Biology subjects

Coggan, A. R.

Publications and source records attributed to Coggan, A. R..

4 recordsLinked to original sources

bioRxiv2026

Dietary nitrate does not alter the rate of torque development during maximal voluntary isometric or electrically evoked tetanic contractions in young men or women

We determined the effects of NO3- ingestion on voluntary and electrically evoked rate of torque development (RTD) in young men and women. Using double-blind, placebo-controlled crossover designs, 14 men or 12 women (tested during both early and late follicular phases) acutely ingested 200 mol/kg of NO3- from beetroot juice (BRJ) or a NO3--free BRJ placebo. Voluntary RTD (0 30 ms, 0 50 ms, 0-200 ms, maximal) was measured during maximal voluntary isometric contractions. The maximal tetanic RTD was also determined during stimulation at 100 Hz. Muscles tested included the triceps surae and triceps brachii in men and the quadriceps femoris in women. Dietary NO3- had no significant effect on initial or maximal voluntary RTD in men in either muscle group (P[≥]0.31) or in women during either menstrual phase (P[≥]0.69). Similarly, acute NO3- intake did not alter maximal tetanic RTD in men (P[≥]0.87) or women (P[≥]0.70). We conclude that acute dietary NO3- supplementation has no apparent effect on RTD during maximal voluntary or electrically evoked isometric contractions of the lower or upper limbs in young, untrained individuals. These findings argue against changes in neural activation or actomyosin crossbridge cycling rate as mechanisms driving NO3--induced improvements in muscle contractile function.

physiology↗

bioRxiv2025

Post activation potentiation is greater in human triceps brachii versus triceps surae muscles

Introduction/AimsPost activation potentiation (PAP) is an inherent characteristic of muscle wherein an increase in twitch force is observed after voluntary activation. This phenomenon is believed to be largely due to phosphorylation of the regulatory light chain of myosin. In rodents and other species, PAP occurs predominantly or exclusively in fast twitch muscles. However, it has been suggested that in humans PAP occurs more or less independently of muscle fiber type. Methods18 healthy men and women (27{+/-}8 y) underwent an electrical muscle stimulation protocol during which two sets of four twitches were elicited both pre and post 6 s maximal voluntary contractions of both the triceps surae (60-70% slow twitch) and triceps brachii (60-70% fast twitch) muscles. ResultsUnpotentiated peak twitch torque (PTT) was higher in the larger triceps surae vs. the smaller triceps brachii (i.e., 13.4{+/-}5.3 vs. 3.4{+/-}2.1 Nm; P = 8.22 x 10-13), but time to peak torque was shorter (i.e., 84{+/-}7 vs. 132{+/-}14 ms; P = 6.92 x 10-14) and the relative rate of torque development (RTD) was greater in the triceps brachii (2294{+/-}257 vs. 1425{+/-}102 %/s; P = 1.93 x 10-11). PAP increased PTT and the absolute RTD by 172{+/-}124% and 240{+/-}170% in triceps brachii versus only 20{+/-}20% and 31{+/-}24% in triceps surae, respectively (P = 1.26 x 10-4 and 1.30 x 10-4, respectively). However, PAP-induced changes in half-relaxation time and the relative rate of relaxation did not differ between the two muscle groups. DiscussionWe conclude that PAP influences contraction but not relaxation of human muscle in a fiber type dependent manner.

physiology↗

bioRxiv2020

Muscle fiber type differences in nitrate and nitrite storage and nitric oxide signaling in rats

Recent studies have emphasized the importance of the nitric oxide synthase (NOS)-independent, nitrate (NO3-) [->] nitrite (NO2-) [->] nitric oxide (NO) pathway in skeletal muscle. In particular, it has been hypothesized that this pathway is especially active in type II, or fast-twitch, muscle fibers, necessitating greater NO3- and NO2- storage. We therefore measured NO3- and NO2- concentrations in the predominantly fast-twitch vastus lateralis and predominantly slow-twitch soleus muscles of rats. Contrary to the above hypothesis, we found that NO3- and NO2- concentrations were 3.4-fold and 1.8-fold higher, respectively, in the soleus. On the other hand, NO signaling (i.e., cyclic guanosine monophosphate (cGMP) level) was comparable in the two muscles. Although the physiological significance of these observations remains to be determined, we speculate that NO production via the NO3- [->] NO2- [->] NO pathway is normally higher in slow-twitch muscles, thus helping compensate for their inherently lower NOS activity.

physiology↗

bioRxiv2019

A single dose of dietary nitrate increases maximal muscle speed and power in healthy older men and women

BackgroundAging results in reductions in maximal muscular strength, speed, and power, which often lead to functional limitations highly predictive of disability, institutionalization, and mortality in the elderly. This may be partially due to reduced nitric oxide (NO) bioavailability. We therefore hypothesized that dietary nitrate (NO3-), a source of NO via the NO3- [->] nitrite (NO2-) [->] NO enterosalivary pathway, could increase muscle contractile function in older subjects. MethodsTwelve healthy older (age 71{+/-}1 y) subjects were studied using a randomized, doubleblind, placebo-controlled, crossover design. After fasting overnight, subjects were tested 2 h after ingesting beetroot juice containing or devoid of 13.4{+/-}0.5 mmol NO3-. Plasma NO3- and NO2- and breath NO were measured periodically, and muscle function was determined using isokinetic dynamometry. ResultsNO3- ingestion increased (P<0.001) plasma NO3-, plasma NO2-, and breath NO by 1050%, 140%, and 110%, respectively. Maximal velocity of knee extension increased (P<0.01) by 1.1{+/-}0.3 rad/s, or by 10.9{+/-}3.5%. Maximal knee extensor power increased (P<0.05) by 0.14{+/-}0.06 W/kg, or by 4.4{+/-}2.3%. ConclusionsAcute dietary NO3- intake improves muscle contractility in older individuals. These findings have important implications for this population, in whom diminished muscle function can lead to functional limitations, dependence, and even premature death.

physiology↗