Influence of muscle fiber type and pedal frequency  on oxygen uptake kinetics of heavy exercise

Barstow, Thomas J.; Jones, Andrew M.; Nguyen, Paul H.; Casaburi, Richard

doi:10.1152/jappl.1996.81.4.1642

Cited by 391 publications

(452 citation statements)

References 41 publications

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“…11 This is in contrast to other work in able-bodied subjects in which we utilized a 3-exponential model. 6,27 The reason for not applying a more complex exponential model to the current data lay in the frequently large breath-to-breath noise levels seen in these patients, which in our judgement precluded con®dent assessment of speci®c components of the Vo 2 response. Ideally, we would have chosen to have each subject perform multiple transitions, and averaged them together as previously done 6 so as to reduce the noise and enhance the underlying response.…”

Section: Discussionmentioning

confidence: 97%

Peak and kinetic cardiorespiratory responses during arm and leg exercise in patients with spinal cord injury

et al. 2000

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Study design: A paired comparison of the peak and submaximal responses of oxygen uptake and heart rate in patients with spinal cord injury (SCI) performing voluntary arm cycle exercise and functional electrical stimulation (FES) leg cycling exercise. Objectives: To test if the blunted heart rate response and slower rate of adjustment of oxygen uptake seen in patients with SCI performing FES leg cycle exercise are also characteristic of arm exercise in these patients. Methods: Eight paraplegics performed incremental and constant work rate (CWR) exercise with the legs and arms. Mean response times (MRT) for Vo 2 during exercise (on) and in recovery (o ) were calculated from the breath-by-breath Vo 2 pro®le. Results: Peak heart rate was higher during incremental arm exercise, and uncorrelated with that observed during incremental FES leg cycling. For the same increase in Vo 2 , constant work rate arm exercise was associated with faster (and normal) Vo 2 kinetics, greater increase in heart rate, and lower end-exercise blood lactate, compared to FES leg cycling. Conclusions: The consistently higher peak heart rate and Vo 2 , and faster Vo 2 kinetics, for voluntary arm compared to FES leg cycle exercise suggest no intrinsic dysfunction of heart rate control in these paraplegics. Rather, these data suggest that during FES leg cycling the changes seen are due to some characteristic speci®c to the injury, such as reduced muscle mass and/or deconditioning of the remaining muscle.

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Section: Discussionmentioning

confidence: 97%

Peak and kinetic cardiorespiratory responses during arm and leg exercise in patients with spinal cord injury

et al. 2000

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“…It has been reported that 86% of the SC occurs within the contracting muscle, 2 and other studies have observed correlations between the magnitude of the SC and the percentage 3 and recruitment 4 of type II muscle fibres. Furthermore, the ratio of phosphate produced per oxygen consumed (P=O ratio) is 18% lower in isolated mitochondria from type II compared to type I muscle, which suggests uncoupling of mitochondrial respiration.…”

Section: Introductionmentioning

confidence: 87%

Slow component of V̇O2 kinetics: the effect of training status, fibre type, UCP3 mRNA and citrate synthase activity

et al. 2002

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OBJECTIVE:In healthy individuals performing constant-load exercise at intensities above the lactate threshold a secondary rise in pulmonary oxygen uptake (V O 2 ) occurs. V O 2 reaches a maximum and exhaustion rapidly prevails for a range of work rates lower than the maximal work rate achieved during a conventional rapid-incremental test. This phenomenon is called the slow component (SC) of V O 2 kinetics and represents an increase in V O 2 without an increase in work rate. Although still under debate, the magnitude of the SC is believed to be associated with the percentage of type II muscle fibres and their recruitment. In this study we investigated the relationship between the magnitude of the relative SC, citrate synthase activity, UCP2 and UCP3 mRNA levels and muscle fibre composition in both endurance-trained and recreationally active subjects. METHOD: The magnitude of the relative SC was measured in 12 endurance-trained (Tr) and 15 recreationally active (RA) male subjects. The magnitude of the relative SC was determined as the difference between the end-exercise V O 2 and 3 min V O 2 divided by the difference between end-exercise V O 2 and baseline V O 2 . UCP2 and UCP3 mRNA expression in the vastus lateralis was measured by RT-PCR with b-actin mRNA used as an internal control. These values were also normalized against cytochromeb mRNA to control for training induced changes in mitochondria when comparing the Tr and RA groups. Type I, IIa and IIx skeletal muscle fibre composition was determined using a routine myosin ATPase histochemical staining technique. Citrate synthase (CS) activity was measured using spectrophotometric detection. RESULTS:The magnitude of the relative SC of the Tr group had the highest correlation with citrate synthase activity (r ¼ 7 0.90, P < 0.001) and that of the RA group with V O 2 peak (r ¼ 7 0.68, P < 0.01). For the Tr group other correlations with the magnitude of the relative SC included UCP3 mRNA levels (r ¼ 0.69, P < 0.05) and the percentage of type I fibres (r ¼ 7 0.58, P < 0.05), while for the RA group they included UCP3 mRNA (r ¼ 0.58, P < 0.05) and the percentage of type IIa muscle fibres (r ¼ 0.59, P < 0.05). The Tr subjects had a lower relative SC (P ¼ 0.04) and a lower expression of UCP2 (P ¼ 0.04), and UCP3 mRNA (P ¼ 0.01) than the RA subjects. When the groups were combined the magnitude of the relative SC correlated with UCP3 mRNA (r ¼ 0.70, P < 0.01), percentage of type IIa muscle fibres (r ¼ 0.60, P < 0.01) and V O 2 peak (r ¼ 7 0.73, P < 0.01). Additionally UCP3 mRNA correlated with the percentage of type IIa muscle fibres (r ¼ 0.63, P < 0.001). CONCLUSION: Citrate synthase activity and V O 2 peak are indicators of aerobic fitness. The high negative correlations between the magnitude of the relative SC and citrate synthase activity and V O 2 peak, of the Tr and RA subjects, respectively, suggests that the magnitude of the relative SC is inversely correlated with aerobic fitness. Additionally the correlations between UCP3 mRNA and the magnitude of the relative SC...

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“…3). The soleus, a slow-twitch muscle, has greater microvascular density than the gastrocnemius, and reacts almost instantly to a change in oxygen demand (24,25). Conversely, the gastrocnemius has comparatively less vasculature and its vessels dilate more during exercise.…”

Section: Discussionmentioning

confidence: 99%

Vasomodulation of skeletal muscle BOLD signal

Bulte

Alfonsi

Bells

et al. 2006

Magnetic Resonance Imaging

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Purpose: To evaluate whether the BOLD signal from skeletal muscle can be modulated by exercise and ingestion of vasoactive substances. Materials and Methods:The right calf muscles of healthy adult volunteers were imaged using a GE 1.5-Tesla scanner and a gradient-echo sequence with spiral readout. Timevarying changes in the BOLD signal were induced through cyclic phases of normoxia (90 seconds of 20.8% O 2 ) and hyperoxia (45 seconds of 100% O 2 at 22 L/minute). Superimposed on this paradigm were pre-and post-exercise regimes, with and without ingestion of caffeine (100 mg) or antihistamine (4 mg chlorpheniramine). The numbers of voxels within slow-twitch (soleus) and fast-twitch (gastrocnemius) muscles that significantly responded to the paradigms were scored and compared using the AFNI software (NIMH).Results: Cycling-inspired O 2 produced a corresponding BOLD modulation that increased in magnitude with exercise. Chlorpheniramine significantly (P Ͻ 0.01) prevented the overall increase in exercise-induced soleus muscle BOLD signal, while caffeine accentuated the increase (P Ͻ 0.05) in the gastrocnemius relative to control (no vasomodulator) conditions. Conclusion:BOLD signal changes with exercise can be modulated by standard doses of chlorpheniramine (antihistamine) and caffeine. We suggest that chlorpheniramine may act detrimentally on slow-twitch muscle contractility, while caffeine appears to improve fast-twitch muscle function. THE BLOOD OXYGEN LEVEL-DEPENDENT (BOLD) signal in MRI, which was first described by Ogawa et al (1) in 1990, is attributed to a change in the blood ratio of oxyhemoglobin (oxyHb) to deoxyhemoglobin (deoxyHb). This signal modulation is the basis for functional MRI (fMRI) studies of brain activation, in which increased local metabolism disproportionately drives increased blood flow and volume, resulting in elevated oxyHb/deoxyHb and BOLD signal enhancement. Recently the BOLD signal has been applied to the study of other tissues, including muscle (2) and tumors (3), and BOLD signal changes have been observed with inspiration of 100% O 2 . In addition, the potential for MR to characterize myocardial perfusion reserve, as indexed by the BOLD response to maximal pharmacological vasodilation, has been documented (4,5).Even though the blood volume of the brain is fairly low (on the order of 4%), BOLD signal changes with activation are still visible. Skeletal muscle at rest has a comparable blood volume; however, activation (through exercise) results in comparatively larger increases in blood flow and volume. In a previous report (2) we demonstrated that cycling inspired gas between hyperoxia (100% O 2 ) and air (20.8% O 2 ) resulted in a time-varying BOLD signal in the lower human leg that was analyzable with routine "block design" fMRI-based methods and software. Using this method we showed clear differences between the soleus (slow-twitch oxidative muscle) and gastrocnemius (fast-twitch anaerobic/glycolytic muscle), which were hypothesized to be due largely to the comparatively greater mic...

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Influence of muscle fiber type and pedal frequency on oxygen uptake kinetics of heavy exercise

Cited by 391 publications

References 41 publications

Peak and kinetic cardiorespiratory responses during arm and leg exercise in patients with spinal cord injury

Peak and kinetic cardiorespiratory responses during arm and leg exercise in patients with spinal cord injury

Slow component of V̇O2 kinetics: the effect of training status, fibre type, UCP3 mRNA and citrate synthase activity

Vasomodulation of skeletal muscle BOLD signal

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