Human skeletal muscle nitrate and nitrite in individuals with peripheral arterial disease: Effect of inorganic nitrate supplementation and exercise.

Skeletal muscle may act as a reservoir for N-oxides following inorganic nitrate supplementation. This idea is most intriguing in individuals with peripheral artery disease (PAD) who are unable to endogenously upregulate nitric oxide. This study analyzed plasma and skeletal muscle nitrate and nitrite concentrations along with exercise performance, prior to and following 12-weeks of exercise training combined with oral inorganic nitrate supplementation (EX+BR) or placebo (EX+PL) in participants with PAD. Non-supplemented, at baseline, there were no differences in plasma and muscle nitrate. For nitrite, muscle concentration was higher than plasma (+0.10 nmol.g-1 ). After 12 -weeks, acute oral nitrate increased both plasma and muscle nitrate (455.04 and 121.14 nmol.g-1 , p < 0.01), which were correlated (r = 0.63, p < 0.01), plasma nitrate increase was greater than in muscle (p < 0.01). Nitrite increased in the plasma (1.01 nmol.g-1 , p < 0.05) but not in the muscle (0.22 nmol.g-1 ) (p < 0.05 between compartments). Peak walk time (PWT) increased in both groups (PL + 257.6 s;BR + 315.0 s). Six-minute walk (6 MW) distance increased only in the (EX+BR) group (BR + 75.4 m). We report no substantial gradient of nitrate (or nitrite) from skeletal muscle to plasma, suggesting a lack of reservoir-like function in participants with PAD. Oral nitrate supplementation produced increases in skeletal muscle nitrate, but not skeletal muscle nitrite. The related changes in nitrate concentration between plasma and muscle suggests a potential for inter-compartmental nitrate "communication". Skeletal muscle did not appear to play a role in within compartment nitrate reduction. Muscle nitrate and nitrite concentrations did not appear to contribute to exercise performance in patients with PAD.

Impact of a Novel Training Approach on Hemodynamic and Vascular Profiles in Older Adults.

Exercise training beneficially moderates the effects of vascular aging. This study compared the efficacy of Peripheral Remodeling through Intermittent Muscular Exercise (PRIME), a novel training regimen, versus aerobic training on hemodynamic profiles in participants ≥70 years at risk for losing functional independence. Seventy-five participants (52 females, age: 76 ± 5 years) were assessed for hemodynamic and vascular function at baseline, after 4 weeks of either PRIME or aerobic training (Phase 1) and again after a further 8 weeks of aerobic and resistance training (Phase 2). Data were analyzed using 2 × 2 repeated-measures analysis of variance models on the change in each dependent variable. PRIME demonstrated reductions in brachial and aortic mean arterial pressure and diastolic blood pressure (p < .05) from baseline after Phase 1, which were sustained throughout Phase 2. Earlier and greater reductions in blood pressure following PRIME support the proposal that peripheral muscular training could beneficial for older individuals commencing an exercise program.

Beet the Best?

RATIONALE: A primary goal of therapy for patients with peripheral artery disease (PAD) and intermittent claudication is increased ambulatory function. Supervised exercise rehabilitation was recently shown to confer superior walking benefits to pharmacological or surgical interventions. Increases in plasma inorganic nitrite, via oral nitrate, have been shown to increase exercise performance in both human and animal models, especially in hypoxic conditions. OBJECTIVE: To determine whether a 36-session exercise rehabilitation program while consuming oral inorganic nitrate (4.2 mmol concentrated beetroot juice) would produce superior benefits over exercise plus placebo in pain-free walking and markers of increased skeletal muscle perfusion in patients with PAD and intermittent claudication. METHODS AND RESULTS: This was a randomized, double-blind, per-protocol study design. After the 12-week protocol, claudication onset time on a maximal treadmill test increased by 59.2±57.3 s for the exercise plus placebo group (n=13) and by 180.3±46.6 s for the exercise plus beetroot juice group (n=11; P≤0.05). This produced a between treatment medium to large standardized effect size (Cohen d) of 0.62 (95% CI, -0.23 to +1.44). The data for 6-minute walk distance showed a similar pattern with increases of 24.6±12.1 and 53.3±19.6 m ( P≤0.05) in the exercise plus placebo and exercise plus beetroot juice groups, respectively. Measures of gastrocnemius perfusion, including ankle-brachial index, peak reactive hyperemic blood flow, and tissue deoxygenation characteristics, during exercise (assessed my near-infrared spectroscopy) all changed significantly for the exercise plus beetroot juice group with moderate-to-large effect sizes over exercise plus placebo changes. CONCLUSIONS: Although it is premature to speculate on overall clinical utility of a nitrate-based therapy for PAD, this early pilot study evidence is encouraging. Specifically, our data suggests that increasing plasma nitrite before exercise may allow PAD subjects to train with less pain, at higher workloads for longer durations at each training session, thereby maximizing the beneficial peripheral vascular and skeletal muscle adaptations. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov . Unique identifier: NCT01684930 and NCT01785524.

PRIME: A Novel Low-Mass, High-Repetition Approach to Improve Function in Older Adults.

INTRODUCTION: The ability to maintain functional independence in a rapidly aging population results in an increased life expectancy without corresponding increases in health care costs. The accelerated decline in V˙O2peak after the age of 65 yr is primarily due to peripheral tissue changes rather than centrally mediated factors. The purpose of this study was to determine whether the Peripheral Remodeling through Intermittent Muscular Exercise (PRIME) approach, consisting of a low-mass, high-repetition/duration skeletal muscle focused training regimen would provide superior functional benefits in participants older than 70 yr old and at risk for losing functional independence. METHODS: In this clinical trial, 107 participants were randomized to 4 wk of either standard aerobic training (AT) or PRIME (phase 1). This was followed by 8 wk of a progressive whole-body aerobic and resistance training (AT + RT) for all participants (phase 2). The major outcome measures were cardiorespiratory fitness (peak oxygen consumption [V˙O2peak]), muscular fitness (1 repetition maximal strength [1RM]), and physical function (Senior Fitness Test [SFT] scores). Results were analyzed under a per-protocol criterion. RESULTS: Thirty-eight PRIME and 38 AT participants completed the 3-month protocols. V˙O2peak, 1RM, and SFT scores all increased significantly after 12 wk for both treatment groups (P < 0.05). However, relative to AT, participants randomized to PRIME demonstrated a greater increase in V˙O2peak (2.37 + 1.83 vs 1.50 + 1.82 mL·kg·min, P < 0.05), 1RM (48.52 + 27.03 vs 28.01 + 26.15 kg, P < 0.01) and SFT (22.50 + 9.98 vs 18.66 + 9.60 percentile, P < 0.05). CONCLUSIONS: Participants experienced greater increases in cardiorespiratory and muscular fitness and physical function when PRIME training was initiated before a combined AT + RT program. This novel exercise approach may be advantageous to individuals with other chronic disease conditions characterized by low functional capacity.

Combined Dietary Nitrate and Exercise Intervention in Peripheral Artery Disease: Protocol Rationale and Design.

BACKGROUND: Peripheral artery disease (PAD) is caused by atherosclerotic occlusions in the legs. It affects approximately 8-12 million people in the United States alone, one-third of whom suffer from intermittent claudication (IC), defined as ischemic leg pain that occurs with walking and improves with rest. Patients with IC suffer a markedly impaired quality of life and a high perception of disability. Improving pain-free walking time is a primary goal of rehabilitation in this population. OBJECTIVE: The nitric oxide (NO)-PAD trial is designed to compare the effects that 12 weeks of supervised exercise training, in combination with a high inorganic nitrate-content (beetroot [BR] juice) beverage or placebo (PL) beverage, has on clinical outcomes of exercise and functional capacity in two groups of PAD+IC patients: exercise training plus beetroot (EX+BR) and exercise training plus placebo (EX+PL). The primary aims of this randomized controlled, double-blind pilot study are to determine group differences following 12 weeks of EX+BR versus EX+PL in the changes for (1) exercise capacity: pain-free walking time (claudication onset time, COT), peak walk time (PWT), and maximal exercise capacity (peak oxygen uptake, VO2peak) during a maximal-graded cardiopulmonary exercise test (max CPX) and (2) functional capacity: 6-minute walk (6MW) distance. The secondary aims will provide mechanistic insights into the exercise outcome measures and will include (1) gastrocnemius muscle oxygenation during exercise via near-infrared spectroscopy (NIRS); (2) gastrocnemius muscle angiogenesis: capillaries per unit area and per muscle fiber, and relative fraction of type I, IIa, IIb, and IId/x fibers; and (3) vascular health/function via brachial artery flow-mediated dilation, lower-limb blood flow via plethysmography, and pulse wave velocity and reflection. METHODS: A total of 30 subjects between 40 and 80 years of age with PAD who are limited by IC will undergo exercise training 3 days per week for 12 weeks (ie, 36 sessions). They will be randomized to either the EX+BR or EX+PL group where participants will consume a beverage high in inorganic nitrate (4.2 mmol) or a low-nitrate placebo, respectively, 3 hours prior to each training session. RESULTS: Data collection from this study has been completed and is in the process of analysis and write-up. While the study is too underpowered-EX+BR, n=11; EX+PL, n=13-to determine between-group differences in the primary outcomes of COT, PWT, and 6MW, preliminary observations are promising with Cohen d effect sizes of medium to large. CONCLUSIONS: Exercise training is currently the most effective therapy to increase functional capacity in PAD+IC. If the addition of inorganic nitrate to an exercise regimen elicits greater benefits, it may redefine the current standard of care for PAD+IC. TRIAL REGISTRATION: ClinicalTrials.gov NCT01684930; https://clinicaltrials.gov/ct2/show/NCT01684930 (Archived by WebCite at http://www.webcitation.org/6raXFyEcP).

Unlocking the barriers to improved functional capacity in the elderly: rationale and design for the "Fit for Life trial".

Advancing age is associated with an increase in physical impairment, functional limitations, disability, and loss of independence. Regular physical activity conveys health benefits, but the yield on physical function in the elderly, is less clear. Current exercise guidelines are focused predominantly on aerobic programs despite evidence that age-associated declines are mediated by peripheral tissue changes. The Fit for Life trial proposes a new paradigm of exercise training for the elderly that uses a low-mass high-repetition training regimen specifically focused on peripheral tissue beds or body regions (Regional Specific Training Stimulus - RSTS). RSTS is designed to deliver a localized stimulus to the peripheral vasculature, bone and muscle, without imposing a significant central cardiorespiratory strain. The purpose of this study is three-fold; 1) to derive effect sizes from the RSTS intervention by which to power a subsequent larger, confirmatory trial; 2) to assess fidelity of the RSTS intervention; and 3) to assess the interrelationship of the primary endpoints of physical impairment/fitness (VO(2peak), 1 repetition maximal contraction) and function (Senior Fitness Test scores) following two versions of a 4 + 8 week protocol. Men and women over 70 years, at risk for losing independence will be randomized to either 4 weeks of RSTS or "aerobic" exercise, followed by an identical 8 weeks of progressive whole-body training (aerobic plus resistance). The guiding hypothesis is that the magnitude of adaptation after 12 weeks will be greatest in those initially randomized to RSTS. Possible mediators of the intervention effect - physical impairment/fitness and function relationship, including vascular function, muscle mass, strength, and physiology will also be assessed.

The relationship between serum and salivary cortisol levels in response to different intensities of exercise.

PURPOSE: The effect of exercise intensity on the tracking of serum and salivary cortisol responses was examined in 12 endurance-trained males (maximal oxygen uptake [VO2max] = 58.2 ± 6.4 mL/kg/min). METHODS: Subjects rested for 30 min (control) and exercised on a cycle ergometer for 30 min at 40% (low), 60% (moderate), and 80% (high intensity) of VO2max on separate days. Serum and saliva samples were collected pretrial, immediately posttrial, and 30 min into the recovery period from each trial. RESULTS: Cortisol responses increased significantly for both serum (40.4%; P = .001) and saliva (170.6%; P = .007) only in response to high-intensity exercise. Peak saliva cortisol occurred at 30 min of recovery, whereas peak serum was at the immediate posttrial sampling time point. The association between serum and saliva cortisol across all trials was examined using concordance correlation (Rc) analysis, which accounts for repeated measures. The overall correlation between serum and saliva cortisol levels in all matched samples was significant (Rc = 0.728; P = .001). The scatter plot revealed that salivary cortisol responses tracked closely to those of serum at lower concentrations, but not as well at higher concentrations. CONCLUSIONS: Findings suggest salivary measurements of cortisol closely mirror those in the serum and that peak salivary concentrations do not occur until at least 30 min into the recovery from intense exercise.

Comparison of the hormonal responses to exhaustive incremental exercise in adolescent and young adult males.

OBJECTIVE: Evaluate hormonal responses to incremental-stage exercise (EX) test to exhaustion in adolescents. SUBJECTS AND METHODS: Adolescents were tested at 16 years of age in Tanner Stage 4 (TS4) and at 17 years of age in Tanner Stage 5 (TS5) (n = 6). Adults were tested at 21 ± 1 y. (X ± SD) (n = 4) and served as controls. Blood samples were taken at rest, at the end of each EX stage. RESULTS: Main effects for EX in cortisol (p < 0.01, increasing with each EX stage) and for subject group for testosterone (T) occurred (p < 0.01; TS4 < TS5, adults). Interaction effect of group by EX stage occurred for GH (p < 0.05). GH increased in response to EX in all groups, however, the magnitude of increase was significantly less for TS5 and adults than TS4. CONCLUSIONS: Differences in T and GH responses for TS4 than those for TS5 and adults reflect the differing maturation levels of the endocrine system between Tanner Stages. TS5 adolescents are more similar to young adults in hormonal responses to EX than are TS4 adolescents.

Dietary nitrate supplementation enhances exercise performance in peripheral arterial disease.

Peripheral arterial disease (PAD) results in a failure to adequately supply blood and oxygen (O(2)) to working tissues and presents as claudication pain during walking. Nitric oxide (NO) bioavailability is essential for vascular health and function. Plasma nitrite (NO(2)(-)) is a marker of vascular NO production but may also be a protected circulating "source" that can be converted to NO during hypoxic conditions, possibly aiding perfusion. We hypothesized that dietary supplementation of inorganic nitrate in the form of beetroot (BR) juice would increase plasma NO(2)(-) concentration, increase exercise tolerance, and decrease gastrocnemius fractional O(2) extraction, compared with placebo (PL). This was a randomized, open-label, crossover study. At each visit, subjects (n = 8) underwent resting blood draws, followed by consumption of 500 ml BR or PL and subsequent blood draws prior to, during, and following a maximal cardiopulmonary exercise (CPX) test. Gastrocnemius oxygenation during the CPX was measured by near-infrared spectroscopy. There were no changes from rest for [NO(2)(-)] (152 ± 72 nM) following PL. BR increased plasma [NO(2)(-)] after 3 h (943 ± 826 nM; P ≤ 0.01). Subjects walked 18% longer before the onset of claudication pain (183 ± 84 s vs. 215 ± 99 s; P ≤ 0.01) and had a 17% longer peak walking time (467 ± 223 s vs. 533 ± 233 s; P ≤ 0.05) following BR vs. PL. Gastrocnemius tissue fractional O(2) extraction was lower during exercise following BR (7.3 ± 6.2 vs. 10.4 ± 6.1 arbitrary units; P ≤ 0.01). Diastolic blood pressure was lower in the BR group at rest and during CPX testing (P ≤ 0.05). These findings support the hypothesis that NO(2)(-)-related NO signaling increases peripheral tissue oxygenation in areas of hypoxia and increases exercise tolerance in PAD.

Comparison of the hormonal responses to exhaustive incremental exercise in adolescent and young adult males / Comparação das respostas hormonais ao exercício incremental até exaustão em adolescentes e adultos jovens do sexo masculino

OBJECTIVE: Evaluate hormonal responses to incremental-stage exercise (EX) test to exhaustion in adolescents. SUBJECTS AND METHODS: Adolescents were tested at 16 years of age in Tanner Stage 4 (TS4) and at 17 years of age in Tanner Stage 5 (TS5) (n = 6). Adults were tested at 21 ± 1 y. (X ± SD) (n = 4) and served as controls. Blood samples were taken at rest, at the end of each EX stage. RESULTS: Main effects for EX in cortisol (p < 0.01, increasing with each EX stage) and for subject group for testosterone (T) occurred (p < 0.01; TS4 < TS5, adults). Interaction effect of group by EX stage occurred for GH (p < 0.05). GH increased in response to EX in all groups, however, the magnitude of increase was significantly less for TS5 and adults than TS4. CONCLUSIONS: Differences in T and GH responses for TS4 than those for TS5 and adults reflect the differing maturation levels of the endocrine system between Tanner Stages. TS5 adolescents are more similar to young adults in hormonal responses to EX than are TS4 adolescents.

OBJETIVO: Avaliar as respostas hormonais ao teste de exercício em estágios incrementais (EX) até exaustão. SUJEITOS E MÉTODOS: Foram examinados adolescentes com 16 anos de idade e índice Tanner 4 (TS4) e com 17 anos de idade e índice Tanner Stage 5 (TS5) (n = 6), e adultos com 21 ± 1 anos de idade. (X ± SD) (n = 4), estes últimos compondo o grupo controle. As amostras de sangue foram retiradas no repouso e ao final de cada estágio EX. RESULTADOS: Os principais efeitos observados no EX ocorreram no cortisol (p < 0,01, aumentou com a elevação do estágio EX) e no grupo de testosterona (p < 0,01; TS4 < TS5, adultos). Houve efeito de interação entre grupos e por estágio de EX no grupo de hormônio de crescimento (p < 0,05). O hormônio de crescimento aumentou em todos os grupos em resposta ao EX, no entanto, a magnitude dos aumentos observados foi significativamente menor em TS5 e nos adultos do que em TS4. CONCLUSÕES: As diferenças verificadas nas respostas dos grupos de testosterona e hormônio de crescimento em TS4 em relação ao TS5 e adultos refletem os diferentes níveis de maturação do sistema endócrino entre os estágios do índice de Tanner. Os adolescentes no TS5 se assimilam mais aos jovens adultos do que aos adolescentes TS4, quanto a suas respostas hormonais ao EX.