Showing papers in "Medicine and Science in Sports and Exercise in 2012"

Best practices for using physical activity monitors in population-based research

Abstract: The use of physical activity monitors in population-based research has increased dramatically in the past decade. In this report, we review the major purpose for using physical activity monitors in different types of population-based studies (i.e., surveillance, intervention, association studies) and discuss the strengths and weaknesses for the various behavioral outcomes derived from monitors for each study type. We also update and extend previous recommendations for use of these instruments in large-scale studies, particularly with respect to selecting monitor systems in the context of technological advances that have occurred in recent years. The current state of the science with respect to optimal measurement schedules for use of physical activity monitors is also discussed. A checklist and flowchart are provided so that investigators have more guidance when reporting key elements of monitor use in their studies.

Foot strike and injury rates in endurance runners: a retrospective study.

Abstract: DAOUD, A. I., G. J. GEISSLER, F. WANG, J. SARETSKY, Y. A. DAOUD, and D. E. LIEBERMAN. Foot Strike and Injury Rates in Endurance Runners: A Retrospective Study. Med. Sci. Sports Exerc., Vol. 44, No. 7, pp. 1325‐1334, 2012. Purpose: This retrospective study tests if runners who habitually forefoot strike have different rates of injury than runners who habitually rearfoot strike. Methods: We measured the strike characteristics of middle- and long-distance runners from a collegiate cross-country team and quantified their history of injury, including the incidence and rate of specific injuries, the severity of each injury, and the rate of mild, moderate, and severe injuries per mile run. Results: Of the 52 runners studied, 36 (69%) primarily used a rearfoot strike and 16 (31%) primarily used a forefoot strike. Approximately 74% of runners experienced a moderate or severe injury each year, but those who habitually rearfoot strike had approximately twice the rate of repetitive stress injuries than individuals who habitually forefoot strike. Traumatic injury rates were not significantly different between the two groups. A generalized linear model showed that strike type, sex, race distance, and average miles per week each correlate significantly (P G 0.01) with repetitive injury rates. Conclusions: Competitive cross-country runners on a college team incur high injury rates, but runners who habitually rearfoot strike have significantly higher rates of repetitive stress injury than those who mostly forefoot strike. This study does not test the causal bases for this general difference. One hypothesis, which requires further research, is that the absence of a marked impact peak in the ground reaction force during a forefoot strike

Assessing physical activity using wearable monitors: measures of physical activity.

Abstract: BackgroundPhysical activity may be defined broadly as “all bodily actions produced by the contraction of skeletal muscle that increase energy expenditure above basal level.” Physical activity is a complex construct that can be classified into major categories qualitatively, quantitatively, o

Strength training with blood flow restriction diminishes myostatin gene expression.

Abstract: Purpose: The aim of the study was to determine whether the similar muscle strength and hypertrophy responses observed after either low-intensity resistance exercise associated with moderate blood flow restriction or high-intensity resistance exercise are associated with similar changes in messenger RNA (mRNA) expression of selected genes involved in myostatin (MSTN) signaling. Methods: Twenty-nine physically active male subjects were divided into three groups: low-intensity (20% one-repetition maximum (1RM)) resistance training (LI) (n = 10), low-intensity resistance exercise associated with moderate blood flow restriction (LIR) (n = 10), and high-intensity (80% 1RM) resistance exercise (HI) (n = 9). All of the groups underwent an 8-wk training program. Maximal dynamic knee extension strength (1RM), quadriceps cross-sectional area (CSA), MSTN, follistatin-like related genes (follistatin (FLST), follistatin-like 3 (FLST-3)), activin IIb, growth and differentiation factor�associated serum protein 1 (GASP-1), and MAD-related protein (SMAD-7) mRNA gene expression were assessed before and after training. Results: Knee extension 1RM significantly increased in all groups (LI = 20.7%, LIR = 40.1%, and HI = 36.2%). CSA increased in both the LIR and HI groups (6.3% and 6.1%, respectively). MSTN mRNA expression decreased in the LIR and HI groups (45% and 41%, respectively). There were no significant changes in activin IIb (P > 0.05). FLST and FLST-3 mRNA expression increased in all groups from pre- to posttest (P < 0.001). FLST-3 expression was significantly greater in the HI when compared with the LIR and LI groups at posttest (P = 0.024 and P = 0.018, respectively). GASP-1 and SMAD-7 gene expression significantly increased in both the LIR and HI groups. Conclusions: We concluded that LIR was able to induce gains in 1RM and quadriceps CSA similar to those observed after traditional HI. These responses may be related to the concomitant decrease in MSTN and increase in FLST isoforms, GASP-1, and SMAD-7 mRNA gene expression.

ActiGraph and Actical physical activity monitors: a peek under the hood.

Abstract: Since the 1980s, accelerometer-based activity monitors have been used by researchers to quantify physical activity. The technology of these monitors has continuously evolved. For example, changes have been made to monitor hardware (type of sensor (e.g., piezoelectric, piezoresistive, capacitive)) and output format (counts vs raw signal). Commonly used activity monitors belong to the ActiGraph and the Actical families. This article presents information on several electromechanical aspects of these commonly used activity monitors. The majority of the article focuses on the evolution of the ActiGraph activity monitor by describing the differences among the 7164, the GT1M, and the GT3X models. This is followed by brief descriptions of the influences of device firmware and monitor calibration status. We also describe the Actical, but the discussion is short because this device has not undergone any major changes since it was first introduced. This article may help researchers gain a better understanding of the functioning of activity monitors. For example, a common misconception among physical activity researchers is that the ActiGraph GT1M and GT3X are piezoelectric sensor-based monitors. Thus, this information may also help researchers to describe these monitors more accurately in scientific publications.

Effects of footwear and strike type on running economy.

Abstract: PERL, D. P., A. I. DAOUD, and D. E. LIEBERMAN. Effects of Footwear and Strike Type on Running Economy. Med. Sci. Sports Exerc., Vol. 44, No. 7, pp. 1335‐1343, 2012. Purpose: This study tests if running economy differs in minimal shoes versus standard running shoes with cushioned elevated heels and arch supports and in forefoot versus rearfoot strike gaits. Methods: We measured the cost of transport (mL O2Ikg j1 Im j1 ) in subjects who habitually run in minimal shoes or barefoot while they were running at 3.0 mIs j1 on a treadmill during forefoot and rearfoot striking while wearing minimal and standard shoes, controlling for shoe mass and stride frequency. Force and kinematic data were collected when subjects were shod and barefoot to quantify differences in knee flexion, arch strain, plantar flexor force production, and Achilles tendon‐triceps surae strain. Results: After controlling for stride frequency and shoe mass, runners were 2.41% more economical in the minimal-shoe condition when forefoot striking and 3.32% more economical in the minimal-shoe condition when rearfoot striking (P G 0.05). In contrast, forefoot and rearfoot striking did not differ significantly in cost for either minimal- or standard-shoe running. Arch strain was not measured in the shod condition but was significantly greater during forefoot than rearfoot striking when barefoot. Plantar flexor force output was significantly higher in forefoot than in rearfoot striking and in barefoot than in shod running. Achilles tendon‐triceps surae strain and knee flexion were also lower in barefoot than in standardshoe running. Conclusions: Minimally shod runners are modestly but significantly more economical than traditionally shod runners regardless of strike type, after controlling for shoe mass and stride frequency. The likely cause of this difference is more elastic energy

Assessment of wear/nonwear time classification algorithms for triaxial accelerometer.

Abstract: AB Purpose: The objective of this study is to assess the performance of existing wear/nonwear time classification algorithms for accelerometry data collected in the free-living environment using a wrist-worn triaxial accelerometer and a waist-worn uniaxial accelerometer in older adults. Methods: Twenty-nine adults age 76 to 96 yr wore wrist accelerometers for approximately 24 h per day and waist accelerometers during waking for approximately 7 d of free living. Wear and nonwear times were classified by existing algorithms (Alg[ActiLife], Alg[Troiano], and Alg[Choi]) and compared with wear and nonwear times identified by data plots and diary records. With the use of bias and probability of correct classification, the performance of the algorithms, two time windows (60 and 90 min), and vector magnitude (VM) versus vertical axis (V) counts from a triaxial accelerometer were compared. Results: Automated algorithms (Alg[Choi] and Alg[Troiano]) classified wear/nonwear time intervals more accurately from VM than V counts. The use of the 90-min time window improved wear/nonwear classification accuracy when compared with the 60-min window. The Alg[Choi] and Alg[Troiano] performed better than the manufacturer-provided algorithm (Alg[ActiLife]), and the Alg[Choi] performed better than the Alg[Troiano] for wear/nonwear time classification using the data collected by both accelerometers. Conclusions: Triaxial wrist-worn accelerometer can be used for an accurate wear/nonwear time classification in free-living older adults. The use of the 90-min window and the VM counts improves the performance of commonly used algorithms for wear/nonwear classification for both uniaxial and triaxial accelerometers. (C)2012The American College of Sports Medicine

Effect of acute static stretch on maximal muscle performance: A systematic review

Abstract: INTRODUCTION: The benefits of preexercise muscle stretching have been recently questioned after reports of significant poststretch reductions in force and power production. However, methodological issues and equivocal findings have prevented a clear consensus being reached. As no detailed systematic review exists, the literature describing responses to acute static muscle stretch was comprehensively examined. METHODS: MEDLINE, ScienceDirect, SPORTDiscus, and Zetoc were searched with recursive reference checking. Selection criteria included randomized or quasi-randomized controlled trials and intervention-based trials published in peer-reviewed scientific journals examining the effect of an acute static stretch intervention on maximal muscular performance. RESULTS: Searches revealed 4559 possible articles; 106 met the inclusion criteria. Study design was often poor because 30% of studies failed to provide appropriate reliability statistics. Clear evidence exists indicating that short-duration acute static stretch ( 60 s, with limited evidence for an effect on eccentric strength. CONCLUSIONS: The detrimental effects of static stretch are mainly limited to longer durations (≥60 s), which may not be typically used during preexercise routines in clinical, healthy, or athletic populations. Shorter durations of stretch (<60 s) can be performed in a preexercise routine without compromising maximal muscle performance

Exercise in Pregnancy: Effect on Fitness and Obstetric Outcomes—A Randomized Trial

Abstract: Background: Exercise is an inconsistently managed area in the health of expectant mothers. It is an area where family doctors have an opportunity to be well informed and willing to give advice. Objective: To provide simple advice on safe exercise practice in pregnancy. Discussion: Exercise in pregnancy has multiple benefits for the mother, including reduced risk of mental health problems, diabetes and hypertension, and faster recovery after delivery. There are no proven risks to the fetus if practiced safely. Understanding the physiological changes of pregnancy and the possible complications of high-intensity or contact sport is important but in general, moderate levels of exercise 3-4 times per week is safe for both mother and baby in low-risk pregnancies.

Initial Validation of an Exercise “Vital Sign” in Electronic Medical Records

Abstract: PurposeThe objective of this study is to describe the face and discriminant validity of an exercise vital sign (EVS) for use in an outpatient electronic medical record.MethodsEligible patients were 1,793,385 adults 18 yr and older who were members of a large health care system in Southern Ca

Mechanics of the human hamstring muscles during sprinting.

Abstract: Purpose: An understanding of hamstring mechanics during sprinting is important for elucidating why these muscles are so vulnerable to acute strain-type injury. The purpose of this study was twofold: first, to quantify the biomechanical load (specifically, musculotendon strain, velocity, force, power, and work) experienced by the hamstrings across a full stride cycle; and second, to determine how these parameters differ for each hamstring muscle (i.e., semimembranosus (SM), semitendinosus (ST), biceps femoris long head (BFLH), biceps femoris short head (BFSH)). Methods: Full-body kinematics and ground reaction force data were recorded simultaneously from seven subjects while sprinting on an indoor running track. Experimental data were integrated with a three-dimensional musculoskeletal computer model comprised of 12 body segments and 92 musculotendon structures. The model was used in conjunction with an optimization algorithm to calculate musculotendon strain, velocity, force, power, and work for the hamstrings. Results: SM, ST, and BFLH all reached peak strain, produced peak force, and formed much negative work (energy absorption) during terminal swing. The biomechanical load differed for each hamstring muscle: BFLH exhibited the largest peak strain, ST displayed the greatest lengthening velocity, and SM produced the highest peak force, absorbed and generated the most power, and performed the largest amount of positive and negative work. Conclusions: As peak musculotendon force and strain for BFLH, ST, and SM occurred around the same time during terminal swing, it is suggested that this period in the stride cycle may be when the biarticular hamstrings are at greatest injury risk. On this basis, hamstring injury prevention or rehabilitation programs should preferentially target strengthening exercises that involve eccentric contractions performed with high loads at longer musculotendon lengths.

Preschoolers' physical activity, screen time, and compliance with recommendations.

Abstract: Purpose: Little evidence exists about the prevalence of adequate levels of physical activity and of appropriate screen-based entertainment in preschool children. Previous studies have generally relied on small samples. This study investigates how much time preschool children spend being physically active and engaged in screen-based entertainment. The study also reports compliance with the recently released Australian recommendations for physical activity (=3 h·d-1) and screen entertainment (=1 h·d-1) and the National Association for Sport and Physical Education physical activity guidelines (=2 h·d-1) and American Academy of Pediatrics screen-based entertainment recommendations (=2 h·d-1) in a large sample of preschool children. Methods: Participants were 1004 Melbourne preschool children (mean age = 4.5 yr, range = 3�5 yr) and their families in the Healthy Active Preschool Years study. Physical activity data were collected by accelerometry during an 8-d period. Parents reported their child�s television/video/DVD viewing, computer/Internet, and electronic game use during a typical week. A total of 703 (70%) had sufficient accelerometry data, and 935 children (93%) had useable data on time spent in screen-based entertainment. Results: Children spent 16% (approximately 127 min·d-1) of their time being physically active. Boys and younger children were more active than were girls and older children, respectively. Children spent an average of 113 min·d-1 in screen-based entertainment. Virtually no children (<1%) met both the Australian recommendations and 32% met both the National Association for Sport and Physical Education and American Academy of Pediatrics recommendations. Conclusions: The majority of young children are not participating in adequate amounts of physical activity and in excessive amounts of screen-based entertainment. It is likely that physical activity may decline and that screen-based entertainment may increase with age. Compliance with recommendations may be further reduced. Strategies to promote physical activity and reduce screen-based entertainment in young children are required.

Accelerometer-Determined Physical Activity in Adults and Older People

Abstract: Purpose: There is a lack of large-scale comparable data on the population levels of physical activity (PA) and sedentary activity. We conducted a cross-sectional population-based multicenter study to describe the levels of PA and sedentary activity and to determine adherence to current national PA recommendations in Norwegian adults and older people. Methods: In 2008 and 2009, PA was assessed objectively for seven consecutive days using the ActiGraph GT1M accelerometer in 3867 participants age 20�85 yr. A total of 3267 participants provided valid PA assessments that met all inclusion criteria. Results: Women and men did not differ in the overall activity levels (335 and 342 counts per minute, respectively) or in steps per day (8113 and 7951 steps per day, respectively). However, for intensity-specific PA, men accumulated significantly more minutes of sedentary activity and moderate-to-vigorous PA (MVPA) compared with women (557 vs 533 min of sedentary activity, P = 0.001 and 35 vs 33 min of MVPA, P = 0.01). Both overall activity levels and steps per day remained steady with age, until 65 yr, after which activity levels declined. Conclusions: Overall, the study sample spent 62% of their time being sedentary, 25% in low-intensity PA, 9% in lifestyle activity, and 4% in MVPA. One in five people met current national PA recommendations. These results suggest that adults and older people spend the majority of their time being sedentary and that adherence to PA recommendations is low

Destination and Route Attributes Associated with Adults' Walking: A Review.

Abstract: BACKGROUND: Increasing adults' physical activity through environmental initiatives that promote walking is a public health priority. To this end, evidence relevant to the urban planning and transport sectors is required. This review synthesized findings on destination and route attributes associated with utilitarian and recreational walking. METHODS: Literature search was conducted in April 2011 using Web of Science, PubMed, Transport Research Information Services (TRIS), GEOBASE, and SPORTDiscus. Environmental attributes were classified into the domains of utilitarian and recreational destinations (presence, proximity, quality) and route (sidewalks, connectivity, aesthetics, traffic, safety). Forty-six studies examining associations of these attributes with utilitarian and/or recreational walking were identified. Specific destination and routes attributes associated with each type of walking were summarized. RESULTS: Adults' utilitarian walking was consistently associated with presence and proximity of retail and service destinations (in 80% of the studies reviewed). It was also associated with functional aspects of routes (sidewalks and street connectivity) in 50% of studies. Recreational walking was associated with presence, proximity, and quality of recreational destinations (35% of studies) and route aesthetic (35% of studies). Both types of walking were found unrelated to route safety and traffic in most studies. CONCLUSIONS: There is consistent evidence that better access to relevant neighborhood destinations (e.g., local stores, services, transit stops) can be conducive to adults' utilitarian walking. Some evidence also suggests that availability of sidewalks and well-connected streets can facilitate utilitarian walking. In order to better inform initiatives to promote adults' walking in the planning and transport sectors, future studies need to examine how accessible such destinations should be, as well as the impact of the quality of recreational destinations. Language: en

Optimal Force-Velocity Profile in Ballistic Movements—Altius: Citius or Fortius?

Abstract: Purpose: The study�s purpose was to determine the respective influences of the maximal power ( Equation (Uncited) Image Tools ) and the force�velocity (F�v) mechanical profile of the lower limb neuromuscular system on performance in ballistic movements. Methods: A theoretical integrative approach was proposed to express ballistic performance as a mathematical function of Equation (Uncited) Image Tools and F�v profile. This equation was (i) validated from experimental data obtained on 14 subjects during lower limb ballistic inclined push-offs and (ii) simulated to quantify the respective influence of Equation (Uncited) Image Tools and F�v profile on performance. Results: The bias between performances predicted and obtained from experimental measurements was 4%�7%, confirming the validity of the proposed theoretical approach. Simulations showed that ballistic performance was mostly influenced not only by Equation (Uncited) Image Tools but also by the balance between force and velocity capabilities as described by the F�v profile. For each individual, there is an optimal F�v profile that maximizes performance, whereas unfavorable F�v balances lead to differences in performance up to 30% for a given Equation (Uncited) Image Tools . This optimal F�v profile, which can be accurately determined, depends on some individual characteristics (limb extension range, Equation (Uncited) Image Tools ) and on the afterload involved in the movement (inertia, inclination). The lower the afterload, the more the optimal F�v profile is oriented toward velocity capabilities and the greater the limitation of performance imposed by the maximal velocity of lower limb extension. Conclusions: High ballistic performances are determined by both maximization of the power output capabilities and optimization of the F�v mechanical profile of the lower limb neuromuscular system.

Validity of two wearable monitors to estimate breaks from sedentary time.

Abstract: AB Investigations using wearable monitors have begun to examine how sedentary time behaviors influence health. Purpose: The objective of this study is to demonstrate the use of a measure of sedentary behavior and to validate the activPAL (PAL Technologies Ltd., Glasgow, Scotland) and ActiGraph GT3X (Actigraph, Pensacola, FL) for estimating measures of sedentary behavior: absolute number of breaks and break rate. Methods: Thirteen participants completed two 10-h conditions. During the baseline condition, participants performed normal daily activity, and during the treatment condition, participants were asked to reduce and break up their sedentary time. In each condition, participants wore two ActiGraph GT3X monitors and one activPAL. The ActiGraph was tested using the low-frequency extension filter (AG-LFE) and the normal filter (AG-Norm). For both ActiGraph monitors, two count cut points to estimate sedentary time were examined: 100 and 150 counts per minute. Direct observation served as the criterion measure of total sedentary time, absolute number of breaks from sedentary time, and break rate (number of breaks per sedentary hour (brk[middle dot]sed-h-1)). Results: Break rate was the only metric sensitive to changes in behavior between baseline (5.1 [3.3-6.8] brk[middle dot]sed-h-1) and treatment conditions (7.3 [4.7-9.8] brk[middle dot]sed-h-1) (mean (95% confidence interval)). The activPAL produced valid estimates of all sedentary behavior measures and was sensitive to changes in break rate between conditions (baseline, 5.1 [2.8-7.1] brk[middle dot]sed-h-1; treatment, 8.0 [5.8-10.2] brk[middle dot]sed-h-1). In general, the AG-LFE and AG-Norm were not accurate in estimating break rate or the absolute number of breaks and were not sensitive to changes between conditions. Conclusion: This study demonstrates the use of expressing breaks from sedentary time as a rate per sedentary hour, a metric specifically relevant to free-living behavior, and provides further evidence that the activPAL is a valid tool to measure components of sedentary behavior in free-living environments. (C)2012The American College of Sports Medicine

Calibration and validation of wearable monitors

Abstract: Background Wearable monitors are increasingly being used to objectively monitor physical activity in research studies within the field of exercise science. Calibration and validation of these devices are vital to obtaining accurate data. This article is aimed primarily at the physical activity measurement specialist, although the end user who is conducting studies with these devices also may benefit from knowing about this topic. Best Practices Initially, wearable physical activity monitors should undergo unit calibration to ensure interinstrument reliability. The next step is to simultaneously collect both raw signal data (e.g., acceleration) from the wearable monitors and rates of energy expenditure, so that algorithms can be developed to convert the direct signals into energy expenditure. This process should use multiple wearable monitors and a large and diverse subject group and should include a wide range of physical activities commonly performed in daily life (from sedentary to vigorous). Future Directions New methods of calibration now use "pattern recognition" approaches to train the algorithms on various activities, and they provide estimates of energy expenditure that are much better than those previously available with the single-regression approach. Once a method of predicting energy expenditure has been established, the next step is to examine its predictive accuracy by cross-validating it in other populations. In this article, we attempt to summarize the best practices for calibration and validation of wearable physical activity monitors. Finally, we conclude with some ideas for future research ideas that will move the field of physical activity measurement forward.

Physical activity classification using the GENEA wrist-worn accelerometer.

Abstract: Introduction: Most accelerometer-based activity monitors are worn on the waist or lower back for assessment of habitual physical activity. Output is in arbitrary counts that can be classified by activity intensity according to published thresholds. The purpose of this study was to develop methods to classify physical activities into walking, running, household, or sedentary activities based on raw acceleration data from the GENEA (Gravity Estimator of Normal Everyday Activity) and compare classification accuracy from a wrist-worn GENEA with a waist-worn GENEA. Methods: Sixty participants (age = 49.4 ± 6.5 yr, body mass index = 24.6 ± 3.4 kg·m-2) completed an ordered series of 10�12 semistructured activities in the laboratory and outdoor environment. Throughout, three GENEA accelerometers were worn: one at the waist, one on the left wrist, and one on the right wrist. Acceleration data were collected at 80 Hz. Features obtained from both fast Fourier transform and wavelet decomposition were extracted, and machine learning algorithms were used to classify four types of daily activities including sedentary, household, walking, and running activities. Results: The computational results demonstrated that the algorithm we developed can accurately classify certain types of daily activities, with high overall classification accuracy for both waist-worn GENEA (0.99) and wrist-worn GENEA (right wrist = 0.97, left wrist = 0.96). Conclusions: We have successfully developed algorithms suitable for use with wrist-worn accelerometers for detecting certain types of physical activities; the performance is comparable to waist-worn accelerometers for assessment of physical activity

Assessment of physical activity using wearable monitors: recommendations for monitor calibration and use in the field.

Abstract: This article provides recommendations for the use of wearable monitors for assessing physical activity. We have provided recommendations for measurement researchers, end users, and developers of activity monitors. We discuss new horizons and future directions in the field of objective measurement of physical activity and present challenges that remain for the future. These recommendations are based on the proceedings from the workshop "Objective Measurement of Physical Activity: Best Practices and Future Direction," held on July 20-21, 2009, and also on data and information presented since the workshop.

Nutritional intake and gastrointestinal problems during competitive endurance events.

Abstract: There is little information about the actual nutrition and fluid intake habits and gastrointestinal (GI) symptoms of athletes during endurance events.PurposeThis study aimed to quantify and characterize energy, nutrient, and fluid intakes during endurance competitions and investigate associa

Blood Pressure Responses to Acute and Chronic Exercise Are Related in Prehypertension

Abstract: LIU, S., J. GOODMAN, R. NOLAN, S. LACOMBE, and S. G. THOMAS. Blood Pressure Responses to Acute and Chronic Exercise Are Related in Prehypertension. Med. Sci. Sports Exerc., Vol. 44, No. 9, pp. 1644–1652, 2012. Purpose: Aerobic exercise is recommended as a way to prevent hypertension. However, about 25% of individuals receive minimal antihypertensive benefits associated with chronic exercise training. Thus, we attempt to identify those ‘‘nonresponders’’ to chronic exercise on the basis of their blood pressure (BP) responses to acute exercise (single session). Our primary objective was to correlate the magnitude of BP decrease after acute exercise to the magnitude of BP reduction after chronic exercise. Our secondary objective was to examine the correlates of BP reduction after acute and chronic exercise. Methods: Seventeen prehypertensive (120 to 139/80 to 89 mm Hg) males and females (45–60 yr old) underwent acute exercise assessments before an 8-wk walking/jogging program (four times per week, 30 min per session, 65% maximum oxygen consumption). BP, hemodynamics, HR variability, and baroreflex sensitivity were assessed before and after acute exercise and chronic training. Results: BP was significantly reduced j7.2 T 1.2/j4.2 T 1.0 and j7.0 T 1.4/j5.2 T 1.2 mm Hg relative to baseline after acute (30 min at 65% maximum oxygen consumption) and chronic exercise, respectively (P G 0.01). The magnitude of change in systolic BP after acute exercise was strongly correlated with change in resting systolic BP after chronic training, r = 0.89, P G 0.01. A similar correlation was observed with diastolic BP, r = 0.75, P G 0.01. After acute exercise, significant reductions in total power (ms 2 ) and baroreflex sensitivity were observed in both sexes (P G 0.01). However, after chronic exercise, only men demonstrated a significant reduction in the low-frequency-to-high-frequency ratio (j36%), P G 0.01. Conclusions: The magnitude of the acute BPlowering with exercise may predict the extent of BP lowering after chronic training interventions in prehypertensive individuals.

Metabolic Cost of Running Barefoot Versus Shod: Is Lighter Better?

Abstract: PURPOSE Based on mass alone, one might intuit that running barefoot would exact a lower metabolic cost than running in shoes. Numerous studies have shown that adding mass to shoes increases submaximal oxygen uptake (V˙O(2)) by approximately 1% per 100 g per shoe. However, only two of the seven studies on the topic have found a statistically significant difference in V˙O(2) between barefoot and shod running. The lack of difference found in these studies suggests that factors other than shoe mass (e.g., barefoot running experience, foot strike pattern, shoe construction) may play important roles in determining the metabolic cost of barefoot versus shod running. Our goal was to quantify the metabolic effects of adding mass to the feet and compare oxygen uptake and metabolic power during barefoot versus shod running while controlling for barefoot running experience, foot strike pattern, and footwear. METHODS Twelve males with substantial barefoot running experience ran at 3.35 m·s with a midfoot strike pattern on a motorized treadmill, both barefoot and in lightweight cushioned shoes (∼150 g per shoe). In additional trials, we attached small lead strips to each foot/shoe (∼150, ∼300, and ∼450 g). For each condition, we measured the subjects' rates of oxygen consumption and carbon dioxide production and calculated metabolic power. RESULTS V˙O(2) increased by approximately 1% for each 100 g added per foot, whether barefoot or shod (P < 0.001). However, barefoot and shod running did not significantly differ in V˙O(2) or metabolic power. A consequence of these two findings was that for footwear conditions of equal mass, shod running had ∼3%-4% lower V˙O(2) and metabolic power demand than barefoot running (P < 0.05). CONCLUSIONS Running barefoot offers no metabolic advantage over running in lightweight, cushioned shoes.

Prevalence of the Portuguese population attaining sufficient physical activity.

Abstract: BAPTISTA, F., D. A. SANTOS, A. M. SILVA, J. MOTA, R. SANTOS, S. VALE, J. P. FERREIRA, A. M. RAIMUNDO, H. MOREIRA, and L. B. SARDINHA. Prevalence of the Portuguese Population Attaining Sufficient Physical Activity. Med. Sci. Sports Exerc., Vol. 44, No. 3, pp. 466–473, 2012. Purpose: Physical activity has many health benefits, and to implement strategies, mainly in those groups with insufficient levels of practice, it is important to evaluate physical activity. The main purpose of this study was to describe the prevalence of physical activity in the Portuguese population aged 10 yr and older using accelerometry. Methods: The accelerometers were worn for four consecutive days, and a valid record was defined as at least 3 d with 10 h of wear time, including one weekend day. Considering these conditions, 4696 participants were included. Results: According to the recommendations of 60 minId j1 of physical activity, 36% of participants age 10–11 yr (boys = 51.6%, girls = 22.5%) and 4% age 16–17 yr (boys = 7.9%, girls = 1.2%) were considered sufficiently active. In adulthood, E70% of participants age 18–64 yr (men = 76.6%, women = 65.2%) and 35% age older than 64 yr (men = 46%, women = 29%) reached the recommendation of 30 minId j1 of physical activity, when counting every minute of moderate or greater intensity. Considering bouts of 10 min or more of moderate or greater intensity in participants older than 17 yr, the prevalence was 4%–6% at 18–39 yr, 7%–9% at 40–64 yr, and E3% in persons age 65 yr or older. Conclusions: The design and implementation of strategies to promote physical activity for health among children and adolescents and older adults, particularly girls/women, should be encouraged.

Protein ingestion before sleep improves postexercise overnight recovery.

Abstract: IntroductionThe role of nutrition in modulating postexercise overnight recovery remains to be elucidated. We assessed the effect of protein ingestion immediately before sleep on digestion and absorption kinetics and protein metabolism during overnight recovery from a single bout of resistanc

Daily step target to measure adherence to physical activity guidelines in children.

Abstract: PurposeThere is a lack of robust evidence to support a daily step count target that equates to current physical activity guidelines in children and youth. This information would be useful to researchers and practitioners who are using pedometers to monitor physical activity.MethodsAccelerome

Scheduled exercise phase shifts the circadian clock in skeletal muscle.

Abstract: AB Purpose: It has been well established in mammals that circadian behavior as well as the molecular clockwork can be synchronized to the light-dark cycle via the suprachiasmatic nucleus of the hypothalamus (SCN). In addition to light, it has been demonstrated that nonphotic time cues, such as restricting the time of food availability, can alter circadian behavior and clock gene expression in selected peripheral tissues such as the liver. Studies have also suggested that scheduled physical activity (exercise) can alter circadian rhythms in behavior and clock gene expression; however, currently, the effects of exercise alone are largely unknown and have not been explored in skeletal muscle. Methods: Period2::Luciferase (Per2::Luc) mice were maintained under 12 h of light followed by 12 h of darkness then exposed to 2 h of voluntary or involuntary exercise during the light phase for 4 wk. Control mice were left in home cages or moved to the exercise environment (sham). A second group of mice had restricted access to food (4 h[middle dot]d-1 for 2 wk) to compare the effects of two nonphotic cues on PER2::LUC bioluminescence. Skeletal muscle, lung, and SCN tissue explants were cultured for 5-6 d to study molecular rhythms. Results: In the exercised mice, the phase of peak PER2::LUC bioluminescence was shifted in the skeletal muscle and lung explants but not in the SCN suggesting a specific synchronizing effect of exercise on the molecular clockwork in peripheral tissues. Conclusions: These data provide evidence that the molecular circadian clock in peripheral tissues can respond to the time of exercise suggesting that physical activity contributes important timing information for synchronization of circadian clocks throughout the body. (C)2012The American College of Sports Medicine

Validity of the occupational sitting and physical activity questionnaire

Abstract: Purpose: Sitting at work is an emerging occupational health risk. Few instruments designed for use in population-based research measure occupational sitting and standing as distinct behaviors. This study aimed to develop and validate brief measure of occupational sitting and physical activity. Methods: A convenience sample (n = 99, 61% female) was recruited from two medium-sized workplaces and by word-of-mouth in Sydney, Australia. Participants completed the newly developed Occupational Sitting and Physical Activity Questionnaire (OSPAQ) and a modified version of the MONICA Optional Study on Physical Activity Questionnaire (modified MOSPA-Q) twice, 1 wk apart. Participants also wore an ActiGraph accelerometer for the 7 d in between the test and retest. Analyses determined test�retest reliability with intraclass correlation coefficients and assessed criterion validity against accelerometers using the Spearman ?. Results: The test�retest intraclass correlation coefficients for occupational sitting, standing, and walking for OSPAQ ranged from 0.73 to 0.90, while that for the modified MOSPA-Q ranged from 0.54 to 0.89. Comparison of sitting measures with accelerometers showed higher Spearman correlations for the OSPAQ (r = 0.65) than for the modified MOSPA-Q (r = 0.52). Criterion validity correlations for occupational standing and walking measures were comparable for both instruments with accelerometers (standing: r = 0.49; walking: r = 0.27�0.29). Conclusions: The OSPAQ has excellent test�retest reliability and moderate validity for estimating time spent sitting and standing at work and is comparable to existing occupational physical activity measures for assessing time spent walking at work. The OSPAQ brief instrument measures sitting and standing at work as distinct behaviors and would be especially suitable in national health surveys, prospective cohort studies, and other studies that are limited by space constraints for questionnaire items.

Redefining the roles of sensors in objective physical activity monitoring.

Abstract: BackgroundBecause physical activity researchers are increasingly using objective portable devices, this review describes the current state of the technology to assess physical activity, with a focus on specific sensors and sensor properties currently used in monitors and their strengths and

Clinical pilates versus general exercise for chronic low back pain: randomized trial.

Abstract: This single-assessor-blinded randomized controlled trial aimed to compare the efficacy of physiotherapy-delivered clinical Pilates and general exercise for chronic low back pain. Methods: Eighty-seven community volunteers with low back pain for >=3 months and age 18-70 were randomized to either the Pilates (n = 44) or general exercise (n = 43) group. The primary outcome was pain/disability measured with the Quebec scale. Secondary outcomes included pain on a numeric rating scale, Patient-Specific Functional Scale, Pain Self-efficacy Questionnaire, quality of life, and global perceived effect of treatment. All participants attended 60-min exercise sessions twice weekly for 6 wk supervised by a physiotherapist and performed daily home exercises that were continued during the follow-up. Participants from the clinical Pilates group received an individualized direction-specific exercise program prescribed by the physiotherapist after a clinical examination. The general exercise group received a generic set of exercises that were multidirectional and nonspecific. Outcomes were assessed after 6 wk (primary time point) and at 12 and 24 wk. Differences in mean change were compared between groups using ANCOVA adjusted for baseline values of the outcome. Results: Eighty-three participants (96%) completed the 6-wk intervention and 60 (69%) completed the 24-wk follow-up. At 6 wk, no difference was found between groups for change in the Quebec scale (3.5, 95% confidence interval = -7.3 to 0.3, P = 0.07); both groups showed significant improvements. Similar results were found at the 12- and 24-wk follow-up and for the secondary outcome measures. Conclusions: An individualized clinical Pilates program produced similar beneficial effects on self-reported disability, pain, function and health-related quality of life as a general exercise program in community volunteers with chronic low back pain. (C)2012The American College of Sports Medicine

Muscular Interleukin-6 and Its Role as an Energy Sensor

Abstract: During recent years, accumulating data have shown that muscle cells are able to produce and secrete several hundred myokines. The finding that muscles produce and release myokines provides a conceptual basis for understanding some of the molecular mechanisms underlying organ cross talk, including muscle�liver and muscle�fat cross talk. The myokine prototype is interleukin-6 (IL-6). During exercise, contracting skeletal muscles release IL-6. It seems that IL-6 works as an energy sensor and exerts both local and endocrine metabolic effects. Given that the skeletal muscle is the largest organ in the human body, the discovery of contracting muscle as a cytokine-producing organ opens for a whole new paradigm: If the endocrine function of the muscle is not stimulated through contractions, it will cause malfunction of several organs and tissues of the body.