Vertical Jumping Performance: Recording the Effects of Proprioceptive Neuromuscular Facilitation Stretching at Different Plantar Flexor Lengths

Abstract

Introduction: Flexibility seems to be an essential part of both the training and rehabilitation processes. Several stretching techniques have been used to improve the range of motion (ROM) of the joints with the proprioceptive neuromuscular facilitation (PNF) method being the most effective one. Although plantar flexors are ideal to compare the acute effects of synergistic muscle groups on performance, it is not clear whether the PNF stretch at different muscle lengths could result in different alterations.

Material and methods: Sixteen male students randomly performed 2 levels of stretching (PNF with bended knees, or PNFshort, and with extended knee, or PNFlong) and 3 types of jumps, separated by 48 hours (7 sessions in total). Jumping parameters were recorded by a force plate, and the final jumping height (H) and ground reaction forces (Fz) were analyzed. Furthermore, the ROM of the ankle joint was recorded before, right after, and 15 minutes after the stretches. Results: The ankle joint's ROM joint was increased after both interventions. No significant changes were found in the jumping height of all jumps. The Fz, during the squat jump (SJ) and countermovement jump (CMJ), were increased after PNFshort. Similarly, a significant increase was found in Fz in drop jumps (DJ) right after the PNFshort.

Conclusion: Our findings demonstrated that PNF stretches of different lengths could potentially alter the stretch-shortening cycle's performance, possibly leading to a non-optimal muscle-tendon interaction.

Keywords: ankle joint; ground reaction forces; jumping height; proprioceptive neuromuscular facilitation (pnf); tricep surae.

Figure 1. Experimental procedure

SJ = squat jump, CMJ = countermovement jump, DJ₃₀ = drop jump from 30 cm, PNFlong = proprioceptive neuromuscular facilitation with extended knees, PNFshort = proprioceptive neuromuscular facilitation with bended knees at 90°

Figure 2. Fz values during SJ at the three time points, after the PNFshort condition, * indicates significant change (p < .05) compared to the previous time point

Fz: ground reaction forces, SJ: squat jump, PNFshort: proprioceptive neuromuscular facilitation with bended knees at 90°, TB: baseline timepoint, T0: immediately after the stretch time point, T15: 15 minutes after the stretch time point

Figure 3. Fz at PNFlong (squares), Fz at PNFshort (circles) in CMJ at three time points, $ indicates a significant difference (p < .05) between PNFshort and PNFlong at each time point

Fz: ground reaction forces, PNFlong: proprioceptive neuromuscular facilitation with extended knees, PNFshort: proprioceptive neuromuscular facilitation with bended knees at 90°, CMJ: countermovement jump, TB: baseline time point, T0: immediately after the stretch time point, T15: 15 minutes after the stretch time point

Figure 4. Fz values after PNFshort in drop jump from 30 cm at three time points, * indicates significant change (p < .05) compared to the previous time point

Fz: ground reaction forces, PNFshort: proprioceptive neuromuscular facilitation with bended knees at 90°, TB: baseline time point, T0: immediately after the stretch time point, T15: 15 minutes after the stretch time point