Showing papers in "Medicine and Science in Sports and Exercise in 2004"

Exercise and Hypertension

Abstract: SUMMARY Hypertension (HTN), one of the most common medical disorders, is associated with an increased incidence of all-cause and cardiovascular disease (CVD) mortality. Lifestyle modifications are advocated for the prevention, treatment, and control of HTN, with exercise being an integral component. Exercise programs that primarily involve endurance activity prevent the development of HTN and lower blood pressure (BP) in adults with normal BP and those with HTN. The BP lowering effects of exercise are most pronounced in people with HTN who engage in endurance exercise with BP decreasing approximately 5–7 mm Hg after an isolated exercise session (acute) or following exercise training (chronic). Moreover, BP is reduced for up to 22 h after an endurance exercise bout (e.g., postexercise hypotension), with the greatest decreases among those with the highest baseline BP. The proposed mechanisms for the BP lowering effects of exercise include neurohumoral, vascular, and structural adaptations. Decreases in catecholamines and total peripheral resistance, improved insulin sensitivity, and alterations in vasodilators and vasoconstrictors are some of the postulated explanations for the antihypertensive effects of exercise. Emerging data suggest genetic links to the BP reductions associated with acute and chronic endurance exercise. Nonetheless, definitive conclusions regarding the mechanisms for the BP reductions following endurance exercise cannot be made at this time. Individuals with controlled HTN and no CVD or renal complications may participate in an exercise program or competitive athletics, but should be evaluated, treated, and monitored closely. Preliminary peak or symptom-limited exercise testing may be warranted, especially for men over 45 and women over 55 yr planning a vigorous exercise program (i.e., 60% u VO2R, oxygen uptake reserve). In the interim, while formal evaluation and management are taking place, it is reasonable for the majority of patients to begin moderate intensity exercise training (40 –60% u VO2R) such as walking. When pharmacologic therapy is indicated in physically active people it should, ideally: a) lower BP at rest and during exertion; b) decrease total peripheral resistance; and, c) not adversely affect exercise capacity. For these reasons, angiotensin converting enzyme (ACE) inhibitors (or angiotensin II receptor blockers in case of ACE inhibitor intolerance) and calcium channel blockers are currently the drugs of choice for recreational exercisers and athletes who have HTN. Exercise remains a cornerstone therapy for the primary prevention, treatment, and control of HTN. The optimal training frequency, intensity, time, and type (FITT) need to be better defined to optimize the BP lowering capacities of exercise, particularly in children, women, older adults, and

Fundamentals of resistance training: progression and exercise prescription.

Abstract: KRAEMER, W. J., and N. A. RATAMESS. Fundamentals of Resistance Training: Progression and Exercise Prescription. Med. Sci. Sports Exerc., Vol. 36, No. 4, pp. 674–688, 2004. Progression in resistance training is a dynamic process that requires an exercise prescription process, evaluation of tr

Use of RPE-based training load in soccer

Abstract: Purpose The ability to accurately control and monitor internal training load is an important aspect of effective coaching. The aim of this study was to apply in soccer the RPE-based method proposed by Foster et al. to quantify internal training load (session-RPE) and to assess its correlations with various methods used to determine internal training load based on the HR response to exercise. Methods Nineteen young soccer players (mean +/- SD: age 17.6 +/- 0.7 yr, weight 70.2 +/- 4.7 kg, height 178.5 +/- 4.8 cm, body fat 7.5 +/- 2.2%, VO2max, 57.1 +/- 4.0 mL x kg x min) were involved in the study. All subjects performed an incremental treadmill test before and after the training period during which lactate threshold (1.5 mmol x L above baseline) and OBLA (4.0 mmol x L) were determined. The training loads completed during the seven training weeks were determined multiplying the session RPE (CR10-scale) by session duration in minutes. These session-RPE values were correlated with training load measures obtained from three different HR-based methods suggested by Edwards, Banister, and Lucia, respectively. Results Individual internal loads of 479 training sessions were collected. All individual correlations between various HR-based training load and session-RPE were statistically significant (from r = 0.50 to r = 0.85, P Conclusion The results of this study show that the session-RPE can be considered a good indicator of global internal load of soccer training. This method does not require particular expensive equipment and can be very useful and practical for coaches and athletic trainer to monitor and control internal load, and to design periodization strategies.

Physical activity levels and patterns of 9- and 15-yr-old European children.

Abstract: RIDDOCH, C. J., L. B. ANDERSEN, N. WEDDERKOPP, M. HARRO, L. KLASSON-HEGGEBO, L. B. SARDINHA, A. R. COOPER, and U. EKELUND. Physical Activity Levels and Patterns of 9- and 15-yr-Old European Children. Med. Sci. Sports Exerc., Vol. 36, No. 1, pp. 86–92, 2004.PurposeThe purpose of this study wa

Core stability measures as risk factors for lower extremity injury in athletes.

Abstract: LEETUN, D. T., M. L. IRELAND, J. D. WILLSON, B. T. BALLANTYNE, and I. M. DAVIS. Core Stability Measures as Risk Factors for Lower Extremity Injury in Athletes. Med. Sci. Sports Exerc., Vol. 36, No. 6, pp. 926 –934, 2004. Introduction/Purpose: Decreased lumbo-pelvic (or core) stability has been suggested to contribute to the etiology of lower extremity injuries, particularly in females. This prospective study compares core stability measures between genders and between athletes who reported an injury during their season versus those who did not. Finally, we looked for one or a combination of these strength measures that could be used to identify athletes at risk for lower extremity injury. Methods: Before their season, 80 female (mean age 19.1 1.37 yr, mean weight 65.1 10.0 kg) and 60 male (mean age 19.0 0.90 yr, mean weight 78.8 13.3 kg) intercollegiate basketball and track athletes were studied. Hip abduction and external rotation strength, abdominal muscle function, and back extensor and quadratus lumborum endurance was tested for each athlete. Results: Males produced greater hip abduction (males 32.6 7.3%BW, females 29.2 6.1%BW), hip external rotation (males 21.6 4.3%BW, females 18.4 4.1%BW), and quadratus lumborum measures (males 84.3 32.5 s, females 58.9 26.0 s). Athletes who did not sustain an injury were significantly stronger in hip abduction (males 31.6 7.1%BW, females 28.6 5.5%BW) and external rotation (males 20.6 4.2%BW, females 17.9 4.4%BW). Logistic regression analysis revealed that hip external rotation strength was the only useful predictor of injury status (OR 0.86, 95% CI 0.77, 0.097). Conclusion: Core stability has an important role in injury prevention. Future study may reveal that differences in postural stability partially explain the gender bias among female athletes. Key Words: GENDER, HIP STRENGTH, TRUNK ENDURANCE, BASKETBALL, TRACK

Physical Activity and Bone Health

Abstract: Weight-bearing physical activity has beneficial effects on bone health across the age spectrum. Physical activities that generate relatively highintensity loading forces, such as plyometrics, gymnastics, and high-intensity resistance training, augment bone mineral accrual in children and adolescents. Further, there is some evidence that exercise-induced gains in bone mass in children are maintained into adulthood, suggesting that physical activity habits during childhood may have long-lasting benefits on bone health. It is not yet possible to describe in detail an exercise program for children and adolescents that will optimize peak bone mass, because quantitative dose-response studies are lacking. However, evidence from multiple small randomized, controlled trials suggests that the following exercise prescription will augment bone mineral accrual in children and adolescents:

Pedometer measures of free-living physical activity: comparison of 13 models.

Abstract: PATRICK L. SCHNEIDER, SCOTT E. CROUTER, and DAVID R. BASSETT, JR. Pedometer Measures of Free-Living Physical Activity: Comparison of 13 Models. Med. Sci. Sports Exerc., Vol. 36, No. 2, pp. 331–335, 2004.PurposeThe purpose of this study was to compare the step values of multiple brands of ped

Defining Accelerometer Thresholds for Activity Intensities in Adolescent Girls

Abstract: Purpose To derive a regression equation that estimates metabolic equivalent (MET) from accelerometer counts, and to define thresholds of accelerometer counts that can be used to delineate sedentary, light, moderate, and vigorous activity in adolescent girls.

Development and validation of a Pregnancy Physical Activity Questionnaire.

Abstract: CHASAN-TABER, L., M. D. SCHMIDT, D. E. ROBERTS, D. HOSMER, G. MARKENSON, and P. S. FREEDSON. Development and Validation of a Pregnancy Physical Activity Questionnaire. Med. Sci. Sports Exerc., Vol. 36, No. 10, pp. 1750 –1760, 2004. Purpose: The effect of physical activity during pregnancy on maternal and fetal health remains controversial and studies have yet to identify the optimal dose of physical activity associated with favorable pregnancy outcomes. The aim of this study was to develop and validate a pregnancy physical activity questionnaire (PPAQ). Methods: To ascertain the type, duration, and frequency of physical activities performed by pregnant women, three 24-h physical activity recalls were administered to 235 ethnically diverse prenatal care patients at a large tertiary care facility in western Massachusetts. The relative contribution of each activity to between-person variance in energy expenditure was used to establish the list of activities for the PPAQ. The PPAQ is self-administered and asks respondents to report the time spent participating in 32 activities including household/caregiving, occupational, sports/exercise, transportation, and inactivity. To validate the PPAQ, 54 pregnant women completed the PPAQ and then wore a Manufacturing Technology, Inc. actigraph for the following 7 d. At the end of the 7-d period, the PPAQ was repeated. Results: Intraclass correlation coefficients used to measure reproducibility of the PPAQ were 0.78 for total activity, 0.82 for moderate activity, 0.81 for vigorous activity, and ranged from 0.83 for sports/exercise to 0.93 for occupational activity. Spearman correlations between the PPAQ and three published cut points used to classify actigraph data ranged from 0.08 to 0.43 for total activity, 0.25 to 0.34 for vigorous activity, 0.20 to 0.49 for moderate activity, and 0.08 to 0.22 for light-intensity activity. Correlations were higher for sports/exercise and occupational activities as compared to household/caregiving activities. Conclusions: The PPAQ is a reliable instrument and a reasonably accurate measure of a broad range of physical activities during pregnancy. Key Words: ACTIVITY ASSESSMENT, EPIDEMIOLOGIC METHODS, EXERCISE, REPRODUCIBILITY OF RESULTS, WOMEN

The impact of stretching on sports injury risk: a systematic review of the literature.

Abstract: THACKER, S. B., J. GILCHRIST, D. F. STROUP, and C. D. KIMSEY, JR. The Impact of Stretching on Sports Injury Risk: A Systematic Review of the Literature. Med. Sci. Sports Exerc., Vol. 36, No. 3, pp. 371–378, 2004. Purpose: We conducted a systematic review to assess the evidence for the effectiveness of stretching as a tool to prevent injuries in sports and to make recommendations for research and prevention. Methods: Without language limitations, we searched electronic data bases, including MEDLINE (1966 –2002), Current Contents (1997–2002), Biomedical Collection (1993–1999), the Cochrane Library, and SPORTDiscus, and then identified citations from papers retrieved and contacted experts in the field. Meta-analysis was limited to randomized trials or cohort studies for interventions that included stretching. Studies were excluded that lacked controls, in which stretching could not be assessed independently, or where studies did not include subjects in sporting or fitness activities. All articles were screened initially by one author. Six of 361 identified articles compared stretching with other methods to prevent injury. Data were abstracted by one author and then reviewed independently by three others. Data quality was assessed independently by three authors using a previously standardized instrument, and reviewers met to reconcile substantive differences in interpretation. We calculated weighted pooled odds ratios based on an intention-to-treat analysis as well as subgroup analyses by quality score and study design. Results: Stretching was not significantly associated with a reduction in total injuries (OR 0.93, CI 0.78 –1.11) and similar findings were seen in the subgroup analyses. Conclusion: There is not sufficient evidence to endorse or discontinue routine stretching before or after exercise to prevent injury among competitive or recreational athletes. Further research, especially well-conducted randomized controlled trials, is urgently needed to determine the proper role of stretching in sports. Key Words: ATHLETES, CONDITIONING, META-ANALYSIS, SYNTHESIS

Prediction of activity energy expenditure using accelerometers in children.

Abstract: PUYAU, M. R., A. L. ADOLPH, F. A. VOHRA, I. ZAKERI, and N. F. BUTTE. Prediction of Activity Energy Expenditure Using Accelerometers in Children. Med. Sci. Sports Exerc., Vol. 36, No. 9, pp. 1625–1631, 2004. Purpose: To validate two accelerometerbased activity monitors as measures of children’s physical activity using energy expenditure as the criterion measure. Methods: Actiwatch (AW) and Actical (AC) activity monitors were validated against continuous 4-h measurements of energy expenditure (EE) in a respiratory room calorimeter and 1-h measurements in an exercise laboratory using a portable calorimeter and treadmill in 32 children, ages 7–18 yr. The children performed structured activities including basal metabolic rate (BMR), playing Nintendo, using a computer, cleaning, aerobic exercise, ball toss, treadmill walking, and running. Equations were developed to predict activity energy expenditure (AEE EE BMR), and physical activity ratio (PAR EE/BMR) from a power function of AW or AC, and age, sex, weight, and height. Thresholds were determined to categorize sedentary, light, moderate, and vigorous levels of physical activity. Results: Activity counts accounted for the majority of the variability in AEE and PAR, with small contributions of age, sex, weight, and height. Overall, AW equations accounted for 76 –79% and AC equations accounted for 81% of the variability in AEE and PAR. Relatively wide 95% prediction intervals suggest the accelerometers are best applied to groups rather than individuals. Sensitivities were higher for the vigorous threshold (97%) than the other thresholds (86 –92%). Specificities were on the order of 66 –73%. The positive predictive values for sedentary, light, moderate, and vigorous categories were 80, 66, 69, and 74% for AW, respectively, and 81, 68, 72, 74% for AC, respectively. Conclusion: Both accelerometer-based activity monitors provided valid measures of children’s AEE and PAR, and can be used to discriminate sedentary, light, moderate, and vigorous levels of physical activity but require further development to accurately predict AEE and PAR of individuals. Key Words: MOTION SENSORS, ACTIWATCH, ACTICAL, CALORIMETRY, EXERCISE, THRESHOLDS

Physical fitness, injuries, and team performance in soccer.

Abstract: ARNASON, A., S. B. SIGURDSSON, A. GUDMUNDSSON, I. HOLME, L. ENGEBRETSEN, and R. BAHR. Physical Fitness, Injuries, and Team Performance in Soccer. Med. Sci. Sports Exerc., Vol. 36, No. 2, pp. 278 –285, 2004. Purpose: To investigate the relationship between physical fitness and team success in soccer, and to test for differences in physical fitness between different player positions. Methods: Participants were 306 male soccer players from 17 teams in the two highest divisions in Iceland. Just before the start of the 1999 soccer season, the following variables were tested: height and weight, body composition, flexibility, leg extension power, jump height, and peak O2 uptake. Injuries and player participation in matches and training were recorded through the 4-month competitive season. Team average physical fitness was compared with team success (final league standing) using a linear regression model. Physical fitness was also compared between players in different playing positions. Results: A significant relationship was found between team average jump height (countermovement jump and standing jump) and team success (P 0.009 and P 0.012, respectively). The same trend was also found for leg extension power (P 0.097), body composition (% body fat, P 0.07), and the total number of injury days per team (P 0.09). Goalkeepers demonstrated different fitness characteristics from outfield players. They were taller and heavier, more flexible in hip extension and knee flexion, and had higher leg extension power and a lower peak O2 uptake. However, only minor differences were observed between defenders, midfield players, and attackers. Conclusion: Coaches and medical support teams should pay more attention to jump and power training, as well as preventive measures and adequate rehabilitation of previous injuries to increase team success. Key Words: PHYSICAL PERFORMANCE, MAXIMAL O 2 UPTAKE, JUMPING ABILITY, LEG POWER, FLEXIBILITY, BODY COMPOSITION

Impact and overuse injuries in runners.

Abstract: Forces that are repeatedly applied to the body could lead to positive remodeling of a structure if the forces fall below the tensile limit of the structure and if sufficient time is provided between force applications. On the other hand, an overuse injury could result if there is inadequate rest time between applied forces. Running is one of the most widespread activities during which overuse injuries of the lower extremity occur. The purpose of this article is to review the current state of knowledge related to overuse running injuries, with a particular emphasis on the effect of impact forces. Recent research has suggested that runners who exhibit relatively large and rapid impact forces while running are at an increased risk of developing an overuse injury of the lower extremity. Modifications in training programs could help an injured runner return to running with decreased rehabilitation time, but it would be preferable to be able to advise a runner regarding injury potential before undertaking a running program. One of the goals of future research should be to focus on the prevention or early intervention of running injuries. This goal could be accomplished if some easily administered tests could be found which would predict the level of risk that a runner may encounter at various levels of training intensity, duration, and frequency. The development of such a screening process may assist medical practitioners in identifying runners who are at a high risk of overuse injury.

Effect of gender and defensive opponent on the biomechanics of sidestep cutting

Abstract: MCLEAN, S. G., S. W. LIPFERT, and A. J. VAN DEN BOGERT. Effect of Gender and Defensive Opponent on the Biomechanics of Sidestep Cutting. Med. Sci. Sports Exerc., Vol. 36, No. 6, pp. 1008 –1016, 2004. Purpose: Anterior cruciate ligament (ACL) injuries often occur in women during cutting maneuvers to evade a defensive player. Gender differences in knee kinematics have been observed, but it is not known to what extent these are linked to abnormal neuromuscular control elsewhere in the kinetic chain. Responses to defense players, which may be gender-dependent, have not been included in previous studies. This study determined the effects of gender and defense player on entire lower extremity biomechanics during sidestepping. Methods: Eight male and eight female subjects performed sidestep cuts with and without a static defensive opponent while 3D motion and ground reaction force data were recorded. Peak values of eight selected motion and force variables were, as well as their between-trial variabilities, submitted to a two-way (defense gender) ANOVA. A Bonferroni-corrected alpha level of 0.003 denoted statistical significance. Results: Females had less hip and knee flexion, hip and knee internal rotation, and hip abduction. Females had higher knee valgus and foot pronation angles, and increased variability in knee valgus and internal rotation. Increased medial ground reaction forces and flexion and abduction in the hip and knee occurred with the defensive player for both genders. Conclusions: A simulated defense player causes increased lower limb movements and forces, and should be a useful addition to laboratory protocols for sidestepping. Gender differences in the joint kinematics suggest that increased knee valgus may contribute to ACL injury risk in women, and that the hip and ankle may play an important role in controlling knee valgus during sidestepping. Consideration of the entire lower extremity contributes to an understanding of injury mechanisms and may lead to better training programs for injury prevention. Key Words: ANTERIOR CRUCIATE LIGAMENT, INJURY, LOWER LIMB KINEMATICS, SIMULATED DEFENSE, FEMALES, NEUROMUSCULAR CONTROL

Reliability of accelerometry-based activity monitors: a generalizability study.

Abstract: Introduction Numerous studies have examined the validity of accelerometry-based activity monitors but few studies have systematically studied the reliability of different accelerometer units for assessing a standardized bout of physical activity. Improving understanding of error in these devices is an important research objective because they are increasingly being used in large surveillance studies and intervention trials that require the use of multiple units over time. Methods Four samples of college-aged participants were recruited to collect reliability data on four different accelerometer types (CSA/MTI, Biotrainer Pro, Tritrac-R3D, and Actical). The participants completed three trials of treadmill walking (3 mph) while wearing multiple units of a specific monitor type. For each trial, the participant completed a series of 5-min bouts of walking (one for each monitoring unit) with 1-min of standing rest between each bout. Generalizability (G) theory was used to quantify variance components associated with individual monitor units, trials, and subjects as well as interactions between these terms. Results The overall G coefficients range from 0.43 to 0.64 for the four monitor types. Corresponding intraclass correlation coefficients (ICC) ranged from 0.62 to 0.80. The CSA/MTI was found to have the least variability across monitor units and trials and the highest overall reliability. The Actical was found to have the poorest reliability. Conclusion The CSA/MTI appeared to have acceptable reliability for most research applications (G values above 0.60 and ICC values above 0.80), but values with the other devices indicate some possible concerns with reliability. Additional work is needed to better understand factors contributing to variability in accelerometry data and to determine appropriate calibration protocols to improve reliability of these measures for different research applications.

The effect of carbohydrate mouth rinse on 1-h cycle time trial performance

Abstract: PURPOSE AND METHOD: To investigate the possible role of carbohydrate (CHO) receptors in the mouth in influencing exercise performance, seven male and two female endurance cyclists (VO(2max) 63.2 +/- 2.7 (mean +/- SE) mL.kg*(-1).min(-1)) completed two performance trials in which they had to accomplish a set amount of work as quickly as possible (914 +/- 40 kJ). On one occasion a 6.4% maltodextrin solution (CHO) was rinsed around the mouth for every 12.5% of the trial completed. On the other occasion, water (PLA) was rinsed. Subjects were not allowed to swallow either the CHO solution or water, and each mouthful was spat out after a 5-s rinse. RESULTS: Performance time was significantly improved with CHO compared with PLA (59.57 +/- 1.50 min vs 61.37 +/- 1.56 min, respectively, P = 0.011). This improvement resulted in a significantly higher average power output during the CHO compared with the PLA trial (259 +/- 16 W and 252 +/- 16 W, respectively, P = 0.003). There were no differences in heart rate or rating of perceived exertion (RPE) between the two trials (P > 0.05). CONCLUSION: The results demonstrate that carbohydrate mouth rinse has a positive effect on 1-h time trial performance. The mechanism responsible for the improvement in high-intensity exercise performance with exogenous carbohydrate appears to involve an increase in central drive or motivation rather than having any metabolic cause. The nature and role of putative CHO receptors in the mouth warrants further investigation.

An acute bout of static stretching: effects on force and jumping performance.

Abstract: Static stretching (SS) is used pervasively throughout the exercise science and sporting communities as a fundamental element of the pre-exercise warm-up procedure. While SS has been proven effective to increase range of motion (ROM), its proposed benefits are questionable and relatively unsubstantiated. Moreover, in recent years researchers have demonstrated that pre-exercise SS may in fact be detrimental to subsequent performance due to impaired force and power output. Yet the practical application of these relatively recent findings is limited due to the prolonged SS protocols utilized. In addition, timelines associated with enhanced ROM and performance decrements have not been established. Thus, the objectives of this study were to determine if a typical SS routine decreased force, activation, and power while improving ROM. Secondly, the study attempted to compare the duration of the performance decrement to the duration of the augmented ROM.

Reliability and validity of the International Physical Activity Questionnaire (IPAQ).

Abstract: Dear Editor-in-Chief:In the August 2003 issue of Medicine & Science in Sports & Exercise®, Craig et al. (2) published an important article on the validation of the International Physical Activity Questionnaire (IPAQ). Lack of comparability was always a major limitation among studies aim

Evaluation of the SenseWear Pro Armband to assess energy expenditure during exercise.

Abstract: JAKICIC, J. M., M. MARCUS, K. I. GALLAGHER, C. RANDALL, E. THOMAS, F. L. GOSS, and R. J. ROBERTSON. Evaluation of the SenseWear Pro Armband™ to Assess Energy Expenditure during Exercise. Med. Sci. Sports Exerc., Vol. 36, No. 5, pp. 897–904, 2004.Purpose:To assess the accuracy of the SenseWea

Interaction of Step Length and Step Rate during Sprint Running

Abstract: HUNTER, J. P., R. N. MARSHALL, and P. J. MCNAIR. Interaction of Step Length and Step Rate during Sprint Running.Med. Sci. Sports Exerc., Vol. 36, No. 2, pp. 261–271, 2004. A “negative interaction” between step length and step rate refers to an increase in one factor resulting in a decrease in the other. Purposes: There were three main purposes: a) to investigate the relative influence of the determinants of step length and step rate, b) to determine the sources of negative interaction between step length and step rate, and c) to investigate the effects of manipulation of this interaction. Methods: Thirty-six athletes performed maximal-effort sprints. Video and ground reaction force data were collected at the 16-m mark. Sprint velocity, step length, step rate, and their underlying determinants were calculated. Analyses included correlations, multiple linear regressions, paired t-tests, and a simple simulation based on alterations in flight determining parameters. Results: A wide range of step length and step rate combinations was evident, even for subgroups of athletes with similar sprint velocities. This was partly due to a negative interaction that existed between step length and step rate; that is, those athletes who used a longer step length tended to have a lower step rate and vice versa. Vertical velocity of takeoff was the most prominent source of the negative interaction. Conclusions: Leg length, height of takeoff, and vertical velocity of takeoff are all possible sources of a negative interaction between step length and step rate. The very high step lengths and step rates achieved by elite sprinters may be possible only by a technique that involves a high horizontal and low vertical velocity of takeoff. However, a greater vertical velocity of takeoff might be of advantage when an athlete is fatigued and struggling to maintain a high step rate. Key Words: STRIDE LENGTH, STRIDE RATE, NEGATIVE INTERACTION, GROUND REACTION IMPULSE

Validity of a multi-sensor armband in estimating rest and exercise energy expenditure.

Abstract: FRUIN, M. L., and J. WALBERG RANKIN. Validity of a Multi-Sensor Armband in Estimating Rest and Exercise Energy Expenditure. Med. Sci. Sports Exerc., Vol. 36, No. 6, pp. 1063–1069, 2004. The SenseWear™ Armband (SWA; BodyMedia, Inc.), using multiple sensors, was designed to estimate energy exp

Effect of acute static stretching on force, balance, reaction time, and movement time.

Abstract: BEHM, D. G., A. BAMBURY, F. CAHILL, and K. POWER. Effect of Acute Static Stretching on Force, Balance, Reaction Time, and Movement Time. Med. Sci. Sports Exerc., Vol. 36, No. 8, pp. 1397–1402, 2004.Purpose:The purpose of the study was to investigate the effect of an acute bout of lower limb

Ingestion of casein and whey proteins result in muscle anabolism after resistance exercise

Abstract: TIPTON, K. D., T. A. ELLIOTT, M. G. CREE, S. E. WOLF, A. P. SANFORD, and R. R. WOLFE. Ingestion of Casein and Whey Proteins Result in Muscle Anabolism after Resistance Exercise. Med. Sci. Sports Exerc., Vol. 36, No. 12, pp. 2073–2081, 2004. Purpose: Determination of the anabolic response to exercise and nutrition is important for individuals who may benefit from increased muscle mass. Intake of free amino acids after resistance exercise stimulates net muscle protein synthesis. The response of muscle protein balance to intact protein ingestion after exercise has not been studied. This study was designed to examine the acute response of muscle protein balance to ingestion of two different intact proteins after resistance exercise. Methods: Healthy volunteers were randomly assigned to one of three groups. Each group consumed one of three drinks: placebo (PL; N 7), 20 g of casein (CS; N 7), or whey proteins (WH; N 9). Volunteers consumed the drink 1 h after the conclusion of a leg extension exercise bout. Leucine and phenylalanine concentrations were measured in femoral arteriovenous samples to determine balance across the leg. Results: Arterial amino acid concentrations were elevated by protein ingestion, but the pattern of appearance was different for CS and WH. Net amino acid balance switched from negative to positive after ingestion of both proteins. Peak leucine net balance over time was greater for WH (347 50 nmol·min 1 ·100 mL 1 leg) than CS (133 45 nmol·min 1 ·100 mL 1 leg), but peak phenylalanine balance was similar for CS and WH. Ingestion of both CS and WH stimulated a significantly larger net phenylalanine uptake after resistance exercise, compared with the PL (PL 5 15 mg, CS 84 10 mg, WH 62 18 mg). Amino acid uptake relative to amount ingested was similar for both CS and WH (10–15%). Conclusions: Acute ingestion of both WH and CS after exercise resulted in similar increases in muscle protein net balance, resulting in net muscle protein synthesis despite different patterns of blood amino acid responses. Key Words: MUSCLE PROTEIN SYNTHESIS, ARTERIOVENOUS BALANCE, NET MUSCLE PROTEIN BALANCE, MUSCLE BIOPSIES

Validation of the RT3 Triaxial Accelerometer for the Assessment of Physical Activity

Abstract: ROWLANDS, A V, P W M THOMAS, R G ESTON, and R TOPPING Validation of the RT3 Triaxial Accelerometer for the Assessment of Physical Activity Med Sci Sports Exerc, Vol 36, No 3, pp 518–524, 2004PurposeThe aims of this study were to assess and compare the validity of the RT3 acc

Predicting hamstring strain injury in elite athletes.

Abstract: BROCKETT, C. L., D. L. MORGAN, and U. PROSKE. Predicting Hamstring Strain Injury in Elite Athletes. Med. Sci. Sports Exerc., Vol. 36, No. 3, pp. 379–387, 2004.IntroductionEccentric exercise, where the contracting muscle is lengthened, produces microscopic damage in muscle fibers, and sensati

Associations of muscle strength and fitness with metabolic syndrome in men.

Abstract: PURPOSE: To examine the associations for muscular strength and cardiorespiratory fitness with the prevalence of metabolic syndrome among men. METHODS: Participants were 8570 men (20-75 yr) for whom an age-specific muscular strength score was computed by combining the body weight adjusted one-repetition maximum measures for the leg press and the bench press. Cardiorespiratory fitness was quantified by age-specific maximal treadmill exercise test time. RESULTS: Separate age and smoking adjusted logistic regression models revealed a graded inverse association for metabolic syndrome prevalence with muscular strength (beta = -0.37, P or= 30) men, respectively, being strong and fit was associated with lower odds (73%, 69%, and 62% respectively, P < 0.0001) of having prevalent metabolic syndrome. CONCLUSIONS: Muscular strength and cardiorespiratory fitness have independent and joint inverse associations with metabolic syndrome prevalence.

Physical activity levels among breast cancer survivors.

Abstract: IRWIN, M. L., A. MCTIERNAN, L. BERNSTEIN, F. D. GILLILAND, R. BAUMGARTNER, K. BAUMGARTNER, and R. BALLARD-BARBASH. Physical Activity Levels among Breast Cancer Survivors. Med. Sci. Sports Exerc., Vol. 36, No. 9, pp. 1484–1491, 2004.Introduction:Obesity and weight gain are negative prognostic

Evaluation of a Two-Year Middle-School Physical Education Intervention: M-SPAN

Abstract: MCKENZIE, T. L., J. F. SALLIS, J. J. PROCHASKA, T. L. CONWAY, S. J. MARSHALL, and P. ROSENGARD. Evaluation of a Two-Year Middle-School Physical Education Intervention: M-SPAN. Med. Sci. Sports Exerc., Vol. 36, No. 8, pp. 1382–1388, 2004.Purpose:School physical education (PE) is highly recomm

Effects of a carbohydrate-protein beverage on cycling endurance and muscle damage.

Abstract: SAUNDERS, M. J., M. D. KANE, and M. K. TODD. Effects of a Carbohydrate-Protein Beverage on Cycling Endurance and Muscle Damage. Med. Sci. Sports Exerc., Vol. 36, No. 7, pp. 1233–1238, 2004. Introduction: The purpose of this study was to determine whether endurance cycling performance and postexercise muscle damage were altered when consuming a carbohydrate and protein beverage (CHOP; 7.3% and 1.8% concentrations) versus a carbohydrate-only (CHO; 7.3%) beverage. Methods: Fifteen male cyclists (mean V u O2peak 52.6 10.3 mL·kg 1 ·min 1 ) rode a cycle ergometer at 75% V u O2peak to volitional exhaustion, followed 12–15 h later by a second ride to exhaustion at 85% V u O2peak. Subjects consumed 1.8 mL·kg 1 BW of randomly assigned CHO or CHOP beverage every 15 min of exercise, and 10 mL·kg 1 BW immediately after exercise. Beverages were matched for carbohydrate content, resulting in 20% lower total caloric content per administration of CHO beverage. Subjects were blinded to treatment beverage and repeated the same protocol seven to 14 d later with the other beverage. Results: In the first ride (75% V u O2peak), subjects rode 29% longer (P 0.05) when consuming the CHOP beverage (106.3 45.2 min) than the CHO beverage (82.3 32.6 min). In the second ride (85% V u O2peak), subjects performed 40% longer when consuming the CHOP beverage (43.6 12.5 min) than when consuming the CHO beverage (31.2 8.7 min). Peak postexercise plasma CPK levels, indicative of muscle damage, were 83% lower after the CHOP trial (216.3 122.0 U·L 1 ) than the CHO trial (1318.1 1935.6 U·L 1 ). There were no significant differences in exercising levels of V u O2, ventilation, heart rate, RPE, blood glucose, or blood lactate between treatments in either trial. Conclusion: A carbohydrate beverage with additional protein calories produced significant improvements in time to fatigue and reductions in muscle damage in endurance athletes. Further research is necessary to determine whether these effects were the result of higher total caloric content of the CHOP beverage or due to specific protein-mediated mechanisms. Key Words: CYCLING, RECOVERY, SUBSTRATE UTILIZATION, SPORTS DRINKS