A longitudinal examination of improved access on park use and physical activity in a low-income and majority African American neighborhood park.

This study sought to evaluate the impact of street crossing infrastructure modifications on park use and park-based physical activity in a low-income and African American community. A five-lane major highway created an access barrier between low-income housing units and the local neighborhood park in Columbia, Missouri. The installation of a signalized pedestrian crosswalk provided an opportunity to conduct a natural experiment to examine the effect of improved safe access upon community active living behaviors. Direct observation using SOPARC was collected prior to the crosswalk instillation in June 2012, after the crosswalk installation in June 2013 and again as a follow up in June 2014 during the same two-week period to assess changes in total park use and total energy expenditure by age, gender and race/ethnicity. Analysis of covariance models, controlling for temperature examined changes in total counts and total energy expenditure using pairwise Sidak post-hoc comparisons. Total park use increased from 2012 (n=2080) to 2013 (n=2275) and remained constant in 2014 (n=2276). However, despite increases in safe access and overall park use, there was a significant decrease in total energy expenditure following the installation of the crosswalk that was sustained in 2014. This study shows that increasing safe access to parks primarily positively influences park use but not park-based physical activity. While improved safe access is encouraging greater park use, there is a need for future research to examine additional factors such as social support, programming and environmental changes to engage community members in park-based physical activity.

Improvement in functional performance with high-speed power training in older adults is optimized in those with the highest training velocity.

PURPOSE: To identify whether variability in limb movement velocity during high-speed power training (HSPT) may impact physical functioning in older adults. METHODS: 42 older men and women (71.3 ± 6.6 years) were randomized to lower extremity HSPT (n = 28) or control (CON; n = 14) (Analysis 1) for 12 weeks. A second analysis (Analysis 2) allocated HSPT into high-velocity (n = 14) or low-velocity (n = 14) based on a limb movement speed above or below the median average velocity during the 12-week HSPT intervention. Habitual gait speed, maximal gait speed, timed up-and-go, and the short physical performance battery were measured at baseline and 12 weeks. Change scores were compared between HSPT and CON (Analysis 1), and high-velocity, low-velocity, and CON (Analysis 2) using ANCOVA. Statistical significance was accepted at p < 0.05. RESULTS: Analysis 1 There were no group differences in habitual gait speed, maximal gait speed, or timed up-and-go between HSPT and CON (all p > 0.05). Short physical performance battery was greater in HSPT (0.96 ± 0.19) compared to CON (0.10 ± 0.26; p = 0.01). Analysis 2 There were no group differences in the change in habitual GS (p = 0.33) among high-velocity, low-velocity and CON. There were significant group differences in the change in maximal GS (p = 0.007), timed up-and-go (p = 0.03), and short physical performance battery (p = 0.03). CONCLUSIONS: There is considerable variation in self-selected maximal limb velocity during HSPT in older adults. In the present cohort, an average limb velocity of 0.88 m/s during HSPT was necessary to ensure optimal improvement in functional performance for older adults, but this threshold will need further investigation.

Effect of Physical and Academic Stress on Illness and Injury in Division 1 College Football Players.

Stress-injury models of health suggest that athletes experience more physical injuries during times of high stress. The purpose of this study was to evaluate the effect of increased physical and academic stress on injury restrictions for athletes (n = 101) on a division I college football team. Weeks of the season were categorized into 3 levels: high physical stress (HPS) (i.e., preseason), high academic stress (HAS) (i.e., weeks with regularly scheduled examinations such as midterms, finals, and week before Thanksgiving break), and low academic stress (LAS) (i.e., regular season without regularly scheduled academic examinations). During each week, we recorded whether a player had an injury restriction, thereby creating a longitudinal binary outcome. The data were analyzed using a hierarchical logistic regression model to properly account for the dependency induced by the repeated observations over time within each subject. Significance for regression models was accepted at p ≤ 0.05. We found that the odds of an injury restriction during training camp (HPS) were the greatest compared with weeks of HAS (odds ratio [OR] = 2.05, p = 0.0003) and LAS (OR = 3.65, p < 0.001). However, the odds of an injury restriction during weeks of HAS were nearly twice as high as during weeks of LAS (OR = 1.78, p = 0.0088). Moreover, the difference in injury rates reported in all athletes during weeks of HPS and weeks of HAS disappeared when considering only athletes that regularly played in games (OR = 1.13, p = 0.75) suggesting that HAS may affect athletes that play to an even greater extent than HPS. Coaches should be aware of both types of stressors and consider carefully the types of training methods imposed during times of HAS when injuries are most likely.

The Impact of a Signalized Crosswalk on Traffic Speed and Street-Crossing Behaviors of Residents in an Underserved Neighborhood.

Infrastructure improvements such as pedestrian crosswalks that calm traffic and increase access to physical activity opportunities could alleviate important barriers to active living in underserved communities with outdated built environments. The purpose of this study was to explore how the built environment influences street-crossing behaviors and traffic speeds in a low-income neighborhood with barriers to active living in Columbia, Missouri. In 2013, a signalized pedestrian crosswalk and 400-ft-long median was constructed along a busy 5-lane, high-speed arterial highway linking low-income housing with a park and downtown areas. Data collection occurred prior to June 2012, and after June 2013, completion of the project at the intervention site and control site. Direct observation of street-crossing behaviors was performed at designated intersections/crosswalks or non-designated crossing points. Traffic volume and speed were captured using embedded magnetic traffic detectors. At the intervention site, designated crossings increased at the new crosswalk (p < 0.001), but not at non-designated crossings (p = 0.52) or designated crossings at intersections (p = 0.41). At the control site, there was no change in designated crossings (p = 0.94) or non-designated crossings (p = 0.79). Motor vehicles traveling above the speed limit of 35 mph decreased from 62,056 (46 %) to 46,256 (35 %) (p < 0.001) at the intervention site and increased from 57,891 (49 %) to 65,725 (59 %) (p < 0.001) at the control site. The installation of a signalized crosswalk facilitated an increase in safe street crossings and calmed traffic volume and speed in an underserved neighborhood. We believe these findings have significant public health implications that could be critical to advocacy efforts to improve infrastructure projects in similar communities.

High-speed power training in older adults: a shift of the external resistance at which peak power is produced.

Studies have shown that power training increases peak power (PP) in older adults. Evaluating the external resistance (% 1 repetition maximum [1RM]) at which PP is developed is critical given that changes in the components of PP (force and velocity) are dependent on the %1RM at which PP occurs. The purpose of this study was to compare the changes in PP (and the external resistance at which PP occurred) after 12 weeks of high-speed power training (HSPT) vs. traditional slow-speed strength training (SSST). Seventy-two older men and women were randomized to HSPT at 40% of the 1RM (HSPT: n = 24 [70.8 ± 6.8 years]); traditional resistance training at 80% 1RM (SSST: n = 22 [68.6 ± 7.8 years]); or control (CON: n = 18 [71.5 ± 6.1 years]). Measures of muscle performance were obtained at baseline and after the 12-week training intervention. Changes in muscle power and 1RM strength improved similarly with both HSPT and SSST, but HSPT shifted the external resistance at which PP was produced to a lower external resistance (from 67% 1RM to 52% 1RM) compared with SSST (from 65% 1RM to 62% 1RM) (p ≤ 0.05), thus increasing the velocity component of PP (change: HSPT = 0.18 ± 0.21 m·s; SSST = -0.03 ± 0.15 m·s) (p ≤ 0.05). Because sufficient speed of the lower limb is necessary for functional tasks related to safety (crossing a busy intersection, fall prevention), HSPT should be implemented in older adults to improve power at lower external resistances, thus increasing the velocity component of power and making older adults safer in their environment. These data provide clinicians with the necessary information to tailor exercise programs to the individual needs of the older adult, affecting the components of power.

A comparison of high-speed power training and traditional slow-speed resistance training in older men and women.

Muscle power, the product of force × velocity, is a critical determinant of function in older adults. Resistance training (RT) at high speed has been shown to improve peak muscle power in this population; however, different functional tasks may benefit from the improvement of power at values other than "peak" values, for example, tasks that require a greater velocity component or a greater force component. This study compared the effect of high-speed RT on muscle performance (peak power [PP] and its components [PP force and PP velocity] and overall peak velocity [VEL]) across a broad range of external resistances. Thirty-eight older men and women were randomized to high-speed power training at 40% of the 1-repetition maximum (1RM) (n = 13 [74.1 ± 6.4 years]); traditional RT at 80% 1RM (n = 13 [70.1 ± 7.0 years]); or control (n = 12 [72.8 ± 4.1 years]). Measures of muscle performance were obtained at baseline and after the 12-week training intervention. Muscle power and 1RM strength improved similarly with both high-speed and traditional slow-speed RT. However, speed-related muscle performance characteristics, PP velocity and overall VEL, were most positively impacted by high-speed power training, especially at lower external resistances. Because gains in speed-related measures with high-speed training compared to traditional RT do not come at the expense of other muscle performance outcomes, we recommend using an RT protocol in older adults that emphasizes high-speed movements at low external resistances.

The effect of autoregulatory progressive resistance exercise vs. linear periodization on strength improvement in college athletes.

Autoregulatory progressive resistance exercise (APRE) is a method by which athletes increase strength by progressing at their own pace based on daily and weekly variations in performance, unlike traditional linear periodization (LP), where there is a set increase in intensity from week to week. This study examined whether 6 weeks of APRE was more effective at improving strength compared with traditional LP in division I College football players. We compared 23 division 1 collegiate football players (2.65 +/- 0.8 training years) who were trained using either APRE (n = 12) or LP (n = 11) during 6 weeks of preseason training in 2 separate years. After 6 weeks of training, improvements in total bench press 1 repetition maximum (1RM), squat 1RM, and repeated 225-lb bench press repetitions were compared between the APRE and LP protocol groups. Analysis of variance (ANOVA) and analysis of covariance (ANCOVA) were used to determine differences between groups. Statistical significance was accepted at p < or = 0.05. Autoregulatory progressive resistance exercise demonstrated greater improvement in 1RM bench press strength (APRE: 93.4 +/- 103 N vs. LP: -0.40 +/- 49.6 N; ANCOVA: F = 7.1, p = 0.02), estimated 1RM squat strength (APRE: 192.7 +/- 199 N vs. LP: 37.2 +/- 155 N; ANOVA: F = 4.1, p = 0.05) and the number of repetitions performed at a weight of 225 lb (APRE: 3.17 +/- 2.86 vs. LP: -0.09 +/- 2.40 repetitions; ANCOVA: F = 6.8, p = 0.02) compared with the LP group over the 6-week training period. Our findings indicate that the APRE was more effective than the LP means of programming in increasing the bench press and squat over a period of 6 weeks.

The effect of a high-intensity interval training program on high-density lipoprotein cholesterol in young men.

This study examined the impact of an 8-week program of high-intensity interval training on high-density lipoprotein cholesterol (HDL-C), total cholesterol (TC), and the atherogenic index (TC/HDL-C) in 36 untrained men ages 21-36 years. Participants were randomly assigned to an interval training group (n = 20) or a control group (n = 16). Participants in the experimental group performed 3.2 km of interval running (1:1 work:rest ratio) 3 times a week for 8 weeks at an intensity of 90% of maximal heart rate ( approximately 423 kcal per session). Results indicated significant pre- to posttraining changes in HDL-C (1.1 vs. 1.3 mmolxL, p < 0.0001) and TC/HDL-C (3.8 vs. 3.1, p < 0.0001) but no significant changes in TC (3.9 vs. 3.8 mmolxL, p > 0.05) with interval training. It was concluded that an 8-week program of high-intensity interval training is effective in eliciting favorable changes in HDL-C and TC/HDL-C but not TC in young adult men with normal TC levels. Our findings support the recommendations of high-intensity interval training as an alternative mode of exercise to improve blood lipid profiles for individuals with acceptable physical fitness levels.

Accuracy of a non-radiographic method of measuring varus/valgus alignment in knees with osteoarthritis.

Knee alignment has been shown to affect incidence, progression and treatment of knee osteoarthritis (OA). The gold standard for measuring alignment is a radiograph that is often difficult to obtain. This study demonstrates that a clinical non-radiographic measure can serve as a surrogate assessment of knee alignment in older adults with knee OA. We believe these findings will allow more widespread evaluation of one critical mechanical factor essential to the study of knee OA.

Robotic gait-assisted therapy in patients with neurological injury.

Robotic gait training in the treatment of mobility deficits resulting from cerebral vascular injury is gaining popularity in U.S. hospitals and rehabilitation facilities. Advantages of robotic training include patient safety, early mobility training, increased training time per session and reduced physical burden to the therapist. Disadvantages include limited variance of movement and reduced interaction between patient and therapist. Although research has demonstrated positive effects of these devices on mobility improvements, future research with larger patient populations is warranted.

Muscle impairments and behavioral factors mediate functional limitations and disability following stroke.

BACKGROUND AND PURPOSE: Stroke remains the leading cause of disability in the United States. The purposes of this study were to examine whether quantitative measures of muscle strength and power in the involved lower extremity predict functional limitations and to evaluate the contributions of behavioral factors to mediating disability and quality of life in people who have survived a stroke. SUBJECTS AND METHODS: A cross-sectional study design was used, and measurements of muscle impairment, lower-body function, disability, quality of life, and behavioral factors were obtained for 31 community-dwelling volunteers who had experienced a single ischemic stroke in the past 6 to 24 months. RESULTS: Stepwise regression models including impairment and behavioral measures were strong predictors of function, disability, and quality of life. Involved-extremity muscle strength and power and self-efficacy were independently associated with function, whereas depression and self-efficacy were strong predictors of disability and quality of life. DISCUSSION AND CONCLUSION: The findings warrant future studies to determine whether interventions that address muscle strength and power, depressive symptoms, and low self-efficacy effectively improve function, reduce disability, and enhance quality of life in people who have survived a stroke.

Effect of leg muscle contraction velocity on functional performance in older men and women.

OBJECTIVES: To explore the relationship between impairment (skeletal muscle strength and contraction velocity) and function in community-dwelling older adults. DESIGN: Cross-sectional. SETTING: University-based human physiology laboratory. PARTICIPANTS: One hundred one men and women (aged 75-90). MEASUREMENTS: Muscle strength and contraction velocity during bilateral leg press (LP) were calculated during one-repetition maximum (1RM) and 40% 1RM. A short physical performance battery (SPPB) and gait speed (GS) from a 400-m self-paced walk assessed function. Sex differences in LP strength and contraction velocity (at 40% 1RM) were assessed. The relationship between these variables and function was also examined. RESULTS: Lower extremity strength and contraction velocity were significantly associated with GS (P=.02 and P=.005, respectively) and SPPB (P<.001 and P=.009, respectively) in men only. Contraction velocity, but not muscle strength, was significantly associated with GS (P<.001) and SPPB (P=.02) in women. CONCLUSION: Sex differences exist in the relationship between impairment (muscle strength and contraction velocity) and function. Older men and women may employ different strategies to achieve success on different functional tasks. These findings may have important implications for clinicians practicing geriatric rehabilitation.

Validation of the Late-Life Function and Disability Instrument.

OBJECTIVES: To assess the concurrent and predictive validity of the Late-Life Function and Disability Instrument (LLFDI). DESIGN: Cross-sectional. SETTING: University-based human physiology laboratory. PARTICIPANTS: One hundred one men and women aged 80.8 +/- 0.4. MEASUREMENTS: A short physical performance battery (SPPB) and a self-paced 400-m walk (400-m W) were used as performance tests of lower extremity function. The LLFDI was used to assess self-reported function and physical disability. Partial correlations adjusted for age and body mass index were used to determine the concurrent and predictive validity of the LLFDI. Statistical significance was accepted at P<.004 using a testwise correction. RESULTS: LLFDI Overall Function scores were moderately associated with the SPPB (r=0.65, P<.001), 400-m W gait speed (r=0.69, P<.001), and measures of lower extremity function. Correlations of the two lower extremity subscores of the LLFDI (correlation coefficient (r)=0.63-0.73, P<.001) were greater than for the LLFDI upper extremity subscores (r=0.19-0.26, P>.004). Performance measures of function predicted disability limitations in the range of r=0.37-0.44 (P<.001) and disability frequency in the range of r=0.16-0.20 (P>.004). CONCLUSION: These findings support the concurrent and predictive validity of the LLFDI. Results support the use of the LLFDI scales as a substitute for physical performance tests when self-report is a preferred data-collection format.

Use of self-report to predict ability to walk 400 meters in mobility-limited older adults.

OBJECTIVES: To determine whether the ability to walk 400 m could be predicted from self-reported walking habits and abilities in older adults and to develop an accurate self-report measure appropriate for observational trials of mobility when functional measures are impractical to collect. DESIGN: Cross-sectional. SETTING: University-based human physiology laboratory. PARTICIPANTS: One hundred fifty community-dwelling older men and women (mean age+/-standard error= 79.8+/-0.3). MEASUREMENTS: An 18-item questionnaire assessing walking habits and ability was administered to each participant, followed by a 400-m walk test. Ninety-eight (65%) volunteers were able to complete the 400-m walk; 52 (35%) were unable. Logistic regression was performed using response items from a questionnaire as predictors and 400-m walk as the outcome. RESULTS: Three questions (Do you think you could walk one-quarter of a mile now without sitting down to rest. Because of a health or physical problem, do you have difficulty walking 1 mile? Could you walk up and down every aisle of a grocery store without sitting down to rest or leaning on a cart?) were predictive of 400-m walking ability and were included in the model. If participants answered all three questions compatible with the inability to walk 400 m, there was a 91% probability that they were unable to walk 400 m, with a sensitivity of 46% and a specificity of 97%. CONCLUSION: A three-item self-report developed in the study was able to accurately predict mobility disability. The utility of this instrument may be in evaluating self-reported mobility in large observational trials on mobility when functional mobility tasks are impractical to collect.

Short-term immobilization after eccentric exercise. Part II: creatine kinase and myoglobin.

PURPOSE: Although creatine kinase (CK) is commonly used as a marker of muscle damage, there is large variability in the response to exercise. We previously found short-term immobilization blunted the rise in plasma CK after eccentric exercise, suggesting subsequent movement of damaged muscle may contribute to variability. We hypothesized that immobilization decreases lymphatic transport of CK from damaged muscle, blunting the CK response. In this study, we compared changes in plasma CK and myoglobin (Mb), as Mb is released from damaged muscle directly into the bloodstream whereas CK is released first into the lymph. METHODS: Twenty-five college-age males were matched according to force loss after 50 maximal eccentric contractions of the elbow flexors and placed into an immobilization (IMM, N = 12) or control (CON, N = 13) group. IMM had their arm immobilized at 90 degrees and secured in a sling for 4 d (treatment). Venipuncture was performed during baseline, treatment, and for 5 d after treatment (recovery) to assess plasma CK activity and Mb. Urine specific gravity (USG) and muscle activity (ACT) were assessed. RESULTS: Immobilization significantly blunted increases in CK activity (IMM: 955 +/- 316 IU.L-1 vs CON: 2884 +/- 1083 IU.L-1; P < 0.05) but not increases in Mb (IMM: 712 +/- 278 ng.mL-1 vs CON: 891 +/- 253 ng.mL-1; P > 0.05). There were no differences in USG between groups over time (P > 0.05) and no group differences in ACT (P > 0.05). CONCLUSIONS: Short-term immobilization after eccentric exercise blunted the CK response but not the Mb response, suggesting lymphatic transport of CK may be responsible. Because hydration status and muscular activity after exercise were not different between groups, the blunted CK response was likely due to inactivation of CK activity before entering circulation.

Short-term immobilization after eccentric exercise. Part I: contractile properties.

PURPOSE: The purpose of this study was to examine the compound muscle action potential (M-wave) and evoked contractile properties of immobilized muscle after high-force eccentric exercise. We believed that changes in these variables would contribute to the enhanced recovery of maximal voluntary force observed after short-term immobilization of damaged muscle. We hypothesized that immobilization after eccentric exercise would result in an enhanced M-wave and a change in contractile properties toward characteristics of faster muscle fibers. METHODS: Twenty-five college-age males were matched according to force loss after 50 maximal eccentric contractions of the elbow flexors and placed into an immobilization (IMM, N = 12) or control (CON, N = 13) group. IMM had their arm immobilized at 90 degrees and secured in a sling during a 4-d treatment. Maximal isometric torque (MVC) was assessed at baseline and for 8 d after treatment. M-wave and evoked contractile properties of the muscle (twitch torque [TT], maximal rate of torque development [MRTD], time to peak torque [TPT], and one-half relaxation time [HRT]) were assessed at baseline and for the first 5 d after treatment. RESULTS: Immediately postexercise, MVC was reduced 43% and 42% in IMM and CON, respectively. Recovery of MVC was significantly greater in IMM during recovery (P < 0.05), 95% of baseline MVC compared with 83% in CON. M-wave was reduced 32%, and all contractile properties were altered immediately postexercise. M-wave, MRTD, TPT, and HRT were not significantly different between groups during recovery (P > 0.05). TT demonstrated enhanced recovery in IMM (P < 0.05). CONCLUSIONS: Short-term immobilization after eccentric exercise resulted in enhanced recovery of maximal voluntary force. However, enhanced force recovery cannot be explained by muscle activation and evoked contractile properties of the muscle.

The effect of fasting on indicators of muscle damage.

Many studies have tested the consumption of foods and supplements to reduce exercise-induced muscle damage, but fasting itself is also worthy of investigation due to reports of beneficial effects of caloric restriction and/or intermittent fasting on inflammation and oxidative stress. This preliminary investigation compared indicators of exercise-induced muscle damage between upper-body untrained participants (N=29, 22yrs old (SD=3.34), 12 women) who completed 8h water-only fasts or ate a controlled diet in the 8h prior to five consecutive laboratory sessions. All sessions were conducted in the afternoon hours (i.e., post meridiem) and the women completed the first session while in the follicular phase of their menstrual cycles. Measures of muscle pain, resting elbow extension, upper arm girth, isometric strength, myoglobin (Mb), total nitric oxide (NO), interleukin 1beta (IL1b), and tumor necrosis factor alpha (TNFa) were collected before and after eccentric contractions of the non-dominant elbow flexors were completed. The fasting group's loss of elbow extension was less than the post-prandial group (p<.05, eta(2)=.10), but the groups did not change differently across time for any other outcome measures. However, significantly higher NO (p<.05, eta(2)=.22) and lower TNFa (p<.001, eta(2)=.53) were detected in the fasting group than the post-prandial group regardless of time. These results suggest intermittent fasting does not robustly inhibit the signs and symptoms of exercise-induced muscle damage, but such fasting may generally affect common indirect markers of muscle damage.

Effects of high-speed power training on muscle performance and braking speed in older adults.

We examined whether high-speed power training (HSPT) improved muscle performance and braking speed using a driving simulator. 72 older adults (22 m, 50 f; age = 70.6 ± 7.3 yrs) were randomized to HSPT at 40% one-repetition maximum (1RM) (HSPT: n = 25; 3 sets of 12-14 repetitions), slow-speed strength training at 80%1RM (SSST: n = 25; 3 sets of 8-10 repetitions), or control (CON: n = 22; stretching) 3 times/week for 12 weeks. Leg press and knee extension peak power, peak power velocity, peak power force/torque, and braking speed were obtained at baseline and 12 weeks. HSPT increased peak power and peak power velocity across a range of external resistances (40-90% 1RM; P < 0.05) and improved braking speed (P < 0.05). Work was similar between groups, but perceived exertion was lower in HSPT (P < 0.05). Thus, the less strenuous HSPT exerted a broader training effect and improved braking speed compared to SSST.