Role of the endothelium in modulating sympathetic vasoconstriction in contracting skeletal muscle of young and older adults

2016 Spring.Includes bibliographical references.Aerobic capacity is a powerful independent predictor of all-cause mortality in healthy and disease populations. Healthy (primary) ageing is associated with a decline in maximal aerobic capacity, exercise intolerance and elevated risk for ischemic cardiovascular disease. Specifically, ageing is characterized by impaired regulation of vascular tone during exercise, due in part to lower vasodilatory signaling and elevated sympathetic vasoconstrictor activity in the peripheral vasculature. Impaired regulation of peripheral vascular tone results in attenuated blood flow and oxygen delivery to contracting skeletal muscle during exercise and is a primary contributor to the age-associated decline in aerobic capacity. The overall aim of this dissertation is to determine the vascular signaling mechanisms responsible regulating sympathetic vasoconstrictor signaling during exercise in young healthy adults and translate these findings to improve vascular function during exercise in older adults. The regulation of blood flow and oxygen delivery during exercise depends on the proper integration of local vasodilatation and neural sympathetic vasoconstriction. In healthy humans, the integration of these competing signals results in attenuation of sympathetic vasoconstriction, or “sympatholysis”, to ensure adequate blood flow to contracting skeletal muscle. The signaling mechanisms responsible for sympatholysis in healthy humans are unknown. To date, the only exogenous vasodilator shown to mimic exercise in its ability to attenuate sympathetic vasoconstriction in humans is adenosine triphosphate (ATP). The first aim of this dissertation is to determine if smooth muscle cell hyperpolarization (via activation of inwardly-rectifying potassium (KIR) channels), the primary vasodilatory pathway of ATP, is responsible for ATP-mediated attenuation of sympathetic vasoconstriction. In contrast to smooth muscle specific signaling, vasodilatory stimuli such as ATP and exercise can act through endothelium-dependent pathways. The second aim of this dissertation tests the hypothesis that endothelium-dependent signaling is capable of attenuating sympathetic vasoconstriction during exercise in young healthy humans. With age, impaired endothelial function and elevated sympathetic vasoconstrictor activity results in impaired functional sympatholysis. The third aim is to determine if augmentation of endothelium-dependent signaling during exercise improves age-associated impairments in functional sympatholysis. The primary findings of this dissertation are that 1) similar to exercise, the ability of ATP to attenuate sympathetic vasoconstriction is independent of smooth muscle cell hyperpolarization via activation of KIR channels, 2) activation of endothelium-dependent signaling during exercise significantly enhances the ability of contracting skeletal muscle to attenuate sympathetic vasoconstriction, and 3) that augmentation of endothelium-dependent signaling during exercise significantly improves functional sympatholysis in older adults. These findings are the first to identify endothelium-dependent modulation of sympathetic vasoconstriction in humans, and identifies vascular signaling pathways capable of improving the regulation of vascular tone during exercise in older adults. These findings are clinically significant for patient populations and disease states characterized by impaired functional sympatholysis including ageing, hypertension, and heart failure

The Effect of Prophylactic Knee Braces on Balance and Uninjured Knee Range of Motion

There has been numerous studies performed regarding the effectiveness of prophylactic knee braces (PKB) preventing knee injuries or the effect of PKB on injured knees, but minimal research is available on the effect of how PKB affect the functioning capacity of uninjured knees. PURPOSE: To examine the effects of two different types of PKB, hinged (HGB) and non-hinged (NHB), on uninjured preferred knee joint range of motion and dynamic balance in males and females. METHODS: Thirty subjects were recruited (male=15, female=15) with ages ranging from 18-28 years. Only participants with no history of any knee injuries or current knee problems were allowed to participate. Subjects were blinded to the purpose of the study, but were allowed practice trials for the dynamic balance test (Y-Balance test). Prior to experimental trials subjects were measured for body composition and knee brace size. All subjects underwent three experimental trials [HGB, NHB, and a no PKB control (CON)] on the same day in balanced cross-over design. During the treatment trials, the subjects wore the braces on their preferred leg. Each experimental trial was comprised of a test for dynamic balance and four tests for knee joint range of motion. Dynamic balance composite score, knee extension/flexion (°), and internal/external knee rotation (°) were compared between sex (M, F) and across PKB (HGB, NHB, CON) using an ANOVA (1 between, 1 within), α=0.05. Age and body composition differences between sex were examined using independent t-tests, α=0.05. RESULTS: M and F did not differ (p\u3e0.05) with regard to age, but did differ significantly (p\u3c0.05) in body mass, body stature, and percent body fat. For the sex main effect, when pooled across PKB (CON, HGB, NHG) M and F did not differ (p\u3e0.05) in knee flexion, internal knee rotation, right/left leg balance, but did differ significantly (p\u3c0.05) in knee extension (M=+0.8±1.8°, F=-0.6±2.4°) and external knee rotation (M=29.7±7.5°, F=35.9±9.7°). For the main effect for PKB, when pooled across sex external knee rotation and right/left leg balance did not differ (p\u3e0.05) between HGB, NHB, and CON, but both HGB and NHB differed significantly (p\u3c0.05) from CON for internal rotation (HGB=21.9±10.3°, NHB=22.5±9.8°, CON=24.8±10.0°), flexion (HGB=126.9±17.7°, NHB=125.7±15.9°, CON=139.0±6.8°), and extension (HGB=+0.7±1.4°, NHB=+=1.3±1.8°, CON=-1.7±2.2°). The sex x knee brace interaction was not significant (p\u3e0.05). CONCLUSION: PKB have no effect on dynamic balance, but appear to hinder the range of motion for most motions of the knee

Acute Responses to High Intensity Interval Exercise and Moderate Aerobic Exercise on Anaerobically and Aerobically Trained Athletes

High Intensity Interval Training (HIIT) is emerging as the popular method of training recently for its ability to deliver an exercise that still elicits almost the same health benefits, when compared to traditional methods of training. Those who are trained possess higher lactate thresholds than those who are not trained. However, there is little research on males whom are trained as anaerobically or aerobically, and their differences on lactate or blood glucose recovery. PURPOSE: The purpose of this study is to compare the acute effects of high intensity interval exercise and moderate aerobic exercise on lactic acid and blood glucose levels on athletes who are either anaerobically trained or aerobically trained. METHODS: Males (20± 2.774) of average cardiorespiratory fitness (VO2max =35 ±5.95 ) participated in a high intensity interval exercise (HIIE) and a moderate aerobic trial in a balanced cross-over design in which the subject was randomized and assessed for changes in blood lactate levels and glucose levels during exercise. The HIIE is a 4 x 4 trial in which the subject pedaled on a cycle for four intervals of 4 minutes at 90-95% of maximal aerobic capacity (VO2max), interspersed with 3 minutes of active recovery at 60% VO2max. The subjects were assessed for blood lactate and blood glucose via finger stick prior to exercise, at minute 4, 13, 24, 32 and every 10 minutes post-exercise up to 30 minutes following the cessation of the exercise bout. The subjects also participated in a moderate aerobic trial at 60% of VO2max. The subjects were assessed for blood lactate and blood glucose via finger stick however time points are varied per subject due to variations in total work outputs. RESULTS: The main effect for recovery was not significant in lactate when comparing training status across both HIIE/Mod (Ana=5.7± 4.3, Aer=8.3± 4.7) (p=0.3470). The main effect for glucose was also not significant when comparing training status across both HIIE/Mod (Ana=93± 12.5, Aer=102.7± 12.5) (p=0.2350). The main effect for lactate when comparing training (Aer/Ana) across intensity (HIIE/Mod) was not significant (AnaHi=4.6± 1.2, AnaMod=6.9± 8.2, AerHi=5.7± 1.3, AerMod=10.9± 9.0) (p=0.5620). The main effect for glucose when comparing training (Aer/Ana) across intensity (HIIE/Mod) was also not significant (AnaGlucHi=93.5± 20.1, AnaGlucMod=92.5± 13.6, AerGlucHi=112.8± 20.1, AerGlucMod=92.6± 13.6) (p=0.2100) CONCLUSIONS: Although lactate nor glucose were statistically significant in this study, when comparing the values, anaerobically trained males buffered lactic acid more efficiently than those who are aerobically trained. This might suggest that those whom are anaerobically trained possess higher lactate threshold than those who are aerobically trained

Heat Stress and Injury Prevention Practices During Summer High School Football Training in South Texas

Int J Exerc Sci 3(2) : 55-63, 2010. The purpose was to describe practice conditions influencing the risk of heat stress to athletes in summer football training in South Texas high schools, and to compare these conditions to ACSM recommendations for heat stress/injury risk reduction in this population. Thirty (N=30) high school summer football practices were observed. Wet bulb globe temperature (WBGT) was measured before/after practices and practices were observed for: duration/ structure; athlete clothing; and rest break frequency/duration/content. Practices averaged 125+31 min and WBGT (pre- to post-practice) was 29.7+2.1°C to 31.2+2.2°C for morning, and 31.2+1.6°C to 28.9+1.2°C for evening practices. Most practices included contact (93%), and a majority were full-contact (53%). Most athletes wore full pads (83%) and medium/dark colored clothing (73%). Outside of scheduled breaks athletes removed helmets (63%), sat/knelt (63%), and had access to fluid (90%). Athletic trainers were present at 93% of the practices. A typical practice had 3 rest breaks, each lasting approximately 5 min. During breaks, athletes were provided fluid (93%), removed helmets (89%), and sat/knelt (76%), but were rarely provided shade (2%). While none of the practice sessions were conducted in conditions warranting the cancellation of outside activity (WBGT\u3e33.1°C), the environmental data confirms that this region presents athletes with a very high risk of heat stress/injury. While a majority of the schools were taking many of the precautionary measures recommended by ACSM, many of the guidelines were not being followed. Governing bodies of high school athletics need to encourage compliance with recommendations for the reduction of heat stress/injury in this population

Comparison of Acute Cardiometabolic Responses in a 7-Minute Body Weight Circuit to 7-Minute HIIT Training Protocol

International Journal of Exercise Science 13(2): 395-409, 2020. To investigate the acute cardiometabolic responses of a 7-minute bodyweight resistance exercise circuit (HICE) compared to a 7-minute high intensity interval training cycle protocol (HIIE). Methods: Twelve apparently healthy and active young adults were enrolled in a randomized crossover study (HICE vsHIIE). The 12 HICE exercises used a 30:5 second exercise to rest ratio, followed by a 3-minute cool-down and was replicated in the HIIE cycle protocol. Following each protocol, subjects were seated for the next hour. Measurements included blood pressure (BP) heart rate, blood glucose and triglycerides, taken prior to exercise, immediately after, 15, 30, 45, and 60-minutes post-exercise. Blood glucose and triglycerides were only taken, immediately after and at 60-minutes. General mixed linear modeling was used to analyze the data and Cohen’s dwas calculated for effect size. Post hocanalysis of individual time points used Bonferroni adjustment. Results: There was no significant difference in overall systolic BP between HIIE and HICE (p = 0.168). However, there was a significant difference in overall diastolic BP resulting a higher response in HIIE (p = 0.002). Immediately after exercise exhibited significant (p = 0.001) and trending, respectfully, higher values in diastolic BP for HIIE. The overall post-exercise heart rate was lower for HIIE vsHICE (p \u3c 0.001). Blood glucose and Triglycerides had no overall difference between the two protocols (p = 0.104). Conclusion: The HICE protocol had a similar cardiometabolic response post-exercise to HIIE but did have a reduction in diastolic BP post-exercise. However, post-exercise heart rate was higher

Blood Lactate Response to Active Recovery in Athletes vs. Non-Athletes

Previous research has indicated an optimal intensity for active recovery following a bout of exercise for the removal of blood lactate to be at 80% of the individual’s lactate threshold. However, these previous research studies have relied primarily on highly trained athletes. Therefore, the 80% of lactate threshold might not be the optimal intensity for non-athlete populations attempting to recover from lactate producing exercise. Purpose: To investigate the acute blood lactate response during active recovery at 80% of lactate threshold for athletes vs. non-athletes following a vigorous bout of activity. Methods: Apparently healthy and active young adults (N=16, 56% male, 21±1 yr, BMI: 26.5±3.6 kg/m2, SBP: 122±13 mmHg, DBP: 71±8 mmHg) were enrolled in a cohort study design that separates subjects into highly trained collegiate athletes (participating in a NCAA sport) and non-athletes. Each subject had two study visits. Visit one included collection of subject characteristics including baseline values of blood pressure and heart rate via an automated device, and blood lactate via finger stick. Additionally, subjects underwent a Bruce Protocol on a treadmill to determine lactate threshold as well as VO2max. Visit two consisted of a treadmill warm up at 5 mph and 0% incline followed by a brief running protocol at 90% of their VO2max for 5 minutes. Immediately following the 5 minutes, subjects engaged in active recovery at 80% of the subject’s lactate threshold until baseline lactate levels were reached or until 32 minutes of active recovery was completed. Measurements of heart rate and blood lactate were taken at rest, post-warm up, post-exercise bout, and every four minutes during active recovery for day two. Area under the curve (AUC) was calculated for blood lactate and general mixed linear modeling was used to compare AUC for athletes vs. non-athletes while Cohen’s d was calculated to determine effect size. Post hoc analysis of individual time points used Bonferroni adjustment. Alpha level was set at p\u3c0.05. Results: There was a significant difference in overall lactate (b= -109.8 mmol/L, p\u3c0.001, d= 2.32) as well as at each time point during the active recovery (all p\u3c0.005). There was also a significant difference in overall heart rate in favor of athletes having lower heart rate response throughout (b= -14 bpm, p=0.003, d= 0.164). When individual time points were analyzed, there was a significant difference in heart rate at time point 7 (b=-20 bpm, p\u3c0.005, d= 2.243), time point 8 (b=-21 bpm, p\u3c0.005, d= 2.305), and at time point 10 (b=-18.533 bpm, p\u3c0.005, d= 2.080) in favor of lower heart rate for athletes. Conclusion: Active Recovery at 80% of lactate threshold demonstrated a significant difference in the removal of lactate for athletes compared to non-athletes. Future research should investigate the most efficient workload for the removal of blood lactate in non-athletes, potentially an intensity that lowers non-athletes heart rates more than the intensity used in this study

Effect of Acute Exercise Mode on Test Anxiety: Aerobic vs. Resistance

Test anxiety is a specific type of state anxiety when a person experiences perceived pressure to excel on a test. Test anxiety not only hinders test performance, but the person\u27s long term psychophysiological health. Many students struggle with test anxiety, but females have a higher incidence of test anxiety than males. Bouts of aerobic exercise have been shown to decrease state anxiety, but no work has been done examining the effects of resistant training on state anxiety. PURPOSE: the purpose of this study was to compare the effects of acute aerobic and resistance exercise bouts on test anxiety among recreationally active females. METHODS: Recreationally females (n=30, 23±4 yr., 79±15 kg, 161±7 cm) participated in three experimental trials [bout of aerobic exercise (AER), bout of resistance exercise (RES); and a control bout with no exercise (CON)] where a balanced cross-over design was used. During the exercise bouts the subjects were required to exercise at a moderate intensity equal to 40%-59% of their peak oxygen consumption rate, which was determined relative to the subject\u27s age predicted maximal heart rate (65-75% HRmax). Subjects were asked to perform the exercise bout in their target heart rate range (65-75% HRmax) for approximately 20 min. For the CON trial, the subject rested quietly for 20 min. After each bout, the subjects were required to take a standardized mathematics examination where they were told that they would be classified based on how they performed (good, average, poor). At the beginning, middle, and end of the standardized math exam perceived test anxiety (emotionality, worry, overall) was assessed via the Spielberg’s Test Anxiety Inventory (TAI). TAI scores were not different between the three administrations (p\u3e0.05), so the middle assessment was used for the subsequent analyses. RESULTS: The exercise heart rates (Mn + SD) did not differ(p\u3e0.05) between exercise trials at 10 min (AER= 133.6 + 3.8 bpm; RES=133 + 4.1 bpm) and 20 min (AER=133.5 + 3.3 bpm; RES=134.3 + 3.5 bpm), confirming that subjects were in a steady state and that exercise intensities were similar between the modes. Perceived emotionality (TAI score=8-32) was not different (p\u3e0.05) between trials (Md, Range: CON=18,8-31; AER=19,8-32; RES= 18,8-32). Perceived worry (TAI score= 8-32) was not different (p\u3e0.05) between trials (Md, Range: CON=16, 8-32); AER=18, 8-32; RES=17, 9-32). Overall anxiety scores (TAI score=20-78) was not different (p\u3e0.05) between trials (Md, Range: CON=46, 20-78); AER=49, 20-75; RES= 46, 24-73). CONCLUSION: Acute exercise had no effect on test anxiety in the recreationally active young females who participated in the study, regardless of mode. It is possible that the test administration in the study did not effectively simulate the anxiety-inducing effects of a test in a real-world setting

The Acute Effects of Self-Myofascial Release on Range of Motion and Fatigue Rate in the Lower Extremities

There has been a growing popularity in a technique similar to a massage that is easily accessible known as self-myofascial release, or more commonly as “foam rolling”. While research has been conducted to examine the effects on a smooth foam roller, little research has been conducted regarding a more aggressive form of deep tissue self-myofascial release on muscular strength and fatigability. PURPOSE: To examine the acute effect of deep tissue self-myofascial release on hip range of motion and fatigue rate of the quadriceps in uninjured individuals. METHODS: Nineteen males, ages 20-35, with no prior knee surgery/injury on their preferred leg regardless of current functional status were recruited. Subjects were allowed familiarity trials for goniometry of hip flexion/extension, self-myofascial release, and the isokinetic strength/fatigability test prior to exercise testing. All subjects underwent three experimental trials [self-myofascial release (SMR), static stretching (STS), no additional warm-up control (CON)] in a balanced crossover design. During the treatment trials, subjects were required to perform a 10 minute warm-up on a stationary rate independent cycle ergometer (50 W) followed by one of the treatments applied to the hamstrings and quadriceps of the preferred leg; SMR (1 set; 2 min), STS (4 sets; 30 secs). Subjects were required to perform the Thorstensson test, using a single-chair isokinetic dynamometer, which consisted of 50 voluntary maximal isokinetic leg extensions on their preferred leg where the rate of force production was controlled as 180°.sec-1. Measurement of hip flexion (HF) and extension (HE), absolute peak quadriceps force production (AF), relative peak quadriceps force production (RF), quadriceps fatigue rate (FR), and perceived local leg fatigue (PF) were recorded. One-way ANOVA with repeated measures was used to analyze for differences between trials (STS, SMR, CON), except for FR where a Friedman ANOVA was used, α=0.05. RESULTS: HF did differ significantly between the treatments (p\u3c0.05) where SMR (113.7±4.8°) and STS (114.7±4.9°) \u3e CON (106.2±5.0°). The treatments also differed significantly (p\u3c0.05) in HE, where SMR (19.7±3.3°) and STS (18.2±4.3°) \u3e CON (13.2±3.6°). AF did not differ significantly (p\u3e0.05) between the treatments (SMR=175.2±32.1 Nm, STS=180.9±35.6 Nm, CON=177.2±38.3 Nm), nor did RF (SMR=1.9±0.4 Nm/kg, STS=1.9±0.4 Nm/kg, CON=1.9±0.4). FR also did not differ (p\u3e0.05) between treatments (SMR=59.7±9.4%, STS=61.3±11.0%, CON=61.5±8.8%). PF was seen to be more frequently greater with most subjects in CON, but there were no significant difference (p\u3e0.05) between trials. CONCLUSION: While SMR had no effect on muscular strength and fatigability, SMR did have similar significant effect as static stretching on hip range of motion

The Effect of a Commercially Available Pre-Workout Supplement (The Bracket™) on Wingate Anaerobic Cycle Test Performance in Athletic Females

The Bracket™ is a proprietary blend, pre-workout supplement whose primary active ingredients consists mostly of a mixture of creatine, B-complex vitamins, and a glycerol/taurine combination. It has been third party tested for ingredient accuracy, and is also certified by NSF, meaning that it is certified for sports consumption. Previous research has been done on the ingredients within the supplement utilizing male demographics. However, there is limited research done on the pre-workout supplement as a whole. The little research done has showed no increases in any variables such as power output (relative/absolute) and/or rate of fatigue. Very little research has been done utilizing a female population, let alone athletic females. PURPOSE: To examine the effect of a commercially available pre-workout supplement (The Bracket™), in athletic females, on absolute peak power (APP), absolute mean power (AMP), relative peak power (RPP), relative mean power (RMP), rate of fatigue (FTR), absolute total work (ATW), and relative total work (RTW) utilizing the Wingate Anaerobic Cycle Test (WACT), a 30-s supra maximal exercise protocol. METHODS: Thirteen athletic females, ages 18-30, with no prior hamstrings or quadriceps injuries within the last years were recruited. All subjects underwent three experimental trials [treatment (TRT, supplement with Gatorade®), placebo (PLC, Gatorade®), and a control (CON, water)] in a single blind balanced crossover design. During the trials the subjects had to ingest one of the three liquids in an 8 ounce serving thirty minutes prior to engaging in the WACT. Each trial was performed approximately one week apart. The differences in the dependent variables between treatments were analyzed using an ANOVA (0 between, 1 within), α=0.05. RESULTS: No significant difference between trials were seen for APP (TRT=715 ± 126 W; PLC=71 6± 125 W; CON=696 ± 147 W) (p=0.2940), AMP (TRT=446 ± 94 W; PLC=436 ± 85 W; CON=441 ± 91 W)(p=0.3930), RPP (TRT=11.6 ±. 1.4 W·kg-1; PLC=11.6 ±. 1.5 W·kg-1; CON=11.3 ±. 1.5 W·kg-1)(p=0.2280), RMP (TRT=7.3 ±. 1.4 W·kg-1; PLC=7.1 ± 1.1 W·kg-1; CON=7.2 ±. 1.3 W·kg-1)(p=0.3920), FTR (TRT=62 ± 13%; PLC=61 ± 11%; CON=59 ± 11%) (p=0.1920), ATW (TRT=13368 ± 2798 J; PLC=13066 ± 2550 J; CON=13246 ± 2749 J)(p=0.4100), or RTW (TRT=218 ± 42 J·kg-1; PLC=212 ± 33 J·kg-1; CON= 215 ± 38 J·kg-1)(p=0.4080). CONCLUSION: Ingestion of (The Bracket™) prior to exercise does not affect performance on the WACT in athletic females

Factors Associated with Diabetes Risk in South Texas College Students

International Journal of Exercise Science 7(2) : 110-118, 2014. South Texas has a high prevalence of diabetes and college students may be particularly at risk. While increased BMI, sedentary activity and depression have been associated with diabetes progression in the general population, it has not been established whether these factors contribute to increased diabetes risk in college students. The purpose of this study was to assess diabetes risk and determine whether depressive symptoms or physical activity patterns are associated with increased diabetes risk in college students. Sixty-nine college students were assessed for diabetes risk using the Finnish Diabetes Risk Score (FINDRISC) . Each participant completed the International Physical Activity Questionnaire (IPAQ) which included a sitting subscale, the Zung Self-Rated Depression Scale, and had anthropometric measures taken. Of the participants, 21.7% reported elevated risk (FINDRISC score 7-11), and 4.3% of participants had a moderate-to-high risk of developing diabetes (FINDRISC \u3e12). On average, the sample was overweight (BMI = 26.81±0.75 kg . m-2), and BMI was associated with diabetes risk (r = 0.626, p \u3c 0.001). While diabetes risk was not correlated with IPAQ total physical activity score (r = 0.019, p = 0.874), it was modestly correlated with time spent sitting (r = 0.295, p = 0.015). There was no association between self-reported depressive symptoms and diabetes risk (r =0.078, p = 0.525). Although diabetes risk was not associated with total activity and depressive symptoms, it was associated with time spent sitting and BMI. These results suggest that in this population, sitting less and reducing weight may help lower the risk of developing diabetes