Which factor can lead to overtraining syndrome?

Insufficient recovery time is a primary factor that can lead to overtraining syndrome. When athletes or individuals engage in high-intensity training without allowing adequate time for their bodies to recover, it can result in accumulated fatigue and stress. Recovery is essential for the body to repair muscle tissue, replenish energy stores, and restore hormonal balance. Without sufficient recovery, the body's ability to adapt to training diminishes, which can result in decreased performance, fatigue, and even psychological effects such as irritability or decreased motivation. Over time, this relentless cycle of training without enough recovery can lead to overtraining syndrome, characterized by a decline in performance and increased risk of injury. In this context, the other options do not contribute positively to the training process or prevent overtraining; however, they do not directly correlate with leading to overtraining syndrome like insufficient recovery time does.