Purpose:
There is some recent evidence that temporal specificity is important for optimizing training for muscular performance. This study was to examine the long-term effects of static stretching performed at different times of day on hamstring torque and flexibility.

Methods:
The total of 60 trained male subjects with tight hamstring were selected and randomly divided into 3 equal groups. Group A received static stretch in the morning (07:00–9:00), group B in the afternoon (13:00–16:00), and group C in the evening (18:00–20:00). The hamstring isokinetic concentric and eccentric peak torque and knee extension range of motion were assessed before and after 6 weeks of static stretching (3 repetitions of 30 s, 5 times/week).

Results:
A statistically significant increase was observed in hamstring concentric and eccentric torque, and flexibility after static stretching at different times of day (p < 0.05). The concentric and eccentric torque post-training values were significantly higher than the pre-training values (p < 0.05). The hamstring flexibility post-training values of groups B and C were significantly higher than for group A (p < 0.05). The torque and flexibility change scores of groups B and C were significantly higher than for group A (p < 0.05), without any significant difference between groups B and C (p > 0.05).

Conclusions:
Afternoon and evening static stretching is more effective than morning stretching in improving the hamstring concentric and eccentric torque and flexibility. Therefore, static stretching is a time-dependent task and should be scheduled by clinicians, coaches, and athletes in the afternoon or evening.