ABSTRACTGonzalez, AM and Trexler, ET. Effects of citrulline supplementation on exercise performance in humansA review of the current literature. J Strength Cond Res 34(5)1480–1495, 2020—L-citrulline, ...a nonessential amino acid found primarily in watermelon, has recently garnered much attention for its potential to augment L-arginine bioavailability, nitric oxide production, and exercise performance. Over the past decade, L-citrulline has received considerable scientific attention examining potentially ergogenic properties for both aerobic and anaerobic exercise performance. Thus, the purpose of this article is to summarize the theoretical rationale behind L-citrulline supplementation and to comprehensively review the available scientific evidence assessing the potential ergogenic value of L-citrulline supplementation on vascular function and exercise performance in humans. In addition, research that has investigated the potential synergistic effects of L-citrulline with other dietary ingredients (e.g., arginine, antioxidants, nitrates, and branched-chain amino acids) is reviewed. Oral L-citrulline and citrulline malate supplementation have shown to increase plasma citrulline and arginine concentrations, along with total nitrate and nitrite concentrations. Although blood flow enhancement is a proposed mechanism for the ergogenic potential of L-citrulline, evidence supporting acute improvements in vasodilation and skeletal muscle tissue perfusion after supplementation is scarce and inconsistent. Nevertheless, several studies have reported that L-citrulline supplementation can enhance exercise performance and recovery. Given the positive effects observed from some investigations, future studies should continue to investigate the effects of both acute and chronic supplementation with L-citrulline and citrulline malate on markers of blood flow and exercise performance and should seek to elucidate the mechanism underlying such effects.
Abstract
We report the detection of a rapid occultation event in the nearby Seyfert galaxy NGC 6814, simultaneously captured in a transient light curve and spectral variability. The intensity and ...hardness ratio curves capture distinct ingress and egress periods that are symmetric in duration. Independent of the selected continuum model, the changes can be simply described by varying the fraction of the central engine that is covered by transiting obscuring gas. Together, the spectral and timing analyses self-consistently reveal the properties of the obscuring gas, its location to be in the broad-line region, and the size of the X-ray source to be ∼ 25
r
g
. Our results demonstrate that obscuration close to massive black holes can shape their appearance, and can be harnessed to measure the active region that surrounds the event horizon.
ABSTRACTGonzalez, AM. Acute anabolic response and muscular adaptation after hypertrophy-style and strength-style resistance exercise. J Strength Cond Res 30(10)2959–2964, 2016—Resistance training ...paradigms are often divided into protocols designed to promote an increase in either hypertrophy or strength. Hypertrophy-style protocols (HYPs) typically involve greater volume (3–6 sets; 8–12 repetitions), moderate intensities (<85% 1 repetition maximum 1RM), and short rest intervals (30–90 seconds), whereas strength-style protocols (STRs) typically involve higher intensities (≥85% 1RM), low volumes (2–6 sets; ≤6 repetitions), and longer rest intervals (3–5 minutes). However, the literature supporting such classifications is surprisingly sparse in trained individuals, and the distinct classifications of such protocols may be an oversimplification. Thus, the purpose of this review was to examine the acute anabolic responses and training-induced muscular adaptations after HYP and STR styles of resistance exercise in trained individuals. Despite the classification of training paradigms, HYP and STR resistance training routines appear to elicit similar magnitudes of muscle growth, although STR routines appear to be more conducive to increasing strength in resistance-trained individuals. Current evidence suggests that the classification of HYP and STR is an oversimplification, and practitioners are advised to look beyond the classification of resistance exercise protocols when aiming to elicit specific physiological responses.
Nitric-oxide-stimulating dietary supplements are widely available and marketed to strength athletes and weightlifters seeking to increase muscle performance and augment training adaptations. These ...supplements contain ingredients classified as nitric oxide (NO) precursors (i.e., "NO boosters"). Endogenous NO is generated via a nitric oxide synthase (NOS)-dependent pathway and a NOS-independent pathway that rely on precursors including L-arginine and nitrates, with L-citrulline serving as an effective precursor of L-arginine. Nitric oxide plays a critical role in endothelial function, promoting relaxation of vascular smooth muscle and subsequent dilation which may favorably impact blood flow and augment mechanisms contributing to skeletal muscle performance, hypertrophy, and strength adaptations. The aim of this review is to describe the NO production pathways and summarize the current literature on the effects of supplementation with NO precursors for strength and power performance. The information will allow for an informed decision when considering the use of L-arginine, L-citrulline, and nitrates to improve muscular function by increasing NO bioavailability.
Resistance training may differentially affect morphological adaptations along the length of uni-articular and bi-articular muscles. The purpose of this study was to compare changes in muscle ...morphology along the length of the rectus femoris (RF) and vastus lateralis (VL) in response to resistance training. Following a 2-wk preparatory phase, 15 resistance-trained men (24.0 ± 3.0 y, 90.0 ± 13.8 kg, 174.9 ± 20.7 cm) completed pre-training (PRE) assessments of muscle thickness (MT), pennation angle (PA), cross-sectional area (CSA), and echo-intensity in the RF and VL at 30, 50, and 70% of each muscle's length; fascicle length (FL) was estimated from respective measurements of MT and PA within each muscle and region. Participants then began a high intensity, low volume (4 x 3-5 repetitions, 3min rest) lower-body resistance training program, and repeated all PRE-assessments after 8 weeks (2 d ∙ wk-1) of training (POST). Although three-way (muscle RF, VL x region 30, 50, 70% x time PRE, POST) repeated measures analysis of variance did not reveal significant interactions for any assessment of morphology, significant simple (muscle x time) effects were observed for CSA (p = 0.002) and FL (p = 0.016). Specifically, average CSA changes favored the VL (2.96 ± 0.69 cm2, p < 0.001) over the RF (0.59 ± 0.20 cm2, p = 0.011), while significant decreases in average FL were noted for the RF (-1.03 ± 0.30 cm, p = 0.004) but not the VL (-0.05 ± 0.36 cm, p = 0.901). No other significant differences were observed. The findings of this study demonstrate the occurrence of non-homogenous adaptations in RF and VL muscle size and architecture following 8 weeks of high-intensity resistance training in resistance-trained men. However, training does not appear to influence region-specific adaptations in either muscle.
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Citrulline malate (CitMal) is a dietary supplement that is suggested to enhance strength training performance. However, there is conflicting evidence on this matter. Thus, the purpose of this ...meta-analysis was to determine whether supplementing with CitMal prior to strength training could increase the total number of repetitions performed before reaching voluntary muscular failure. A systematic search was conducted wherein the inclusion criteria were double-blind, placebo-controlled studies in healthy participants that examined the effect of CitMal on repetitions to failure during upper body and lower body resistance exercises. The Hedges's g standardized mean differences (SMD) between the placebo and CitMal trials were calculated and used in a random effect model. Two separate subanalyses were performed for upper body and lower body exercises. Eight studies, including 137 participants who consisted of strength-trained men (n = 101) and women (n = 26) in addition to untrained men (n = 9), fulfilled the inclusion criteria. Across the studies, 14 single-joint and multijoint exercises were performed with an average of 51 ± 23 total repetitions during 5 ± 3 sets per exercise at ∼70% of one-repetition maximum. Supplementing with 6-8 g of CitMal 40-60 min before exercise increased repetitions by 3 ± 5 (6.4 ± 7.9%) compared with placebo (p = .022) with a small SMD (0.196). The subanalysis for the lower body resulted in a tendency for an effect of the supplement (8.1 ± 8.4%, SMD: 0.27, p = .051) with no significant effect for the upper body (5.7 ± 8.4%, SMD: 0.16, p = .131). The current analysis observed a small ergogenic effect of CitMal compared with placebo. Acute CitMal supplementation may, therefore, delay fatigue and enhance muscle endurance during high-intensity strength training.
ABSTRACT
Introduction: Variations in transverse point of measure on the vastus lateralis (VL) may significantly affect the relationship between structure and function. The purpose of this study was ...to compare changes in muscle architecture at 2 commonly used points of measure (VL0 and VL5). Methods: Maximal strength (1‐repetition maximum 1RM barbell squat) and muscle architecture were assessed PRE and POST 15 weeks of periodized resistance training. VL0 was 50% of the straight line distance between the greater trochanter and lateral epicondyle of the femur. VL5 was 5cm medial to VL0. Results: Increases in 1RM strength (3.7 ± 2.4 kg; P = 0.004) were observed. Changes in muscle thickness (MT) at VL5 were significantly greater than at VL0 (P = 0.006). Changes in strength correlated with changes in muscle architecture at VL0 only (MT: r = 0.561; fascicle length: r = 0.503). Conclusions: Changes in muscle architecture appear to occur in a non‐homogeneous manner. Muscle Nerve 50: 785–793, 2014
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This investigation compared the effect of high‐volume (VOL) versus high‐intensity (INT) resistance training on stimulating changes in muscle size and strength in resistance‐trained men. Following a ...2‐week preparatory phase, participants were randomly assigned to either a high‐volume (VOL; n = 14, 4 × 10–12 repetitions with ~70% of one repetition maximum 1RM, 1‐min rest intervals) or a high‐intensity (INT; n = 15, 4 × 3–5 repetitions with ~90% of 1RM, 3‐min rest intervals) training group for 8 weeks. Pre‐ and posttraining assessments included lean tissue mass via dual energy x‐ray absorptiometry, muscle cross‐sectional area and thickness of the vastus lateralis (VL), rectus femoris (RF), pectoralis major, and triceps brachii muscles via ultrasound images, and 1RM strength in the back squat and bench press (BP) exercises. Blood samples were collected at baseline, immediately post, 30 min post, and 60 min postexercise at week 3 (WK3) and week 10 (WK10) to assess the serum testosterone, growth hormone (GH), insulin‐like growth factor‐1 (IGF1), cortisol, and insulin concentrations. Compared to VOL, greater improvements (P < 0.05) in lean arm mass (5.2 ± 2.9% vs. 2.2 ± 5.6%) and 1RM BP (14.8 ± 9.7% vs. 6.9 ± 9.0%) were observed for INT. Compared to INT, area under the curve analysis revealed greater (P < 0.05) GH and cortisol responses for VOL at WK3 and cortisol only at WK10. Compared to WK3, the GH and cortisol responses were attenuated (P < 0.05) for VOL at WK10, while the IGF1 response was reduced (P < 0.05) for INT. It appears that high‐intensity resistance training stimulates greater improvements in some measures of strength and hypertrophy in resistance‐trained men during a short‐term training period.
We investigated the effect of 8 weeks of resistance training that focused on high‐volume or high‐intensity training on stimulating changes in muscle strength and size in resistance‐trained men. Our biochemical analysis revealed greater growth hormone and cortisol responses to exercise in the high‐volume group, while no group differences were observed in the testosterone, insulin‐like growth factor‐1, or insulin responses. Nevertheless, we observed greater changes in upper body strength and size following high‐intensity training, while lower body changes were equal between groups.
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ABSTRACTSell, KM, Prendergast, JM, Ghigiarelli, JJ, Gonzalez, AM, Biscardi, LM, Jajtner, AR, and Rothstein, AS. Comparison of physical fitness parameters for starters vs. nonstarters in an NCAA ...division I menʼs lacrosse team. J Strength Cond Res XX(X)000–000, 2018—The purpose of this study was to present a fitness profile of Division I male lacrosse players and compare the fitness attributes across different positions and starting status. Forty-one Division I menʼs lacrosse players (19.6 ± 1.6 years, 82.5 ± 9.5 kg, 182.0 ± 5.4 cm) volunteered to participate in the study. Fitness attributes assessed included aerobic fitness (1.5-mile run), muscular strength (1 repetition maximum bench press, squat, and hang clean), grip strength (hand dynamometer), explosive power (vertical jump), agility (3-cone drill, pro-agility), body composition (7-site skinfold), and speed (20- and 40-yard sprint). All testing was conducted by a certified strength and conditioning coach and occurred at the conclusion of pre-season training. The only significant difference across positions was for body mass, whereby defensemen were significantly heavier than attacking players (p < 0.05). Starters were significantly faster on the 3-cone drill, 20- and 40-yard sprint, and jumped significantly higher on the vertical jump compared with nonstarters (p < 0.05). Attributes pertaining to anaerobic fitness (speed, agility, and explosive power) may be better predictors of starting status than aerobic fitness in menʼs NCAA Division I lacrosse players. This differs from previous research on menʼs club lacrosse players where a difference in aerobic fitness and body composition was shown between starters and nonstarters. The normative data presented in this study may assist strength and conditioning coaches in the development of sport-specific training programs and motivate athletes toward achieving sport-specific fitness goals by helping identify areas of weakness before the start of the season.
The unprecedented COVID-19 pandemic has put a great strain on the physical and mental health of health care workers across the globe. This commentary provides an overview of mental health initiatives ...implemented at an academic medical center to support health care workers during this challenging time and highlights lessons learned.
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