The improvement in the fitness level is a consequence of the applied training load, which causes certain adaptations in the organism of the athlete. Every training modality leads to its own unique adaptations. To optimize the training efficiency, one should understand what kind of adaptations could be achieved by using different training methods.

Regarding aerobic endurance, it is believed that there are 3 major factors accounting for performance: work economy, lactate threshold, and maximal oxygen uptake [1]. In this post we will review the results of the research by Helgerud with colleagues on the adaptations caused by common conditioning protocols [2]: 

1. Long slow distance running (LSD): a continuous run at 70% HRmax for 45 min 
2. Lactate threshold running (LT): a continuous run at LT (85% HRmax) for 24 min
3. 4x4 min interval running (4x4): 4 min run at 90-95% HRmax with 3 min of active recovery at 70% HRmax x 4 reps (25 min)
4. 15:15 sec interval running (15:15): 15 sec run at 90-95% HRmax with 15 sec of active recovery at 70% HRmax x 47 reps (24 min)

The obtained results after 8 weeks of training confirmed that the best strategy for LT enhancement is continuous work at the corresponding intensity level. At the same time, it is important to remember that LT will significantly differ depending on the exercise mode. For example, average LT of hockey players riding a bicycle is 155 bpm, while skating on ice - 180 bpm. 

For movement economy and VO2max improvement, more intense interval training protocols are optimal. 

Finally, LSD is a good option for cardiovascular function, mitochondrial energy production, oxidative capacity of muscle, and utilization of fat as a fuel improvement [3].