Toshiyasu Yamamoto

Agonist contractions against electrically stimulated antagonists

OBJECTIVE To assess an exercise program that uses electrically stimulated antagonists to resist agonist muscle contractions. DESIGN In 1 limb, electrically stimulated antagonists resisted elbow flexion and extension. In the other, stimulation occurred without volitional muscle contraction. SETTING A biomechanics laboratory in Japan. PARTICIPANTS Twelve men between the ages of 19 and 24 years. Subjects served as their own controls. INTERVENTION Subjects trained 3 times a week for 12 weeks. Each session consisted of 10 sets of 10 elbow flexor and extensor contractions. MAIN OUTCOME MEASURES Isokinetic elbow extension and flexion torques. Biceps and triceps brachii cross-sectional areas. RESULTS Elbow extension torques increased (32.85% at 30 degrees/s, 27.20% at 60 degrees/s, 26.16% at 90 degrees/s; all P<or=.02) over the training period in limbs that trained against electrically stimulated antagonists. Control limb extension torque increases were smaller (8.52% -14.91%) and did not reach statistical significance. Elbow flexion torques improved in both groups, but the changes did not reach statistical significance. Cross-sectional areas increased in all muscles but were most marked in the antagonist stimulated limbs: triceps 16.20% versus 4.25% (P=.01) and biceps 16.65% versus 7.00% (P=.005). CONCLUSIONS Exercises that use electrically stimulated antagonist muscles may be effective in increasing muscle strength and mass.

MRI quantification of muscle activity after volitional exercise and neuromuscular electrical stimulation

Ogino M, Shiba N, Maeda T, Iwasa K, Tagawa Y, Matsuo S, Nishimura H, Yamamoto T, Nagata K, Basford JR: Magnetic resonance imaging quantification of muscle activity after volitional exercise and neuromuscular electrical stimulation. Am J Phys Med Rehabil 2002;81:446–451. Objective The efficacy, and even the depth, of muscle stimulation during surface electrode neuromuscular electrical stimulation (NMES) is a matter of debate. This study addresses these issues by assessing the utility of a magnetic resonance imaging (MRI) technique in localizing and quantitating changes in the nature of MRI signals in the quadriceps muscle after volitional exercise and NMES. Design Volitional isometric and NMES-evoked quadriceps muscle activity was evaluated in two controlled trials. In the first, isometric quadriceps strength was determined during NMES and maximal volitional isometric exercise in six healthy men. In the second, changes in the ratio of MRI T2 signal intensities before and after volitional isometric exercise and NMES were used to quantitate MRI signal changes associated with muscle activation in 12 additional healthy men. Results MRI clearly detected quadriceps muscle tissue activation after both volitional and stimulated contractions, even though the NMES knee extension torque was only 23.5% that of maximal volitional isometric exercise. In particular, the T2 intensity ratios increased 26.5% ± 17.3% (mean ± standard deviation) after volitional exercise and 12.9% ± 12.8% after NMES. This pattern of volitional isometric exercise, producing larger T2 intensity ratio values than NMES, was present in both deep and superficial layers and throughout the quadriceps muscle. Conclusions Although volitional muscle contractions were several times stronger than those induced by NMES in this study, our findings support the idea that MRI can provide a noninvasive way to quantitate and localize volitional and electrically stimulated muscle activation.

Development of the surface stimulating electrodes system for gait training

A new surface electrodes system was quantitatively evaluated, based on the distribution profile of the superficial muscle. The stimulated muscle has been quantitatively estimated, to be a practical muscle force output. The musculoskeletal model was improved using these data. Its estimated stimulating pattern was useful for gait training.

On an estimation of the location of the axes of wrist joint movements

The relation between the muscular force of the electrically stimulated muscle and the moment of a joint in vivo, is not understood clearly yet. This is a problem for the Functional Electrical Stimulation (FES) to create a useful movement. For this reason, it is important to estimate the location of the joint axes also for kinematic studies. This type of study has been carried out with a cadaver specimen. In many cases. 2 kinds of motion of the wrist joint (radial-ulnar deviation and flexion-extension) in vivo were measured with a magnetic tracking device, which was used to estimate the location of helical axes along a motion of wrist joint. Here we propose a basic parameter for the skeletal model of the wrist.<<ETX>>