The time course of passive stiffness responses following an acute bout of static stretching in healthy, elderly men.

BACKGROUND: The time course of passive stiffness responses following an acute bout of static stretching has received little research attention, particularly in older adults. OBJECTIVE: To determine the time course of the acute effects of static stretching on passive stiffness of the hamstrings in healthy, elderly men. METHODS: Fifteen elderly men (age = 70 ± 7 years) underwent two randomized conditions that included a control treatment and an experimental treatment of four, 15-s straight-leg raise static stretches. Passive stiffness was calculated as the slopes of the initial and final phases of the angle-torque curve at pre-treatment (Pre) and post-treatment time points of zero (Post0), five (Post5), and ten (Post10) minutes. RESULTS: Passive stiffness collapsed across phase was lower at Post0 (P= .029, d= 0.64) and Post5 (P= .042, d= 0.54) but not Post10 (P> .999, d= 0.15) compared to Pre for the stretching treatment. There were no significant differences in passive stiffness (collapsed across phase) between any of the time points (P> .999, d≤ 0.14) for the control. CONCLUSIONS: An acute bout of static stretching produced significant decreases in the passive stiffness characteristics of elderly men; however, these decreases returned to baseline values within 5 to 10 minutes.

The Acute Effects of Fast-Paced Walking on Isometric Peak Torque and Rate of Torque Development in Regularly Exercising and Inactive Older Women.

This study aimed to examine the acute effects of fast-paced walking on isometric peak torque and rate of torque development (RTD) in regular exercising and inactive older women. Ten regular exercising (67 ± 4 years) and 10 inactive (68 ± 4 years) older women performed three isometric knee extension contractions before and after a control condition (quiet resting) and an experimental condition of fast-paced walking for 6 min. Peak torque and early (RTD100), late (RTD200), and maximum (peak RTD) RTD measurements were obtained from each contraction. Results showed no significant changes in peak torque, peak RTD, or RTD200 after walking for either group (p > .050). A significant decrease in RTD100 was observed after walking for the inactive group (p = .005) but not for the regular exercisers (p = .909). These findings highlight the importance of physical activity and suggest that a task as simple as walking may impair the rapid strength capacities of inactive older women.

Utility of peak torque and rate of torque development characteristics to identify walking performance ability in older women.

OBJECTIVES: It is unclear whether peak torque and rate of torque development (RTD) measurements can characterize functional differences in older adults according to their performance on a six-minute walk test. This study aimed to examine the efficacy of isometric peak torque and RTD characteristics of the knee extensors to differentiate between functional status in older women who are able (higher functioning) versus those who are unable (lower functioning) to walk 550 m in six minutes. METHODS: Ten higher functioning (67±4 years) and 10 lower functioning (68±4 years) older women performed three isometric knee extension maximal voluntary contractions followed by a six-minute walk test. Peak torque and early (RTD100), late (RTD200), and maximum (Peak RTD) RTD measurements were obtained from each contraction. RESULTS: The higher functioning group exhibited greater peak torque, Peak RTD, RTD100, and RTD200 compared to the lower functioning group (P≤0.011), with larger differences occurring for RTD characteristics (39.9-54.9%) than peak torque (20.3%). Multiple regression analysis indicated that RTD200 was the single best predictor of the distance covered during the six-minute walk test (R2=0.437, P=0.002). CONCLUSIONS: These findings suggest that knee extensor muscle strength, and in particular RTD, may be an effective discriminator and predictor of walking performance ability in older women.

Real-time measurement of isometric peak torque and rate of torque development using a novel strength testing device: a validity and reliability study.

Objective: Isometric peak torque (PT) and rate of torque development (RTD) are important characteristics relevant to athletic performance. A novel device called the Dynamo Torque Analyzer calculates and displays real-time measurements of isometric PT and RTD. However, the ability of the Dynamo to provide valid and reliable isometric PT and RTD measurements similar to those of an isokinetic dynamometer remains unclear. This study aimed to compare the reliability and magnitude of isometric leg extension and flexion PT and RTD measurements between an isokinetic dynamometer and the Dynamo Torque Analyzer.Approach: Twenty healthy, recreationally-active adults (age = 22 ± 3 years; height = 169 ± 10 cm; mass = 71 ± 18 kg) performed three isometric leg extension and flexion maximal voluntary contractions on two different occasions, from which isometric PT and early (RTD100), late (RTD200), and maximum (Peak RTD) RTD characteristics were measured by an isokinetic dynamometer and the Dynamo.Main results: Isometric leg extension and flexion PT and RTD characteristics were highly consistent across sessions for both the isokinetic dynamometer and Dynamo devices, with intraclass correlation coefficients of 0.935-0.984 and standard errors of measurement expressed as a percentage of the mean of 4.93-14.46%. There were significant positive relationships between the isokinetic dynamometer and Dynamo for all PT and RTD characteristics (r≥ 0.994;P< 0.001). Moreover, no significant differences between devices were observed for these variables (P= 0.107-0.555).Significance: These findings suggest that the Dynamo Torque Analyzer may be a valid and reliable device for measuring isometric PT and RTD of the lower-body musculature.

Effects of age on vertical jump performance and muscle morphology characteristics in females.

BACKGROUND: Declines in muscle morphology and function are commonly reported as a consequence of aging. However, few studies have investigated the influence of age on a comprehensive set of muscle function-related measures (i.e., reactive strength, power, etc.) that focuses on a dynamic performance task such as the vertical jump across the adult life span. This study aimed to examine the effects of age on muscle morphology characteristics (muscle cross-sectional area [CSA] and echo intensity [EI]) and vertical jump height, power, and reactive strength index (RSI) in females. METHODS: Twenty-six young (22±2 years), 30 middle-aged (36±5 years), and 23 older (71±5 years) females participated in this study. Muscle CSA and EI were determined from ultrasound scans of the vastus lateralis. Countermovement jumps were used to assess jump height, RSI, movement time, and peak power (Pmax). RESULTS: Muscle CSA, jump height, and Pmax were higher for the young compared to the old and middle-aged (P≤0.027) and for the middle-aged compared to the old (P<0.001). Movement time and EI values were lower (P≤0.004) and RSI values were higher (P<0.001) for the young and middle-aged compared to the old; however, no differences were observed between the young and middle-aged (P=0.367-0.620). CONCLUSIONS: Of all the variables assessed in this study, RSI exhibited the greatest decline (76%) between the young and old females. Such findings highlight the importance of reactive strength when assessing age-related changes in neuromuscular performance.

Duration-Dependent Effects of Passive Static Stretching on Musculotendinous Stiffness and Maximal and Rapid Torque and Surface Electromyography Characteristics of the Hamstrings.

Palmer, TB, Pineda, JG, Cruz, MR, and Agu-Udemba, CC. Duration-dependent effects of passive static stretching on musculotendinous stiffness and maximal and rapid torque and surface electromyography characteristics of the hamstrings. J Strength Cond Res 33(3): 717-726, 2019-This study aimed to examine the effects of stretching duration on passive musculotendinous stiffness and maximal and rapid torque and surface electromyography (EMG) characteristics of the hamstrings. Thirteen young females (age = 21 ± 2 years) underwent 2 passive straight-leg raise (SLR) assessments and 2 isometric maximal voluntary contractions (MVCs) of the hamstrings before and after 4 randomized conditions that included a control treatment and 3 experimental treatments of passive static stretching for 30-, 60-, and 120-second durations. Passive stiffness was calculated during each SLR as the slope of the final 10% of the angle-torque curve. Isometric peak torque (PT), rate of torque development (RTD), peak EMG amplitude (PEMG), and rate of EMG rise (RER) were extracted from each MVC. Results indicated that PT and PEMG were not affected (p = 0.993 and 0.422, respectively) by any of the experimental treatments. Rate of torque development and RER decreased from pre- to post-treatment for 120 seconds (p = 0.001 and 0.001) but not for the control (p = 0.616 and 0.466), 30- (p = 0.628 and 0.612), and 60-second (p = 0.396 and 0.815) interventions. The slope coefficient decreased from pre- to post-treatment for the 30- (p = 0.001), 60- (p = 0.002), and 120-second (p = 0.001) stretching interventions but not for the control (p = 0.649). Given the significant stiffness reductions and lack of changes in PT and RTD for the 30- and 60-second interventions, it may be advantageous for practitioners who are using hamstring passive stretching as part of a warm-up routine, to perform such stretching on their clients for short (30-60 seconds) rather than moderate (120-second) stretching durations.

Acute effects of static stretching on passive stiffness and postural balance in healthy, elderly men.

OBJECTIVES: This study aimed to examine the acute effects of straight-leg raise (SLR) static stretching on passive stiffness and postural balance in healthy, elderly men. An additional aim of this study was to examine the relationships between stiffness and balance at baseline (prior to stretching) and the relationships between the stretch-induced changes in these variables. METHODS: Eleven elderly men (age = 69 ± 6 years; height = 177 ± 7 cm; mass = 83 ± 13 kg) underwent postural balance and passive stiffness assessments before and after: 1) a stretching treatment consisting of four, 15-s SLR static stretches performed by the primary investigator and 2) a control treatment consisting of no static stretching. Passive stiffness was calculated from the slopes of the initial (phase 1) and final (phase 2) portions of the angle-torque curve. Unilateral postural balance was assessed on the right leg using a commercially designed balance testing device, which provides a measurement of static stability based on the overall stability index (OSI). RESULTS: The slope coefficients and OSI values decreased from pre- to post-treatment for the stretching intervention (P = 0.015 and 0.018, respectively); however, there were no changes for the control (P = 0.654 and 0.920). For the stretching intervention, a significant positive relationship was observed between OSI and the slope coefficient of phase 1 at baseline (r = 0.619; P = 0.042). A significant positive relationship was also observed between the stretched-induced changes in OSI and the slope coefficient of phase 1 (r = 0.731; P = 0.011). No relationship was observed between OSI and the slope coefficient of phase 2 at baseline (r = 0.262; P = 0.437) nor was there a relationship between the changes in these variables (r = 0.419; P = 0.200). CONCLUSION: A short, practical bout of SLR static stretching may be an effective intervention for reducing passive stiffness and improving postural balance in healthy, elderly men.