Strength and conditioning coaches maintain that all athletes should continue weight training during the season for various reasons. Most prominent is that the athletes must maintain their already achieved levels of strength. I think everyone can agree with this objective.
Maintenance of strength during the season is especially important for maintaining reliable execution of the necessary sports skills. Decreases in strength will change technique execution even if appears to be insignificant.
Understand that on all levels of performance, skill technique is foremost in ensuring success of on-field play and prevention of injury. To ensure effective technique execution in season the player needs specific strength, i.e., strength of the muscles as they are involved in the same neuromuscular pathway and range of motion as used in execution of the skill.
Losses in general strength do not have the same effect on technique. Nor is general strength the key to the prevention of injury.
Most coaches also believe that the athletes can and should gain additional strength in season. This however is a fallacy since increases in strength have the same negative effect on skill execution as decreases in strength. Because of this maintenance of strength is the key to enabling the athlete to perform at his best during the season.
What is often overlooked in their zeal to do more weight training in-season is that the athlete is involved in many more activities that he was in the off-season. In season emphasis is on recuperation with active recovery especially after difficult games. In addition, the athlete is involved in many game practices to carry out the coach’s game strategy and tactics.
For the practices to be most effective the athlete must be as fully energized as possible. The athlete should not be experiencing fatigue from the heavy weight training which is what most coaches do in season. The weight training for maintenance is much lighter and usually involves only one set of the key exercises once a week.
In answer to the question posed in the title of this article it should be noted that many of these strength and conditioning coaches believe that it is necessary to increase strength in order to maintain strength. This however, is not necessary since it is possible to maintain the already achieved levels of strength without additional gains. Additional strength at this time has more negative consequences than positive.
For more information on this topic see Build a Better Athlete or one of the sport specific books such as Explosive Running and Explosive Basketball Training.