Abstract
Purpose
Dietary nitrate (NO3−) supplementation has been shown to improve skeletal muscle contractile function and reduce fatigue, potentially due to alterations in skeletal muscle Ca2+ handling/sensitivity. Because aging muscle can have impaired Ca2+ handling, the aim of the study was to evaluate the effects of dietary NO3− supplementation on muscle contractile properties in young and older adults.
Methods
Eleven older (69 ± 4 yr, O) and 11 young (26 ± 2 yr, YG) adults consumed either NO3−-rich beetroot juice (BR) or placebo (PLA), for 7 d. After supplementations, plantar flexors of dominant leg were evaluated as follow: a) maximal voluntary isometric contraction (MVIC), b) potentiated single twitches (Twpot) and double twitches electrical stimulations at the frequency of 100 Hz (Db100) on the tibial posterior nerve, c) a fatigue isometric (70% of MVIC) test until exhaustion. The force–frequency relationship was assessed with trains of electrical pulses across a wide range of frequencies on the muscle belly of the nondominant leg.
Results
BR supplementation increased plasma [NO3−] and nitrite [NO2−] in both O and YG compared with PLA (more than sevenfold; all P ≤ 0.02). No changes were observed in MVC, Twpot, and Db100 force after BR compared with PLA in both YG and O. Only in O, Db100 area under the curve (−7 ± 6 N·s change from PLA) and half relaxation time (−0.05 ± 0.06 s change from PLA) were significantly reduced, and time to exhaustion (+32 ± 43 s change from PLA) was significantly longer (all P < 0.02) after BR. In O, BR also significantly increased submaximal force produced by trains of electrical pulses (P < 0.001).
Conclusions NO3− supplementation positively affects muscle contractile proprieties, submaximal electrically evoked force production, and fatigue resistance in older adults, whereas these positive results were not found in young.
Dietary nitrate (NO3−) supplementation has been shown to improve skeletal muscle contractile function and reduce fatigue, potentially due to alterations in skeletal muscle Ca2+ handling/sensitivity. Because aging muscle can have impaired Ca2+ handling, the aim of the study was to evaluate the effects of dietary NO3− supplementation on muscle contractile properties in young and older adults.
Methods
Eleven older (69 ± 4 yr, O) and 11 young (26 ± 2 yr, YG) adults consumed either NO3−-rich beetroot juice (BR) or placebo (PLA), for 7 d. After supplementations, plantar flexors of dominant leg were evaluated as follow: a) maximal voluntary isometric contraction (MVIC), b) potentiated single twitches (Twpot) and double twitches electrical stimulations at the frequency of 100 Hz (Db100) on the tibial posterior nerve, c) a fatigue isometric (70% of MVIC) test until exhaustion. The force–frequency relationship was assessed with trains of electrical pulses across a wide range of frequencies on the muscle belly of the nondominant leg.
Results
BR supplementation increased plasma [NO3−] and nitrite [NO2−] in both O and YG compared with PLA (more than sevenfold; all P ≤ 0.02). No changes were observed in MVC, Twpot, and Db100 force after BR compared with PLA in both YG and O. Only in O, Db100 area under the curve (−7 ± 6 N·s change from PLA) and half relaxation time (−0.05 ± 0.06 s change from PLA) were significantly reduced, and time to exhaustion (+32 ± 43 s change from PLA) was significantly longer (all P < 0.02) after BR. In O, BR also significantly increased submaximal force produced by trains of electrical pulses (P < 0.001).
Conclusions NO3− supplementation positively affects muscle contractile proprieties, submaximal electrically evoked force production, and fatigue resistance in older adults, whereas these positive results were not found in young.
| Original language | English |
|---|---|
| Pages (from-to) | 1721-1731 |
| Number of pages | 11 |
| Journal | Medicine & Science in Sports & Exercise |
| Volume | 57 |
| Issue number | 8 |
| DOIs | |
| Publication status | Published - 1 Aug 2025 |