The Effects of Protein and Carbohydrate Supplementation, with and without Creatine, on Occupational Performance in Firefighters.

BACKGROUND: The purpose of this study was to assess the effects of protein and carbohydrate supplementation, with and without creatine, on occupational performance in firefighters. METHODS: Using a randomized, double-blind approach, thirty male firefighters (age: 34.4 ± 8.4 yrs., height: 1.82 ± 0.07 m; weight: 88.6 ± 12.5 kg; BF%: 17.2 ± 5.8%) were randomized to receive either (A.) 25 g of whey protein isolate + 25 g of carbohydrate powder (ProCarb group); or (B.) ProCarb + 5 g of creatine (Creatine group) in a double-blind fashion over a period of 21-26 days (depending on shift rotations) to evaluate the impact of supplementation on occupation-specific performance. At baseline and following supplementation, firefighters completed a battery of tests. These tests included an aerobic speed test on an air-braked cycle ergometer followed by the hose carry, body drag, stair climb, and Keiser sled hammer for time. RESULTS: No significant differences in measures of performance were observed at baseline (p > 0.05). There was a significant main effect for time observed for rescue, stair climb, total time to completion, and time trial performance (p < 0.05). There was a significant group × time (p < 0.05) interaction for rescue and forcible entry. Independent sample t-tests indicated that the Creatine group experienced a greater reduction (from baseline) in completion time for the rescue (1.78 ± 0.57 s, 95% CI: 0.61, 2.95 s, p = 0.004) and forcible entry (2.66 ± 0.97 s, 95% CI: 0.68, 4.65 s, p = 0.01) tests compared to the ProCarb group. No significant group × time interactions were observed for the hose line advance, stair climb, total time to completion, and time trial performance (p > 0.05). CONCLUSIONS: The addition of supplemental creatine to a protein and carbohydrate supplement to the diet of career firefighters throughout a three week period improves occupational performance in firefighters in specific areas of high-intensity, repetitive actions.

Branched-Chain Amino Acids Supplementation Does Not Accelerate Recovery after a Change of Direction Sprinting Exercise Protocol.

BCAAs supplementation has been widely used for post-exercise recovery. However, no evidence is currently available to answer the question of whether BCAAs supplementation can attenuate muscle damage and ameliorate recovery after a bout of change of direction (COD) sprinting, which is an exercise motion frequently used during team sport actions. This study aimed to assess the effect of BCAAs supplementation on muscle damage markers, subjective muscle soreness, neuromuscular performance, and the vascular health of collegiate basketball players during a 72 h recovery period after a standardized COD protocol. Participants orally received either BCAAs (0.17 g/kg BCAAs + 0.17 g/kg glucose) or placebo (0.34 g/kg glucose) supplementation before and immediately after a COD exercise protocol in a randomized, crossover, double-blind, and placebo-controlled manner. Creatine kinase increased immediately after exercise and peaked at 24 h, muscle soreness remained elevated until 72 h, whilst arterial stiffness decreased after exercise for both supplemented conditions. A negligibly lower level of interleukin-6 was found in the BCAAs supplemented condition. In conclusion, the results of this study do not support the benefits of BCAAs supplementation on mitigating muscle damage and soreness, neuromuscular performance, and arterial stiffness after COD for basketball players.

L-Citrulline supplementation attenuates aortic pulse pressure and wave reflection responses to cold stress in older adults.

BACKGROUND AND AIMS: Augmented aortic systolic blood pressure (SBP) and wave reflection via sympathetic-mediated vasoconstriction elevates the risk for adverse cardiovascular events in older adults. L-citrulline (L-CIT) supplementation has shown to reduce aortic SBP and pulse pressure (PP) responses to cold pressor test (CPT) induced sympathoactivation in young men. The aim of this study was to elucidate the efficacy of L-CIT supplementation to attenuate aortic hemodynamic responses to CPT in older adults. METHODS AND RESULTS: Sixteen older adults were randomly assigned to placebo or L-CIT (6 g/day) for 14-days in a crossover, double-blind, placebo-controlled design. Brachial SBP and aortic SBP, PP, augmented pressure (AP), augmentation index standardized at 75 bpm (AIx@75), and pressure of the forward (Pf) and reflected (Pb) waves were evaluated at rest and during CPT pre- and post-intervention. Although no hemodynamic changes at rest, brachial SBP (Δ-12 ± 18 vs. Δ4 ± 14 mmHg; P = 0.008) and aortic SBP (Δ-10 ± 14 vs. Δ4 ± 12 mmHg; P = 0.005), PP (Δ-10 ± 12 vs. Δ4 ± 11 mmHg; P = 0.002), AP (Δ-4 ± 4 vs. Δ2 ± 7 mmHg; P = 0.004), AIx@75 (Δ-3.2 ± 7.2 vs. Δ2.2 ± 6.9%; P = 0.038), Pf (Δ-6 ± 10 vs. Δ3 ± 9 mmHg; P = 0.019), and Pb (Δ-4 ± 6 vs. Δ2 ± 6 mmHg; P = 0.008) responses to the CPT were significantly attenuated following L-CIT supplementation vs. placebo. CONCLUSIONS: L-CIT supplementation attenuated aortic pulsatile pressure and pressure wave reflection responses to CPT in older adults, providing possible cardioprotection during cold-induced sympathoactivation in older adults.

Does Branched-Chain Amino Acids (BCAAs) Supplementation Attenuate Muscle Damage Markers and Soreness after Resistance Exercise in Trained Males? A Meta-Analysis of Randomized Controlled Trials.

Previous studies have reported the positive effects of branched-chain amino acids (BCAAs) supplementation on lowering plasma markers of muscle damage and subjective soreness after resistance exercise. However, a variety of factors can potentially moderate its efficacy. This meta-analysis aimed to summarize the evidence regarding the effect of BCAAs supplementation on plasma muscle damage markers and soreness after resistance exercise in only trained males, by considering the plasma lactate dehydrogenase (LDH) and creatine kinase (CK). Randomized controlled trials were identified through a computerized literature search for the period 2010-2020. The pooled data were analyzed with the random-effects model and heterogeneity using I2. Cochrane Collaboration tools was used for the assessment of risk of bias. Nine studies met the inclusion criteria. A positive effect was found for CK at <24, 24, and 48 h after exercise and for muscle soreness at <24 h only. However, the positive effect was not evident for plasma LDH at any follow-up time. Different outcomes for post-exercise responses may suggest that BCAAs supplementation can attenuate muscle damage and ameliorate muscle soreness after resistance exercise in trained males.

L-Citrulline Supports Vascular and Muscular Benefits of Exercise Training in Older Adults.

Age-associated reduction in endothelial nitric oxide (NO) synthesis contributes to the development of cardiovascular diseases and sarcopenia. L-Citrulline is a precursor of NO with the ability to improve vascular function and muscle protein synthesis. We hypothesize that vascular and muscular benefits associated with oral L-citrulline supplementation might be augmented by concomitant supplementation with exercise training in older adults.

Effects of Montmorency Tart Cherry Juice Consumption on Cardiometabolic Biomarkers in Adults with Metabolic Syndrome: A Randomized Controlled Pilot Trial.

Greater than one-third of adults in the United States have metabolic syndrome (MetS), a cluster of risk factors highly associated with the development of cardiovascular diseases. Premature vascular dysfunction in MetS may lead to accelerated age-related atherogenesis and arterial stiffening, thereby increasing cardiovascular risk. Montmorency tart cherries (Prunus cerasus L.) are rich in bioactive compounds, such as anthocyanins, known to exert cardiovascular protective effects. Previous research suggests that tart cherry juice consumption may improve cardiovascular health. The objective of this study was to evaluate the effects of daily consumption of tart cherry juice on hemodynamics, arterial stiffness, and blood biomarkers of cardiovascular and metabolic health in men and women with MetS. In a randomized, single-blind, placebo-controlled, parallel-arm pilot clinical trial, 19 men and women 20 to 60 years of age with MetS consumed 240 mL of tart cherry juice (Tart Cherry; n = 5 males, 4 females) or an isocaloric placebo-control drink (Control; n = 5 males, 5 females) twice daily for 12 weeks. Arterial stiffness (pulse wave velocity), brachial and aortic blood pressures, wave reflection (augmentation index), and blood biomarkers of cardiovascular and metabolic health were assessed at baseline and 6 and 12 weeks. Oxidized low-density lipoprotein and soluble vascular cell adhesion molecule-1 were significantly lower (P = .047 and P = .036, respectively) in Tart Cherry than Control at 12 weeks, but were not significantly lower than baseline values. There was a trend for total cholesterol to be lower (P = .08) in Tart Cherry than Control at 12 weeks. No significant changes were observed in hemodynamics, arterial stiffness, or other blood biomarkers assessed. These results suggest that daily tart cherry consumption may attenuate processes involved in accelerated atherogenesis without affecting hemodynamics or arterial stiffness parameters in this population. The pilot nature of this study warrants interpreting these findings with caution, and future clinical trials with a larger sample size are needed to confirm these findings.

Influence of L-citrulline and watermelon supplementation on vascular function and exercise performance.

PURPOSE OF REVIEW: L-Citrulline, either synthetic or in watermelon, may improve vascular function through increased L-arginine bioavailability and nitric oxide synthesis. This article analyses potential vascular benefits of L-citrulline and watermelon supplementation at rest and during exercise. RECENT FINDINGS: There is clear evidence that acute L-citrulline ingestion increases plasma L-arginine, the substrate for endothelial nitric oxide synthesis. However, the subsequent acute improvement in nitric oxide production and mediated vasodilation is inconsistent, which likely explains the inability of acute L-citrulline or watermelon to improve exercise tolerance. Recent studies have shown that chronic L-citrulline supplementation increases nitric oxide synthesis, decreases blood pressure, and may increase peripheral blood flow. These changes are paralleled by improvements in skeletal muscle oxygenation and performance during endurance exercise. The antihypertensive effect of L-citrulline/watermelon supplementation is evident in adults with prehypertension or hypertension, but not in normotensives. However, L-citrulline supplementation may attenuate the blood pressure response to exercise in normotensive men. SUMMARY: The beneficial vascular effects of L-citrulline/watermelon supplementation may stem from improvements in the L-arginine/nitric oxide pathway. Reductions in resting blood pressure with L-citrulline/watermelon supplementation may have major implications for individuals with prehypertension and hypertension. L-Citrulline supplementation, but not acute ingestion, have shown to improve exercise performance in young healthy adults.

l-Citrulline supplementation attenuates blood pressure, wave reflection and arterial stiffness responses to metaboreflex and cold stress in overweight men.

Combined isometric exercise or metaboreflex activation (post-exercise muscle ischaemia (PEMI)) and cold pressor test (CPT) increase cardiac afterload, which may lead to adverse cardiovascular events. l-Citrulline supplementation (l-CIT) reduces systemic arterial stiffness (brachial-ankle pulse wave velocity (baPWV)) at rest and aortic haemodynamic responses to CPT. The aim of this study was to determine the effect of l-CIT on aortic haemodynamic and baPWV responses to PEMI+CPT. In all, sixteen healthy, overweight/obese males (age 24 (sem 6) years; BMI 29·3 (sem 4·0) kg/m2) were randomly assigned to placebo or l-CIT (6 g/d) for 14 d in a cross-over design. Brachial and aortic systolic blood pressure (SBP), diastolic blood pressure (DBP) and mean arterial pressure (MAP), aortic augmented pressure (AP), augmentation index (AIx), baPWV, reflection timing (Tr) and heart rate (HR) were evaluated at rest and during isometric handgrip exercise (IHG), PEMI and PEMI+CPT at baseline and after 14 d. No significant effects were evident after l-CIT at rest. l-CIT attenuated the increases in aortic SBP and wave reflection (AP and AIx) during IHG, aortic DBP, MAP and AIx during PEMI, and aortic SBP, DBP, MAP, AP, AIx and baPWV during PEMI+CPT compared with placebo. HR and Tr were unaffected by l-CIT in all conditions. Our findings demonstrate that l-CIT attenuates aortic blood pressure and wave reflection responses to exercise-related metabolites. Moreover, l-CIT attenuates the exaggerated arterial stiffness response to combined metaboreflex activation and cold exposure, suggesting a protective effect against increased cardiac afterload during physical stress.

Combined whole-body vibration training and l-citrulline supplementation improves pressure wave reflection in obese postmenopausal women.

Postmenopausal women have increased wave reflection (augmentation pressure (AP) and index (AIx)) and reduced muscle function that predispose them to cardiac diseases and disability. Our aim was to examine the combined and independent effects of whole-body vibration training (WBVT) and l-citrulline supplementation on aortic hemodynamics and plasma nitric oxide metabolites (NOx) in postmenopausal women. Forty-one obese postmenopausal women were randomized to 3 groups: l-citrulline, WBVT+l-citrulline and WBVT+Placebo for 8 weeks. Brachial and aortic systolic blood pressure, diastolic blood pressure, AP, AIx, AIx adjusted to 75 beats/min (AIx@75), and NOx were measured before and after 8 weeks. All groups similarly decreased (P < 0.05) brachial and aortic pressures as well as AP, and similarly increased (P < 0.05) NOx levels. AIx and AIx@75 decreased (P < 0.01) in the WBVT+l-citrulline and WBVT+Placebo groups, but not in the l-citrulline group. The improvement in AIx@75 (-10.5% ± 8.8%, P < 0.05) in the WBVT+l-citrulline group was significant compared with the l-citrulline group. l-Citrulline supplementation and WBVT alone and combined decreased blood pressures. The combined intervention reduced AIx@75. This study supports the effectiveness of WBVT+l-citrulline as a potential intervention for prevention of hypertension-related cardiac diseases in obese postmenopausal women.