Ischemia causes muscle fatigue

Abstract

Tlie purpose of this investigation was to determine whether iscliemia, which reduces oxygenation in the extensor carpi radialis (ECR) muscle, causes a reduction in muscle force production. In eight subjects, muscle oxygenation (TOz) of the right ECR was measured noninvasively and continuously using near infrared spectroscopy (NIRS) while muscle twitch force was elicited by transcutaneous electrical stimulation ( 1 Hz, 0.1 ms). Baseline measurements of blood volume, muscle oxygenation and twitch force were recorded continuously, then a tourniquet on the upper arm was inflated to one of five different pressure levels: 20, 40, 60 mm Hg (randomized order) and diastolic (69 * 9.8 mm Hg) and systolic (106 f 12.8 mm Hg) blood pressures. Each pressure level was maintained for 3-5 niin, and was followed by a recovery period sufficient to allow measurements to return to baseline. For each respective tourniquet pressure level, mean TO2 decreased from resting baseline ( 100% TO?) to 99 f 1.2% (SEM), 96 f I .9'% 93 f 2.8%. 90 2~ 2.5%, and 86 i 2.7'!4, and mean twitch force decreased from resting baseline (100% force) to 99 f 0.7'/'0 (SEM), 96 i 2.7'%1, 93 j , 3.1'J/~~, 88 & 3.2'!'11, and 86 & 2.6' /11. Muscle oxygenation and twitch force at 60 mm Hg tourniquet compression and above were significantly lower ( P < 0.05) than baseline value. Reduced twitch force was correlated in a dose-dependent manner with reduced muscle oxygenation ( I , = 0.78,P < 0.001). Although the correlation does not prove causation, the results indicate that ischemia leading to a 7'90 or greater reduction in muscle oxygenation causes decreased muscle force production in the forearm extensor muscle. Thus, ischemia associated with a modest decline in TOz causes muscle fatigue.

Intramuscular pressure, tissue oxygenation and EMG fatigue measured during isometric fatigue-inducing contraction of the multifidus muscle

“…When the compartment pressure rises above a physiological threshold, the blood supply is reduced and the tissue's oxygen content decreases [11,28,44]. The decreasing oxygen content of the tissue leads to muscle fatigue and muscular dysfunction [8,26]. Therefore the central hypotheses on which this model is based are as follows:…”

Biogenêse mitocondrial e exercício físico: hipótese do acoplamento elétrico-transcripcional

“…Foi demonstrado que mesmo a 10% da MVC já é possível reduzir a disponibilidade de O 2 para a fi bra muscular durante o exercício físico 58 . Portanto, durante a corrida o músculo esquelético passa por pequenos ciclos de contração e relaxamento seguidos de isquemia e reperfusão.…”

Measurement of changes in the oxygenation of quadriceps muscles during the voluntary and involuntary fatigue test in normal healthy sedentary subjects

“…(2006) found that the muscle oxygenation is not always related to a reduction of fatigue levels. Murthy et al (2001) conducted the study to solve this controversy suggesting that the development of fatigue depends upon the muscle oxygenation only, if the oxygenation is reduced more than 7%. The results from some non-human studies also found controversial because of above two variables (Stainsby et al, 1990;Eiken et al, 1984;Hogan et al, 1994).…”