In the study “Changes in balance ability, power output, and stretch-shortening cycle utilisation after two high-intensity intermittent training protocols in endurance runners” published in 2016 in the Journal of Sport and Health Science, researchers aimed to track the acute effects of 2 different high-intensity intermittent trainings (HIITs) on postural control, countermovement jump (CMJ), squat jump (SJ), and stretch-shortening cycles (SSC) utilization. The data was then compared to the changes induced by both protocols in those variables in endurance runners.
For the study, 18 recreationally trained endurance runners were tested under two sets of circumstances: 10 runs of 400 meters with 90 seconds of recovery time between running bout, and 40 runs of 100 meters with 30 seconds recovery time between runs. Heart rate was monitored during both HIITs. Blood lactate accumulation and rate of perceived exertion were recorded after both protocols. Vertical jump ability (CMJ and SJ), SSC, and postural control were controlled during both HIITs.
The study found a significant improvement in CMJ and SJ during the 10 x 400 m (p<0.05). It was also found that there were no significant changes were present during 40 x 100 m HIITs. Indexes related to SSC did not experience significant changes during any protocols. In terms of posture control, there were significant impairments during the 10 x 400 m protocol (p<0.05), while no significant changes were present in the postural control data gathered from 40 x 100 m protocol.
Researchers concluded that a protocol with a higher number of shorter runs (in this case 40 x 100 m) resulted in different changes in neuromuscular parameters than those with fewer and longer runs (for the case of the study 10 x 400 m). It was found that the 40 x 100 m protocol did not cause any significant changes in vertical jump ability, postural control, or SSC utilization. On the other hand, data showed that the 10 x 400 m protocol resulted in impaired postural control. The 10 x 400 m also caused improvement s in vertical jumping tests.