Robert S. Axtell

Promoting physical activity for elders with compromised function: the lifestyle Interventions and Independence for elders (LIFE) study physical activity intervention

The Lifestyle Interventions and Independence for Elders (LIFE) Study is a Phase III randomized controlled clinical trial (Clinicaltrials.gov identifier: NCT01072500) that will provide definitive evidence regarding the effect of physical activity (PA) on major mobility disability in older adults (70–89 years old) who have compromised physical function. This paper describes the methods employed in the delivery of the LIFE Study PA intervention, providing insight into how we promoted adherence and monitored the fidelity of treatment. Data are presented on participants’ motives and self-perceptions at the onset of the trial along with accelerometry data on patterns of PA during exercise training. Prior to the onset of training, 31.4% of participants noted slight conflict with being able to meet the demands of the program and 6.4% indicated that the degree of conflict would be moderate. Accelerometry data collected during PA training revealed that the average intensity – 1,555 counts/minute for men and 1,237 counts/minute for women – was well below the cutoff point used to classify exercise as being of moderate intensity or higher for adults. Also, a sizable subgroup required one or more rest stops. These data illustrate that it is not feasible to have a single exercise prescription for older adults with compromised function. Moreover, the concept of what constitutes “moderate” exercise or an appropriate volume of work is dictated by the physical capacities of each individual and the level of comfort/stability in actually executing a specific prescription.

Dose of physical activity, physical functioning and disability risk in mobility-limited older adults: Results from the LIFE study randomized trial

Understanding the minimal dose of physical activity required to achieve improvement in physical functioning and reductions in disability risk is necessary to inform public health recommendations. To examine the effect of physical activity dose on changes in physical functioning and the onset of major mobility disability in The Lifestyle Interventions and Independence for Elders (LIFE) Study. We conducted a multicenter single masked randomized controlled trial that enrolled participants in 2010 and 2011 and followed them for an average of 2.6 years. 1,635 sedentary men and women aged 70–89 years who had functional limitations were randomized to a structured moderate intensity walking, resistance, and flexibility physical activity program or a health education program. Physical activity dose was assessed by 7-day accelerometry and self-report at baseline and 24 months. Outcomes included the 400 m walk gait speed, the Short Physical Performance Battery (SPPB), assessed at baseline, 6, 12, and 24 months, and onset of major mobility disability (objectively defined by loss of ability to walk 400 m in 15 min). When the physical activity arm or the entire sample were stratified by change in physical activity from baseline to 24 months, there was a dose-dependent increase in the change in gait speed and SPPB from baseline at 6, 12, and 24 months. In addition, the magnitude of change in physical activity over 24 months was related to the reduction in the onset of major mobility disability (overall P < 0.001) (highest versus the lowest quartile of physical activity change HR 0.23 ((95% CI:0.10–0.52) P = 0.001) in the physical activity arm. We observed a dose-dependent effect of objectively monitored physical activity on physical functioning and onset of major mobility disability. Relatively small increases (> 48 minutes per week) in regular physical activity participation had significant and clinically meaningful effects on these outcomes. Trial registration: ClinicalsTrials.gov NCT00116194

Effects of sprint interval training and body weight reduction on power to weight ratio in experienced cyclists.

Lunn, WR, Finn, JA, and Axtell, RS. Effects of sprint interval training and body weight reduction on power to weight ratio in experienced cyclists. J Strength Cond Res 23(4): 1217-1224, 2009-The purpose of this study was to determine the effect of supramaximal sprint interval training (SIT), body weight reduction, and a combination of both treatments on peak and average anaerobic power to weight ratio (PPOan:Wt, APOan:Wt) by manipulating peak and average anaerobic power output (PPOan, APOan) and body weight (BW) in experienced cyclists. Participants (N = 34, age = 38.0 ± 7.1 years) were assigned to 4 groups for a 10-week study. One group performed twice-weekly SIT sessions on a cycle ergometer while maintaining body weight (SIT). A second group did not perform SIT but intentionally reduced body weight (WR). A third group simultaneously performed SIT sessions and reduced body weight (SIT+WR). A control group cycled in their normal routine and maintained body weight (CON). The 30-second Wingate Test assessed pretest and posttest POan:Wt scores. There was a significant mean increase (p < 0.05) from pretest to posttest in PPOan:Wt and APOan:Wt (W·kg−1) scores in both SIT (10.82 ± 1.71 to 11.92 ± 1.77 and 8.05 ± 0.64 to 8.77 ± 0.64, respectively) and WR (10.33 ± 2.91 to 11.29 ± 2.80 and 7.04 ± 1.45 to 7.62 ± 1.24, respectively). PPOan and APOan (W) increased significantly only in SIT (753.7 ± 121.0 to 834.3 ± 150.1 and 561.3 ± 62.5 to 612.7 ± 69.0, respectively). Body weight (kg) decreased significantly in WR and SIT + WR (80.3 ± 13.7 to 75.3 ± 11.9 and 78.9 ± 10.8 to 73.4 ± 10.8, respectively). The results demonstrate that cyclists can use SIT sessions and body weight reduction as singular training interventions to effect significant increases in anaerobic power to weight ratio, which has been correlated to enhanced aerobic cycling performance. However, the treatments were not effective as combined interventions, as there was no significant change in either PPOan:Wt or APOan:Wt in SIT + WR.

Effects of a Long-Term Physical Activity Program on Activity Patterns in Older Adults

Purpose To examine the effect of a long-term structured physical activity (PA) intervention on accelerometer-derived metrics of activity pattern changes in mobility-impaired older adults. Methods Participants were randomized to either a PA or health education (HE) program. The PA intervention included a walking regimen with strength, flexibility, and balance training. The HE program featured health-related discussions and a brief upper body stretching routine. Participants (n = 1341) wore a hip-worn accelerometer for ≥10 h·d−1 for ≥3 d at baseline and again at 6, 12, and 24 months postrandomization. Total PA (TPA)—defined as movements registering 100+ counts per minute—was segmented into the following intensities: low-light PA (LLPA; 100–759 counts per minute), high light PA (HLPA; 760–1040 counts per minute), low moderate PA (LMPA; 1041–2019 counts per minute), and high moderate and greater PA (HMPA; 2020+ counts per minute). Patterns of activity were characterized as bouts (defined as the consecutive minutes within an intensity). Results Across groups, TPA decreased an average of 74 min·wk−1 annually. The PA intervention attenuated this effect (PA = −68 vs HE: −112 min·wk−1, P = 0.002). This attenuation shifted TPA composition by increasing time in LLPA (10+ bouts increased 6 min·wk−1), HLPA (1+, 2+, 5+, and 10+ bouts increased 6, 3, 2, and 1 min·wk−1, respectively), LMPA (1+, 2+, 5+, and 10+ bouts increased: 19, 17,16, and 8 min·wk−1, respectively), and HMPA (1+, 2+, 5+, and 10+ bouts increased 23, 21, 17, and 14 min·wk−1, respectively). Conclusions The PA intervention increased PA by shifting the composition of activity toward higher-intensity activity in longer-duration bouts. However, a long-term structured PA intervention did not completely eliminate overall declines in total daily activity experienced by mobility-impaired older adults.

Actigraphy features for predicting mobility disability in older adults

Actigraphy has attracted much attention for assessing physical activity in the past decade. Many algorithms have been developed to automate the analysis process, but none has targeted a general model to discover related features for detecting or predicting mobility function, or more specifically, mobility impairment and major mobility disability (MMD). Men (N  =  357) and women (N  =  778) aged 70-89 years wore a tri-axial accelerometer (Actigraph GT3X) on the right hip during free-living conditions for 8.4  ±  3.0 d. One-second epoch data were summarized into 67 features. Several machine learning techniques were used to select features from the free-living condition to predict mobility impairment, defined as 400 m walking speed  <0.80 m s-1. Selected features were also included in a model to predict the first occurrence of MMD-defined as the loss in the ability to walk 400 m. Each method yielded a similar estimate of 400 m walking speed with a root mean square error of ~0.07 m s-1 and an R-squared values ranging from 0.37-0.41. Sensitivity and specificity of identifying slow walkers was approximately 70% and 80% for all methods, respectively. The top five features, which were related to movement pace and amount (activity counts and steps), length in activity engagement (bout length), accumulation patterns of activity, and movement variability significantly improved the prediction of MMD beyond that found with common covariates (age, diseases, anthropometry, etc). This study identified a subset of actigraphy features collected in free-living conditions that are moderately accurate in identifying persons with clinically-assessed mobility impaired and significantly improve the prediction of MMD. These findings suggest that the combination of features as opposed to a specific feature is important to consider when choosing features and/or combinations of features for prediction of mobility phenotypes in older adults.

Evaluating Accelerometry Thresholds for Detecting Changes in Levels of Moderate Physical Activity and Resulting Major Mobility Disability

Background An important decision with accelerometry is the threshold in counts per minute (CPM) used to define moderate to vigorous physical activity (MVPA). We explore the ability of different thresholds to track changes in MVPA due to a physical activity (PA) intervention among older adults with compromised function: 760 CPM, 1,041 CPM, and an individualized threshold. We also evaluate the ability of change in accelerometry and self-reported PA to attenuate treatment effects on major mobility disability (MMD). Methods Data from a week of hip worn accelerometers and self-reported PA data (30-day recall) were examined from baseline, 6-, 12-, and 24-months of follow-up on 1,528 older adults. Participants were randomized to either PA or Health Education (HE). MMD was objectively defined by loss of ability to walk 400 m during the follow-up. Results The three thresholds yielded similar and higher levels of MVPA for PA than HE (p < .001), however, this difference was significantly attenuated in participants with lower levels of physical function. Self-reported PA that captured both walking and strength training totally attenuated the intervention effect for MMD, an 18% reduction to a 3% increase. Accelerometer CPMs showed less attenuation of the intervention effect. Conclusions Accelerometry assessment within the LIFE study was not sensitive to change in level in physical activity for older adults with very low levels of physical function. A combination of self-report and objective measures are recommended for use in physical activity intervention studies of the elderly; limitations of accelerometry deserve closer attention.

Device‐Measured Physical Activity As a Predictor of Disability in Mobility‐Limited Older Adults

To examine associations between objectively measured physical activity (PA) and incidence of major mobility disability (MMD) and persistent MMD (PMMD) in older adults in the Lifestyle Interventions and Independence for Elders (LIFE) Study.

Spontaneous baroreflex sensitivity in young normotensive African-American women

The prevalence of hypertension among African-Americans in the United States is among the highest in the world, and continues to increase [5, 14]. Furthermore, hypertension-related mortality rates are three times higher in African-American (AA) men (49 %) compared with non-Hispanic white men (16 %) and more than double in AA (37 %) compared with non-Hispanic white women (14 %) [14]. Given the higher prevalence of hypertension and the associated poor prognosis in African-Americans, early identification of biological mechanisms that contribute to the pathogenesis and clinical sequelae of hypertension in this group is critical. Baroreflex sensitivity (BRS) is impaired when hypertension is associated with increased arterial stiffness [6]. Prior work by our group revealed the presence of significant differences in BRS between normotensive AA men and Caucasian American (CA) men [19]. These findings in AA men were recently corroborated by others [8]. There are many proposed mechanisms involved in the development and maintenance of hypertension [5]. However, both short-term and long-term blood pressures are modulated via baroreflex-mediated adjustments [1, 7, 8]. Moreover, loss of BRS has been shown to be a significant predictor of mortality in post-myocardial infarct patients [10, 11]. Thus, the knowledge that BRS may be altered in patients with cardiovascular disease is not new. One of the first clinical studies [10] and the subsequent ATRAMI trial [11] found that a low BRS (\3 ms/mmHg) significantly predicted total cardiac mortality in post-myocardial infarction patients but evidence of the prognostic value of this threshold in otherwise healthy individuals is lacking. However, early knowledge of an altered BRS in young normotensive humans may have significant clinical and therapeutic implications, particularly in view of the high prevalence of hypertension in AA women [14]. To our knowledge, no studies have compared BRS between young normotensive AA women and CA women who have similar levels of physical activity. Therefore, our aim was to compare BRS between young AA women and CA women. Specifically, we hypothesized that normotensive AA women matched for age, BMI, physical activity history and family history of hypertension would demonstrate an attenuated BRS when compared to CA women. To test this hypothesis, we measured BRS changes while at rest. All tests were non-invasive, unobtrusive and mimicked real life.

The Effects of a Carbon Fiber Shoe Insole on Athletic Performance in Collegiate Athletes

Sports equipment such as athletic footwear is designed to prevent injury and/or improve performance. There is limited research about the effects of foot orthoses or shoe insoles on performance improvement via enhanced energetics. One possible solution to improve the energy storage and return of athletic footwear is to utilize a carbon fiber shoe insole (CFI) optimally tuned for the human body-footwear system. The purpose of this study was to examine the effects of a CFI on athletic performance. Thirty-four (15 males, 19 females) collegiate athletes performed a vertical jump, a pro agility test, and a 10-yard sprint while wearing normal athletic footwear and footwear incorporating a CFI. Vertical jump height was measured using a commercial Vertec device; pro agility test and 10-yard sprint times were measured using a laser timing system. The use of a CFI resulted in significant improvements in the vertical jump (+2.5%, p = 0.012) and the 10-yard sprint (+1.5%, p = 0.020), but not in the pro agility test. These results demonstrated a CFI can enhance speed/acceleration and power in collegiate athletes. Individual anatomical and biomechanical differences may influence the appropriate CFI stiffness required for each athlete to achieve maximal performance in sports involving running, jumping, and change-of-direction.

Body Composition In Division II Football Players

In recent years body composition studies on American Football players have focused on participants at the professional, NCAA Division I and NCAA Division III levels. Recent data utilizing skinfold and hydrostatic weighing to measure the body composition of NCAA Division II football players is currently not available. Purpose: The purpose of the present investigation was to examine the body composition of NCAA Division II football players utilizing both hydrostatic weighing and skinfold measurements. Methods: Sixty-eight NCAA Division II (DII) football players volunteered for this study. Body height (HT), body weight (BW), forced vital capacity and percent body fat were measured. Percent body fat was assessed across all playing positions: offensive line/tightends (OL/TE), defensive line (DL), offensive backs/receivers (OB/WR), defensive backs (DB), linebackers (LB) and quarterbacks/kickers (QB/K) through eight skinfold measurements (chest, abdominal, thigh, calf, subscapular, suprailliac, triceps & biceps) and hydrostatic weighing. Body density was calculated from skinfold measurements utilizing six regression equations with a pooled median value utilized for analysis. Percent body fat was calculated using the Schutte equation for African Americans and the Siri equation for Caucasian athletes. Results: Percent body fat calculated from skinfold measurements: OL/TE = 28.26 (± 1.19%) DL = 25.04 (± 2.82%) OB/WR = 15.12 (± 1.24%) DB = 15.40 (± 0.66%) LB = 18.63 (± 1.20%) QB/K = 17.86 (± 1.70%). Percent body fat calculated from hydrostatic weighing: OL/TE = 25.29 (± 1.42%) DL = 22.05 (± 3.21%) OB/WR = 11.98 (± 1.35%) DB = 12.76 (± 1.03%) LB = 14.99 (± 1.39%) QB/K = 14.53 (± 1.73%). Discussion: Upon inspection, these data show DII football players possessed a higher percentage of body fat when compared to their Division I (DI) counterparts published by Noel, Vanheest, Zaneteas & Rodgers (2003) (See table 1.). Practical Application: These data will allow strength and conditioning professionals and nutritionists to better monitor training and dietary programs of NCAA Division II football players.