J Strength Cond Res. 2011 Nov 5. [Epub ahead of print]
Maximal strength, number of repetitions, and total volume are differently affected by static-, ballistic-, and PNF- stretching.
Barroso R, Tricoli V, Gil S, Ugrinowitsch C, Roschel H.
Stretching exercises have been traditionally incorporated into warm-up routines prior to training sessions and sport events. However, the effects of stretching on maximal strength and strength endurance performance seem to depend on the type of stretching employed. The objective of this study was to compare the effects of static (SS), ballistic (BS) and proprioceptive neuromuscular facilitation (PNF) stretching on maximal strength, number of repetitions at a submaximal load, and total volume (i.e. number of repetitions x external load) in a multiple-set resistance training bout. Twelve strength-trained men (20.4 ± 4.5 yrs, 67.9 ± 6.3 kg, 173.3 ± 8.5 cm) volunteered to participate in the present study. All of the subjects completed eight experimental sessions. Four experimental sessions were designed to test maximal strength in the leg-press (i.e. 1RM) after each stretching condition [SS, BS, PNF or no-stretching (NS)]. During the other four sessions, the number of repetitions performed at 80% 1RM was assessed after each stretching condition. All of the stretching protocols significantly improved the range of motion (ROM) in the sit-and-reach test when compared to NS. Further, PNF induced greater changes in the sit-and-reach test than BS (4.7 ± 1.6, 2.9 ± 1.5 and 1.9 ± 1.4 cm for PNF, SS and BS, respectively). Leg-press 1RM values were decreased only after the PNF condition (5.5%, p<0.001). All of the stretching protocols significantly reduced the number of repetitions (SS: 20.8%, p<0.001; BS: 17.8%, p=0.01; PNF: 22.7%, p<0.001) and total volume (SS: 20.4%, p<0.001; BS: 17.9%, p=0.01; PNF: 22.4%, p<0.001) when compared to NS. The results from this study suggest that, in order to avoid a decrease in both the number of repetitions and total volume, stretching exercises should not be performed prior to a resistance training session. Additionally, strength-trained individuals may experience reduced maximal dynamic strength after PNF stretching.