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

Abstract

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.

FNDC5 relates to skeletal muscle IGF-I and mitochondrial function and gene expression in obese men with reduced growth hormone

“…31 P-magnetic resonance spectroscopy ( 31 P-MRS) was used to assess in vivo skeletal muscle mitochondrial function after submaximal exercise based on phosphocreatine (PCr) recovery [15]. Details of the procedure are reported elsewhere [7].…”

Simple and effective exercise design for assessing in vivo mitochondrial function in clinical applications using 31P magnetic resonance spectroscopy

“…A limitation to the wider application of the technique remains the need for MR-compatible exercise equipment suitable for use in clinical contexts. Commercial MR-compatible ergometers are increasingly available 6 7 8 , but these can be expensive and there is a long tradition of in-house construction of exercise equipment 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 . Exercise may be static (isometric) or dynamic (isotonic); isometric exercise is conveniently scaled to maximum voluntary contraction in situ 10 11 14 16 17 18 24 , but adjusting exercise intensity by interpreting force feedback 10 13 14 16 18 23 can be challenging.…”

“…Exercise may be static (isometric) or dynamic (isotonic); isometric exercise is conveniently scaled to maximum voluntary contraction in situ 10 11 14 16 17 18 24 , but adjusting exercise intensity by interpreting force feedback 10 13 14 16 18 23 can be challenging. Calibrated dynamic exercise typically requires complex resistance equipment 7 11 16 17 or pulley systems to transfer the workload outside the bore 15 19 20 22 , and in all systems participant posture is an important comfort consideration.…”

Insulin Resistance and Impaired Mitochondrial Function in Obese Adolescent Girls

“…Mitochondrial function was assessed by dynamic 31P-MRS on the same 3T MRI using an MR-compatible lower leg exercise device 26 for investigation of in vivo mitochondrial function. For 31P-MRS, a custom-built single-tuned 31P surface coil was placed in contact with posterior calf muscles.…”