Michael Whitehurst

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.

Caffeine enhances upper body strength in resistance-trained women

BackgroundResearch has indicated that low-to-moderate dosages of caffeine supplementation are ergogenic for sustained endurance efforts as well as high-intensity exercise. The effects of caffeine supplementation on strength-power performance are equivocal, with some studies indicating a benefit and others demonstrating no change in performance. The majority of research that has examined the effects of caffeine supplementation on strength-power performance has been carried out in both trained and untrained men. Therefore, the purpose of this study was to determine the acute effects of caffeine supplementation on strength and muscular endurance in resistance-trained women.MethodsIn a randomized manner, 15 women consumed caffeine (6 mg/kg) or placebo (PL) seven days apart. Sixty min following supplementation, participants performed a one-repetition maximum (1RM) barbell bench press test and repetitions to failure at 60% of 1RM. Heart rate (HR) and blood pressure (BP) were assessed at rest, 60 minutes post-consumption, and immediately following completion of repetitions to failure.ResultsRepeated measures ANOVA indicated a significantly greater bench press maximum with caffeine (p ≤ 0.05) (52.9 ± 11.1 kg vs. 52.1 ± 11.7 kg) with no significant differences between conditions in 60% 1RM repetitions (p = 0.81). Systolic blood pressure was significantly greater post-exercise, with caffeine (p < 0.05) (116.8 ± 5.3 mmHg vs. 112.9 ± 4.9 mmHg).ConclusionsThese findings indicate a moderate dose of caffeine may be sufficient for enhancing strength performance in resistance-trained women.

Knee Extensor and Flexor Torque Characteristics Before and After Unilateral Total Knee Arthroplasty

Rossi MD, Brown LE, Whitehurst M: Knee extensor and flexor torque characteristics before and after unilateral total knee arthroplasty. Am J Phys Med Rehabil 2006;85:737–746. Objective:The purpose of this study was to document torque characteristics and strength recovery of the knee extensors and flexors before and up to 1 yr after unilateral total knee arthroplasty. Our goal was to also document the responsiveness of isokinetic testing over repeated measures. Design:Thirteen individuals voluntarily participated in this study. Torque production of the knee extensors and flexors was assessed isokinetically at 1.047 and 3.142 radians/sec. Results:Regardless of time, the knee extensors and flexors on the involved side generated a range of 76 and 82% of the average peak torque produced by the uninvolved side at both 1.047 and 3.142 radians/sec, respectively. At 30 days after surgery, there was a “dip” in both knee extensor and flexor torque production. Responsiveness indices for the knee extensors and flexors ranged from 0.95 to 2.12 at 1.047 radians/sec. At 3.142 radians/sec, the responsiveness indices for the knee extensors and flexors ranged from 0.65 to 2.87. Conclusion:One year after surgery, there continues to be knee extensor and flexor strength asymmetry between limbs. Moreover, within the first month after surgery, the knee extensors and flexors are at the weakest point compared with before, 60 days, and 1 yr after surgery. Isokinetic testing is a useful tool to document torque production before and in the early time after unilateral total knee arthroplasty.

THE BENEFITS OF A FUNCTIONAL EXERCISE CIRCUIT FOR OLDER ADULTS

The physical benefits of a functional exercise circuit are not well known in an elderly population. The purpose of this study was to evaluate the effect of a functional exercise circuit on mobility and perceived health in the elderly. Subjects were 119 men and women (aged 74 [64.2] years) who received preand posttests of mobility (e.g., sit to stand, get up and go, timed walk), flexibility (sit and reach), and balance (standing reach) and who completed the Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36). A supervised functional exercise circuit that included 10 different upper- and lower-body exercises performed under time constraints was performed 3 times per week for 12 consecutive weeks. Paired t-tests showed significant differences at posttest for the get up and go (p < 0.001), standing reach (p < 0.001), sit and reach (p < 0.001), and selected items from the SF-36, including physical functioning (p < 0.001), pain (p = 0.001), vitality (p = 0.001), and number of doctor visits (p < 0.001). A functional exercise circuit such as the one employed in this study may offer promise as an effective means of promoting mobility and perceived health in older adults.

Reliability of the Biodex System 2 Isokinetic Dynamometer Concentric Mode

∎ The purpose of this study was to assess the test-retest reliability of the Biodex System 2 isokinetic dynamometer . Twenty subjects performed knee concentric reciprocal extension/flexion exercise on 2 consecutive days, separated by 24 hours . Peak torque (PT), total work (TW), average power (AP), and joint angle at peak torque (JA) were collected from three repetitions across a velocity spectrum of 60, 120, 180, 240, 360, and 450 deg/sec . Correlation values between days 1 and 2 for PT, TW, and AP for both extension and flexion ranged from 0 .86 to 0 .98. The JA correlations ranged from 0 .22 to 0 .69 . Also, extension and flexion mean values for PT, TW, AP, and JA on day 1 were not significantly different (p < 0 .05) from the mean values derived from day 2, with the exception of flexion JA at 60 deg/sec . It was concluded that the Biodex System 2 isokinetic dynamometer is a highly reliable instrument for assessing reciprocal concentric isokinetic parameters of knee extension/flexion .

Reaction time unchanged in older women following aerobic training

The effect of aerobic exercise on reaction time in older women was investigated. 14 women (M age = 65 yr.) were carefully screened for health status and lifestyle, then assigned to a random order of the exercise and control groups (ns = 7). Pre- and posttraining tests of aerobic capacity, simple reaction time, and choice reaction time were administered. The exercise group rode a stationary bicycle ergometer for 8 consecutive weeks for 3 35- to 40-min. sessions per week. There were no significant pretraining differences between groups on simple reaction time, choice reaction time, or estimated VO2 max. No posttraining differences for simple and choice reaction time were found even though the exercise group had a significantly higher VO2 max than the controls. Contrary to some other findings, the data indicate that reaction time may be independent of aerobic training in healthy older women.

A review of selected longitudinal studies on aging: past findings and future directions.

A review of the 51 longitudinal aging studies currently in the National Institute on Aging Database of Longitudinal Studies was conducted to identify major information gaps and areas for future research. Database information, which included posted study summaries, study details from principal investigators or directors of these projects, and more than 300 recent publications based on the studies, were reviewed to identify significant findings of each study. This review summarizes the main findings and identifies the need for future work within six broad study topics: cognitive function, socioeconomic status, health and physical performance, morbidity and mortality predictors, healthcare costs, and genetics. The percentages of these 51 studies addressing the four most common topics are as follows: cognitive function (44%), health and physical performance (51%), socioeconomic factors (55%), and predictors of morbidity/mortality (63%). Important areas not addressed to any major degree were healthcare costs and genetics. Only two studies reported findings on genetics or epigenetics of human aging, and only a single study reported on associations between aging and financial costs, especially healthcare costs, which have been postulated to be important determinants of care and life quality. The results of this review, together with the specific directions proposed by other investigators with longitudinal study expertise, will inform the strategic planning of future long‐term studies of aging.

High-Intensity Interval Training: An Alternative for Older Adults

High-intensity interval training (HIT) is characterized by intermittent periods of work and rest and may include work bouts lasting seconds to minutes. HIT has typically been applied to older, diseased, and at-risk populations using longer work intervals (2-4 minutes), whereas more recent definitions of HIT include work intervals of 30 to 60 s. Both traditional endurance training (TET) and HIT exert a peripheral affect increasing the capacity of muscle cells to oxidize substrate via signaling cascades that support the activation of transcription factors that orchestrate the coexpression of nuclear and mitochondrial genes, with HIT triggering these benefits following minutes of training. With 1 exception, reports of central adaptations (eg, increased stroke volume) have been based on longer work intervals (eg, 4 minutes). Recent investigations have tied HIT to increased lipolysis and enhanced insulin sensitivity. HIT favors the activation of oxidative as opposed to hypertrophic pathways. Although the length of the work interval may need to be adjusted to fit the needs and capacity of the participant, HIT should be considered as an alternative to TET for older adults with the expectation that it requires less time to execute, yet promotes peripheral and perhaps central adaptations.

EARLY STRENGTH RESPONSE OF THE KNEE EXTENSORS DURING EIGHT WEEKS OF RESISTIVE TRAINING AFTER UNILATERAL TOTAL KNEE ARTHROPLASTY

The purpose of this study was to document the early history of knee extensor torque production before and after total knee arthroplasty (TKA), explore the relationship between strength assessments, and describe an 8-week resistive-training protocol. Thirty-eight individuals (19 men, 19 women) with unilateral TKA volunteered to participate in this repeated-measures study. For this group, the mean age was 72.23 ± 5.34 years; height was 168.00 ± 8.57 cm; and weight was 79.42 ± 14.57 kg. Torque production of the knee extensors was assessed isokinetically at 60 and 1808·s-1 before surgery, 30 days after unilateral TKA (130), and 60 days after unilateral TKA (160). Torque production was significantly different between limbs at both 60 and 1808·s-1 (p < 0.0125) before surgery. Torque production was lower at 130 compared with before surgery at both 60 and 1808·s-1 (p < 0.002). By 160, torque production was greater than at 130 at both 60 and 1808·s-1 (p < 0.002).

Kinematics of biophysically asymmetric limbs within rate of velocity development.

The purpose of this study was to investigate the movement speed characteristics of 2 intrinsically different limbs. Twenty subjects volunteered to participate (10 men and 10 women). Each subject performed 5 repetitions of concentric knee and elbow extension and flexion movements at 60 through 500 d·s-1 on an isokinetic dynamometer. Kinematic data were collected at 1,000 Hz and separated into rate of velocity development (RVD) and peak torque. Results demonstrated a significant (p < 0.05) main effect for sex for RVD and peak torque. Significant (p < 0.05) differences were also demonstrated between knee and elbow RVD and between knee and elbow peak torque at every speed tested. Neither knee and elbow RVD nor peak torque demonstrated any significant Pearson correlations at any speed tested (r = 20.17–0.41). These results collectively point to the specificity of limb speed and torque as a result of biophysical differences such as length and mass. Therefore, strength and speed may be modulated by neuromotor patterns that differ based on individual limbs.