Anthony P. Marsh

The effect of age on the attentional demands of postural control

A dual-task paradigm was used to determine the attentional demands of several postural control tasks in 16 older women (age, 71.5+/-3.4 years) and 14 young women (age, 25.5+/-2.4 years). Older women had slower verbal reaction times (VRT) compared with the younger women and increased reaction time more from a sitting to standing posture. Compared with the younger women, older women required more cognitive resources to maintain a simple eyes open standing posture versus an eyes open seated posture. Further, older women had significantly greater VRT during the dual-task conditions compared with younger women. However, VRT did not significantly change as the difficulty of the primary task increased in either group. These data have implications for older adults who may be at risk for falls in situations where they may be engaged in concurrent tasks, even when those tasks are considered automated and/or lower order operations.

The relationship between cadence and lower extremity EMG in cyclists and noncyclists.

Male cyclists (N = 8) and noncyclists (N = 8) pedaled under six randomly ordered cadences (50, 65, 80, 95, 110 rpm and the preferred cadence) at 200 W to test the hypothesis that electromyographic activity of selected lower limb muscles is minimized at the preferred cadence. Average preferred cadences for cyclists (85.2 +/- 9.2 rpm) and noncyclists (91.6 +/- 10.5 rpm) were not statistically different. Only gastrocnemius EMG was affected substantially and systematically by cadence changes, increasing linearly with cadence increases. Rectus femoris and vastus lateralis EMG displayed significant quadratic and linear relationships with cadence, respectively, but EMG differences between cadences were small for both muscles. Noncyclists did not exhibit significantly different patterns of muscle activity from cyclists, although there was a trend for soleus and gastrocnemius EMG to be higher in noncyclists. The results did not support our hypothesis that lower extremity muscle activation is minimized at an individuals preferred pedaling cadence. Thus, preferred cadence selection does not appear to be related to minimization of muscle activation. Given the nonlinear relationships between muscle mechanical properties, force, and EMG it is unlikely that a simple relationship exists between EMG and muscle stress.

Effect of cycling experience, aerobic power, and power output on preferred and most economical cycling cadences

To determine the effects of cycling experience, fitness level, and power output on preferred and most economical cycling cadences: 1) the preferred cadence (PC) of 12 male cyclists, 10 male runners, and 10 less-trained male noncyclists was determined at 75, 100, 150, 200, and 250 W for cyclists and runners and 75, 100, 125, 150, and 175 W for the less-trained group; and 2) steady-state aerobic demand was determined at six cadences (50, 65, 80, 95, 110 rpm and PC) at 100, 150, and 200 W for cyclists and runners and 75, 100, and 150 W for less-trained subjects. Cyclists and runners (VO2max: 70.7 +/- 4.1 and 72.5 +/- 2.2 mL.kg-1.min-1, respectively) maintained PC between 90 and 100 rpm at all power outputs and both groups selected similar cadences at each power output. In contrast, the less-trained group (VO2max = 44.2 +/- 2.8 mL.kg-1.min-1) selected lower cadences at all common power outputs and reduced cadence from approximately 80 rpm at 75 W to 65 rpm at 175 W. The preferred cadences of all groups were significantly higher than their respective most economical cadences at all power outputs. Changes in power output had little effect on the most economical cadence, which was between 53.3 and 59.9 rpm, in all groups. It was concluded that cycling experience and minimization of aerobic demand are not critical determinants of PC in well-trained individuals. It was speculated that less-trained noncyclists, who cycled at a higher percentage of VO2max, may have selected lower PC to reduce aerobic demand.

The association between cycling experience and preferred and most economical cadences.

The purpose of this study was to compare 1) the preferred cadences and 2) the aerobic demand response to cadence manipulation of highly fit, experienced cyclists and equally fit noncyclists. Eight cyclists (C) and eight non-cyclists (NC) pedaled at 200 W under six randomly ordered cadence conditions (50, 65, 80, 95, 110 rpm and preferred cadence) on a Velodyne trainer. The VO2 responses of C and NC to cadence manipulation were similar. Both groups displayed lower VO2 values at lower cadences. VO2 differences between C and NC across cadences were not significant. Mean preferred pedaling cadence surprisingly was somewhat higher for NC (91.6 +/- 10.5 rpm) than C (85.2 +/- 9.2 rpm), but the difference was not significant. The most economical cadence was significantly lower for C (56.1 +/- 6.9 rpm) than NC (62.9 +/- 4.7 rpm). Thus, cycling experience did not substantially influence preferred cadence nor economy during moderate intensity cycling by highly fit athletes. We speculate that preferred cadence and economy similarities between C and NC are associated with similarities in the dynamic muscular training of the groups.

Enhancing quality of life in older adults: A comparison of muscular strength and power training

BackgroundAlthough progressive resistance strength training (ST) has been found to improve various measures of physical functioning in older adults, the benefit to quality of life is unclear. Additionally, recent evidence suggests that high velocity power training (PT) may be more beneficial for physical functioning than ST, but it is not known whether this type of training impacts quality of life. The purpose of this study was to compare changes in multiple measures of quality of life resulting from ST vs. PT in older adults. A no exercise group was also included as control comparison condition.MethodsForty-five older adults (M age = 74.8 years; SD = 5.7) were randomly assigned to either a) PT, b) ST, or c) control group (no exercise). Measures of self-efficacy (SE), satisfaction with physical function (SPF), and the Satisfaction with Life Scale (SWL) were assessed at baseline and following training. The resistance training conditions met 3 times per week for 12 weeks at an intensity of 70% 1 repetition maximum.ResultsA series of ANCOVAs comparing between group differences in change and controlling for baseline values revealed significant group differences in all three measures: SE (F(2,31) = 9.77; p < .001); SPF (F(2,32) = 3.36; p = .047); SWL (F(2,31) = 4.76; p = .016). Follow up analyses indicated that the PT group reported significantly more change in SE, SPF, and SWL than the control group whereas the ST group reported greater change than the control group only in SE.ConclusionThese pilot data indicate that high velocity power training may influence multiple levels of quality of life over and above the benefits gained through traditional strength training.

The Lifestyle Interventions and Independence for Elders Pilot (LIFE-P): 2-Year Follow-up

BACKGROUND It is well recognized that physical activity (PA) is important for older adults; yet, clinicians remain pessimistic about the ability of older adults with compromised function to adhere to long-term treatment and to maintain behavior change once treatment has been terminated. METHODS We examined the functional status of older adults at a field center (Wake Forest University) 2 years after completing 12 months of treatment in the Lifestyle Interventions and Independence for Elders Pilot study. At baseline, participants were randomized to either a PA or a successful aging (SA) control group. Outcome measures included an interview assessment of PA, the Short Physical Performance Battery (SPPB), and performance on a 400-m self-paced walking test. RESULTS Two years after the formal intervention had ended, participants who were originally in the PA group continued to engage in more minutes of moderate PA and tended to have better SPPB and walking speed than those in the SA group (effect sizes [ES]: SPPB = 0.40, walking speed = 0.37). Seven (12.7%) participants in the PA group failed the 400-m walk at the 36-month follow-up assessment, whereas this number was 11 (21.6%) in the SA group. CONCLUSION Older adults who have compromised physical function are able to sustain some of the benefits derived from participating in structured PA 2 years after supervised treatment has been terminated.

Lifestyle Interventions and Independence for Elders Study: Recruitment and Baseline Characteristics

BACKGROUND Recruitment of older adults into long-term clinical trials involving behavioral interventions is a significant challenge. The Lifestyle Interventions and Independence for Elders (LIFE) Study is a Phase 3 multicenter randomized controlled multisite trial, designed to compare the effects of a moderate-intensity physical activity program with a successful aging health education program on the incidence of major mobility disability (the inability to walk 400 m) in sedentary adults aged 70-89 years, who were at high risk for mobility disability (scoring ≤ 9 on the Short Physical Performance Battery) at baseline. METHODS Recruitment methods, yields, efficiency, and costs are described together with a summary of participant baseline characteristics. Yields were examined across levels of sex, race and ethnicity, and Short Physical Performance Battery, as well as by site. RESULTS The 21-month recruiting period resulted in 14,812 telephone screens; 1,635 participants were randomized (67.2% women, 21.0% minorities, 44.7% with Short Physical Performance Battery scores ≤ 7). Of the telephone-screened participants, 37.6% were excluded primarily because of regular participation in physical activity, health exclusions, or self-reported mobility disability. Direct mailing was the most productive recruitment strategy (59.5% of randomized participants). Recruitment costs were

Measuring disability in older adults: The International Classification System of Functioning, Disability and Health (ICF) framework

840 per randomized participant. Yields differed by sex and Short Physical Performance Battery. We accrued 11% more participant follow-up time than expected during the recruitment period as a result of the accelerated recruitment rate. CONCLUSIONS The LIFE Study achieved all recruitment benchmarks. Bulk mailing is an efficient method for recruiting high-risk community-dwelling older persons (including minorities), from diverse geographic areas for this long-term behavioral trial.

Is a joint moment-based cost function associated with preferred cycling cadence?

Background:  Despite the importance of disability to geriatric medicine, no large scale study has validated the activity and participation domains of the International Classification System of Functioning, Disability, and Health (ICF) in older adults. The current project was designed to conduct such as analysis, and then to examine the psychometric properties of a measure that is based on this conceptual structure.

Muscle Strength and BMI as Predictors of Major Mobility Disability in the Lifestyle Interventions and Independence for Elders Pilot (LIFE-P)

Eight experienced male cyclists (C), eight well-trained male runners (R), and eight less-trained male noncyclists (LT) were tested under multiple cadence and power output conditions to determine: (1) if the cadence at which lower extremity net joint moments are minimized (cost function cadence) was associated with preferred pedaling cadence (PC), (2) if the cost function cadence increased with increases in power output, and (3) if the association is generalizable across groups differing in cycling experience and aerobic power. Net joint moments at the hip, knee, and ankle were computed from video records and pedal reaction force data using 2-D inverse dynamics. The sum of the average absolute hip, knee, and ankle joint moments defined a cost function at each power output and cadence and provided the basis for prediction of the cadence which minimized net joint moments for each subject at each power output. The cost function cadence was not statistically different from the PC at each power output in all groups. As power output increased, however, the cost function cadence increased for all three subject groups (86 rpm at 100 W, 93 rpm at 150 W, 98 rpm at 200 W, and 96 rpm at 250 W). PC showed little change (R) or a modest decline (C, LT) with increasing power output. Based upon the similarity in the mean data but different trends in the cost function cadence and PC in response to changes in power output as well as the lack of significant correlations between these two variables, it was concluded that minimiking net joint moments is a factor modestly associated with preferred cadence selection.