Heart Rate Variability and Cortisol Levels Before and After a Brief Anaerobic Exercise in Handball Players.

ABSTRACT: Kayacan, Y, Makaraci, Y, Ucar, C, Amonette, WE, and Yildiz, S. Heart rate variability and cortisol levels before and after a brief anaerobic exercise in handball players. J Strength Cond Res 37(7): 1479-1485, 2023-Evaluating stress in athletes is important for monitoring overall physiologic load and is a core practice for sport performance teams. This study examined relationships between 2 metrics of training stress, heart rate variability (HRV) and cortisol, before and after intense anaerobic power testing. Electrocardiogram recordings and saliva samples were collected before and immediately after a Wingate anaerobic power test (WAnT-30) from professional handball players ( n = 20) and sedentary controls ( n = 18). Between-group differences and correlations were computed to assess study hypotheses. No differences were observed in HRV frequency-dependent parameters between groups, but in athletes, Min. R-R ( p < 0.01) and Avg.R-R ( p = 0.03) before WAnT-30 and the percentage of successive normal cardiac beat intervals greater than 50 milliseconds (i.e., pNN50; p = 0.03) after WAnT-30 were elevated. A high positive correlation was detected between the pretest and post-test cortisol levels in athletes ( p = 0.0001; r = 0.87) but not in sedentary individuals. No correlations were observed between the cortisol levels and WAnT-30 power parameters in either group. Relationships were evident in the standard deviation of RR intervals ( p = 0.02, r = -0.53), square root of the mean squared difference of successive RR intervals ( p = 0.043, r = -0.46), very low frequency ( p = 0.032; r = -0.480), high-frequency ( p = 0.02; r = -0.52) variables, and pretesting cortisol in athletes. These findings suggest that HRV analysis is a valuable tool for examining cardiovascular regulation, independent of cortisol; the data may provide valuable information for performance teams in evaluating acute stress.

Cross-Sectional Analysis of Ground Reaction Forces During Jumps in Professional Baseball Players.

ABSTRACT: Amonette, WE, Vazquez, J, and Coleman, AE. Cross-sectional analysis of ground reaction forces during jumps in professional baseball players. J Strength Cond Res 37(8): 1616-1622, 2023-This study described and compared force plate kinetics in major (MLB) and minor (MiLB) baseball players while performing vertical jumps (CMVJ), squat jumps (SSJ), and depth jumps (DJ). Second, comparisons were made between playing positions. Data were collected on 101 professional baseball players. Peak force, eccentric and concentric impulses, peak power, and jump height were determined from each test. Reactive strength index was computed from the DJ. Data were compared using factorial analysis of variances, alpha was set at p ≤ 0.05, and effect sizes were reported using Cohen's d . During CMVJ, MiLB players generated more force ( p = 0.04; d = 0.48), power ( p = 0.02; d = 0.42), and jumped higher ( p = 0.03; d = 0.32) than MLB players. Pitchers generated higher propulsive impulses than catchers ( p = 0.004; d = 0.93). Outfielders generated more power ( p = 0.02; d = 0.98) and jumped higher ( p = 0.049; d = 1.08) than catchers and infielders ( p = 0.025; d = 0.32). Minor league baseball players generated more force ( p = 0.002; d = 0.62), power ( p = 0.001; d = 0.84), and jumped higher ( p = 0.02; d = 0.48) than MLB players in SSJ. No differences were observed by position in SSJ. Minor league baseball players jumped higher than MLB players in the DJ ( p = 0.01; d = 0.57) and outfielders generated more power in the DJ than pitchers ( p = 0.05; d = 0.43) and catchers ( p = 0.007; d = 1.61). Reactive strength index was greater in outfielders compared with catchers ( p = 0.01; d = 1.20). These data indicate that MiLB players were generally more powerful and jumped higher than MLB players in the 3 performance tasks. The difference observed by playing level were likely related to physical preparedness at the beginning of spring training; positional differences were the result of athletic skill sets required for tactical excellence at each position.

Relationships Between Lower Extremity Power and Fastball Spin Rate and Ball Velocity in Professional Baseball Pitchers.

ABSTRACT: Wong, R, Laudner, K, Amonette, W, Vazquez, J, Evans, D, and Meister, K. Relationships between lower extremity power and fastball spin rate and ball velocity in professional baseball pitchers. J Strength Cond Res 37(4): 823-828, 2023-Lower extremity power has been hypothesized to increase ball spin and velocity during pitching in baseball. Therefore, the purpose of this study was to determine the relationship between lower extremity power and fastball spin rate in professional baseball pitchers. A secondary purpose was to determine the relationship between lower extremity power and ball velocity. Fifty-three asymptomatic professional pitchers participated (24.5 ± 3.6 years; 189.9 ± 6.1 cm; 92.6 ± 10.3 kg). Each athlete performed 3 separate bilateral jump tests on force plates: countermovement jump (CMJ), squat jump (SJ), and drop jump (DJ). The average fastball spin rate and ball velocity for each pitcher was calculated using a 3-dimensional Doppler radar and video system over the course of a competitive season. Standard multiple regression analyses ( p ≤ 0.05) revealed significant relationship between ball spin and summation of variables for the CMJ (peak force, peak power, rate of power development, and jump height) ( R2 = 0.20, F = 3.1, p = 0.03). However, no individual variable was significantly associated ( p > 0.09). There was also a significant amount of variance in ball spin explained by summation of variables for the SJ (peak force, peak power, rate of power development, and jump height) ( R2 = 0.19, F = 2.8, p = 0.04); rate of power development was the only variable that significantly predicted ball spin within this model ( B = 0.27; 95% confidence interval [CI]: 0.003-0.75, p = 0.05). Ball spin was not associated with summation of DJ variables (peak power, rate of power development, jump height, reactive strength index, and total peak power in watts) ( R2 = 0.18, F = 2.0, p = 0.09). For ball velocity, there were no significant relationships for the summation of either the CMJ variables ( R2 = 0.10, p = 0.28) or the SJ variables ( R2 = 0.07, p = 0.44). However, there was a significant amount of variance in ball velocity explained by summation of variables for the DJ ( R2 = 0.30, F = 3.93, p = 0.005). The reactive strength index was the sole unique contribution to this model ( B = 1.18; 95% CI: -10.34 to 2.36, p = 0.002). These findings highlight the relevance of increased lower extremity power on increasing fastball spin rate and ball velocity.

Postural control and physiological responses to a simulated match in U-20 judo competitors.

The aim was to evaluate the effects of judo combat on the athletes' postural control (PC) and physiological loading before, during and after a simulated match. Seventeen under-20 regional and national level athletes completed one modified 7-min match. At baseline, during the combat (3rd and 7th minutes) and 2-min post-match centre of pressure (CoP) parameters were assessed. Heart rate (HR), blood lactate (BLa) and rating of perceived exertion (RPE) and local RPE (LRPE) were collected. Significant increments were observed in CoP mean positioning and velocity at 3rd and 7th minutes, but the CoP deviation in both axes was unaffected. HR and BLa were elevated at 3rd and 7th minutes, and they remained elevated 2-min post-match. However, CoP returned to baseline 2-min post-match. RPE was elevated at 3rd and 7th minutes and the greatest effort was displayed in the Deltoid and Quadriceps. Thus, one simulated judo match stimulates a significant metabolic response and balance is degraded, with the greatest effects on the anterior-posterior axis and it recovers to baseline level after 2 min of passive rest. The physiological load cannot be regarded as a potential predictor variable of CoP. Overall, a judo match predominantly affects the upper body than the other body parts.

Effects of whole-body vibration exercise on bone mineral content and density in thermally injured children.

BACKGROUND: Loss of bone mass, muscle mass, and strength leads to significant disability in severely burned children. We assessed the effects of exercise combined with whole-body vibration (WBV) on bone mass, lean mass (LM), and muscle strength in children recovering from burns. METHODS: Nineteen burned children (≥30% total body surface area [TBSA] burns) were randomly assigned to a 6-week exercise regimen either alone (EX; n=10) or in combination with a 6-week WBV training regimen (EX+WBV; n=9). WBV was performed concurrent to the exercise regimen for 5days/week on a vibrating platform. Dual-energy X-ray absorptiometry quantified bone mineral content (BMC), bone mineral density (BMD), and LM; knee extension strength was assessed using isokinetic dynamometry before and after training. Alpha was set at p<0.05. RESULTS: Both groups were similar in age, height, weight, TBSA burned, and length of hospitalization. Whole-body LM increased in the EX group (p=0.041) and trended toward an increase in the EX+WBV group (p=0.055). On the other hand, there were decreases in leg BMC for both groups (EX, p=0.011; EX+WBV, p=0.047), and in leg BMD for only the EX group (EX, p<0.001; EX+WBV, p=0.26). Truncal BMC decreased in only the EX group (EX, p=0.009; EX+WBV, p=0.61), while BMD decreased in both groups (EX, p<0.001; EX+WBV group, p<0.001). Leg strength increased over time in the EX group (p<0.001) and the EX+WBV group (p<0.001; between-group p=0.31). CONCLUSIONS: Exercise in combination with WBV may help attenuate regional bone loss in children recovering from burns. Studies are needed to determine the optimal magnitude, frequency, and duration of the vibration protocol, with attention to minimizing any potential interference with wound healing and graft closure.

Sprint Accelerations to First Base Among Major League Baseball Players With Different Years of Career Experience.

The purpose of this article was to compare times to first base in Major League Baseball games to determine whether running velocity decreases to the foul line and first base among players with differing years of playing experience. From 1998 to 2012, 1,185 sprint times to first base were analyzed: 469 outfielders, 601 infielders, and 115 catchers. The players were divided into differing experience categories depending on their years of service in Major League Baseball: 1-5, 6-10, 11-15, and 16-20+ years. Velocity at the foul line and first base was compared and interval accelerations were reported. Comparisons were completed by playing position, and within left- and right-handed batters. Left-handed outfielders exhibited reduced velocities at 6-10 (p = 0.04), 11-15 (p = 0.004), and 16-20 years (p < 0.001) compared with 1-5 years; there were no statistical differences in velocity at the foul line. Right-handed outfielders exhibited significantly reduced velocities at first base in 6-10 (p = 0.002) and 11-15 years (p = 0.001); they also had a reduced velocities at the foul line in 6-10 (p = 0.004) and 11-15 years (p = 0.009). Right-handed infielders had reduced velocities at first base in 11-15 years (p < 0.001). No other differences were observed within infielders at first base or the foul line. There were no differences within the compared variables for catchers. Decreases in running velocity to first base with experience are seen in outfielders but are less prominent in infielders and catchers. Although physical capabilities for sprinting may decline with age, it is possible that through repetition more experienced players perfect the skill-related component of running to first base, thus preserving speed.

Neurocognitive responses to a single session of static squats with whole body vibration.

The purpose of this study was to determine if the head accelerations using a common whole body vibration (WBV) exercise protocol acutely reduced neurocognition in healthy subjects. Second, we investigated differential responses to WBV plates with 2 different delivery mechanisms: vertical and rotational vibrations. Twelve healthy subjects (N = 12) volunteered and completed a baseline (BASE) neurocognitive assessment: the Immediate Postconcussion Assessment and Cognitive Test (ImPACT). Subjects then participated in 3 randomized exercise sessions separated by no more than 2 weeks. The exercise sessions consisted of five 2-minute sets of static hip-width stance squats, with the knees positioned at a 45° angle of flexion. The squats were performed with no vibration (control [CON]), with a vertically vibrating plate (vertical vibration [VV]), and with a rotational vibrating plate (rotational vibration [RV]) set to 30 Hz with 4 mm of peak-to-peak displacement. The ImPACT assessments were completed immediately after each exercise session and the composite score for 5 cognitive domains was analyzed: verbal memory, visual memory, visual motor speed, reaction time, and impulse control. Verbal memory scores were unaffected by exercise with or without vibration (p = 0.40). Likewise, visual memory was not different (p = 0.14) after CON, VV, or RV. Significant differences were detected for visual motor speed (p = 0.006); VV was elevated compared with BASE (p = 0.01). There were no significant differences (p = 0.26) in reaction time or impulse control (p = 0.16) after exercise with or without vibration. In healthy individuals, 10 minutes of 30 Hz, 4-mm peak-to-peak displacement vibration exposure with a 45° angle of knee flexion did not negatively affect neurocognition.

Blunted IL-6 and IL-10 response to maximal aerobic exercise in patients with traumatic brain injury.

INTRODUCTION: In healthy individuals, strenuous exercise typically results in a transient increase in the inflammatory cytokine, interleukin-6 (IL-6). This increase in IL-6 is reported to have pleiotropic effects including increased glucose uptake, increased fat oxidation, and anti-inflammatory actions. PURPOSE: The purpose of this study was to determine if patients with a traumatic brain injury (TBI) have a differential cytokine response to exercise compared to healthy control subjects (CON). METHODS: Eight patients with a TBI and eight age- and sex-matched controls completed an exercise test to volitional exhaustion. Metabolic data were collected continuously, and blood was collected at baseline, immediately post-exercise, and every 10 min for an hour post-exercise. Serum was analyzed for IL-6, tumor necrosis factor-alpha, interleukin-10 (IL-10), and cortisol. RESULTS: Peak oxygen consumption (CON 33 ± 2 ml kg(-1) min(-1); TBI 29 ± 2 ml kg(-1) min(-1)) and respiratory exchange ratio during exercise were equivalent between groups. There were no baseline differences between groups for cytokine or cortisol concentrations. Exercise did not increase IL-6 in TBI, whereas IL-6 was elevated from baseline in CON at 0, 40, and 50 min post-exercise (p < 0.05). IL-10 and cortisol increased from baseline in CON at 40 min post-exercise (p < 0.05). CONCLUSIONS: These data indicate that patients recovering from TBI have blunted IL-6, IL-10, and cortisol responses following a peak exercise test compared to non-TBI controls. This lack of an exercise response may represent impaired hypothalamic-pituitary-adrenal axis function.

Physical determinants of interval sprint times in youth soccer players.

Relationships between sprinting speed, body mass, and vertical jump kinetics were assessed in 243 male soccer athletes ranging from 10-19 years. Participants ran a maximal 36.6 meter sprint; times at 9.1 (10 y) and 36.6 m (40 y) were determined using an electronic timing system. Body mass was measured by means of an electronic scale and body composition using a 3-site skinfold measurement completed by a skilled technician. Countermovement vertical jumps were performed on a force platform - from this test peak force was measured and peak power and vertical jump height were calculated. It was determined that age (r=-0.59; p<0.01), body mass (r=-0.52; p<0.01), lean mass (r=-0.61; p<0.01), vertical jump height (r=-0.67; p<0.01), peak power (r=-0.64; p<0.01), and peak force (r=-0.56; p<0.01) were correlated with time at 9.1 meters. Time-to-complete a 36.6 meter sprint was correlated with age (r=-0.71; p<0.01), body mass (r=-0.67; p<0.01), lean mass (r=-0.76; p<0.01), vertical jump height (r=-0.75; p<0.01), peak power (r=-0.78; p<0.01), and peak force (r=-0.69; p<0.01). These data indicate that soccer coaches desiring to improve speed in their athletes should devote substantive time to fitness programs that increase lean body mass and vertical force as well as power generating capabilities of their athletes. Additionally, vertical jump testing, with or without a force platform, may be a useful tool to screen soccer athletes for speed potential.

Ventilatory anaerobic thresholds of individuals recovering from traumatic brain injury compared with noninjured controls.

OBJECTIVE: The purpose of this study was to compare the peak aerobic capacities and ventilatory anaerobic thresholds (VAT) of individuals with a traumatic brain injury (TBI) to age- and gender-matched controls. METHODS: Nineteen participants that previously suffered a mild to moderate TBI and 19 apparently healthy controls volunteered as subjects. Traumatic brain injury and healthy controls were matched for age and gender and were similar in weight and body mass index. Volunteers performed a maximal graded treadmill test to volitional failure where oxygen consumption ((Equation is included in full-text article.)O2), carbon dioxide production ((Equation is included in full-text article.)CO2, ventilation ((Equation is included in full-text article.)E, and heart rate were measured continuously. From metabolic and ventilatory data, VAT was measured using a previously described method. VAT and peak exercise responses of participants with a TBI were compared with healthy controls. RESULTS: The (Equation is included in full-text article.)O2, and (Equation is included in full-text article.)CO2 at VAT and peak exercise were lower for TBI compared with healthy controls. (Equation is included in full-text article.)E was also lower for TBI at VAT and peak exercise. Heart rate was lower for TBI at VAT; however, TBI had similar heart rate to healthy controls at peak exercise. CONCLUSIONS: The VAT and peak exercise capacities of participants with a TBI were below the metabolic demands of many routine daily activities. The data suggest that therapeutic interventions for individuals with a TBI should include targeted exercise prescriptions to improve cardiorespiratory fitness.

Immediate effects of lower cervical spine manipulation on handgrip strength and free-throw accuracy of asymptomatic basketball players: a pilot study.

OBJECTIVE: The purpose of this pilot study was to collect preliminary information for a study to determine the immediate effects of a single unilateral chiropractic manipulation to the lower cervical spine on handgrip strength and free-throw accuracy in asymptomatic male recreational basketball players. METHODS: For this study, 24 asymptomatic male recreational right-handed basketball players (age = 26.3 ± 9.2 years, height = 1.81 ± 0.07 m, body mass = 82.6 ± 10.4 kg [mean ± SD]) underwent baseline dominant handgrip isometric strength and free-throw accuracy testing in an indoor basketball court. They were then equally randomized to receive either (1) diversified left lower cervical spine chiropractic manipulative therapy (CMT) at C5/C6 or (2) placebo CMT at C5/C6 using an Activator adjusting instrument on zero force setting. Participants then underwent posttesting of isometric handgrip strength and free-throw accuracy. A paired-samples t test was used to make within-group pre to post comparisons and between-group pre to post comparisons. RESULTS: No statistically significant difference was shown between either of the 2 basketball performance variables measured in either group. Isometric handgrip strength marginally improved by 0.7 kg (mean) in the CMT group (P = .710). Free-throw accuracy increased by 13.2% in the CMT group (P = .058). The placebo CMT group performed the same or more poorly during their second test session. CONCLUSIONS: The results of this preliminary study showed that a single lower cervical spine manipulation did not significantly impact basketball performance for this group of healthy asymptomatic participants. A slight increase in free-throw percentage was seen, which deserves further investigation. This pilot study demonstrates that a larger study to evaluate if CMT affects handgrip strength and free-throw accuracy is feasible.

Peak vertical jump power estimations in youths and young adults.

The purpose of this study was to develop and validate a regression equation to estimate peak power (PP) using a large sample of athletic youths and young adults. Anthropometric and vertical jump ground reaction forces were collected from 460 male volunteers (age: 12-24 years). Of these 460 volunteers, a stratified random sample of 45 subjects representing 3 different age groups (12-15 years [n = 15], 16-18 years [n = 15], and 19-24 years [n = 15]) was selected as a validation sample. Data from the remaining 415 subjects were used to develop a new equation ("Novel") to estimate PP using age, body mass (BM), and vertical jump height (VJH) via backward stepwise regression. Independently, age (r = 0.57), BM (r = 0.83), and VJ (r = 0.65) were significantly (p < 0.05) correlated with PP. However, age did not significantly (p = 0.53) contribute to the final prediction equation (Novel): PP (watts) = 63.6 × VJH (centimeters) + 42.7 × BM (kilograms) - 1,846.5 (r = 0.96; standard error of the estimate = 250.7 W). For each age group, there were no differences between actual PP (overall group mean ± SD: 3,244 ± 991 W) and PP estimated using Novel (3,253 ± 1,037 W). Conversely, other previously published equations produced PP estimates that were significantly different than actual PP. The large sample size used in this study (n = 415) likely explains the greater accuracy of the reported Novel equation compared with previously developed equations (n = 17-161). Although this Novel equation can accurately estimate PP values for a group of subjects, between-subject comparisons estimating PP using Novel or any other previously published equations should be interpreted with caution because of large intersubject error (± >600 W) associated with predictions.

Pure acceleration is the primary determinant of speed to first-base in major-league baseball game situations.

The purposes of this research were to (a) quantify interval sprint times between Home-Plate and the Foul-Line and the Foul-Line and First-Base, (b) determine if differences exist in interval velocities and acceleration between left- and right-handed batters or between-position groupings, and (c) to quantify determinants of time to First-Base in Major-League Baseball players during actual games. A total of 1,896 sprint times to the Foul-Line (13.7 m) and First-Base (27.4 m) were recorded in 302 baseball players by a single coach, positioned in the dugout with a hand-held stopwatch. Interval velocities and accelerations were computed between Home-Plate and the Foul-Line and the Foul-Line and First-Base; average velocity and acceleration were also determined over the entire 27.4 m. Velocity and acceleration for left-handed batters were greater than for right-handed batters from Home-Plate to the Foul-Line and from Home-Plate to First-Base; however, there were no differences in velocity or acceleration from the Foul-Line to First-Base. Interval velocity was significantly greater for outfielders and infielders compared with that for catchers from Home-Plate to the Foul-Line and from the Home-Plate to First-Base. Outfielders were faster than catchers from the Foul-Line to First-Base; no other between-group differences were evident. Accelerations from Home-Plate to the Foul-Line and from Home-Plate to First-Base were greater for outfielders compared with infielders and catchers. Infielders accelerated at greater rates than did catchers between these intervals. There were no between-position differences in acceleration from the Foul-Line to First-Base. These data indicate that time to First-Base is most affected by acceleration from Home-Plate to the Foul-Line. Coaches should implement strategies that encourage players to sprint maximally over the first 13.7 m to maximize chances of successfully reaching First-Base.

Metabolic responses of upper-body accelerometer-controlled video games in adults.

Historically, video games required little physical exertion, but new systems utilize handheld accelerometers that require upper-body movement. It is not fully understood if the metabolic workload while playing these games is sufficient to replace routine physical activity. The purpose of this study was to quantify metabolic workloads and estimate caloric expenditure while playing upper-body accelerometer-controlled and classic seated video games. Nineteen adults completed a peak oxygen consumption treadmill test followed by an experimental session where exercising metabolism and ventilation were measured while playing 3 video games: control (CON), low activity (LOW) and high activity (HI). Resting metabolic measures (REST) were also acquired. Caloric expenditure was estimated using the Weir equation. Mean oxygen consumption normalized to body weight for HI condition was greater than LOW, CON, and REST. Mean oxygen consumption normalized to body weight for LOW condition was also greater than CON and REST. Mean exercise intensities of oxygen consumption reserve for HI, LOW, and CON were 25.8% ± 5.1%, 6.4% ± 4.8%, and 0.8% ± 2.4%, respectively. Estimated caloric expenditure during the HI was significantly related to aerobic fitness, but not during other conditions. An active video game significantly elevated oxygen consumption and heart rate, but the increase was dependent on the type of game. The mean oxygen consumption reserve during the HI video game was below recommended international standards for moderate and vigorous activity. Although upper-body accelerometer-controlled video games provided a greater exercising stimulus than classic seated video games, these data suggest they should not replace routine moderate or vigorous exercise.

Anthropometric and performance differences among high-school football players.

The purpose of this study was to examine physical and performance differences between grade levels and playing positions within High-School football players. Two thousand three hundred and twenty-seven athletes were tested for height, weight, 40-yd sprint time, proagility time, and vertical jump height. Mean scores across age groups and playing positions were compared using repeated-measures analysis of variance (ANOVA) and 1-way ANOVAs. The results indicate that defensive players in the 11th and 12th grades were significantly faster in the 40-yd sprint, quicker in the proagility, and generated more power than 9th and 10th grade defensive players across all positions (p < 0.05). Similarly, offensive players in the 11th and 12th grades were significantly faster, quicker, and jumped higher than did football players in lower grades (p < 0.05). Overall, these data suggest that there are distinct differences in the physical and performance characteristics of high-school football players. The greatest difference is observed between the sophomore and junior years. Older, more mature athletes are faster, quicker, and capable of generating more power than younger athletes. Practically, these data lend support to the common 3-tiered approach (i.e., Freshman, Junior Varsity, and Varsity) most high schools use for their football programs. This approach is likely indicated to allow for physical maturation of young players and to allow time for the development of strength, power, speed, and agility necessary to compete with older players.

Nullius in verba: a call for the incorporation of evidence-based practice into the discipline of exercise science.

Evidence-based practice (EBP) is a concept that was popularized in the early 1990s by several physicians who recognized that medical practice should be based on the best and most current available evidence. Although this concept seems self-evident, much of medical practice was based on outdated textbooks and oral tradition passed down in medical school. Currently, exercise science is in a similar situation. Due to a lack of regulation within the exercise community, the discipline of exercise science is particularly prone to bias and misinformation, as evidenced by the plethora of available programmes with efficacy supported by anecdote alone. In this review, we provide a description of the five steps in EBP: (i) develop a question; (ii) find evidence; (iii) evaluate the evidence; (iv) incorporate evidence into practice; and (v) re-evaluate the evidence. Although objections have been raised to the EBP process, we believe that its incorporation into exercise science will improve the credibility of our discipline and will keep exercise practitioners and academics on the cutting edge of the most current research findings.

Endurance training and cardiorespiratory conditioning after traumatic brain injury.

OBJECTIVE: To examine the importance of cardiorespiratory conditioning after traumatic brain injury (TBI) and provide recommendations for patients recovering from TBI. METHOD: Review of literature assessing the effectiveness of endurance training programs. MAIN OUTCOMES AND RESULTS: A sedentary lifestyle and lack of endurance are common characteristics of individuals with TBI who have a reduction in peak aerobic capacity of 25% to 30% compared with healthy sedentary persons. Increased physical activity and exercise training improves cardiorespiratory fitness in many populations with physical and cognitive impairments. Therefore, increasing the endurance and cardiorespiratory fitness of persons with TBI would seem to have important health implications. However, review of the TBI literature reveals that there have been few well-designed, well-controlled studies of physiologic and psychological adaptations of fitness training. Also lacking are long-term follow-up studies of persons with TBI. CONCLUSIONS: Assessing endurance capacity and cardiorespiratory fitness early in the TBI rehabilitation process merits consideration as a standard of care by professional rehabilitation societies. Also, providing effective, safe, and accessible training modalities would seem to be an important consideration for persons with TBI, given the mobility impairments many possess. Long-term follow-up studies are needed to assess the effectiveness of cardiorespiratory training programs on overall morbidity and mortality.

Effects of different lifting cadences on ground reaction forces during the squat exercise.

The purpose of this investigation was to determine the effect of different lifting cadences on the ground reaction force (GRF) during the squat exercise. Squats performed with greater acceleration will produce greater inertial forces; however, it is not well understood how different squat cadences affect GRF. The hypotheses were that faster squat cadences would result in greater peak GRF and that the contributions of the body and barbell, both of equivalent mass, to total system inertial force would not be different. Six experienced male subjects (31 +/- 4 years, 180 +/- 9 cm, 88.8 +/- 13.3 kg) performed 3 sets of 3 squats using 3 different cadences (fast cadence [FC] = 1-second descent/1-second ascent; medium cadence [MC] = 3-second descent/1-second ascent; and slow cadence [SC] = 4-second descent/2-second ascent) while lifting a barbell mass equal to their body mass. Ground reaction force and velocity sensor data were used to calculate inertial force contributions of both the body and barbell to total inertial force. Peak GRF were significantly higher in FC squats compared to MC (p = 0.0002) and SC (p = 0.0002). Ranges of GRF were also significantly higher in FC compared to MC (p < 0.05) and higher in MC compared to SC (p < 0.05). The inertial forces associated with the body were larger than those associated with the barbell, regardless of cadence. Faster squat cadences result in significantly greater peak GRF as a result of the inertia of the system. This study demonstrates that GRF was more dependent on descent cadence than on ascent cadence and that researchers should not use a single point on the body to approximate the location of the center of mass during squat exercise analysis.

Vibration exposure and biodynamic responses during whole-body vibration training.

PURPOSE: Excessive, chronic whole-body vibration (WBV) has a number of negative side effects on the human body, including disorders of the skeletal, digestive, reproductive, visual, and vestibular systems. Whole-body vibration training (WBVT) is intentional exposure to WBV to increase leg muscle strength, bone mineral density, health-related quality of life, and decrease back pain. The purpose of this study was to quantitatively evaluate vibration exposure and biodynamic responses during typical WBVT regimens. METHODS: Healthy men and women (N = 16) were recruited to perform slow, unloaded squats during WBVT (30 Hz; 4 mm(p-p)), during which knee flexion angle (KA), mechanical impedance, head acceleration (Ha(rms)), and estimated vibration dose value (eVDV) were measured. WBVT was repeated using two forms of vibration: 1) vertical forces to both feet simultaneously (VV), and 2) upward forces to only one foot at a time (RV). RESULTS: Mechanical impedance varied inversely with KA during RV (effect size, eta(p)(2): 0.668, P < 0.01) and VV (eta(p)(2): 0.533, P < 0.05). Ha(rms) varied with KA (eta(p)(2): 0.686, P < 0.01) and is greater during VV than during RV at all KA (P < 0.01). The effect of KA on Ha(rms) is different for RV and VV (eta(p)(2): 0.567, P < 0.05). The eVDV associated with typical RV and VV training regimens (30 Hz, 4 mm(p-p), 10 min.d(-1)) exceeds the recommended daily vibration exposure as defined by ISO 2631-1 (P < 0.01). CONCLUSIONS: ISO standards indicate that 10 min.d(-1) WBVT is potentially harmful to the human body; the risk of adverse health effects may be lower during RV than VV and at half-squats rather than full-squats or upright stance. More research is needed to explore the long-term health hazards of WBVT.

Variation in neuromuscular responses during acute whole-body vibration exercise.

PURPOSE: Leg muscle strength and power are increased after whole-body vibration (WBV) exercise. These effects may result from increased neuromuscular activation during WBV; however, previous studies of neuromuscular responses during WBV have not accounted for motion artifact. METHODS: Sixteen healthy adults performed a series of static and dynamic unloaded squats with and without two different directions of WBV (rotational vibration, RV; and vertical vibration, VV; 30 Hz; 4 mmp-p). Activation of unilateral vastus lateralis, biceps femoris, gastrocnemius, and tibialis anterior was recorded using EMG. During RV and VV, increases in EMG relative to baseline were compared over a range of knee angles, contraction types (concentric, eccentric, isometric), and squatting types (static, dynamic). RESULTS: After removing large, vibration-induced artifacts from EMG data using digital band-stop filters, neuromuscular activation of all four muscles increased significantly (P