Courtenay Dunn-lewis - Academia.edu (original) (raw)

Papers by Courtenay Dunn-lewis

Previous research has shown reduced tissue disruption and inflammatory responses in women as comp... more Previous research has shown reduced tissue disruption and inflammatory responses in women as compared to men following acute strenuous exercise. While the mechanism of this action is not known, estrogen may reduce the inflammatory response through its interaction with granulocytes. The purpose of this study was to determine if estrogen receptor expression on granulocytes is related to sex diVerences in tissue disruption in response to an acute heavy resistance exercise protocol. Seven healthy, resistance-trained, eumenorrheic women (23 § 3 years, 169 § 9.1 cm, 66.4 § 10.5 kg) and 8 healthy, resistance-trained men (25 § 5 years, 178 § 6.7 cm, 82.3 § 9.33 kg) volunteered to participate in the study. Subjects performed an acute resistance exercise test consisting of six sets of Wve squats at 90% of the subject's one repetition maximum. Blood samples were obtained pre-, mid-, post-, and 1-, 6-, and 24-h postexercise. Blood samples were analyzed for 17-estradiol by ELISA, creatine kinase by colorimetric enzyme immunoassay, and estradiol receptors on circulating granulocytes through Xow cytometry. Men had higher CK concentrations than women at baseline/control. Men had signiWcantly higher CK concentrations at 24-h postex-ercise than women. No signiWcant changes in estradiol receptors were expressed on granulocytes after exercise or between sexes. While sex diVerences occur in CK activity in response to strenuous eccentric exercise, they may not be related to estradiol receptor expression on granulocytes. Thus, although there are sex diVerences in CK expression following acute resistance exercise, the diVerences may not be attributable to estrogen receptor expression on granu-locytes.

Purpose: This investigation sought to determine the most predictive measures of performance on a ... more Purpose: This investigation sought to determine the most predictive measures of performance on a repetitive box lifting task (RBLT) and load bearing task (LBT) among 123 women (aged 23±4 years, height 165±7 cm, body mass 64±10 kg).
Methods: To determine the relationship of various predictors to performance on the RBLT and LBT, multiple regres- sion analysis was conducted on body mass, height, leg cross-sectional area, upper and lower body muscular strength, lower body explosive power, upper and lower body local muscular endurance, and aerobic capacity.
Results: The mean±SD (range) number of repetitions for the RBLT was 86±23 (20-159). The mean±SD (range) time to complete the LBT was 2,054±340 seconds (1,307-3,447). The following equations were generated: RBLT (number of repetitions)=57.4+0.2(peak jump power)+0.4(number of pushups in 2 minutes)+0.15(number of repetitions during the squat endurance test)+1.39(one repetition maximal strength boxlift (kg))–0.04(2-mile run time (2MR) in seconds), R=0.81; standard error of the estimate (SEE)=14; LBT (in seconds)=1,831 – 4.28(number of repetitions during the squat endurance test) + 0.95(2MR in seconds) – 13.4(body mass), R=0.73; SEE=232.
Conclusions: We found that the 2MR and squat endurance test were significant predictive factors for performance on both load carriage tasks. These data also imply that women’s performance in combat-related tasks can be improved with training that targets muscular strength, power, and local muscular endurance in addition to aerobic capacity.

Background: A sedentary lifestyle is a major risk factor for cardiovascular and thrombotic compli... more Background: A sedentary lifestyle is a major risk factor for cardiovascular and thrombotic complications. While habitual endurance activity will reduce the risk of these adverse events, the influence of habitual resistance exercise is less clear. This study examined coagulation and fibrinolytic responses to an acute exhaustive resistance exercise test (AERET) in both resistance-trained (RT, min 2 yr, 5 men and 5 women) and untrained (UT, 5 men and 5 women) subjects. Methods: The AERET consisted of six sets of 10 repetitions of squats at 80% of 1-repetition maximum. Venous blood was collected pre-exercise, immediate post exercise (IP), and + 15, + 60, and +120 minutes post exercise. Results: Compared to UT, RT exhibited a lower capacity to form a clot as seen by activated partial Thrombo-plastin time (aPTT) integrated area under the curve over time (iAUC) levels, lower pre-exercise and 120 min post-exercise plasminogen activator inhibitor −1 (PAI-1) activity, and higher tissue plasminogen activator (tPA) activity immediately post-exercise. There were no significant differences between RT and UT for fibrin-ogen, prothrombin fragment 1 + 2 (PTF 1 + 2), and thrombin-antithrombin complexes (TAT). Conclusion: These results suggest that habitual resistance exercise training may provide an enhanced fibrino-lytic state.

Kraemer, WJ, Looney, DP, Martin, GJ, Ratamess, NA, Vingren, JL, French, DN, Hatfield, DL, Fragala... more Kraemer, WJ, Looney, DP, Martin, GJ, Ratamess, NA, Vingren, JL, French, DN, Hatfield, DL, Fragala, MS, Spiering, BA, Howard, RL, Cortis, C, Szivak, TK, Comstock, BA, Dunn-Lewis, C, Hooper, DR, Flanagan, SD, Volek, JS, Ander- son, JM, Maresh, CM, and Fleck, SJ. Changes in creatine kinase and cortisol in national collegiate athletic association division I American football players during a season. J Strength Cond Res 27(2): 434–441, 2013—The purpose of this study was to track creatine kinase (CK) and serum cortisol over an American college football season starting with the preseason practice. A secondary purpose was to observe changes in basic clinical chemistries. Twenty-two National Collegiate Athletic Association Division I football players (age: 20.4 6 1.1 years, height: 188.27 6 8.3 cm, weight: 115.8 6 29.7 kg) volunteered to participate in this study. Each of the players had participated in the summer strength and condition- ing supervised program. Resting blood samples were obtained just before the start of preseason practice (T-1), 2 weeks later (T-2), and the day after game 2 (T-3), game 4 (T-4), game 6 (T-5), and game 9 (T-6) of a 12-game season. Creatine kinase, a panel of clinical chemistries, cortisol, and testosterone were assayed at each time point. No significant changes in CK concentrations were observed over the season with peak val- ues of each range #1,070.0 IU$L21, but the largest range was observedatT-6aftergame9(119–2,834IU$L21.Theanalysis of covariance analysis demonstrated that the number of plays in the ninth game (T-6) explained the magnitude of the changes in CK. No changes in serum cortisol concentrations were observed yet, again large variations existed with peak values of each range #465.0 nmol$L21. Clinical chemistries showed various significant changes from T-1, but none were consid- ered clinically relevant changes for any player over the time course of the study. In conclusion, the strength and condition- ing program before preseason camp or the structure of sum- mer camp practices and the in-season strength and conditioning appeared to mute muscle damage and the stress response of cortisol. Such data demonstrate that changes in muscle damage and adrenal cortical stress over the season are minimal, yet large individual variations can be observed. Management of these variables appears to be related to opti- mal strength and conditioning and sports medicine programs. Thus, the greater concerns for student-athlete safety in the sport of American football are related to preventing sudden death, traumatic injury, and managing concussion syndromes.

The relationship between muscle action and fatigue is not well understood, especially in terms of... more The relationship between muscle action and fatigue is not well understood, especially in terms of potential sex-specific differences. The purpose of this investigation was to determine whether a different number of repetitions could be performed on the individual muscle actions of the bench press and squat in men and women. Ten resistance-trained men (n = 10, age: 25.2±1.2 years, height: 178.6±8.8 cm, weight: 91.4±18.1 kg, body fat: 12.7±3.6%) and women (n = 10, age: 25.4±2.4 years, height: 164±4.0 cm; weight: 58.45±3.3 kg, body fat: 20.8±1.5%) participated in this balanced and randomized within-group study. Using 85% of a one repetition maximum (1-RM), over the course of three visits, subjects performed one eccentric (ECC), concentric (CON), or combined (COMB) set to failure on the squat and bench press. Differences in muscle-action and sex-specific number of repetitions to failure were compared on the squat and bench press, where significance was p≤0.05. Across both exercises and sex, we observed significant differences between each of the three muscle actions, where the number of repetitions decreased from ECC to COMB to CON. While no sex-specific differences were observed in the squat, women performed significantly more repetitions on the ECC and CON muscle actions of the bench press. Men performed more combined repetitions however, indicating a greater reliance on the stretch shortening cycle. Different muscle actions contribute uniquely to the successful performance of a lift and fatigue. These contributions appear to differ in men and women.

ixon, PG, Kraemer, WJ, Volek, JS, Howard, RL, Gomez, AL, Comstock, BA, Dunn-Lewis, C, Fragala, MS... more ixon, PG, Kraemer, WJ, Volek, JS, Howard, RL, Gomez, AL, Comstock, BA, Dunn-Lewis, C, Fragala, MS, Hooper, DR, Ha ̈ kkinen, K, and Maresh, CM. The impact of cold-water immersion on power production in the vertical jump and the benefits of a dynamic exercise warm-up. J Strength Cond Res 24(12): 3313– 3317, 2010—The purpose of this study was to examine the influence of a cold treatment and a dynamic warm-up on lower body power in the form of a countermovement vertical jump (CMVJ). Nine physically active men, who were either current or ex-National Collegiate Athletic Association (NCAA) Division 1 athletes, consented to participate in the study. Using a balanced, randomized presentation and a within-subject design, each subject performed 4 environmental and warm-up protocols (i.e., ambient temperature without warm-up, ambient temperature with warm-up, cold without warm-up, or cold with warm-up). Two sets of 3 maximal effort CMVJs were performed on a force plate at each testing time point. For each protocol, the subjects completed a pretest set of CMVJ (pretreatment [PRE]), were then exposed to 1 of the 2 temperature treatments, completed another set of CMVJ (initial [IT]), then either went through a 15-minute warm-up, or were asked to sit in place. Then a final set of CMVJs was completed (posttreatment [PT]). The primary finding in this study was that warm-up was effective in offsetting the negative effects of cold exposure on CMVJ power. There was a significant main effect for Time (PRE . PT . IT), and there was a significant (p # 0.05) main effect for Trial (AMB = AMBWU . COLDWU . COLD). Because athletic competitions happen in various colder climates, it is important to make sure that a proper warm-up be completed to maximize the athlete’s power output. The results of this study demonstrate that when athletes are exposed to cold conditions, it is recommended that before practice or play, a dynamic warm-up be employed to optimize performance.

International Journal of Breast Cancer, 2012

It is commonly accepted that cancer cells interact with host cells to create a microenvironment f... more It is commonly accepted that cancer cells interact with host cells to create a microenvironment favoring malignant colonization. The complex bone microenvironment produces an ever changing array of cytokines and growth factors. In this study, we examined levels of MCP-1, IL-6, KC, MIP-2, VEGF, MIG, and eotaxin in femurs of athymic nude mice inoculated via intracardiac injection with MDA-MB-231 GFP human metastatic breast cancer cells, MDA-MB-231BRMS1 GFP , a metastasis suppressed variant, or PBS. Animals were euthanized (day 3, 11, 19, 27 after injection) to examine femoral cytokine levels at various stages of cancer cell colonization. The epiphysis contained significantly more cytokines than the diaphysis except for MIG which was similar throughout the bone. Variation among femurs was evident within all groups. By day 27, MCP-1, MIG, VEGF and eotaxin levels were significantly greater in femurs of cancer cell-inoculated mice. These pro-osteoclastic and angiogenic cytokines may manipulate the bone microenvironment to enhance cancer cell colonization.

Journal of Strength and Conditioning Research, 2010

Earp, JE, and Maresh, CM. Performance during squat, countermovement, and depth drop jumps. J Stre... more Earp, JE, and Maresh, CM. Performance during squat, countermovement, and depth drop jumps. J Strength Cond Res 24(3): 722-729, 2010-The purpose of this study was to examine the relationship between lower-body muscle structure and vertical jump performance. Twenty-five resistance-trained men (age, 23.3 6 3.2 years; height, 176.1 6 7.4 cm; and weight, 86.2 6 11.6 kg) took part in both anatomical and jump performance testing. Muscle fascicle thickness, fascicle length, and pennation angle were analyzed for the vastus lateralis (VL) and the lateral gastrocnemius (LG). Jump height and both relative and absolute power were measured for the squat jump (SJ), countermovement jump (CMJ), and depth drop jump (DDJ). Regressions were used to determine if jump performance could be predicted using the aforementioned structures. No VL measurements were significantly correlated with any of the jump measures. Lateral gastrocnemius pennation angle was a significant but weak predictor of jump height for all 3 jump types (SJ: r 2 = 0.212, p = 0.021; CMJ: r 2 = 0.186, p = 0.018; DDJ: r 2 = 0.263, p = 0.005). When comparing jump height at increasing preloads, none of the variables of interest could significantly predict the jump height differences between CMJ and SJ. However, LG fascicle length had a weak but significant inverse relationship with DDJ-CMJ (r 2 = 0.152; p = 0.031). Lateral gastrocnemius thickness was the strongest predictor of absolute power for all jump types and between jump types (SJ: r 2 = 0.181, p = 0.034; CMJ: r 2 = 0.201, p = 0.014; DDJ: r 2 = 0.122, p = 0.049; CMJ-SJ: r 2 = 0.201, p = 0.014; DDJ-CMJ: r 2 = 0.146, p = 0.034). Lateral gastrocnemius pennation angle was also the best predictor of relative power for all 3 jump types and between jump types (SJ: r 2 = 0.172, p = 0.038; CMJ: r 2 = 0.416, p = 0.000; DDJ: r 2 = 0.167, p = 0.024; CMJ-SJ: r 2 = 0.391, p = 0.000; DDJ-CMJ: r 2 = 0.136, p = 0.039). Results for jump performance differ from those previously found for sprinting in that greater pennation and shorter fascicles, positively predicting jumping ability at increased prestretch loads reinforcing the need for training specificity. Our findings in resistance-trained men indicate that where jumping is vital to athletic success one can benefit from developing LG muscle architecture along with addressing eccentric strength.

Growth Hormone & IGF Research, 2015

Exercise Growth hormone isoforms Bioactivity Sexual dimorphism Glutathione Sex steroids Purpose: ... more Exercise Growth hormone isoforms Bioactivity Sexual dimorphism Glutathione Sex steroids Purpose: We sought to determine if an acute heavy resistance exercise test (AHRET) would elicit sex-specific responses in circulating growth hormone (GH), with untreated serum and serum treated with a reducing agent to break disulfide-bindings between GH dimers. Methods: 19 untrained participants (nine men and ten women) participated in an acute heavy resistance exercise test using the back squat. Blood samples were drawn before exercise (Pre), immediate post (IP), + 15 min (+ 15), and + 30 min (+30) afterwards. Serum samples were chemically reduced using glutathione (GSH). ELISAs were then used to compare immunoreactive GH concentrations in reduced (+GSH) and non-reduced (− GSH) samples. Data were analyzed using a three-way (2 sex × 2 treatment × 4 time) mixed methods ANOVA, with significance set at p ≤ 0.05. Results: GSH reduction resulted in increased immunoreactive GH concentrations when compared to non-reduced samples at Pre (1.68 ± 0.33 μg/L vs 1.25 ± 0.25 μg/L), IP (7.69 ± 1.08 μg/L vs 5.76 ± 0.80 μg/L), +15 min (4.39 ± 0.58 μg/L vs 3.24 ± 0.43 μg/L), and +30 min (2.35 ± 0.49 μg/L vs 1.45 ± 0.23 μg/L). Also, women demonstrated greater GH responses compared to men, and this was not affected by reduction. Conclusions: Heavy resistance exercise increases immunoreactive GH dimer concentrations in men and women, with larger increases in women and more sustained response in men. The physiological significance of a sexually dimorphic GH response adds to the growing literature on aggregate GH and may be explained by differences in sex hormones and the structure of the GH cell network.

Journal of strength and conditioning research / National Strength & Conditioning Association, 2014

Exhaustive resistance training programs that have been previously referred to as extreme conditio... more Exhaustive resistance training programs that have been previously referred to as extreme conditioning protocols have increased in popularity in military and civilian populations in recent years. However, because of their highly fatiguing nature, proprioception is likely altered during such programs that would significantly affect the safety and efficacy of such programs. Therefore, the purpose of this study was to assess the alterations in movement patterns that result from extreme conditioning protocols and to evaluate if these protocols can be deemed safe and effective. Twelve men (age 24 ± 4.2 years, height 173.1 ± 3.6 cm, weight 76.9 ± 7.8 kg, body fat percentage 9.0 ± 2.2%) and 13 women (age 24.5 ± 3.8 years, height 166.9 ± 8.5 cm, weight 66.1 ± 9.2 kg, body fat percentage 18.6 ± 4.0%) with at least 6 months of resistance training experience involving barbell bench press, barbell deadlift, and barbell back squat performed a highly fatiguing resistance training workout. During t...

Journal of strength and conditioning research / National Strength & Conditioning Association, 2014

Within and between sexes, universal load prescription (as assigned in extreme conditioning progra... more Within and between sexes, universal load prescription (as assigned in extreme conditioning programs) creates extreme ranges in individual training intensities. Exercise intensity has been proposed to be the main factor determining the degree of muscle damage. Thus, the purpose of this study was to examine markers of muscle damage in resistance-trained men (n = 9) and women (n = 9) from a high intensity (HI) short rest (SR) (HI/SR) resistance exercise protocol. The HI/SR consisted of a descending pyramid scheme starting at 10 repetitions, decreasing 1 repetition per set for the back squat, bench press, and deadlift, as fast as possible. Blood was drawn pre-exercise (pre), immediately postexercise (IP), 15 minutes postexercise (+15), 60 minutes postexercise (+60), and 24 hours postexercise (+24). Women demonstrated significant increases in interleukin 6 (IL-6; IP), creatine kinase (CK; +24), myoglobin (IP, +15, +60), and a greater relative increase when compared with men (+15, +60). M...

Current sports medicine reports

Carnitine (L-3-hydroxytrimethylamminobutanoate) is a naturally occurring compound that can be syn... more Carnitine (L-3-hydroxytrimethylamminobutanoate) is a naturally occurring compound that can be synthesized in mammals from the essential amino acids lysine and methionine or ingested through diet. Primary sources of dietary carnitine are red meat and dairy products; however, commercially produced supplements also are available and have been shown to be safe in humans. Carnitine is stored primarily in skeletal muscle, with lower concentrations in plasma. Biologically, carnitine is essential for the transport of long-chain (carbon chain length = 10) fatty acids across the outer- and inner-mitochondrial membranes (carnitine palmitoyltransferanse I and II, respectively). Conflicting results characterized the early research focused on L-carnitine supplementation's ability to enhance endurance performance, and studies showed no changes occurred in muscle carnitine levels. Nevertheless, promising findings for its use have been observed for various pathologies, including cardiovascular d...

Journal of the American College of Nutrition, 2015

Objective: This study evaluated whether a combination of whey protein (WP), calcium beta-hydroxy-... more Objective: This study evaluated whether a combination of whey protein (WP), calcium beta-hydroxy-betamethylbutyrate (HMB), and carbohydrate exert additive effects on recovery from highly demanding resistance exercise.

Journal of the American College of Nutrition, 2014

The purpose of this study was to determine the effects of a multinutritional supplement including... more The purpose of this study was to determine the effects of a multinutritional supplement including amino acids, β-hydroxy-β-methylbutyrate (HMB), and carbohydrates on cytokine responses to resistance exercise and training. Seventeen healthy, college-aged men were randomly assigned to a Muscle Armor™ (MA; Abbott Nutrition, Columbus, OH) or placebo supplement group and 12 weeks of resistance training. An acute resistance exercise protocol was administered at 0, 6, and 12 weeks of training. Venous blood samples at pre-, immediately post-, and 30-minutes postexercise were analyzed via bead multiplex immunoassay for 17 cytokines. After 12 weeks of training, the MA group exhibited decreased interferon-gamma (IFN-γ) and interleukin (IL)-10. IL-1β differed by group at various times. Granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage colony-stimulating factor (GM-CSF), IL-6, IL-7, IL-8, IL-12p70, IL-13, IL-17, monocyte chemoattractant protein-1 (MCP-1), and macrophage infla...

Journal of Strength and Conditioning Research, 2015

To better understand how sex-specific developmental differences impact performance on a broad sel... more To better understand how sex-specific developmental differences impact performance on a broad selection of common physical fitness measures, we examined changes in boys and girls from fourth to fifth grade. Subjects included 273 boys (age: 9.5±0.6 years; height: 139.86±7.52 cm; mass: 38.00±9.55 kg) and 295 girls (age: 9.6±0.5 years; height: 139.30±7.19 cm; weight: 37.44±9.35 kg). We compared anthropometrics, cardiorespiratory and local muscular endurance, flexibility, power, and strength. A mixed methods ANOVA was used to compare boys and girls at the two time points. Pearson correlation coefficients were used to examine relationships between anthropometric and fitness measurements. Significance was set at P≤0.05. Weight increased significantly (>10%) in both sexes, and girls became significantly taller than boys after growing 4.9% by fifth grade (vs. 3.5%). Both groups improved cardiorespiratory endurance and power, although boys performed better than girls at both time points. Boys were stronger in fourth grade, but girls improved more, leading to similar fifth grade values. Girls were more flexible in fourth grade, but their significant decreases (~32.4%) coupled with large improvements in boys (~105%) resulted in similar fifth grade scores. BMI was positively correlated with run time regardless of grade or sex. Power was negatively correlated with BMI and run time in fourth grade. In conclusion, sex-specific differences in physical fitness are apparent before pubescence. Further, this selection of measures reveals sexually dimorphic changes, which likely reflect the onset of puberty in girls. Coaches and teachers should account these developmental changes and their effects on anthropometrics and fitness in boys and girls.

Current sports medicine reports

Growth hormone (hGH) presents pleiotropic effects in many tissues encompassing a diverse range of... more Growth hormone (hGH) presents pleiotropic effects in many tissues encompassing a diverse range of physiological actions. Its complexity as a family of hormones with different isoforms and different somatotroph molecular functions continues to challenge the status quo of our understanding of its release, function, and signaling. Owing to the fact that the majority of the literature has viewed hGH from the perspective of the primary 22 kD monomer, further investigation is needed as to the influence and biological activity of other aggregate and splice variant isoforms that are released into circulation. Its role over the life span and with supplementation yields equivocal results with more study needed. Testing for the use of hGH has progressed, and the first positive test was recently documented. Understanding of pituitary function and physiology will remain complex until the use of a broader range of analytical techniques, including assays, becomes mainstream.

Brain Sciences, 2012

Cortical activity is thought to reflect the biomechanical properties of movement (e.g., force or ... more Cortical activity is thought to reflect the biomechanical properties of movement (e.g., force or velocity of movement), but fatigue and movement familiarity are important factors that require additional consideration in electrophysiological research. The purpose of this within-group quantitative electroencephalogram (EEG) investigation was to examine changes in cortical activity amplitude and location during four resistance exercise movement protocols emphasizing rate (PWR), magnitude (FOR), or volume (VOL) of force production, while accounting for movement familiarity and fatigue. EEG signals were recorded during each complete repetition and were then grouped by functional region, processed to eliminate artifacts, and averaged to compare overall differences in the magnitude and location of cortical activity between protocols over the course of six sets. Biomechanical, biochemical, and exertional data were collected to contextualize electrophysiological data. The most fatiguing protocols were accompanied by the greatest increases in cortical activity. Furthermore, despite non-incremental loading and lower force levels, VOL displayed the largest increases in cortical activity over time and greatest motor and sensory activity overall. Our findings suggest that cortical activity is strongly related to aspects of fatigue during a high intensity resistance exercise movement. OPEN ACCESS Brain Sci. 2012, 2 650

Thrombosis Research, 2013

Background: A sedentary lifestyle is a major risk factor for cardiovascular and thrombotic compli... more Background: A sedentary lifestyle is a major risk factor for cardiovascular and thrombotic complications. While habitual endurance activity will reduce the risk of these adverse events, the influence of habitual resistance exercise is less clear. This study examined coagulation and fibrinolytic responses to an acute exhaustive resistance exercise test (AERET) in both resistance-trained (RT, min 2 yr, 5 men and 5 women) and untrained (UT, 5 men and 5 women) subjects. Methods: The AERET consisted of six sets of 10 repetitions of squats at 80% of 1-repetition maximum. Venous blood was collected pre-exercise, immediate post exercise (IP), and + 15, + 60, and +120 minutes post exercise. Results: Compared to UT, RT exhibited a lower capacity to form a clot as seen by activated partial Thromboplastin time (aPTT) integrated area under the curve over time (iAUC) levels, lower pre-exercise and 120 min post-exercise plasminogen activator inhibitor −1 (PAI-1) activity, and higher tissue plasminogen activator (tPA) activity immediately post-exercise. There were no significant differences between RT and UT for fibrinogen, prothrombin fragment 1 + 2 (PTF 1 + 2), and thrombin-antithrombin complexes (TAT). Conclusion: These results suggest that habitual resistance exercise training may provide an enhanced fibrinolytic state.

Sports Medicine, 2013

Growth hormone (GH) is regulated, suppressed and stimulated by numerous physiological stimuli. Ho... more Growth hormone (GH) is regulated, suppressed and stimulated by numerous physiological stimuli. However, it is believed that obesity disrupts the physiological and pathological factors that regulate, suppress or stimulate GH release. Pulsatile GH has been potently stimulated in healthy subjects by both aerobic and resistance exercise of the right intensity and duration. GH modulates fuel metabolism, reduces total fat mass and abdominal fat mass, and could be a potent stimulus of lipolysis when administered to obese individuals exogenously. Only pulsatile GH has been shown to augment adipose tissue lipolysis and, therefore, increasing pulsatile GH response may be a therapeutic target. This review discusses the factors that cause secretion of GH, how obesity may alter GH secretion and how both aerobic and resistance exercise stimulates GH, as well as how exercise of a specific intensity may be used as a stimulus for GH release in individuals who are obese. Only five prior studies have investigated exercise as a stimulus of endogenous GH in individuals who are obese. Based on prior literature, resistance exercise may provide a therapeutic target for releasing endogenous GH in individuals who are obese if specific exercise programme variables are utilized. Biological activity of GH indicates that this may be an important precursor to beneficial changes in body fat and lean tissue mass in obese individuals. However, additional research is needed including what molecular GH variants are acutely released and involved at target tissues as a result of different exercise stimuli and what specific exercise programme variables may serve to stimulate GH in individuals who are obese.

Metabolism, 2010

The purpose of this study was to examine the effects of Carnipure tartrate (Lonza, Allendale, NJ)... more The purpose of this study was to examine the effects of Carnipure tartrate (Lonza, Allendale, NJ) supplementation (total dose of 2 g/d of L-carnitine) on markers of performance and recovery from physical exertion in middle-aged men and women. Normally active and healthy men (n = 9, 45.4 ± 5.3 years old) and women (n = 9, 51.9 ± 5.0 years old) volunteered to participate in the investigation. Double-blind, placebo, balanced treatment presentation and crossover design were used with 3 weeks and 3 days of supplementation followed by a 1-week washout period before the other counterbalanced treatment was initiated. After 3 weeks of each supplementation protocol, each participant then performed an acute resistance exercise challenge of 4 sets of 15 repetitions of squat/leg press at 50% 1-repetition maximum and continued supplementation over the recovery period that was evaluated. Blood samples were obtained at preexercise and at 0, 15, 30, and 120 minutes postexercise during the acute resistance exercise challenge and during 4 recovery days as well. Two grams of L-carnitine supplementation had positive effects and significantly (P ≤ .05) attenuated biochemical markers of purine metabolism (ie, hypoxanthine, xanthine oxidase), free radical formation (malondialdehyde), muscle tissue disruption (myoglobin, creatine kinase), and muscle soreness after physical exertion. However, markers of physical performance (ie, strength, power, get up and go) were not affected by supplementation. These findings support our previous findings of L-carnitine in younger people that such supplementation can reduce chemical damage to tissues after exercise and optimize the processes of muscle tissue repair and remodeling.

International Journal of Breast Cancer, 2012

Journal of Strength and Conditioning Research, 2010

Growth Hormone & IGF Research, 2015

Journal of strength and conditioning research / National Strength & Conditioning Association, 2014

Current sports medicine reports

Journal of the American College of Nutrition, 2015

Journal of the American College of Nutrition, 2014

Journal of Strength and Conditioning Research, 2015

Current sports medicine reports

Brain Sciences, 2012

Thrombosis Research, 2013

Background: A sedentary lifestyle is a major risk factor for cardiovascular and thrombotic compli... more Background: A sedentary lifestyle is a major risk factor for cardiovascular and thrombotic complications. While habitual endurance activity will reduce the risk of these adverse events, the influence of habitual resistance exercise is less clear. This study examined coagulation and fibrinolytic responses to an acute exhaustive resistance exercise test (AERET) in both resistance-trained (RT, min 2 yr, 5 men and 5 women) and untrained (UT, 5 men and 5 women) subjects. Methods: The AERET consisted of six sets of 10 repetitions of squats at 80% of 1-repetition maximum. Venous blood was collected pre-exercise, immediate post exercise (IP), and + 15, + 60, and +120 minutes post exercise. Results: Compared to UT, RT exhibited a lower capacity to form a clot as seen by activated partial Thromboplastin time (aPTT) integrated area under the curve over time (iAUC) levels, lower pre-exercise and 120 min post-exercise plasminogen activator inhibitor −1 (PAI-1) activity, and higher tissue plasminogen activator (tPA) activity immediately post-exercise. There were no significant differences between RT and UT for fibrinogen, prothrombin fragment 1 + 2 (PTF 1 + 2), and thrombin-antithrombin complexes (TAT). Conclusion: These results suggest that habitual resistance exercise training may provide an enhanced fibrinolytic state.

Sports Medicine, 2013

Metabolism, 2010