Pablo B. Costa

The Time Course of Musculotendinous Stiffness Responses Following Different Durations of Passive Stretching

STUDY DESIGN Repeated-measures experimental design. OBJECTIVE To examine the acute effects of different durations of passive stretching on the time course of musculotendinous stiffness (MTS) responses in the plantar flexor muscles. BACKGROUND Stretching is often implemented prior to exercise or athletic competition, with the intent to reduce the risk of injury via decreases in MTS. METHODS AND MEASURES Twelve subjects (mean +/- SD age, 24 +/- 3 years; stature, 169 +/- 12 cm; mass, 71 +/- 17 kg) participated in 4 randomly-ordered experimental trials: control with no stretching, 2 minutes (2min), 4 minutes (4min), and 8 minutes (8min) of passive stretching. The passive-stretching trials involved progressive repetitions of 30-second passive stretches, while the control trial involved 15 minutes of resting. MTS assessments were conducted before (prestretching), immediately after (poststretching), and at 10, 20, and 30 minutes poststretching on a Biodex System 3 isokinetic dynamometer. RESULTS MTS decreased (P<.05) immediately after all stretching conditions (2min, 4min, and 8min). However, MTS for the 2min condition returned to baseline within 10 minutes, whereas MTS after the 4min and 8min passive-stretching conditions returned to baseline within 20 minutes. CONCLUSIONS Practical durations of passive stretching resulted in significant decreases in MTS; however, these changes return to baseline levels within 10 to 20 minutes.

The Acute Effects of Different Durations of Static Stretching on Dynamic Balance Performance

Costa, PB, Graves, BS, Whitehurst, M, and Jacobs, PL. The acute effects of different durations of static stretching on dynamic balance performance. J Strength Cond Res 23(1): 141-147, 2009-The purpose of this study was to examine the effects of different durations of static stretching on dynamic balance. Women (N = 28) were tested before and after 2 stretching interventions and a control condition on 3 separate days, at least 48 hours apart. The stretching sessions involved a cycle ergometer warm-up at 70 rpm and 70 W followed by passive stretching of the lower-body muscles. Each stretching position was held at a point of mild discomfort and repeated 3 times with 15 seconds between stretches. In the 2 stretching protocols, the positions were maintained for 15 or 45 seconds. The control condition involved the same cycle ergometer warm-up, with a 26-minute rest period between pre- and posttests. Balance was assessed using the Biodex Balance System. A 2-way repeated-measures analysis of variance was used with the effects of study condition (control, 15 seconds, 45 seconds) and time (pre-, postscores). Post hoc paired t-tests were used when appropriate to determine possible statistical significance between pre- and posttest scores. Analyses indicated no significant main effects for either study condition or time. However, there was a significant condition × time interaction (p < 0.05). Post hoc analyses indicated that the 15-second condition produced a significant improvement in the balance scores (p < 0.01), with no significant effects with the control condition or the 45-second treatment. The results of this study reveal that a stretching protocol of 45-second hold durations does not adversely affect balance when using the current stabilometry testing procedure. Furthermore, a stretching intervention with 15-second hold durations may improve balance performance by decreasing postural instability. Strength and conditioning professionals concerned with reported performance limitations associated with static stretching should consider applying shorter-duration stretching protocols when aiming to improve balance performance.

Acute effects of static stretching on peak torque and the hamstrings-to-quadriceps conventional and functional ratios

Recent evidence has shown acute static stretching may decrease hamstring‐to‐quadriceps (H:Q) ratios. However, the effects of static stretching on the functional H:Q ratio, which uses eccentric hamstrings muscle actions, have not been investigated. This study examined the acute effects of hamstrings and quadriceps static stretching on leg extensor and flexor concentric peak torque (PT), leg flexor eccentric PT, and the conventional and functional H:Q ratios. Twenty‐two women (mean ± SD age=20.6 ± 1.9 years; body mass=64.6 ± 9.1 kg; height=164.5 ± 6.4 cm) performed three maximal voluntary unilateral isokinetic leg extension, flexion, and eccentric hamstring muscle actions at the angular velocities of 60 and 180°/s before and after a bout of hamstrings, quadriceps, and combined hamstrings and quadriceps static stretching, and a control condition. Two‐way repeated measures ANOVAs (time × condition) were used to analyze the leg extension, flexion, and eccentric PT as well as the conventional and functional H:Q ratios. Results indicated that when collapsed across velocity, hamstrings‐only stretching decreased the conventional ratios (P<0.05). Quadriceps‐only and hamstrings and quadriceps stretching decreased the functional ratios (P<0.05). These findings suggested that stretching may adversely affect the conventional and functional H:Q ratios.

Effects of stretching on peak torque and the H:Q ratio.

The purpose of the present study was to examine the acute effects of hamstring and calf stretching on leg extension and flexion peak torque (PT) and the hamstrings-to-quadriceps (H : Q) ratio during maximal, concentric isokinetic muscle actions at 60, 180, and 300 degrees . s (-1) in women. Thirteen women (mean age +/- SD = 20.8 +/- 1.8 yrs; height = 163.0 +/- 5.7 cm; mass = 64.0 +/- 8.3 kg) performed 3 maximal concentric isokinetic leg extension and flexion muscle actions at 3 randomly ordered angular velocities (60, 180, and 300 degrees . s (-1)) before and after a bout of static stretching. The stretching protocol consisted of 1 unassisted and 3 assisted static stretching exercises designed to stretch the posterior muscles of the thigh and leg. Four repetitions of each stretch were held for 30 s with 20 s rest between repetitions. The results indicated that leg flexion PT decreased from pre- to post-stretching (34.9 +/- 3.5 and 32.4 +/- 3.2 Nm, respectively) collapsed across velocity. However, no other changes were observed from pre- to post-stretching for leg extension PT (78.5 +/- 5.9 and 77.8 +/- 5.5 Nm, respectively) and the H : Q ratio (0.47 +/- 0.04 and 0.44 +/- 0.03, respectively). Our findings suggested that despite the stretching-induced decreases in leg flexion PT, leg extension PT and the H : Q ratios were unaltered by the stretching.

Effects of two modes of static stretching on muscle strength and stiffness.

PURPOSE The purpose of the present study was to examine the effects of constant-angle (CA) and constant-torque (CT) stretching of the leg flexors on peak torque (PT), EMGRMS at PT, passive range of motion (PROM), passive torque (PAS(TQ)), and musculotendinous stiffness (MTS). METHODS Seventeen healthy men (mean ± SD: age = 21.4 ± 2.4 yr) performed a PROM assessment and an isometric maximal voluntary contraction of the leg flexors at a knee joint angle of 80° below full leg extension before and after 8 min of CA and CT stretching. PASTQ and MTS were measured at three common joint angles for before and after assessments. RESULTS PT decreased (mean ± SE = 5.63 ± 1.65 N·m) (P = 0.004), and EMG(RMS) was unchanged (P > 0.05) from before to after stretching for both treatments. PROM increased (5.00° ± 1.03°) and PASTQ decreased at all three angles before to after stretching (angle 1 = 5.03 ± 4.52 N·m, angle 2 = 6.30 ± 5.88 N·m, angle 3 = 6.68 ± 6.33 N·m) for both treatments (P ≤ 0.001). In addition, MTS decreased at all three angles (angle 1 = 0.23 ± 0.29 N·m·°(-1), angle 2 = 0.26 ± 0.35 N·m·°(-1), angle 3 = 0.28 ± 0.44 N·m·°(-1)) after the CT stretching treatment (P < 0.005); however, MTS was unchanged after CA stretching (P > 0.05). CONCLUSIONS PT, EMG(RMS), PROM, and PASTQ changed in a similar manner after stretching treatments; however, only CT stretching resulted in a decrease in MTS. Therefore, if the primary goal of the stretching routine is to decrease MTS, these results suggest that CT stretching (constant pressure) may be more appropriate than a stretch held at a constant muscle length (CA stretching).

Influence of exercise order on maximum strength in untrained young men.

It is generally recommended that exercises involving large muscle groups be placed at the beginning of a training session. However, methodological training studies manipulating exercise order and the investigation of its influence on strength have not been conducted. Therefore, the purpose of this study was to examine the influence of exercise order on strength in untrained young men after 8 weeks of training. Prior to the training program, participants were randomly assigned to three groups. One group began with large and progressed toward small muscle group exercises (G1) while another performed the opposite order (G2). The third group did not exercise and served as a control (CG). Training frequency was three sessions per week with at least 48h of rest between sessions for a total of 24 sessions in the 8-week period. One repetition maximum (1RM) was assessed for all exercises at baseline and after 8 weeks of training. Both G1 and G2 resulted in significant increases of 16.3-77.8% in 1RM compared to baseline (p<0.05). However, only the small muscle group exercises revealed significant differences between groups (p<0.05). The results demonstrated exercise order of small muscle group exercises might be particularly important during the initial stages of strength training in untrained young men.

Acute Effects of a Warm-up Including Active, Passive, and Dynamic Stretching on Vertical Jump Performance

Abstract Carvalho, FLP, Carvalho, MCGA, Simão, R, Gomes, TM, Costa, PB, Neto, LB, Carvalho, RLP, and Dantas, EHM. Acute effects of a warm-up including active, passive, and dynamic stretching on vertical jump performance. J Strength Cond Res 26(9): 2447–2452, 2012—The purpose of this study was to examine the acute effects of 3 different stretching methods combined with a warm-up protocol on vertical jump performance. Sixteen young tennis players (14.5 ± 2.8 years; 175 ± 5.6 cm; 64.0 ± 11.1 kg) were randomly assigned to 4 different experimental conditions on 4 successive days. Each session consisted of a general and specific warm-up, with 5 minutes of running followed by 10 jumps, accompanied by one of the subsequent conditions: (a) Control Condition (CC)—5 minutes of passive rest; (b) Passive Stretching Condition (PSC)—5 minutes of passive static stretching; (c) Active Stretching Condition (ASC)—5 minutes of active static stretching; and (d) Dynamic Stretching Condition (DC)—5 minutes of dynamic stretching. After each intervention, the subjects performed 3 squat jumps (SJs) and 3 countermovement jumps (CMJs), which were measured electronically. For the SJ, 1-way repeated measures analysis of variance (CC × PSC × ASC × DC) revealed significant decreases for ASC (28.7 ± 4.7 cm; p = 0.01) and PSC (28.7 ± 4.3 cm; p = 0.02) conditions when compared with CC (29.9 ± 5.0 cm). For CMJs, there were no significant decreases (p > 0.05) when all stretching conditions were compared with the CC. Significant increases in SJ performance were observed when comparing the DC (29.6 ± 4.9 cm; p = 0.02) with PSC (28.7 ± 4.3 cm). Significant increases in CMJ performance were observed when comparing the conditions ASC (34.0 ± 6.0 cm; p = 0.04) and DC (33.7 ± 5.5 cm; p = 0.03) with PSC (32.6 ± 5.5 cm). A dynamic stretching intervention appears to be more suitable for use as part of a warm-up in young athletes.

Determining the minimum number of passive stretches necessary to alter musculotendinous stiffness

Abstract In this study, we examined the minimum number of constant-torque passive stretches necessary to reduce musculotendinous stiffness. Thirteen healthy individuals (mean age 22 years, s = 3; stature 1.67 m, s = 0.1; mass 66 kg, s = 13 kg) volunteered to participate in the investigation and underwent four 30-s constant-torque passive stretches of the plantar flexor muscles. Musculotendinous stiffness was examined from the angle–torque curves generated prior to the passive stretches, at the beginning of each 30-s stretch, and immediately following the four 30-s passive stretches. The results indicated that musculotendinous stiffness of the plantar flexors was reduced following two 30-s constant-torque passive stretches (P < 0.05) compared with the pre- musculotendinous stiffness assessment. Musculotendinous stiffness remained depressed following the third and fourth stretches, but did not decrease further. These findings suggest that two 30-s bouts of constant-torque passive stretching may be necessary to cause a significant decrease in musculotendinous stiffness of the plantar flexor muscles.

Acute effects of two different stretching methods on local muscular endurance performance.

Gomes, TM, Simão, R, Marques, MC, Costa, PB, and da Silva Novaes, J. Acute effects of two different stretching methods on local muscular endurance performance. J Strength Cond Res 25(3): 745-752, 2010-The purpose of this study was to assess the acute effects of the static and proprioceptive neuromuscular facilitation (PNF) stretching methods on local muscular endurance performance at intensities between 40 and 80% of 1 repetition maximum (1RM) for the knee extension (KE) and bench press (BP) exercises. Fifteen male volunteers (23.9 ± 4.3 years; 174.5 ± 8.5 cm; and 77.8 ± 7.6 kg), who were nonathletes but had previous experience in resistance training, volunteered for this study. Participants were assigned to 9 randomly ordered experimental conditions, in which all subjects performed endurance tests at 40, 60, and 80% of 1RM, preceded by static stretching (SS), PNF, and no stretching (NS) in the KE and BP exercises. One-way repeated-measures analysis of variance (NS × SS × PNF) revealed an influence of stretching for all intensities only when the PNF treatment was used. Significant differences (p < 0.05) were found in the KE exercise, with reductions in the number of repetitions when comparing PNF40 (23.7 ± 2.7) to NS40 (27.5 ± 3.6); PNF60 (12.6 ± 2.8) to SS60 (16.5 ± 4.1) and NS60 (17.3 ± 3.2); and PNF80 (6.3 ± 1.7) to SS80 (9.9 ± 2.5) and NS80 (9.8 ± 2.3) conditions. Significant differences (p < 0.05) were also found for the BP exercise with decreases in the number of repetitions when comparing PNF60 (13.7 ± 2.8) to NS60 (17.0 ± 3.0) and PNF80 (6.2 ± 2.2) to NS80 (8.7 ± 2.3) conditions. These findings suggest that for the intensities studied (40, 60, and 80% 1RM), only the PNF method decreased muscle endurance. Strength and conditioning professionals may want to consider avoiding PNF stretching before activities requiring local muscular endurance performance.

Gender differences in musculotendinous stiffness and range of motion after an acute bout of stretching.

Hoge, KM, Ryan, ED, Costa, PB, Herda, TJ, Walter, AA, Stout, JR, and Cramer, JT. Gender differences in musculotendinous stiffness and range of motion after an acute bout of stretching. J Strength Cond Res 24(10): 2618-2626, 2010-The purpose of the present study was to examine musculotendinous stiffness (MTS) and ankle joint range of motion (ROM) in men and women after an acute bout of passive stretching. Thirteen men (mean ± SD age = 21 ± 2 years; body mass = 79 ± 15 kg; and height = 177 ± 7 cm) and 19 women (21 ± 3 years; 61 ± 9 kg; 165 ± 8 cm) completed stretch tolerance tests to determine MTS and ROM before and after a stretching protocol that consisted of 9 repetitions of passive, constant-torque stretching. The women were all tested during menses. Each repetition was held for 135 seconds. The results indicated that ROM increased after the stretching for the women (means ± SD pre to post: 109.39° ± 10.16° to 116.63° ± 9.63°; p ≤ 0.05) but not for the men (111.79° ± 6.84° to 113.93° ± 8.15°; p > 0.05). There were no stretching-induced changes in MTS (womens pre to postchange in MTS: −0.35 ± 0.38; mens MTS: +0.17 ± 0.40; p > 0.05), but MTS was higher for the men than for the women (MTS: 1.34 ± 0.41 vs. 0.97 ± 0.38; p ≤ 0.05). electromyographic amplitude for the soleus and medial gastrocnemius during the stretching tests was unchanged from pre to poststretching (p > 0.05); however, it increased with joint angle during the passive movements (p ≤ 0.05). Passively stretching the calf muscles increased stretch tolerance in women but not in men. But the stretching may not have affected the viscoelastic properties of the muscles. Practitioners may want to consider the possible gender differences in passive stretching responses and that increases in ROM may not always reflect decreases in MTS.