Yoshihiko Tagawa

Agonist contractions against electrically stimulated antagonists

OBJECTIVEnTo assess an exercise program that uses electrically stimulated antagonists to resist agonist muscle contractions.nnnDESIGNnIn 1 limb, electrically stimulated antagonists resisted elbow flexion and extension. In the other, stimulation occurred without volitional muscle contraction.nnnSETTINGnA biomechanics laboratory in Japan.nnnPARTICIPANTSnTwelve men between the ages of 19 and 24 years. Subjects served as their own controls.nnnINTERVENTIONnSubjects trained 3 times a week for 12 weeks. Each session consisted of 10 sets of 10 elbow flexor and extensor contractions.nnnMAIN OUTCOME MEASURESnIsokinetic elbow extension and flexion torques. Biceps and triceps brachii cross-sectional areas.nnnRESULTSnElbow 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).nnnCONCLUSIONSnExercises 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.

Locomotion Assistance for the Person with Mobility Impairment: Fuzzy Control of Cycling Movement by Means of Surface Electrical-Stimulation

Since a wheelchair was originally designed as a transportation vehicle for people who can not walk well due to the degenerative muscles of legs in the case elderly and disabled persons, it was not considered to use lower limbs to drive a wheelchair. Wheelchairs driven by arms cause a shoulder disorder, atrophy of leg muscles and a contracture of leg joints. On the other hand, while wheelchairs driven by legs can prevent or alleviate those symptoms in daily life, it is difficult to drive a wheelchair if the muscles are not strong enough. To solve this problem the functional electrical stimulation is carried out on leg muscles to pedal the wheelchair, and to stabilize the speed a motor is equipped. The leg cycling movement in this paper is controlled by fuzzy logic. Experiments of cycling using three healthy young men are performed on a level surface, and prove the effectiveness of smooth cycling movement. The electrical stimulation is also added to the external oblique of subjects sitting on a chair to examine the possibility to become effective exercise instead of treadmill training by keeping balance.

Electrically Stimulated Antagonist Muscle Contraction Increased Muscle Mass and Bone Mineral Density of One Astronaut - Initial Verification on the International Space Station.

Background Musculoskeletal atrophy is one of the major problems of extended periods of exposure to weightlessness such as on the International Space Station (ISS). We developed the Hybrid Training System (HTS) to maintain an astronaut’s musculoskeletal system using an electrically stimulated antagonist to resist the volitional contraction of the agonist instead of gravity. The present study assessed the system’s orbital operation capability and utility, as well as its preventative effect on an astronaut’s musculoskeletal atrophy. Methods HTS was attached to the non-dominant arm of an astronaut staying on the ISS, and his dominant arm without HTS was established as the control (CTR). 10 sets of 10 reciprocal elbow curls were one training session, and 12 total sessions of training (3 times per week for 4 weeks) were performed. Pre and post flight ground based evaluations were performed by Biodex (muscle performance), MRI (muscle volume), and DXA (BMD, lean [muscle] mass, fat mass). Pre and post training inflight evaluations were performed by a hand held dynamometer (muscle force) and a measuring tape (upper arm circumference). Results The experiment was completed on schedule, and HTS functioned well without problems. Isokinetic elbow extension torque (Nm) changed -19.4% in HTS, and -21.7% in CTR. Isokinetic elbow flexion torque changed -23.7% in HTS, and there was no change in CTR. Total Work (Joule) of elbow extension changed -8.3% in HTS, and +0.3% in CTR. For elbow flexion it changed -23.3% in HTS and -32.6% in CTR. Average Power (Watts) of elbow extension changed +22.1% in HTS and -8.0% in CTR. For elbow flexion it changed -6.5% in HTS and -4.8% in CTR. Triceps muscle volume according to MRI changed +11.7% and that of biceps was +2.1% using HTS, however -0.1% and -0.4% respectively for CTR. BMD changed +4.6% in the HTS arm and -1.2% for CTR. Lean (muscle) mass of the arm changed only +10.6% in HTS. Fat mass changed -12.6% in HTS and -6.4% in CTR. Conclusions These results showed the orbital operation capability and utility, and the preventive effect of HTS for an astronaut’s musculoskeletal atrophy. The initial flight data together with the ground data obtained so far will be utilized in the future planning of human space exploration.

Cycling Exercise with Electrical Stimulation of Antagonist Muscles Increases Plasma Growth Hormone and IL-6

Performing aerobics and resistance exercise at exactly the same time has not been available although combining both types of exercise in one training program has been attempted. The hybrid training system (HTS) is a resistance exercise that combines voluntary concentric muscle contractions with electrically stimulated eccentric muscle contractions. We devised an exercise technique using HTS on a cycle ergometer (HCE). Growth hormone (GH) and lactate are indicators of adequate training intensity. Interleukin-6 (IL-6) reflects enhancing lipid metabolism. The purpose of this study was to show that HCE provides sufficient exercise to stimulate the secretion of GH, lactate and IL-6. We compared an HCE test with cycle ergometer alone (CE). Ten healthy male subjects performed HCE and CE tests for 30 minutes each. The workload of both tests was set the same at 40% of each subjects peak oxygen uptake. For HCE, 2-minute HTS and 1-minute rest intervals were repeated. GH, lactate, and IL-6 were evaluated before and immediately after exercise, and at 15, 30 and 60 minutes. GH and lactate increased immediately after HCE. Moreover, the degree of the increases in GH after HCE (0 and 15 minutes) was higher than that after CE. IL-6 increased after HCE at 30 min, and the rate of change was higher than for CE. These results showed that HCE was more efficient in stimulating acute increases in GH, lactate and IL-6 than CE at the same workload. We may be able to combine electrically stimulated resistance exercise with aerobic exercise using HCE.

Basic study on a walking assist system with electrical stimulation for elderly people

The purpose of this study is to examine the usefulness of a walking assist system using electrical stimulation. Thirty-two elderly people (18 men and 14 women) having no medical problems and five healthy young men participated in the study. The electrical stimulation was carried out in two cases: 1) hybrid training (HYBT) for the elderly subjects, 2) assisted walking aimed at eventual application in elderly individuals. The intensity of the electrical stimulation is 80 % in case 1) and three patterns of 60 %, 70 %, and 80 % of the measured maximum tolerable voltage (mMTV) in case 2). The HYBT effectiveness was the same or greater than that of weight machine training (WMT), and could improve the motor function of the lower limbs. During the assisted walking, the peak value of the vertical acceleration of the third lumber vertebra increased in contrast with the non-assisted walking. Steps and changes in the peak acceleration values in the sagittal plane also showed a tendency to increase due to the electrical stimulation. These results suggest that electrical stimulation can contribute to restore the weakened physical function of elderly individuals. The restoration will reduce the risk of falls and increase the daily activities.

Characteristic activities of lower limbs with body weight support ratio

In this study, we investigated a lower limbs muscle activity during body weight support treadmill training (BWSTT). Informed consent was obtained from 16 healthy men. Experimental system consists of force plate, treadmill, three-dimensional motion analysis system, electromyograph, and body weight support device. Body weight support (BWS) was set every 15% increase from 0% to 45%. Walking speed was 4.17km/h. The measurement data were reaction forces, joint angles, joint moments and lower limbs muscle activities. The vertical reaction force shows two peaks. Two peaks decreased with increase of BWS together. Joint angles did not show significant changes with BWS. However, only the extension of hip angle was decreased with BWS. The peaks of joint moment were decreased. Decrease of ankle joint moment was greatest compared with other moment. Decrease of peaks of muscle activity by BWS was observed during stance phase, and did not almost change during swing phase.

A Countermeasure for Preventing Atrophy of Musculoskeletal System under Microgravity

Weightless environments such as bed rest and spaceflight are associated with dramatic losses of muscle volume and bone mass that hinder patients or astronauts health and reintegration into daily life. We developed a novel hybrid exercise (HYB) as a countermeasure to prevent the losses by using electrically stimulated muscles to provide resistance to the voluntary motion of a muscle undergoing training. Unilateral lower leg suspension (ULLS) of four weeks was carried out for young males as a simulation model of the weightless environment. The HYB for healthy men increased muscle strength and bulk in flexor and extensor around the knee joint. These effects were confirmed in the ULLS group as well as in the case of healthy subjects. The HYB showed good effects on the femurs of the ULLS group, especially on the greater trochanter. Some parameters of electrical stimulation and noise reduction methods were examined for moderating stimulation and for evaluating the effect, respectively

Simulation of oxygen uptake and leg joint reaction force during ergometer exercise under altered gravity

Ergometers are safe devices for patients and elderly individuals, as the exercise intensity can be controlled. Moreover, ergometer exercises, which remove the load from body weight on the leg joint, would better reflect training conditions in locations where the force of gravity is lower than that on Earth, such as the International Space Station or on the surface of Mars. The purpose of this study was not only to validate an ergometer exercise model for measuring oxygen uptake and knee joint reaction force by comparison with experimental results, but also to consider a strategy for electrically stimulating leg joint muscles to modulate them under altered gravity.

A pilot study of the stability of the ankle joint moment and M-wave evoked by intermittent stimulation

We examined the stability of the ankle joint moment (AM) and M-wave amplitude evoked by electrical stimulation of the gastrocnemius and soleus muscle. The use of functional electrical stimulation (FES) is associated with some problems, including the fact that the muscle activity evoked by electrical stimulation decreases with muscle fatigue. Also, when electrical stimulation is delivered via surface electrodes, the stimulation reaching the muscle can vary according to the impedance between the electrode and the skin. In this paper, we performed experiments to (1) examine the relation between AM and stimulation intensity and between M-wave amplitude and stimulation intensity; (2) determine the change in this relation over a long duration; and (3) identify a strategy to allow the muscle to recover from fatigue. In the first experiment, M-wave amplitude and AM changed similarly with respect to the stimulation voltage. In the second experiment, the pattern of the M-wave and AM both showed downward. The pattern, however, was not similar at the soleus. In the third experiment, M-wave and AM remained almost constant compared with fatigued response in the second experiment. We showed that it is possible to generate a stable AM using electrical stimulation of the muscle. To ensure the stability of AM, it is necessary to consider the characteristics of the muscle (e.g., the proportion of fast and slow twitch fibers), the stimulation area, and the state of the muscles (e.g., fatigue).