Oxygen availability and motor unit activity in humans

Moritani, Toshio; Sherman, W. M.; Shibata, Masashi; Matsumoto, Tamaki; Shinohara, Minoru

doi:10.1007/bf00843767

Cited by 221 publications

(195 citation statements)

References 23 publications

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“…In contrast, CMAP amplitudes for EG in the first test and the retest increased from 94.56% to 115.70% over that of Baseline 2; this showed a significant increase of supramaximal electrical stimulation, similar to the amplitude in Baseline 1. An increase in amplitude signifies the recruitment of more muscle fibers, a finding which is identical to the findings of previous studies 13,18) . This means that low-intensity exercise, with a transient restriction in blood flow, offers the same effect of motor unit recruitment as a high-intensity exercise.…”

Section: Discussionsupporting

confidence: 90%

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Changes of Compound Muscle Action Potential after Low-Intensity Exercise with Transient Restriction of Blood Flow: a Randomized, Placebo-Controlled Trial

Kim

2009

J Phys Ther Sci

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Abstract.[Purpose] The purpose of this study was to investigate the mechanism of muscular force improvement after low-intensity exercise with transient restriction of blood flow using compound muscle action potential (CMAP) analysis.[Subjects] Thirty healthy subjects in their 20s (mean age=21.73 years) were randomly assigned to an experimental group (EG) and a placebo control group (PG); each group had 15 subjects. [Methods] CMAP was analyzed by measuring terminal latency and amplitude using a motor nerve conduction velocity test. For Baseline 1, supramaximal electrical stimulation was applied to the median nerves of the EG and PG to obtain CMAP at the abductor pollicis brevis. For Baseline 2, the intensity of the electrical stimulation was decreased to a level at which the CMAP amplitude was about a third ( 1 / 3 ) of the CMAP amplitude obtained by supramaximal electrical stimulation. In the first test, CMAP was obtained under the same conditions as Baseline 2 after low-intensity thumb abduction exercises were performed at subjects' own pace for one minute. EG had blood flow restricted by a sphygmomanometer cuff, but PG did not. In the retest, CMAP was obtained under the same conditions as Baseline 2, one minute after the removal of the sphygmomanometer cuff immediately after the first test.[Results] PG did not show significant changes in CMAP, whereas EG showed a significant increase in CMAP amplitude, signifying that more muscle fibers were recruited. [Conclusion] This study found that low-intensity exercise with transient restriction of blood flow recruited more muscle fibers than low-intensity exercise without transient restriction of blood flow.

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Section: Discussionsupporting

confidence: 90%

“…One study 13) examined motor unit recruitment patterns in order to investigate the mechanism of low-intensity exercise with transient restriction of blood flow. A motor unit consists of single α-motor neuron and all of the corresponding muscle fibers it innervates.…”

Section: Introductionmentioning

confidence: 99%

Changes of Compound Muscle Action Potential after Low-Intensity Exercise with Transient Restriction of Blood Flow: a Randomized, Placebo-Controlled Trial

Kim

2009

J Phys Ther Sci

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“…This enhanced muscle activation at low levels of force generation may relate to a hypoxic intramuscular environment, where low-threshold type I motor units will readily fatigue, requiring activation of more glycolytic (i.e. type II) motor units to maintain the same level of force generation [103,104]. The size principle suggests that type I fibres are recruited first, with type II fibres being recruited with increasing exercise intensities [105].…”

Section: Muscle Fibre Recruitmentmentioning

confidence: 99%

Hypoxia and Resistance Exercise: A Comparison of Localized and Systemic Methods

et al. 2014

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It is generally believed that optimal hypertrophic and strength gains are induced through moderate-or high-intensity resistance training, equivalent at least 60% of an individual's 1-repetition maximum (1RM). However, recent evidence suggests that similar adaptations are facilitated when low-intensity resistance exercise (~20-50% 1RM) is combined with blood flow restriction (BFR) to the working muscles. Although the mechanisms underpinning these responses are not yet firmly established, it appears that localized hypoxia created by BFR may provide an anabolic stimulus by enhancing the metabolic and endocrine response, and increase cellular swelling and signalling function following resistance exercise. Moreover, BFR has also been demonstrated to increase type II muscle fibre recruitment during exercise.However, inappropriate implementation of BFR can result in detrimental effects, including petechial haemorrhage and dizziness. Further, as BFR is limited to the limbs, the muscles of the trunk are unable to be trained under localized hypoxia. More recently, the use of systemic hypoxia via hypoxic chambers and devices has been investigated as a novel way to stimulate similar physiological responses to resistance training as BFR techniques. While little evidence is available, reports indicate that beneficial adaptations, similar to those induced by BFR, are possible using these methods. The use of systemic hypoxia allows large groups to train concurrently within a hypoxic chamber using multi-joint exercises. However, further scientific research is required to fully understand the mechanisms that cause augmented muscular changes during resistance exercise with a localized or systemic hypoxic stimulus.3

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“…This strategy has been shown to increase blood lactate concentration (Takarada et al, 2000) and was proposed to induce a preferential activation of the fast twitch (FT) fibers and to increase the amplitude of the changes from hypoxia to hyperoxia during exercise (Kawada, 2005;Moritani et al, 1992;Takarada et al, 2000). According to this evidence, some weight trainers have employed a maximal isometric contraction prior to normal dynamic lifts in order to simulate vascular occlusion (Gentil, 2005).…”

Section: Introductionmentioning

confidence: 99%

Time under Tension and Blood Lactate Response during Four Different Resistance Training Methods

Gentil

Oliveira

Bottaro

2006

J Physiol Anthropol

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Mechanical stimuli have often been suggested to be the major determinant of resistance training adaptations; however, some studies suggested that metabolic changes also play an important role in the gains of muscle size and strength. Several resistance training methods (RTM) have been employed with the purpose of manipulating mechanical and metabolic stimuli; however, information about their physiological effects are scarce. The objective of this study was to compare the time under tension (TUT) and blood lactate responses among four different RTM reported in the literature. The four RTM were performed in a knee extension machine at 10 repetition maximum (RM) load by 12 recreationally trained young men. The RTM tested were: 10RM, super-slow (SL-subjects performed one 60-second repetition with 30 seconds for eccentric and 30 seconds for concentric phase), functional isometrics (FI-in each repetition, a five-second maximal isometric contraction was executed with the knees fully extended) and adapted vascular occlusion (VO-subjects performed a 20-second maximal isometric contraction with the knees fully extended and immediately proceeded to normal isoinertial lifts). According to the results, all RTM produced significant increases in blood lactate levels. However, blood lactate responses during FI (4.48Ϯ1.57 mM) and VO (4.23Ϯ1.66 mM) methods were higher than the SL method (3.41Ϯ1.14 mM). The TUT for SL (60 s), FI (56.33Ϯ6.46 s), and VO (53.08Ϯ4.76 s) methods were higher than TUT for 10RM (42.08Ϯ3.18 s). Additionally, TUT for the SL method was higher than TUT during the VO method. Therefore, the SL method may not be recommended if one wants to provide a high metabolic stimulus. The FI method appeared to be especially effective in promoting both type of stimuli.

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Oxygen availability and motor unit activity in humans

Cited by 221 publications

References 23 publications

Changes of Compound Muscle Action Potential after Low-Intensity Exercise with Transient Restriction of Blood Flow: a Randomized, Placebo-Controlled Trial

Changes of Compound Muscle Action Potential after Low-Intensity Exercise with Transient Restriction of Blood Flow: a Randomized, Placebo-Controlled Trial

Hypoxia and Resistance Exercise: A Comparison of Localized and Systemic Methods

Time under Tension and Blood Lactate Response during Four Different Resistance Training Methods

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