Fitness throughout the season
It is widely acknowledged that aerobic fitness is a crucial variable that can contribute to success in football. Preseason programs generally seek to improve markers of aerobic fitness (e.g., bleep test performance), and in the majority of cases they achieve this; however, given that once the season starts technical and tactical practice takes priority, and that previously published research (and data presented on this website in the fitness training for football page) suggests that match-play alone is not a high enough stimulus to improve aerobic fitness, does the aerobic fitness of football players remain elevated throughout the full duration of a season?
Without intervention, the answer seems to be no as previous research in professional and semi-professional players has shown that aerobic fitness increases from preseason to midseason but then decreases thereafter (1,2). In one study using players from the English Nationwide Conference North League, testing was routinely performed at selected time points throughout the competitive season; (a) end of season one (April); (b) before preseason training for season 2 (July); (c) after preseason training for season 2 (August); (d) midpoint of season 2 (February); and (e) end of season 2 (April). As one would expect, results showed that in the time between the end of the first season and the start of the next season, all variables deteriorated. Preseason training and match-play in the early part of the season improved markers of aerobic fitness, vertical jump, percent body fat, agility, and sprint performance. However, from February time onwards, decreases in aerobic fitness and the cessation of increases in performances of jumping, sprinting, and agility became evident; possibly due to fatigue or fixture overload in the second half of the season.
Given that fixture overload, fixture cancellation (due to winter weather conditions), or a pre-season break may adversely affect a player's aerobic fitness, some researchers have found it beneficial to implement a concentrated block of fitness training in the mid-season period with the aim of boosting a team's fitness levels until the end of the season. Specific methods for improving fitness have included the use of high intensity interval training and small sided games (for more information see the fitness training for football page). Consequently, the mid-season period, specifically around February time, may be the turning point in your competitive season as your opponents fitness levels may start to deteriorate; however, harnessing the knowledge of available scientific research and applying it to real world match-play, may give you the edge over your opponents for the crucial latter part of the season.
Additional Reading
1. Haritonidis, K, Koutlianos, N, Koudi, E, Haritonidou, M, and Deligiannis, A. (2004). "Seasonal variation of aerobic capacity in elite soccer, basketball and volleyball players." Journal of Human Movement Studies 16: 289-302.
2. Caldwell, B. and Peters, D. (2009). "Seasonal variation in physiological fitness of a semi-professional soccer team." Journal of Strength and Conditioning Research 23: 1370-1377.