This article discusses the balance of volume and intensity of fitness activities in soccer training sessions. Iaia FM et al, performed a study on high performance athletes by replacing their standard aerobic training (45km long distance running) with 3-4 weekly sessions of intermittent high-intensity exercise (8-12 sprint runs of 30 s, separated by 3 min of rest). The training period was 4 weeks long. The total distance covered per week was reduced from 45 to 12 km.

The following training effects of the Intermittent Training were seen:

7% Improvement in Distance covered in a 30-s “all-out” test.
19% Improvement in time to exhaustion during two short-term.
27% Improvement in supramaximal running bouts.
19% Improvement in performance during repeated high-intensity exercise (Yo-Yo IR2.
0% Change in the time to complete a 10Km run.

Conclusions & Recommendations:
Performance during intense exercise can be improved and endurance performance maintained even with a reduction in training volume if the intensity of training is very high. Soccer players may benefit from replacing some aerobic training sessions with speed endurance training during the season. In the last 4 weeks of pre-season (preparation period) there could also be a place for this type of increased intensity and reduced volume.

Additional Reading:

Iaia FM, Thomassen M, Kolding H, Gunnarsson T, Wendell J, Rostgaard T, Nordsborg N, Krustrup P, Nybo L, Hellsten Y, Bangsbo J.
Reduced volume but increased training intensity elevates muscle Na+-K+ pump α1-subunit and NHE1 expression as well as short-term work capacity in humans.
Am J Physiol Regul Integr Comp Physiol. 2008 Mar;294(3):R966-74.