Browse

You are looking at 1 - 10 of 24,965 items

Restricted access

Joowon Lee, Baojiang Chen, Harold W. Kohl III, Carolyn E. Barlow, Chong Do Lee, Nina B. Radford, Laura F. DeFina and Kelley P. Gabriel

The purpose of the current investigation was to examine the cross-sectional associations of participation in muscle-strengthening activities (MSAs) with carotid intima–media thickness (CIMT) among older adults. The data are from 2,557 older adult participants enrolled in an observational cohort who reported no history of cardiovascular disease. MSA was determined using a questionnaire. Carotid ultrasound was performed to measure the CIMT of the common carotid artery bilaterally. Logistic regression models were constructed to estimate the association of MSA with CIMT after adjustment for potential confounders. The participants were aged 68.6 ± 7.0 years, and the majority were male (71.7%) and White (96.5%); 18% had abnormal CIMT. Meeting the physical activity guidelines for MSA was inversely associated with abnormal CIMT after adjustment for age and sex. However, this observed inverse relation became statistically null after further adjustment for cardiovascular disease risk factors, including aerobic physical activity.

Restricted access

Mitali S. Thanawala, Juned Siddique, John A. Schneider, Alka M. Kanaya, Andrew J. Cooper, Swapna S. Dave, Nicola Lancki and Namratha R. Kandula

Background: Eliminating racial/ethnic disparities in physical activity remains a challenge in the United States. South Asian immigrants in the United States have particularly low physical activity levels, and evidence suggests that social context may be important. This study examined associations between personal social networks and moderate to vigorous leisure-time physical activity (MVPA) among South Asians in the United States. Methods: We used cross-sectional data (2014–2017) from 689 South Asians (aged 43–85 y) who participated in the Mediators of Atherosclerosis in South Asians Living in America study. Self-reported physical activity and egocentric network data were collected from participants about their network members. Regression models were used to determine associations between social network characteristics and participants’ MVPA. Results: Participants were on average 59 years old (SD = 9) and reported 1335 metabolic equivalent minutes per week of MVPA (interquartile range = 735, 2212). Having network members who exercised or who were exercise partners associated with increased MVPA in men (β coefficient = 241 MET min/wk [95% confidence interval, 63 to 419] and β = 520 MET min/wk [95% confidence interval, 322 to 718], respectively). For women, the association was only significant if the exercise partner was a spouse. Conclusion: Physical activity interventions utilizing network members as exercise partners may have potential in South Asians but must consider gender differences.

Restricted access

Michelle A. Sandrey, Yu-Jen Chang and Jean L. McCrory

Context: Lower-extremity stress fractures (SFx) are a common occurrence during load-bearing activities of jumping and landing. To detect biomechanical changes during jumping postinjury, a fatigue model could be used. Objective: To evaluate muscle activation in the lower leg and tibial accelerations (TAs) prefatigue to postfatigue following a jumping task in those with and without a history of SFx. Design: Repeated-measures. Setting: Athletic Training Research Lab. Participants: A total of 30 active college-aged students with and without a history of lower-extremity (leg or foot) SFx (15 males and 15 females; 21.5 [5.04] y, height = 173.5 [12.7] cm, weight = 72.65 [16.4] kg). Intervention: A maximal vertical jump on one leg 3 times with arms folded across the chest prefatigue to postfatigue was performed. Fatigue protocol was standing heel raises on a custom-built platform at a pace controlled by a metronome until task failure was reached. Legs were tested using a randomized testing order. Electromyographic (EMG) surface electrodes were placed on the medial gastrocnemius, soleus, and tibialis anterior following a standardized placement protocol. A triaxial accelerometer was attached to the proximal anteromedial surface of the tibia. Main Outcome Measures: Linear envelopes of the medial gastrocnemius, soleus, and tibialis anterior and peak accelerations (resultant acceleration takeoff and landing).Results: Significant interaction for leg × test for tibialis anterior with a posttest difference between SFx and control (P = .05). There were decreases in EMG linear envelope following fatigue for medial gastrocnemius (P < .01) and tibialis anterior (P = .12) pretest to posttest. At takeoff, TA was greater in the SFx contralateral leg in comparison with the control leg (P = .04). At landing, TA was greater in posttest (P < .01) and in the SFx leg compared with SFx contralateral (P = .14). Conclusion: A decrease in muscle activity and an increase in TA following fatigue were noted for all subjects but especially for those with a history of SFx.

Restricted access

J.D. DeFreese, Michael J. Baum, Julianne D. Schmidt, Benjamin M. Goerger, Nikki Barczak, Kevin M. Guskiewicz and Jason P. Mihalik

Context: Concussion baseline testing helps injury evaluation by allowing postinjury comparisons to preinjury measures. To facilitate best practice, common neurocognitive, balance, and symptom report metrics used in concussion baseline testing merit examination relative to participant life stressors. Objective: The purpose of this study was to determine if life stressors are associated with college athlete neurocognitive function, postural control, and symptom scores at preseason baseline assessment. Design: All study variables were collected in a single laboratory session where athletes completed valid and reliable psychometrics as well as a computerized neurocognitive and balance assessments. Setting: Sports medicine research center on an American university campus. Participants: A convenience sample of 123 college student-athletes: 47 females (age = 18.9 [4.3] y) and 76 males (age = 19.4 [1.6] y). Main Outcome Measures: Participants were categorized into low, moderate, or high life stressors groups using scores from the Social Readjustment Rating Scale-Revised. Dependent variables included outcomes from the CNS Vitals Signs test, the Sensory Organization Test, and the graded symptom checklist indexing neurocognition, balance, and symptom severity, respectfully. Results: One-way analysis of variance revealed that the moderate life stressors group performed significantly worse than the low life stressors group on the baseline verbal memory domain of the CNS Vital Signs (F2,119 = 3.28; P = .04) only. Conclusion: In the current college athlete sample, few baseline concussion assessment variables were found to be significantly associated with life stressors. Considering the clinical significance of these variables, psychological life stressors may not be a confounding factor in concussion evaluation.

Restricted access

Diego Alonso-Fernandez, Yaiza Taboada-Iglesias, Tania García-Remeseiro and Águeda Gutiérrez-Sánchez

Context: The architectural characteristics of a muscle determine its function. Objective: To determine the architectural adaptations of the lateral gastrocnemius (LG) and medial gastrocnemius (MG) muscles after a functional eccentric strength training protocol consisting of heel drop exercises, followed by a subsequent detraining period. Design: Pretest and posttest. Setting: Training rooms and laboratory. Participants: The participants (N = 45) who were randomly divided into an experimental group (EG, n = 25) and a control group (CG, n = 20). Interventions: The 13-week intervention included participants (N = 45) who were randomly divided into an EG (n = 25) and a CG (n = 20). The EG performed a week of control and training, 8 weeks of eccentric training, and 4 weeks of detraining. The CG did not perform any type of muscular training. The architectural characteristics of the LG and MG muscles were evaluated at rest in both groups using 2-D ultrasound before (pretest–week 1) and after (posttest–week 9) the training, and at the end of the detraining period (retest–week 13). Main Outcome Measures: One-way repeated measures analysis of variance was used to determine training-induced changes in each of the variables of the muscle architecture. Results: After the training period, the members of the EG experienced a significant increase in the fascicle length of LG (t = −9.85, d = 2.78, P < .001) and MG (t = −8.98, d = 2.54, P < .001), muscle thickness (t = −6.71, d = 2.86, P < .001) and (t = −7.85, d = 2.22, P < .001), and the pennation angle (t = −10.21, d = 1.88, P < .05) and (t = −1.87, d = 0.53, P < .05), respectively. After the detraining period, fascicle length, muscle thickness, and pennation angle showed a significant decrease. In the CG, no significant changes were observed in any of the variables. Conclusions: The heel drop exercise seems to generate adaptations in the architectural conditions of LG and MG, which are also reversible after a detraining period. These results may have practical implications for injury prevention and rehabilitation programs.

Restricted access

Jennifer J. Sherwood, Cathy Inouye, Shannon L. Webb and Jenny O

The study aims were to analyze the reliability and validity of the GymAware linear position transducer’s velocity and power measures during the sit-to-stand, compared with the Dartfish 2D videography analysis, and to assess the relationship of age and handgrip strength with velocity and power in 48 older men and women (77.6 ± 11.1 years). The results showed excellent agreement between GymAware- and Dartfish-derived sit-to-stand velocity (intraclass correlation coefficient2-1 = .94 and power intraclass correlation coefficient2-1 = .98) measures. A moderate and negative relationship was found between age and velocity (r = −.62; p < .001) and age and power (r = −.63; p < .001). A moderate and positive relationship was found between handgrip strength and velocity (r = .43; p = .002) and handgrip strength and power (r = .54; p < .001). The results show the GymAware velocity and power measures during the sit-to-stand in older adults to be reliable and valid.

Restricted access

Junga Lee

Several controversial studies linking handgrip strength and health have suggested that low handgrip strength in older adults may be related to health problems and have investigated whether there is a minimum handgrip strength level associated with reduced mortality. Thus, by meta-analysis, the authors identified an association between handgrip strength in older adults and disease-specific mortality and all-cause mortality. Thirty studies with a total of 194,767 older adult participants were included in this meta-analysis. Higher handgrip strength was associated with an 18% decrease in all-cause mortality. Lower handgrip strength was associated with increased all-cause mortality. The minimum handgrip strength in older women that did not increase all-cause mortality was 18.21 kg. Increased handgrip strength showed a decreased all-cause mortality, whereas decreased handgrip strength was associated with increased all-cause mortality. Strengthening the handgrip may help improve disease-specific mortality in older adults.

Restricted access

Mariana R. Silva, Cristine L. Alberton, Caroline O. Braga and Stephanie S. Pinto

Background: To compare the acute effects of water-based aerobic–resistance and resistance–aerobic concurrent training (CT) sessions on energy expenditure (EE) during and postexercise in young women. Methods: Nine active women (24 [3] y; 60 [5] kg) completed 4 sessions: (1) familiarization, (2) aquatic maximal test to determine the heart rate corresponding to the anaerobic threshold, (3) CT protocol with aerobic–resistance sequence, and (4) CT protocol with resistance–aerobic sequence. Both protocols started and ended with the participants in the supine position for 30 minutes to perform resting and postexercise oxygen consumption measurements. The water-based resistance protocol comprised 4 sets of 15 seconds at maximal velocity, and the water-based aerobic protocol was performed at a continuous intensity (heart rate corresponding to the anaerobic threshold). EE measurements were calculated based on oxygen consumption and the corresponding caloric equivalent. Paired t test was used to compare the EE values between the water-based CT intrasession exercise sequences (α = .05). Results: There was no difference between the water-based aerobic–resistance and resistance–aerobic in total EE (330.78 vs 329.56 kcal; P = .96), EE per minute (7.35 vs 7.32 kcal·min−1; P = .96), and postexercise EE (63.65 vs 59.92 kcal; P = .50). Conclusions: The intrasession exercise sequence during water-based CT had no influence on the EE in young women.

Restricted access

Brigid M. Lynch, Suzanne C. Dixon-Suen, Andrea Ramirez Varela, Yi Yang, Dallas R. English, Ding Ding, Paul A. Gardiner and Terry Boyle

Background: It is not always clear whether physical activity is causally related to health outcomes, or whether the associations are induced through confounding or other biases. Randomized controlled trials of physical activity are not feasible when outcomes of interest are rare or develop over many years. Thus, we need methods to improve causal inference in observational physical activity studies. Methods: We outline a range of approaches that can improve causal inference in observational physical activity research, and also discuss the impact of measurement error on results and methods to minimize this. Results: Key concepts and methods described include directed acyclic graphs, quantitative bias analysis, Mendelian randomization, and potential outcomes approaches which include propensity scores, g methods, and causal mediation. Conclusions: We provide a brief overview of some contemporary epidemiological methods that are beginning to be used in physical activity research. Adoption of these methods will help build a stronger body of evidence for the health benefits of physical activity.

Restricted access

Samuel T. Tebeck, Jonathan D. Buckley, Clint R. Bellenger and Jamie Stanley

Purpose: To investigate the effect of a 5-day short-term heat acclimation (STHA) protocol in dry (43°C and 20% relative humidity) or humid (32°C and 80% relative humidity) environmental conditions on endurance cycling performance in temperate conditions (21°C). Methods: In a randomized, cross-over design, 11 cyclists completed each of the two 5-day blocks of STHA matched for heat index (44°C) and total exposure time (480 min), separated by 30 days. Pre- and post-STHA temperate endurance performance (4-min mean maximal power, lactate threshold 1 and 2) was assessed; in addition, a heat stress test was used to assess individual levels of heat adaptation. Results: Differences in endurance performance were unclear. Following dry STHA, gross mechanical efficiency was likely reduced (between-condition effect size dry vs humid −0.59; 90% confidence interval, −1.05 to −0.15), oxygen uptake was likely increased for a given workload (0.64 [0.14 to 1.07]), and energy expenditure likely increased (0.59 [0.17 to 1.03]). Plasma volume expansion at day 5 of acclimation was similar (within-condition outcome 4.6% [6.3%] and 5.3% [5.1%] dry and humid, respectively) but was retained for 3 to 4 days longer after the final humid STHA exposure (−0.2% [8.1%] and 4.5% [4.2%] dry and humid, respectively). Sweat rate was very likely increased during dry STHA (0.57 [0.25 to 0.89]) and possibly increased (0.18 [−0.15 to 0.50]) during humid STHA. Conclusion: STHA induced divergent adaptations between dry and humid conditions, but did not result in differences in temperate endurance performance.