Acute effect of dietary nitrate on forearm muscle oxygenation, blood volume and strength in older adults: A randomized clinical trial

<div><p>Both recovery time of post-exercise muscle oxygenation and muscle strength decline with aging. Although beetroot consumption has been shown to improve muscle oxygenation and exercise performance in adults, these effects in the elderly has not been addressed. The aim of the present study was to evaluate the effect of a beetroot-based gel (BG) on muscle O₂ saturation, blood volume (tHb) and handgrip strength in the elderly in response to handgrip exercise. In a randomized crossover double-blind design, twelve older subjects consumed BG (100 g of beetroot-based gel containing ~ 12 mmol nitrate) or PLA (100 g of nitrate-depleted gel nitrate-depleted). The subjects performed a rhythmic handgrip exercise which consisted of a one 1-min set at 30% of the maximal voluntary contraction (MVC) of each subject, followed by a 1 min recovery. The muscle oxygenation parameters and tHb were continuously monitored by using near-infrared spectroscopy. MVC was evaluated at baseline, immediately after exercise, and 30 min afterwards. The muscle O₂ resaturation rate during exercise recovery was greater in the BG when compared to PLA condition (1.43 ± 0.77 vs 1.02 ± 0.48%.s^-1; <i>P</i> < 0.05). Significant increase was observed in tHb during exercise recovery (10.25 ± 5.47 vs 6.72 ± 4.55 μM; <i>P</i> < 0.05) and significant reduction of handgrip strength decline was observed 30 min after exercise in BG (- 0.24 ± 0.18 vs—0.39 ± 0.20 N; <i>P</i> < 0.05). In summary, a single dose of a beetroot-based gel speeds up muscle O₂ resaturation, increases blood volume and improves recovery of handgrip strength after handgrip exercise in older adults.</p></div

Hormonal response to L-arginine supplementation in physically active individuals

Background: Nutritional supplements based on the amino acid L-arginine have been hypothesized to improve exercise performance by increasing levels of insulin and growth hormone (GH). Changes of these parameters in response to L-arginine supplementation may clarify the mechanisms underlying its putative physiological effects on physical performance. Objective: The aim of the study was to evaluate the effect of L-arginine supplementation on serum insulin, GH, Growth Factor Insulin-like (IGF-1), and cortisol in response to exercise. Exercise performance was also evaluated. Design: Fifteen trained runners were divided into groups supplemented with 6 g of L-arginine (ARG) or placebo (PLA). Blood samples were collected before supplementation (T0), immediately after the first exercise session (T1), after the second exercise session (T2), and after 20 min of rest (T3). The exercise consisted of two bouts of 5 km time-trial running test. Results: There was a significant increase in serum GH (T0: 3.28±0.95 vs. 3.21±0.5 ng/mL; T1: 4.35±0.23 vs. 4.17±0.13 ng/mL; T2: 4.22±0.25 vs. 4.17±0.09 ng/mL; T3: 4.14±0.29 vs. 4.13±0.18 ng/mL) and cortisol (T0: 198.71±53.77 vs. 207.57±69.51 nmol/L; T1: 458.16±116.12 vs. 433.26±101.77 nmol/L; T2: 454.61±125.21 vs. 431.88±74.82 nmol/L; T3: 311.14±102.91 vs. 362.26±110.42 nmol/L) after T1, T2, and T3, with no significant difference between the ARG and PLA groups, respectively. There was also no significant difference observed in the variables of IGF-1, insulin, and total running time between the ARG and PLA groups. Conclusions: The supplementation of L-arginine did not appear to stimulate the production of insulin, GH, and IGF-1 and, thus, provided no benefit in hormonal response or exercise performance in trained runners

Changes in muscle oxygenation and blood volume parameters.

<p>Changes in muscle oxygenation and blood volume parameters.</p

Values of nitrate and nitrite in both beetroot-based gel and nitrated-depleted gel conditions.

<p>Values of nitrate and nitrite in both beetroot-based gel and nitrated-depleted gel conditions.</p

A Single Dose of Beetroot Gel Rich in Nitrate Does Not Improve Performance but Lowers Blood Glucose in Physically Active Individuals

Background. Beetroot consumption has been proposed to improve exercise performance, since the nitrate content of this food is able to stimulate the synthesis of nitric oxide. Objective. The acute effect of 100 g of a beetroot gel containing ~10 mmol of nitrate was tested on the nitric oxide synthesis, on metabolic and biochemical parameters, and on performance in physically active individuals. Methods. Through a double blind, crossover, placebo-controlled study, 25 healthy runners ingested a single dose of beetroot and placebo gels. Participants performed an aerobic exercise protocol on a treadmill (3 min warm-up of 40% peak oxygen consumption, 4 min at 90% of gas exchange threshold I and 70% (Δ) maximal end speed until volitional fatigue). Results. Urinary levels of nitrite and nitrate increased after 90 min of beetroot gel ingestion. Plasma glucose concentrations lowered after the exercise and the decrease was maintained for 20 min. Systolic and diastolic blood pressures, serum cortisol, and blood lactate were not altered after the beetroot gel ingestion compared to a placebo gel. Conclusion. The single dose of beetroot gel provoked an increase of nitric oxide synthesis although no improvement on the physical performance of athletes during aerobic submaximal exercise was observed