A multimode dynamometer for in vivo MRS studies of human skeletal muscle

Ryschon, Timothy W.; Fowler, M. D.; Arai, Andrew E.; Wysong, R. E.; Leighton, Stephen B.; Tr, Sr. Clem; Balaban, Robert S.

doi:10.1152/jappl.1995.79.6.2139

Cited by 15 publications

(21 citation statements)

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“…However, the work intensities were fairly high for this type of muscle group. Indeed, the highest steady-state (over 6 min) mechanical power for both limbs was 9.4€0.5 W, which is very close to the maximum power sustainable without lactate production, the latter being 4.8 and 4.6 W (one leg only) under similar experimental conditions [26,35]. Additional evidence for the intensity of exercise remaining within the aerobic range was the observation that, even at the highest work loads, [PC], after the initial 3 min, remained stable until the end of the exercise.…”

Section: Exercise Intensitymentioning

confidence: 51%

Relationships between mechanical power, O2 consumption, O2 deficit and high-energy phosphates during calf exercise in humans

Francescato

Cettolo

Prampero

2002

Pflugers Arch - Eur J Physiol

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Whole-body O(2) uptake ( VO(2)), O(2) deficit and the concentration of high-energy phosphates (determined by (31)P spectroscopy) in human calf muscle were measured during moderate aerobic square-wave exercise of increasing intensity in ten volunteers. Net VO(2) (above resting) increased linearly with mechanical power, yielding a delta efficiency of 13.1%. "Gross" O(2) deficit increased linearly with net VO(2). The fraction of phosphocreatine (PC) split at steady state increased linearly with the mechanical power and with the O(2) deficit. If the [PC] in resting muscle is known, the slope of the regression between PC split and O(2) deficit (in millimoles) yields the P/O(2) ratio. To calculate this, the O(2) deficit was corrected for the amount of O(2) derived from the body stores, as obtained from literature data. The value so obtained, for a resting [PC] of 30 mM was 5.9, consistent with canonical textbook values. Furthermore, the ratio of "true" O(2) deficit to steady-state VO(2) is a measure of the time constant of VO(2) kinetics at work onset at the muscle level: assuming a monoexponential time course without time delays it amounted to about 17 s, close to the value that can be expected in mammalian muscle at 37 degrees C.

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Section: Exercise Intensitymentioning

confidence: 51%

Relationships between mechanical power, O2 consumption, O2 deficit and high-energy phosphates during calf exercise in humans

Francescato

Cettolo

Prampero

2002

Pflugers Arch - Eur J Physiol

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“…The highest limit for the elastic cords is an infinite resistance, leading to isometric contractions. The maximal degree of plantar flexion has been reported to be 40° (14, 17) while the maximal frequency of movement is 2–3 Hz (17). These two variables are related to each other and depend essentially on the flexibility of the ankle joint.…”

Section: Methodsmentioning

confidence: 99%

“…In these systems, the speed of contraction is imposed by a rhythmic signal, but neither the displacement of the weight nor the frequency of movement are controlled, so the actual power cannot be precisely measured. Another solution is the incorporation of a servomotor in the system (14, 15); however, this requires a relatively large room so that the servomotor can be placed sufficiently distant from the magnet to avoid interference with the acquisition of MR signals. Only a few of the reported ergometers have been described in detail.…”

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confidence: 99%

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Two‐pedal ergometer for in vivo MRS studies of human calf muscles

Francescato

Cettolo

2001

Magnetic Resonance in Med

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This article describes an ergometer that enables human subjects to exercise one or both limbs while 31 P NMR spectra are obtained. Two independent pedals, equipped with position and force transducers, were mounted on the ergometer in order to calculate mechanical work performance. First, the effect of the magnetic field upon the signal coming from the transducers was investigated. Then the ergometer was tested by performing a series of steady-state exercises of increasing intensity. Experimental data showed that actual mechanical power ranged from 1.5 ؎ 0.2 W to 11.0 ؎ 1.6 W, while the corresponding oxygen consumption increased from 0.28 ؎ 0.04 l/min at rest to 0.48 ؎ 0.10 l/min at the highest load, and the PCr/(PCr؉P i ) ratio, as calculated from the 31 P spectra, decreased from 0.94 ؎ 0.01 at rest to 0.73 ؎ 0.04. These results are consistent with the values reported in the literature and show that this ergometer, which is easy to use, is suitable for in vivo spectroscopy research when metabolic steady-state conditions are required.

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“…Prior reports have described exercise devices that were limited to plantarflexion-only exercise [2], required complex hardware [2–5], were not portable [5], did not support isotonic and isometric exercise [6], and were built for research scanners [7]. These designs do not meet the needs of whole-body MR scanners frequently used in clinical research.…”

Section: Introductionmentioning

confidence: 99%

Modular MR-compatible lower leg exercise device for whole-body scanners

et al. 2011

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Purpose To develop a modular MR-compatible lower leg exercise device for muscle testing using a clinical 3 T MR scanner. Materials and methods An exercise device to provide isotonic resistance to plantar- or dorsiflexion was constructed from nonferrous materials and designed for easy setup and use in a clinical environment. Validation tests were performed during dynamic MR acquisitions. For this purpose, the device was tested on the posterior lower leg musculature of five subjects during 3 min of exercise at 30% of maximum voluntary plantarflexion during 31-phosphorus MR spectroscopy (31P-MRS). Measures of muscle phosphocreatine (PCr), inorganic phosphate (Pi), and pH were obtained before, during, and after the exercise protocol. Results At the end of exercise regimen, muscle PCr showed a 28% decrease from resting levels (to 21.8±3.9 from 30.4±3.0 mM) and the average PCr recovery rate was 35.3±8.3 s. Muscle Pi concentrations increased 123% (to 14.6±4.7 from 6.5±3.3 mM) and pH decreased 1.5% (to 7.06±0.14 from 7.17±0.07) from resting levels. Conclusion The described MR-compatible lower leg exercise was an effective tool for data acquisition during dynamic MR acquisitions of the calf muscles. The modular design allows for adaptation to other whole-body MR scanners and incorporation of custom-built mechanical or electronic interfaces and can be used for any MR protocol requiring dynamic evaluation of calf muscles.

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A multimode dynamometer for in vivo MRS studies of human skeletal muscle

Cited by 15 publications

References 0 publications

Relationships between mechanical power, O2 consumption, O2 deficit and high-energy phosphates during calf exercise in humans

Relationships between mechanical power, O2 consumption, O2 deficit and high-energy phosphates during calf exercise in humans

Two‐pedal ergometer for in vivo MRS studies of human calf muscles

Modular MR-compatible lower leg exercise device for whole-body scanners

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