Interventions
The participants in the PNF group received PNF stretching for 8 weeks, 3 sessions per week. Every session of PNF stretching lasted for 1 hour, including 5 min warm-up, 45 min stretching, and 10 min cool down. PNF stretching includes diagonal and spiral patterns and stretching techniques. The diagonal and spiral patterns included four movement patterns: flexion-abduction-internal, extension-adduction-external, flexion-adduction-external, and extension-abduction-internal rotations. The initial positions of the joints in four spiral-diagonal patterns are shown in 