Jeffery R. Stout

Do practical durations of stretching alter muscle strength? A dose-response study.

PURPOSE To examine the time course (immediate, 10, 20, and 30 min) for the acute effects of 2, 4, and 8 min of passive stretching (PS) on isometric peak torque (PT), percent voluntary activation (%VA), EMG amplitude, peak twitch torque (PTT), rate of twitch torque development (RTD), and range of motion (ROM) of the plantarflexors. METHODS Thirteen volunteers (mean +/- SD age, 22 +/- 3 yr) participated in four randomly ordered experimental trials: control (CON) with no stretching, 2 min (PS2), 4 min (PS4), and 8 min (PS8) of PS. Testing was conducted before (pre), immediately after (post), and at 10, 20, and 30 min poststretching. The PS trials involved varied repetitions of 30-s passive stretches, whereas the CON trial included 15 min of resting. PT, %VA, EMG amplitude, PTT, and RTD were assessed during the twitch interpolation technique, whereas ROM was quantified as the maximum tolerable angle of passive dorsiflexion. RESULTS PT decreased (P < or = 0.05) immediately after all conditions [CON (4%), PS2 (2%), PS4 (4%), and PS8 (6%)] but returned to baseline at 10, 20, and 30 min poststretching. %VA and EMG amplitude were unaltered (P > 0.05) after all conditions. PTT and RTD decreased (P < or = 0.05) immediately after the PS4 (7%) and the PS8 (6%) conditions only; however, these changes were not sufficient to alter voluntary force production. There were also increases (P < or = 0.05) in ROM after the PS2 (8%), the PS4 (14%), and the PS8 (13%) conditions that returned to baseline after 10 min. CONCLUSION Practical durations of stretching (2, 4, or 8 min) of the plantarflexors did not decrease isometric PT compared with the CON but caused temporary improvements in the ROM, thereby questioning the overall detrimental influence of PS on performance.

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.

Acute effects of passive stretching vs vibration on the neuromuscular function of the plantar flexors

This study examined the acute effects of passive stretching (PS) vs prolonged vibration (VIB) on voluntary peak torque (PT), percent voluntary activation (%VA), peak twitch torque (PTT), passive range of motion (PROM), musculotendinous stiffness (MTS), and surface electromyographic (EMG) and mechanomyographic (MMG) amplitude of the medial gastrocnemius (MG) and soleus (SOL) muscles during isometric maximal voluntary contractions (MVCs) of the plantar flexors. Fifteen healthy men performed the isometric MVCs and PROM assessments before and after 20 min of PS, VIB, and a control (CON) conditions. There were 10% and 5% decreases in voluntary PT, non‐significant 3% and 2% decreases in %VA, 9–23% decreases in EMG amplitude of the MG and SOL after the PS and VIB, respectively, with no changes after the CON. PROM increased by 19% and MTS decreased by 38% after the PS, but neither changed after the VIB or CON conditions. Both PS and VIB elicited similar neural deficits (i.e., γ loop impairment) that may have been responsible for the strength losses. However, mechanical factors related to PROM and MTS cannot be ruled out as contributors to the stretching‐induced force deficit.

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.

Acute effects of a thermogenic nutritional supplement on cycling time to exhaustion and muscular strength in college-aged men

BackgroundThe purpose of the present study was to examine the acute effects of a thermogenic nutritional supplement containing caffeine, capsaicin, bioperine, and niacin on muscular strength and endurance performance.MethodsTwenty recreationally-active men (mean ± SD age = 21.5 ± 1.4 years; stature = 178.2 ± 6.3 cm; mass = 76.5 ± 9.9 kg; VO2 PEAK = 3.05 ± 0.59 L/min-1) volunteered to participate in this randomized, double-blinded, placebo-controlled, cross-over study. All testing took place over a three-week period, with each of the 3 laboratory visits separated by 7 days (± 2 hours). During the initial visit, a graded exercise test was performed on a Lode Corival cycle ergometer (Lode, Groningen, Netherlands) until exhaustion (increase of 25 W every 2 min) to determine the maximum power output (W) at the VO2 PEAK (Parvo Medics TrueOne® 2400 Metabolic Measurement System, Sandy, Utah). In addition, one-repetition maximum (1-RM) strength was assessed using the bench press (BP) and leg press (LP) exercises. During visits 2 and 3, the subjects were asked to consume a capsule containing either the active supplement (200 mg caffeine, 33.34 mg capsaicin, 5 mg bioperine, and 20 mg niacin) or the placebo (175 mg of calcium carbonate, 160 mg of microcrystalline cellulose, 5 mg of stearic acid, and 5 mg of magnesium stearate in an identical capsule) 30 min prior to the testing. Testing included a time-to-exhaustion (TTE) ride on a cycle ergometer at 80% of the previously-determined power output at VO2 PEAK followed by 1-RM LP and BP tests.ResultsThere were no differences (p > 0.05) between the active and placebo trials for BP, LP, or TTE. However, for the BP and LP scores, the baseline values (visit 1) were less than the values recorded during visits 2 and 3 (p ≤ 0.05).ConclusionOur findings indicated that the active supplement containing caffeine, capsaicin, bioperine, and niacin did not alter muscular strength or cycling endurance when compared to a placebo trial. The lack of increases in BP and LP strength and cycle ergometry endurance elicited by this supplement may have been related to the relatively small dose of caffeine, the high intensity of exercise, the untrained status of the participants, and/or the potential for caffeine and capsaicin to increase carbohydrate oxidation.

Beta-Alanine Supplementation Improves Aerobic and Anaerobic Indices of Performance

BETA-ALANINE SUPPLEMENTATION HAS BEEN FOUND TO INCREASE INTRAMUSCULAR CARNOSINE, STRENGTH, POWER, VOLUME PER TRAINING SESSION AND A HOST OF OTHER INDICES OF AEROBIC AND ANAEROBIC CAPACITY. HOWEVER, THERE IS A NEED TO SYNTHESIZE THIS RESEARCH SO THAT THE ATHLETE AND STRENGTH COACH ALIKE CAN OPTIMALLY BENEFIT FROM BETA-ALANINE SUPPLEMENTATION. THE PURPOSE OF THIS REVIEW IS TO PROVIDE AN ANALYSIS OF STUDIES CONDUCTED ON BETA-ALANINE. THE REVIEW WILL COVER THE OPTIMAL DOSAGE OF BETA-ALANINE; ITS USE IN RESISTANCE TRAINING, INTERMITTENT, AND ENDURANCE-BASED EXERCISES; AND WHEN COMBINED WITH CREATINE IN TRAINED AND UNTRAINED INDIVIDUALS.

Bioimpedance And Dxa Total Body Water Estimations In The Elderly: A Deuterium Oxide Comparison.

Bioimpedance techniques have the ability to estimate total body water (TBW) and include single frequency bioimpedance (BIA), bioimpedance spectroscopy (BIS), and multiple-frequency bioimpedance (MFBIA). In addition, dual-energy X-ray absorptiometry (DXA) can predict TBW by using fat-free mass and a constant hydration status of 0.737%. However, the validity of the aforementioned methods has not been established in a healthy elderly population. PURPOSE: Compare BIA, BIS, MFBIA, and DXA TBW estimations in elderly men and women to a criterion deuterium oxide (D2O) TBW measurement. METHODS: Thirty-four women and twenty-four men over the age of sixty-five participated in the study (71 +/5yr, 68.8 +/12.0kg, 167.0 +/8.5 cm). Subjects reported to the lab in a fasted state and provided a urine sample before ingesting approximately 11 grams of D2O. Four hours later the subjects provided another urine sample for the calculation of TBW using a standard isotope dilution method. During the four hour equilibration period the subjects had TBW measured using BIA, MFBIA, BIS, and DXA in no particular order. RESULTS: For men, all methods produced similar and high r values (0.890.95) as well as low standard error of the estimate (SEE) values (1.26-1.52 L) with BIA producing the only nonsignificant mean difference (0.29 L, p=0.31). The MFBIA produced the largest mean difference between D2O and over predicted TBW by 3.43 L. DXA and BIS also both significantly over predicted TBW with mean differences of 1.74 and 2.10 L respectively (p<0.001). For women, all methods produced nearly identical and high r values (0.90-0.91) as well as low standard error of the estimate (SEE) values (0.94-1.02 L). All methods significantly (p<0.001) over estimated TBW, but mean differences were low for DXA (0.92 L) and BIA (0.89 L) compared to BIS (2.37 L) and MFBIA (2.47 L). CONCLUSIONS: The added frequencies used in the MFBIA and the complex Cole models of the BIS did not increase the validity of TBW estimation in elderly men and women as the BIA outperform both devices and uses a single frequency of 50 kHz. However, all methods demonstrated high r values and low SEE values and have the potential to accurately estimate TBW in the current population. However, based on the current results the BIA method used in the current study resulted in the most valid estimations of TBW for elderly men and women compared to D2O.

The Relationship Between Selected Performance Variables and 2,000-Meter Rowing Performance in NCAA D1 Female Collegiate Rowers

Critical velocity (CV) has been used as a practical method to predict maximal average velocity in a variety of sports, such as running and swimming. More recently, it has been shown to be highly correlated to 2000 m rowing performance in male rowers. Minimal literature exists examining selected physiological variables in female rowers, and currently, there has been no CV model applied to collegiate, female rowers. PURPOSE: The aim of the present study was to validate the use of the CV test as a means of predicting 2000 m performance in female collegiate rowers, and to study the relationship of selected physiological variables on performance times. METHODS: Thirty-five female collegiate rowers (mean 6 SD; age 19.38 6 1.3 yrs; height: 170.27 6 6.07 cm; weight: 69.58 6 .31kg) volunteered to participate in this study. Rowers were divided into two categories based on rowing experience, varsity (V; .1yr collegiate experience, _ VO2peak: 3.14 6 0.31L/min) and novice (N; ,1 year collegiate experience, _ VO2peak: 2.88 6 0.20 L/min). All rowers performed two continuous graded maximal oxygen consumption tests (familiarization and baseline) to establish peak maximal oxygen uptake ( _ VO2peak, L min), peak power output (PPO) in watts, and ventilatory threshold(VT, L min). A calibrated metabolic cart (Parvomedics True One 2400, Sandy, Utah)with a two-way valve(Hans Rudolph 2700, Kansas City, MO)was used for all gas exchange analysis during the _ VO2peak tests. Rowers then completed a CV test, consisting of four time trials at varying distances (200 m, 600 m, 800 m, and 1000 m) on two separate days, with 15 minutes rest between trials. Following the CV test, rowers completed a 2000m time-trial. All tests were completed on a Concept II, Model D rowing ergometer. RESULTS: _ VO2peak showed the highest correlation to 2000 m performance (r = .923) in V rowers with strong correlations also observed for PPO and CV (r = .866 and r = .856, respectively). Stepwise regression showed that _ VO2peak was the best single predictor of 2000 m performance, accounting for 85% of the variability in performance. In contrast, CV demonstrated the highest correlation to 2000 m performance in N rowers (r = .733), explaining 54% of the variability in