The Effects of Warm-up Duration on Cycling Time Trial Performance in Trained Cyclists

. The purpose of this study was to assess the effects of three different warm-up condi-tions on a 5K cycling time trial (TT). Sixteen trained cyclists completed the study. At the first testing session, participants completed a maximal graded exercise test to assess maximal oxygen consumption (VO2max) and a familiarization of the TT. At three subse-quent visits, the participants completed the TT after no warm up, short warm-up of three minutes at 60% VO2max, or long warm-up of ten minutes at 60% VO2max. The warm-up was assigned in randomized order. VO2, heart rate (HR), lactate, power, and speed were assessed after the warm-up, 1K, and completion of the 5K TT. There was no dif-ference between type of warm-up for time, power, cadence, speed, VO2, HR, or lactate levels at the end of the TT. There was no significant difference between type of warm-up for time, VO2 or HR at the end of the 1K split. Warm-up length was not impactful on 5K TT performance or during the first km of the TT in trained cyclists. These results con-flict with previous evidence indicating that a warm-up in endurance events primarily improved VO2 kinetics at the onset of the exercise

Updating ACSM's Recommendations for Exercise Preparticipation Health Screening

The purpose of the American College of Sports Medicine's (ACSM) exercise preparticipation health screening process is to identify individuals who may be at elevated risk for exercise-related sudden cardiac death and/or acute myocardial infarction. Recent studies have suggested that using the current ACSM exercise preparticipation health screening guidelines can result in excessive physician referrals, possibly creating a barrier to exercise participation. In addition, there is considerable evidence that exercise is safe for most people and has many associated health and fitness benefits; exercise-related cardiovascular events are often preceded by warning signs/symptoms; and the cardiovascular risks associated with exercise lessen as individuals become more physically active/fit. Consequently, a scientific roundtable was convened by the ACSM in June 2014 to evaluate the current exercise preparticipation health screening recommendations. The roundtable proposed a new evidence-informed model for exercise preparticipation health screening on the basis of three factors: 1) the individual's current level of physical activity, 2) presence of signs or symptoms and/or known cardiovascular, metabolic, or renal disease, and 3) desired exercise intensity, as these variables have been identified as risk modulators of exercise-related cardiovascular events. Identifying cardiovascular disease risk factors remains an important objective of overall disease prevention and management, but risk factor profiling is no longer included in the exercise preparticipation health screening process. The new ACSM exercise preparticipation health screening recommendations reduce possible unnecessary barriers to adopting and maintaining a regular exercise program, a lifestyle of habitual physical activity, or both, and thereby emphasize the important public health message that regular physical activity is important for all individuals

New preparticipation health screening recommendations: What exercise professionals need to know

Learning Objectives From this article, the readers should understand the following: • The rationale for updating the ACSM exercise preparticipation screening procedures • How to use the updated ACSM exercise preparticipation screening recommendations • How to use the newly developed exercise preparticipation health screening questionnaire for exercise professionals tool

Cardiovascular, Metabolic and Perceptual Responses to Preferred Walking Speed at Different Inclines and Post Exercise Postural Control in Healthy College Age Adults

Although several studies investigated heart rate (HR) and metabolic responses to preferred walking speed (PWS), there is a limited amount of data on PWS responses during varying inclines. Further, there is no data pertaining to the impact of PWS at various inclines on postural control. The purpose of the study was to measure cardiovascular, metabolic, perceptual, and postural impacts of walking at PWS at various inclines. Twenty-one participants completed two lab sessions, seven days apart. On day one, PWS on the treadmill and maximal oxygen consumption (O2max) were established for each participant. On day two, using a counter balanced design, participants completed three, 15-minute walking sessions at their PWS at 0, 4, and 8% inclines. During the sessions, HR, O2, rating of perceived exertion (RPE), O2 reserve (O2R) and HR reserve (HRR) were measured and recorded. Center of Pressure (COP) motion was recorded while standing upon a force plate immediately following each walking bout with eyes closed (EC) and eyes open (EO). The results of the study demonstrated a significant difference (

Applying the ACSM preparticipation screening algorithm to U.S. adults: National health and nutrition examination survey 2001-2004

Purpose For most people, the benefits of physical activity far outweigh the risks. Research has suggested that exercise preparticipation questionnaires might refer an unwarranted number of adults for medical evaluation before exercise initiation, creating a potential barrier to adoption. The new American College of Sports Medicine (ACSM) prescreening algorithm relies on current exercise participation; history and symptoms of cardiovascular, metabolic, or renal disease; and desired exercise intensity to determine referral status. Our purpose was to compare the referral proportion of the ACSM algorithm to that of previous screening tools using a representative sample of U.S. adults. Methods On the basis of responses to health questionnaires from the 2001-2004 National Health and Nutrition Examination Survey, we calculated the proportion of adults 40 yr or older who would be referred for medical clearance before exercise participation based on the ACSM algorithm. Results were stratified by age and sex and compared with previous results for the ACSM/American Heart Association Preparticipation Questionnaire and the Physical Activity Readiness Questionnaire. Results On the basis of the ACSM algorithm, 2.6% of adults would be referred only before beginning vigorous exercise and 54.2% of respondents would be referred before beginning any exercise. Men were more frequently referred before vigorous exercise, and women were more frequently referred before any exercise. Referral was more common with increasing age. The ACSM algorithm referred a smaller proportion of adults for preparticipation medical clearance than the previously examined questionnaires. Conclusions Although additional validation is needed to determine whether the algorithm correctly identifies those at risk for cardiovascular complications, the revised ACSM algorithm referred fewer respondents than other screening tools. A lower referral proportion may mitigate an important barrier of medical clearance from exercise participation

Pre-Practice Hydration Status and the Effects of Hydration Regimen on Collegiate Division III Male Athletes

Pre-practice euhydration is key in the prevention of heat related injuries. The pre-practice hydration status of male National Collegiate Athletic Association (NCAA)-Division III athletes and the effects of a direct hydration regimen have yet to be investigated therefore; the aim of the study was 1) to analyze the pre-practice hydration status of current NCAA-DIII male athletes and 2) assess the impact of a directed intervention on pre-practice hydration status. The study was divided into baseline, pre and post intervention phases. For baseline, hydration status through urine specific gravity (USG) and anthropometric indices were measured prior to morning practice. Following baseline, pre-intervention commenced and participants were assigned to either control (CON) or experimental (EXP) groups. The CON and EXP group participants were instructed to maintain normal hydration and diet schedules and record fluid intake for seven days leading to post-intervention. The EXP group participants were asked to consume an additional 23.9 fl oz (~ 750 ml) per day for one week (7 days) leading to post-intervention. After 7 days the same measures were taken. At baseline, the majority of the participants were hypohydrated. Following the intervention, the EXP group participants consumed significantly more fluids than the participants in the CON group (3277.91 ± 1360. 23 ml vs 1931.54 ± 881.81 ml; p 0.05) difference in the regression slopes or intercepts between the CON and EXP groups when expressed as daily fluid intake per kg body (ml·kg-1) and change in USG from pre-intervention to post-intervention. Most of the participants were hypohydrated at baseline/pre-intervention and the direct hydration intervention improved post-intervention hydration status but only to a small extent

Comparison of Glycerol and Water Hydration Regimens on Tennis-Related Performance

Purpose: To compare glycerol and water hyperhydration and rehydration on tennis related skill and agility performance. Methods: Eleven male subjects completed two counter-balanced, double-blind trials. Each trial consisted of three phases: 1) hyperhydration with or without glycerol (1.0 g(.)kg(-1)) over 150 min, 2) 120 min of exercise-induced dehydration (EID), and 3) rehydration with or without glycerol (0.5 g(.)kg(-1)) over 90 min. After each phase, subjects performed 5- and 10-m sprint tests, a repeated-effort agility test, and tennis skill tests. Results: Glycerol (G) hyperhydration significantly increased fluid retention by similar to 900 mL over the placebo (P) (P less than or equal to 0.05). After EID, body weight was reduced in both groups but was not significantly different between groups (G: -2.71 +/- 0.08, P: -2.67 +/- 0.09%). At the end of the rehydration phase, PV was significantly greater in the G trial than in the P trial, and the G trial resulted in a significantly greater fluid retention of similar to700 mL over the P trial (P less than or equal to 0.05). Although the magnitude of hypohydration was modest (\u3c3%), sprint times were significantly slower after the EID (P less than or equal to 0.05) compared with post hyperhydration and post rehydration but were not significantly different between trials. No significant difference existed between groups and across time for the repeated effort agility tests and groundstrokes and serve tests. Conclusion: The data demonstrate that relatively modest hypohydration (similar to2.7%) as a result of EID, significantly slows 5- and 10-m sprint times. Furthermore, although the glycerol hydration regimen provided a better hydration status than the placebo hydration regimen, no performance benefits were observed

Muscle-Fiber Type and Blood Oxidative Stress After Eccentric Exercise

Acute strength exercise elicits a transient oxidative stress, but the factors underlying the magnitude of this response remain unknown. The purpose of this investigation was to determine whether muscle-fiber type relates to the magnitude of blood oxidative stress after eccentric muscle activity. Eleven college-age men performed 3 sets of 50 eccentric knee-extensions. Blood samples taken pre-, post-, and 24, 48, 72, and 96 hr postexercise were assayed for comparison of muscle damage and oxidative-stress biomarkers including protein carbonyls (PCs). Vastus lateralis muscle biopsies were assayed for relative percentage of slow-and fast-twitch muscle fibers. There was a mixed fiber composition (Type I = 39.6% +/- 4.5%, Type IIa = 35.7% +/- 3.5%, Type IIx = 24.8% +/- 3.8%; p = .366). PCs were elevated 24, 48, and 72 hr (p = .032) postexercise, with a peak response of 126% (p = .012) above baseline, whereas other oxidative-stress biomarkers were unchanged. There are correlations between Type II muscle-fiber type and postexercise PC. Further study is needed to understand the mechanisms responsible for the observed fast-twitch muscle-fiber oxidative-stress relationship

Muscle-fiber type and blood oxidative stress after eccentric exercise

Acute strength exercise elicits a transient oxidative stress, but the factors underlying the magnitude of this response remain unknown. The purpose of this investigation was to determine whether muscle-fiber type relates to the magnitude of blood oxidative stress after eccentric muscle activity. Eleven college-age men performed 3 sets of 50 eccentric knee-extensions. Blood samples taken pre-, post-, and 24, 48, 72, and 96 hr postexercise were assayed for comparison of muscle damage and oxidative-stress biomarkers including protein carbonyls (PCs). Vastus lateralis muscle biopsies were assayed for relative percentage of slow- and fast-twitch muscle fibers. There was a mixed fiber composition (Type I = 39.6% ± 4.5%, Type IIa = 35.7% ± 3.5%, Type IIx = 24.8% ± 3.8%; p = .366). PCs were elevated 24, 48, and 72 hr (p = .032) postexercise, with a peak response of 126% (p = .012) above baseline, whereas other oxidative-stress biomarkers were unchanged. There are correlations between Type II muscle-fiber type and postexercise PC. Further study is needed to understand the mechanisms responsible for the observed fast-twitch muscle-fiber oxidative-stress relationship

Effect of Moderate Dehydration on Torque, Electromyography, and Mechanomyography

The purpose of the present investigation was to test the hypotheses that the mechanomyographic (MMG) signal would be affected by hydration status due to changes in the intra- and extracellular fluid content (which could affect the degree of fluid turbulence), changes in the filtering properties of the tissues between the MMG sensor and muscle, and changes in torque production that may accompany dehydration. Ten subjects (age 22.5 +/- 1.6 years) were tested for maximal isometric (MVC), submaximal isometric (25, 50, and 75%MVC), and maximal concentric isokinetic muscle strength of the biceps brachii in either a euhydrated or dehydrated state while the electromyographic (EMG) and MMG signals were recorded. Separate three-way and two-way ANOVAs indicated no change in torque, EMG amplitude, EMG mean power frequency (MPF), MMG amplitude, and MMG MPF with dehydration. The lack of dehydration effect suggests that MMG may be more reflective of the intrinsic contractile processes of a muscle fiber (torque production) or the motor control mechanisms (reflected by the EMG) than the tissues and fluids surrounding the muscle fiber. (C) 2002 Wiley Periodicals, Inc