Evaluation of the Feasibility of a Two-Method Measurement Design for the Assessment of Healthy Physical Activity Behavior in Youth

Purpose: Assess the reliability and validity of self- and parent-report survey responses regarding physical activity (PA), sedentary behaviors, and PA self-efficacy and determine if these data can be combined with objective physical activity monitor data to model the latent construct healthy physical activity behavior (HPAB). Methods: 126 underserved 4th-5th grade students participated in a 12-week after-school nutrition, cooking, and physical activity program (WeCook: Fun with Food and Fitness). Participants and parents (n=103) completed surveys pre- and post-program and participants wore PA monitors for one week at PRE and POST. Unidimensionality and internal consistency reliability were assessed for survey measures and objective PA measures (ST=step counts, FL=floors climbed) and predictive validity of survey measures was assessed through correlation with ST and FL. HPAB was modeled using z-scores (standardized across time, averaged) for youth self-reported physical activity (YPA), youth PA self-efficacy (YSE), parent-reported youth PA and sedentary behavior (AS), ST, and FL. Metric and intercept invariance were established across time and between groups selected for assessing construct validity (gender, grade, socioeconomic status, weight status, school, minority, season, grant year). Results: ST, FL, YSE, and AS were unidimensional. For ST coefficient α was 0.735 (PRE) and 0.805 (POST), for FL α was 0.686 and 0.684 (PRE and POST), for YSE, α was 0.829 (PRE) and 0.897 (POST), and for AS α was 0.545 (PRE) and 0.729 (POST). YPA was most predictive of the objective PA measures and was correlated with ST at PRE and POST and FL at PRE (pp\u3e0.05). HPAB exhibited measurement invariance across time and between groups of interest and some evidence for latent construct validity based on nomothetic span and construct representation was established. Conclusions: This study establishes some evidence supporting the feasibility of modeling HPAB using survey and objective measures of PA in youth. Advisor: James A. Bovair

Exertional rhabdomyolysis in a 21-year-old, healthy female after performing three sets of the biceps curl exercise to failure with 30% 1RM: A case report

Background: The optimal resistance training program to elicit muscle hypertrophy has been consistently debated and researched. Although 3 sets of 10 repetitions at 70-80% of the 1-repetition maximum (1RM) is widely recommended, recent studies have shown that low-load (~30% 1RM), high-repetition (3 sets of 30-40 repetitions) resistance training can elicit similar muscular hypertrophy. Therefore, this type of resistance training has gained popularity, perhaps because less weight is lifted for a longer duration. In the process of testing this hypothesis in a research study in our laboratory, a subject diagnosed with exertional rhabdomyolysis after completing a single resistance training session that involved 3 sets to failure at 30% 1RM. Exertional rhabdomyolysis is a condition characterized by the excessive breakdown of striated skeletal muscle that releases proteins from the muscle cell, particularly myoglobin, into the blood that can be toxic to the kidneys and is a significant health concern. Case Report: Reviewed were the events leading up to and throughout the diagnosis of exertional rhabdomyolysis in a healthy, recreationally-trained, 21-year-old female that was enrolled in a study that compared the acute effects of the traditional high-load, low-repetition versus low-load, high-repetition resistance training. The subject completed a total of 143 repetitions of the bilateral dumbbell bicep curl exercise. Three days post-exercise she reported excessive muscle soreness and swelling and sought medical attention. She was briefly hospitalized and then discharged with instructions to take acetaminophen for soreness, drink plenty of water, rest, and monitor her creatine kinase (CK) concentrations. Changes in the subject’s CK concentrations, ultrasound-determined muscle thickness and echo intensity were monitored over a 14-day period are reported. Discussion: This case illustrates the potential risk of developing exertional rhabdomyolysis after a low-load, high-repetition resistance training session in healthy, young, recreationally-trained women. The fact that exertional rhabdomyolysis is a possible outcome is enough to warrant caution when prescribing this type of resistance exercise

High-intensity interval training and beta-hydroxy-beta-methylbutyric free acid improves aerobic power and metabolic thresholds

Background: Previous research combining Calcium beta-hydroxy-beta-methylbutyrate (CaHMB) and running high-intensity interval training (HIIT) have shown positive effects on aerobic performance measures. The purpose of this study was to examine the effect of beta-hydroxy-beta-methylbutyric free acid (HMBFA) and cycle ergometry HIIT on maximal oxygen consumption (VO(2)peak), ventilatory threshold (VT), respiratory compensation point (RCP) and time to exhaustion (T-max) in college-aged men and women. Methods: Thirty-four healthy men and women (Age: 22.7 +/- 3.1 yrs; VO(2)peak: 39.3 +/- 5.0 ml center dot kg(-1)center dot min(-1)) volunteered to participate in this double-blind, placebo-controlled design study. All participants completed a series of tests prior to and following treatment. A peak oxygen consumption test was performed on a cycle ergometer to assess VO(2)peak, Tmax, VT, and RCP. Twenty-six participants were randomly assigned into either a placebo (PLA-HIIT) or 3 g per day of HMBFA (BetaTor (TM) ) (HMBFA-HIIT) group. Eight participants served as controls (CTL). Participants in the HIIT groups completed 12 HIIT (80-120% maximal workload) exercise sessions consisting of 5-6 bouts of a 2: 1 minute cycling work to rest ratio protocol over a four-week period. Body composition was measured with dual energy x-ray absorptiometry (DEXA). Outcomes were assessed by ANCOVA with posttest means adjusted for pretest differences. Results: The HMBFA-HIIT intervention showed significant (p \u3c 0.05) gains in VO(2)peak, and VT, versus the CTL and PLA-HIIT group. Both PLA-HIIT and HMBFA-HIIT treatment groups demonstrated significant (p \u3c 0.05) improvement over CTL for Tmax, and RCP with no significant difference between the treatment groups. There were no significant differences observed for any measures of body composition. An independent-samples t-test confirmed that there were no significant differences between the training volumes for the PLA-HIIT and HMBFA-HIIT groups. Conclusions: Our findings support the use of HIIT in combination with HMBFA to improve aerobic fitness in college age men and women. These data suggest that the addition of HMBFA supplementation may result in greater changes in VO(2)peak and VT than HIIT alone

High-intensity interval training and beta-hydroxy-beta-methylbutyric free acid improves aerobic power and metabolic thresholds

Background: Previous research combining Calcium beta-hydroxy-beta-methylbutyrate (CaHMB) and running high-intensity interval training (HIIT) have shown positive effects on aerobic performance measures. The purpose of this study was to examine the effect of beta-hydroxy-beta-methylbutyric free acid (HMBFA) and cycle ergometry HIIT on maximal oxygen consumption (VO(2)peak), ventilatory threshold (VT), respiratory compensation point (RCP) and time to exhaustion (T-max) in college-aged men and women. Methods: Thirty-four healthy men and women (Age: 22.7 +/- 3.1 yrs; VO(2)peak: 39.3 +/- 5.0 ml center dot kg(-1)center dot min(-1)) volunteered to participate in this double-blind, placebo-controlled design study. All participants completed a series of tests prior to and following treatment. A peak oxygen consumption test was performed on a cycle ergometer to assess VO(2)peak, Tmax, VT, and RCP. Twenty-six participants were randomly assigned into either a placebo (PLA-HIIT) or 3 g per day of HMBFA (BetaTor (TM) ) (HMBFA-HIIT) group. Eight participants served as controls (CTL). Participants in the HIIT groups completed 12 HIIT (80-120% maximal workload) exercise sessions consisting of 5-6 bouts of a 2: 1 minute cycling work to rest ratio protocol over a four-week period. Body composition was measured with dual energy x-ray absorptiometry (DEXA). Outcomes were assessed by ANCOVA with posttest means adjusted for pretest differences. Results: The HMBFA-HIIT intervention showed significant (p \u3c 0.05) gains in VO(2)peak, and VT, versus the CTL and PLA-HIIT group. Both PLA-HIIT and HMBFA-HIIT treatment groups demonstrated significant (p \u3c 0.05) improvement over CTL for Tmax, and RCP with no significant difference between the treatment groups. There were no significant differences observed for any measures of body composition. An independent-samples t-test confirmed that there were no significant differences between the training volumes for the PLA-HIIT and HMBFA-HIIT groups. Conclusions: Our findings support the use of HIIT in combination with HMBFA to improve aerobic fitness in college age men and women. These data suggest that the addition of HMBFA supplementation may result in greater changes in VO(2)peak and VT than HIIT alone

Four weeks of high- versus low-load resistance training to failure on the rate of torque development, electromechanical delay, and contractile twitch properties

The purpose of this study was to investigate the effects of 4-weeks of high- versus low-load resistance training to failure on rate of torque development (RTD), electromechanical delay (EMD), and contractile twitch characteristics. Fifteen men (mean±SD; age=21.7±2.4 yrs) were randomly assigned to either a high- (80% 1RM; n=7) or low-load (30% 1RM; n=8) training group and completed elbow flexion resistance training to failure 3 times per week for 4 weeks. The participants were tested at baseline, 2-, and 4-weeks of training. Peak RTD (pRTDV) and RTD at 0-30 (RTD30V), 0-50 (RTD50V), 0-100 (RTD100V), and 0-200 (RTD200V) ms, integrated EMG amplitude (iEMG) at 0-30, 0-50, and 0-100 ms, and EMD were quantified during maximal voluntary isometric muscle actions. Peak twitch torque, peak RTD, time to peak twitch, 1/2 relaxation time and the peak relaxation rate were quantified during evoked twitches. Four weeks of high-load, but not low-load resistance training, increased RTD200V. There were also increases in iEMG during the first 30 ms of muscle activation for the high- and low-load groups, which may have indirectly indicated increases in early phase motor unit recruitment and/or firing frequency. There were no significant training-induced adaptations in EMD or contractile twitch properties

Four weeks of high- versus low-load resistance training to failure on the rate of torque development, electromechanical delay, and contractile twitch properties

The purpose of this study was to investigate the effects of 4-weeks of high- versus low-load resistance training to failure on rate of torque development (RTD), electromechanical delay (EMD), and contractile twitch characteristics. Fifteen men (mean±SD; age=21.7±2.4 yrs) were randomly assigned to either a high- (80% 1RM; n=7) or low-load (30% 1RM; n=8) training group and completed elbow flexion resistance training to failure 3 times per week for 4 weeks. The participants were tested at baseline, 2-, and 4-weeks of training. Peak RTD (pRTDV) and RTD at 0-30 (RTD30V), 0-50 (RTD50V), 0-100 (RTD100V), and 0-200 (RTD200V) ms, integrated EMG amplitude (iEMG) at 0-30, 0-50, and 0-100 ms, and EMD were quantified during maximal voluntary isometric muscle actions. Peak twitch torque, peak RTD, time to peak twitch, 1/2 relaxation time and the peak relaxation rate were quantified during evoked twitches. Four weeks of high-load, but not low-load resistance training, increased RTD200V. There were also increases in iEMG during the first 30 ms of muscle activation for the high- and low-load groups, which may have indirectly indicated increases in early phase motor unit recruitment and/or firing frequency. There were no significant training-induced adaptations in EMD or contractile twitch properties

Tracking changes in the upper boundary of the heavy-intensity exercise domain: end-test power versus respiratory compensation point

The aim of this study was to compare how respiratory compensation point (RCP) and end-test power (EP) change in response to the same four-week high intensity interval training (HIIT). The power output associated with RCP and EP before and after HIIT were recorded in 24 recreationally-active participants (14 men and 10 women). RCP was determined from an incremental exercise test and EP was derived from a three-minute maximal effort test on a cycle ergometer. A significant time (pretest/posttest) × measurement (EP/RCP) interaction was found (F(1, 23)=5.119, p<.05). Results from a paired-sample t-test indicated that both EP (t(23)= -5.221, p<.05) and RCP (t(23)=-3.049, p<.05) increased significantly from pretest to posttest. Furthermore, a small effect size (d=.36, 90%CI=[.13, .58]) was calculated for the pre/posttest changes in the examined thresholds indicating greater potential improvements in EP compared to RCP. The pre/posttest change in EP (mean=21 W, 90%CI=[14, 28 W]) exceeded its standard error of estimate (14 W), while RCP did not. Correlation analysis revealed that EP correlated with RCP at both pretest (r=.813, p<.05) and posttest (r=.873, p<.05), however, delta values between the two measures were not significantly related. Both EP and RCP can be used to assess the change of aerobic capacity after HIIT, but may be reflective of different physiological adaptations. Further, EP may be preferred over RCP when assessing the effects of HIIT

Evaluation of the Feasibility of a Two-Method Measurement Design for the Assessment of Healthy Physical Activity Behavior in Youth

Purpose: Assess the reliability and validity of self- and parent-report survey responses regarding physical activity (PA), sedentary behaviors, and PA self-efficacy and determine if these data can be combined with objective physical activity monitor data to model the latent construct healthy physical activity behavior (HPAB). Methods: 126 underserved 4th-5th grade students participated in a 12-week after-school nutrition, cooking, and physical activity program (WeCook: Fun with Food and Fitness). Participants and parents (n=103) completed surveys pre- and post-program and participants wore PA monitors for one week at PRE and POST. Unidimensionality and internal consistency reliability were assessed for survey measures and objective PA measures (ST=step counts, FL=floors climbed) and predictive validity of survey measures was assessed through correlation with ST and FL. HPAB was modeled using z-scores (standardized across time, averaged) for youth self-reported physical activity (YPA), youth PA self-efficacy (YSE), parent-reported youth PA and sedentary behavior (AS), ST, and FL. Metric and intercept invariance were established across time and between groups selected for assessing construct validity (gender, grade, socioeconomic status, weight status, school, minority, season, grant year). Results: ST, FL, YSE, and AS were unidimensional. For ST coefficient α was 0.735 (PRE) and 0.805 (POST), for FL α was 0.686 and 0.684 (PRE and POST), for YSE, α was 0.829 (PRE) and 0.897 (POST), and for AS α was 0.545 (PRE) and 0.729 (POST). YPA was most predictive of the objective PA measures and was correlated with ST at PRE and POST and FL at PRE (pp\u3e0.05). HPAB exhibited measurement invariance across time and between groups of interest and some evidence for latent construct validity based on nomothetic span and construct representation was established. Conclusions: This study establishes some evidence supporting the feasibility of modeling HPAB using survey and objective measures of PA in youth. Advisor: James A. Bovair

Exertional rhabdomyolysis in a 21-year-old, healthy female after performing three sets of the biceps curl exercise to failure with 30% 1RM: A case report

Background: The optimal resistance training program to elicit muscle hypertrophy has been consistently debated and researched. Although 3 sets of 10 repetitions at 70-80% of the 1-repetition maximum (1RM) is widely recommended, recent studies have shown that low-load (~30% 1RM), high-repetition (3 sets of 30-40 repetitions) resistance training can elicit similar muscular hypertrophy. Therefore, this type of resistance training has gained popularity, perhaps because less weight is lifted for a longer duration. In the process of testing this hypothesis in a research study in our laboratory, a subject diagnosed with exertional rhabdomyolysis after completing a single resistance training session that involved 3 sets to failure at 30% 1RM. Exertional rhabdomyolysis is a condition characterized by the excessive breakdown of striated skeletal muscle that releases proteins from the muscle cell, particularly myoglobin, into the blood that can be toxic to the kidneys and is a significant health concern. Case Report: Reviewed were the events leading up to and throughout the diagnosis of exertional rhabdomyolysis in a healthy, recreationally-trained, 21-year-old female that was enrolled in a study that compared the acute effects of the traditional high-load, low-repetition versus low-load, high-repetition resistance training. The subject completed a total of 143 repetitions of the bilateral dumbbell bicep curl exercise. Three days post-exercise she reported excessive muscle soreness and swelling and sought medical attention. She was briefly hospitalized and then discharged with instructions to take acetaminophen for soreness, drink plenty of water, rest, and monitor her creatine kinase (CK) concentrations. Changes in the subject’s CK concentrations, ultrasound-determined muscle thickness and echo intensity were monitored over a 14-day period are reported. Discussion: This case illustrates the potential risk of developing exertional rhabdomyolysis after a low-load, high-repetition resistance training session in healthy, young, recreationally-trained women. The fact that exertional rhabdomyolysis is a possible outcome is enough to warrant caution when prescribing this type of resistance exercise