30s that was performed at 90-95%VO2MAX.
The results show that Yo-Yo test performance improved significantly (p < 0.05) by 11%, while no changes were detected for speed or agility. Similarly, VO2MAX did not change. So how do we explain the results?
At the physiological level, the authors demonstrated a significant increase (p<0.05) in monocarboxylate transporter 1 (MCT 1) expression by 9% following speed-endurance training. MCT 1 is a lactate transport protein found in many human and animal tissues, including skeletal muscle. So when exercising at high intensity for 30s, lactate which is locally produced can be transported to adjacent muscles that are perfused. Bonen et al (2000) have shown a good relationship between MCT 1 expression and lactate transport (0.92), indicating that the recovery ability to perform repeated high-intensity exercise is an important indicator of performance improvement, independent of improvements in physical capacity.
Note that in this test, neither speed nor VO2MAX improved. In fact, the relative number of IIx fibres decreased significantly after training (p < 0.05). There a number of possible explanations for this observation: 1) training did not specifically target the high power ATP-PCr system where recruitment type IIx fibres is favoured (see graph below) 2) the protocol did not adequately stress aerobic power capacity due to intervals of 30s only 3) players could not improve their as VO2MAX they had previously achieved their limit.
During maximal intensity sprinting, PCr stores are rapidly diminished while ATP stores are defended. If maximal effort continues for 8s, exhaustion ensues. As the exercise protocol included repeated 30s speed-endurance efforts, a significant aerobic-anaerobic contribution is likely to have been favoured with concomitant up-regulation of associated muscle fibres.
At the biomechanical level, running automatically improves biomechanics efficiency as we have previously described here. It is likely that the players improved their running economy from the repeated practise of high intensity running.
Application of 6-9 * 30s high intensity training
The protocol could be a useful intervention mid-way through the season or towards the end of the season if notable dips in match performance occur in your players. It could also be useful for players that respond poorly to traditional aerobic power training (LSD, interval training).