EMG-angle relationship of the hamstring muscles during maximum knee flexion

EMG-angle relationship of the hamstring muscles during maximum knee flexion

Journal of Electromyography and Kinesiology 12 (2002) 399–406 www.elsevier.com/locate/jelekin EMG-angle relationship of the hamstring muscles during ...

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Journal of Electromyography and Kinesiology 12 (2002) 399–406 www.elsevier.com/locate/jelekin

EMG-angle relationship of the hamstring muscles during maximum knee flexion Hideaki Onishi a,∗, Ryo Yagi b, Mineo Oyama c, Kiyokazu Akasaka d, Kouji Ihashi e, Yasunobu Handa f a

Niigata University of Health and Welfare, 1398 Shimani-cho, Niigata-city, 950-3198, Japan b Toyohashi City Hospital, Toyohashi, Japan c Institute of Miyagi Industrial Organization, Sendai, Japan d Saitama Medical Center Saitama Medical School, Saitama, Japan e Yamagata School of Health Science, Yamagata, Japan f New Industry Creation Hatchery Center Tohoku University, Sendai, Japan

Received 12 July 2000; received in revised form 23 February 2002; accepted 29 March 2002

Abstract The aim of the present study was to investigate the EMG–joint angle relationship during voluntary contraction with maximum effort and the differences in activity among three hamstring muscles during knee flexion. Ten healthy subjects performed maximum voluntary isometric and isokinetic knee flexion. The isometric tests were performed for 5 s at knee angles of 60 and 90°. The isokinetic test, which consisted of knee flexion from 0 to 120° in the prone position, was performed at an angular velocity of 30°/s (0.523 rad/s). The knee flexion torque was measured using a KIN-COM isokinetic dynamometer. The individual EMG activity of the hamstrings, i.e. the semitendinosus, semimembranosus, long head of the biceps femoris and short head of the biceps femoris muscles, was detected using a bipolar fine wire electrode. With isometric testing, the knee flexion torque at 60° knee flexion was greater than that at 90°. The mean peak isokinetic torque occurred from 15 to 30° knee flexion angle and then the torque decreased as the knee angle increased (p⬍0.01). The EMG activity of the hamstring muscles varied with the change in knee flexion angle except for the short head of the biceps femoris muscle under isometric condition. With isometric contraction, the integrated EMGs of the semitendinosus and semimembranosus muscles at a knee flexion angle of 60° were significantly lower than that at 90°. During maximum isokinetic contraction, the integrated EMGs of the semitendinosus, semimembranosus and short head of the biceps femoris muscles increased significantly as the knee angle increased from 0 to 105° of knee flexion (p⬍0.05). On the other hand, the integrated EMG of the long head of the biceps femoris muscle at a knee angle of 60° was significantly greater than that at 90° knee flexion with isometric testing (p⬍0.01). During maximum isokinetic contraction, the integrated EMG was the greatest at a knee angle between 15 and 30°, and then significantly decreased as the knee angle increased from 30 to 120° (p⬍0.01). These results demonstrate that the EMG activity of hamstring muscles during maximum isometric and isokinetic knee flexion varies with change in muscle length or joint angle, and that the activity of the long head of the biceps femoris muscle differs considerably from the other three heads of hamstrings.  2002 Published by Elsevier Science Ltd. Keywords: Hamstrings; EMG; Wire electrode; Maximum voluntary contraction; Knee angle; Torque

1. Introduction The hamstrings muscle group, composed of four muscle bellies, i.e. the semitendinosus (ST), the semimembranosus (SM) and the long and short heads of the biceps

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femoris (BF long and BF short) muscles, are active during knee flexion. These muscles are often classified as medial hamstrings (ST and SM) and the lateral hamstrings (BF long and BF short) according to their rotational function on the tibia, and into bi-articular muscles (ST, SM and BF long) or monoarticular muscle (BF short) according to the number of joints they act upon. In addition, several investigators have reported on the morphological features of the individual hamstring muscles [1–4]. These reports showed that the muscle

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weight, muscle volume, pennation angle, physiological cross sectional area and muscle fiber length differ among different hamstring muscles. Despite these differences, the hamstring muscles are often examined as one functional group using a single pair of electrodes when the EMG activity of the hamstring muscles are assessed or as two groups, comprising the medial and lateral hamstrings, using two pairs of electrodes [5–9]. Lunnen et al. [9] investigated the relationship between hip angle and the EMG activity of the biceps femoris muscle using one bipolar surface EMG electrode, and found that the activity of the biceps femoris muscle at a hip flexion angle of 135° was significantly lower than that at 0 or 45° hip flexion. However, the detection volume may have altered as the hip angle changed from 0 to 135° under the surface electrode [10]. Furthermore, the relationship between the knee angle and the activity of each hamstring muscle was not clarified. In the vast majority of cases, several muscles combine to produce the contractile torque measured externally on a limb. Howard et al. [11] described the differences in EMG activity between the biceps brachii and the brachioradialis muscles during elbow flexion. In addition, several investigators have demonstrated selective activation in the human triceps surae muscles [12–14]. For example, Tamaki et al. [14] reported that the triceps surae muscles show a different EMG pattern during isokinetic plantarflexions at various angular velocities and knee angle under submaximum contraction. Thus, the agonist muscles, which are composed of several synergistic muscles, sometimes showed different EMG patterns. However, the differences in EMG activity among the hamstring muscles remain unclear during knee flexion. The aim of the present study was to investigate the EMG–joint angle relationship during maximum effort voluntary contraction and identify the differences in activity among the four hamstring muscle bellies.

2.2. Procedure Fine wire electrodes were inserted (see below) into the right side ST, SM, BF long and BF short. Each subject was then immobilized on a table in the prone position with a hip flexion angle of 0° and the tibia maintained in a neutral position of rotation. The hip joint was fixed with a strap and the foot and lower thigh immobilized with a splint to avoid rotational movements of the tibia and to fix the ankle joint in the neutral position ( Fig. 1). Immobilization was necessary because the ST, SM and BF long are bi-articular muscles and the hamstrings function during knee flexion and tibial rotation. An isokinetic dynamometer (KIN-COM, Chattanooga, TN) was used to obtain quantitative measurements of isometric and isokinetic strength. The error of KINCOM at various velocities is within 1%. The axis of the knee was placed in line with the axis of rotation of the dynamometer. The lever arm was mechanically prevented from movement until torque was produced above 40 Nm to avoid the measurements of tension produced by the activation processes at the beginning of muscle contraction in the initial stage of isokinetic contraction. The experimental protocol consisted of four isometric knee flexion movements and two isokinetic knee flexion movements with maximum effort. The isometric tests were performed for 5 s at angles of 60 and 90°. The isokinetic test, which consisted of maximum knee flexion from 0 to 120°, was performed at an angular velocity of 30°/s (0.523 rad/s). Each subject performed an initial warm-up of five reciprocal extension/flexion movements at an angular velocity of 60°/s (1.924 rad/s) with a mild-effort level after insertion of electrodes. After 5 min of rest, the subjects performed two maximal contractions for each test. The trial that produced the highest torque for each test was chosen for analysis. To

2. Methods 2.1. Subjects Ten healthy males (aged 21–36 years; mean±standard deviation: 30.2±4.5 years) participated in the study. The subjects had no previous history of injury to their thigh muscles or knee joints, and none were participating in any regular exercise regime. Body weight ranged from 53 to 90 kg (71.7±10.1 kg), and body height ranged from 163 to190 cm (172.6±8.1 cm). Informed consent was obtained from all subjects.

Fig. 1. Electrode placement for each of the four hamstring muscles. Wire electrodes were fixed to the skin and a 2 cm loop formed just proximal to the fixation tape to avoid pulling on the intramuscular site during muscle contraction and/or knee angle transition.

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avoid muscle fatigue, a 3-min rest was allowed between each trial. 2.3. Electrode insertion Intramuscular bipolar Teflon coated stainless steel fine wire electrodes were used for EMG detection (A-M systems, WA). The diameter of each electrode was 75 µm, and each electrode tip was bared for about 2 mm. Each inter-tip distance was set at 5 mm [15,16]. Two wires of each pair of electrodes were attached to each other with nontoxic adhesives to prevent a change in inter-tip distance. The Teflon coating of the wire was treated with a fluoroplastic finishing agent before adherence. Electrodes were inserted into the muscle using a 25-gauge needle. Electrode placements in individual muscles were performed according to Delagi et al. [17]. Electrode depth was confirmed by electrical stimulation using an electrical stimulator (FES-MATE1300, NEC, Tokyo). A rectangular pulse train with frequencies of 3 and 20 Hz was used for stimulation. The pulse width was 0.2 ms. The difference between ST and SM was confirmed by palpation of each distal tendon during electrical stimulation. The difference between BF long and BF short was verified by palpation of muscle contraction at the ischial attachment during electrical stimulation. The surface ground electrode was placed on the greater trochanter. Wire electrodes were fixed to the skin and a 2 cm loop formed just proximal to the fixation tape to avoid pulling on the intramuscular site during muscle contraction and/or knee angle transition (Fig. 2). 2.4. Data collection and analysis EMG signals were connected to a differential preamplifier (DPA-10M, Dia-Medical System, Japan;

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CMRR⬎60dB, input impedance 10M⍀) located no further than 5 cm from the point of electrode insertion and filtered using a bandwidth ranging from 5 to 1000 Hz (Biotop6R12, NEC Co., Ltd, Japan; CMRR 86dB, input impedance 10M⍀) [18]. The EMG signals and torque data were simultaneously recorded and digitized at a sampling rate of 2500 Hz using a 12 bit A/D converter (ADXM-98FX, Contec, Kobe). For isometric testing, the EMG signals were full-wave rectified and integrated (IEMG) for 500 ms from the peak-torque point. For isokinetic testing, the EMG signals were full-wave rectified and integrated for consecutive 15° windows of the knee flexion angle from 0 to 120° (IEMG). Torque data was also obtained at every 15° of the knee angle, and the maximum torque data within each 15° range was taken to represent that range during isokinetic knee flexion. 2.5. Statistical analysis With isometric testing, the knee flexion torque and the EMGs of the hamstring muscles at a knee angle of 60° were normalized with the value at 90°. The torque and the IEMGs obtained during isokinetic knee flexion were normalized with the values collected between 75 and 90° knee angle during isokinetic testing (%Torque and NIEMG). Routine statistical methods were used to calculate the mean and standard error (SE). A paired t-test was used to test for differences in %torque and NIEMG values between the knee angles of 90 and 60° for isometric testing. One-way analysis of variance (ANOVA) for repeated measurements and the Tukey’s HSD posthoc test were used to test for differences in %torque and NIEMG between the knee angles for isokinetic testing. Statistical significance was established at the p⬍0.05 level.

3. Results 3.1. Isometric testing

Fig. 2. Experimental arrangement for the measurement of knee flexor torque. The hip joint was fixed at 0° with a strap and the foot and lower thigh were covered with a foot splint to avoid rotational movement of the tibia and to fix the ankle joint in a neutral position. The axis of the knee was placed in line with the axis of rotation of the dynamometer.

With isometric testing, the maximum knee flexion torque at a knee angle of 60° was 121.1±6.6% (mean±SE) of the value at 90° knee flexion. The torque differences between the knee angles of 60 and 90° were significantly different (p⬍0.01). The NIEMGs of the hamstring muscles during maximum isometric knee flexion are shown in Table 1. The NIEMGs of ST and SM, which were obtained at 60° knee flexion, were significantly lower than the value at 90° knee flexion. On the other hand, the NIEMG of BF long at 60° flexion was significantly greater than the value at 90° knee flexion. No significant differences in the NIEMG of BF short were observed between the knee flexion angles of 60 and 90°.

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Table 1 NIEMG of four hamstring muscles during maximum isometric knee flexiona Knee angle (degree) 60 ST SM BF long BF short a

78.2 ± 6.4 79.6 ± 7.2 135.9 ± 9.7 98.7 ± 7.8

90 ∗∗100 ∗100 ∗∗100 n.s. 100

Mean SE, paired t-test, ∗∗: p⬍0.01, ∗: p⬍0.05, n.s: p⬎0.1

3.2. Isokinetic testing Typical raw EMG signals of the hamstring muscles are shown in Fig. 3, along with knee flexion torque, knee angle and angular velocity during isokinetic knee flexion. These results indicate that knee flexion movement begins when the torque produced exceeds 40 Nm. In the early stages of knee flexion, the EMG signals of ST, SM and BF short were relatively small and gradually increased as knee angle increased. Conversely, BF long was strongly activated when the maximum torque was initiated and then decreased in activity with increasing knee angle. The mean peak isokinetic torque was 124.0±20.1%, which occurred between 15 and 30° of knee flexion, and then significantly decreased as the knee angle increased (Fig. 4a). The NIEMGs of the four hamstring muscles bellies during maximum isokinetic knee flexion varied with knee angle changes. The NIEMGs of ST, SM and BF short significantly increased as the knee flexion angle increased from 0 to 105° (p⬍0.05). The maximum

Fig. 3. Typical data from one subject: knee flexion torque, raw EMG data of the four hamstring muscles, knee angle and knee angular velocity during isokinetic knee flexion.

NIEMGs were 112.1±10.6% in ST, 107.0±5.5% in SM and 102.2±4.1% in BF short at the knee angle between 90 and 105° (Fig. 5b-d). On the other hand, the maximum NIEMG of BF long was 130.9±9.1%, which occurred between 15 and 30° knee angle, and then NIEMG significantly decreased as knee angle increased from 30 to 120° (p⬍0.01) (Fig. 5e).

4. Discussion In the present study, the knee flexion torque was modified by changes in knee angle during isometric and isokinetic knee flexion. The peak torque of isokinetic knee flexion at 30°/s (0.523 rad/s) was found at a knee angle between 15 and 30° and then decreased as the knee flexion angle increased. This relationship between flexion torque and angle of the knee was expected and supported by previous reports [19–23]. These reports show that the peak torque of the knee flexor is achieved between 21 and 49° of knee flexion and then decreases as knee flexion angle increases. In this study, we found that the EMG activity of the four hamstring muscle bellies varied as knee flexion angle changed during maximum isometric and isokinetic knee flexion, except for BF short under isometric conditions. There were no significant differences in the EMG of BF short when the joint angle changed between 60 and 90° during isometric contraction, possibly because the range of angular displacement in which the EMG variation of the BF short was obtained relatively small (60–90°) compared to that under isokinetic conditions (0–120°). These results indicate that the EMG amplitudes of agonist muscles are not always contracting at a maximum when knee flexion is performed with maximum effort. When the torque–angle relationship during voluntary contraction is investigated, the influences of not only the sarcomere length and the moment arm, but also the muscle activity of the agonist muscles, must be considered. This result of the present study agrees with previous reports obtained in the tibialis anterior muscle by Inman et al. [24] and Libet et al. [25], in the quadriceps muscle by Haffajee et al. [26] and Salzman et al. [27] and in the biceps femoris muscle by Lunnen et al. [9], who found that for maximum contraction at different muscle length, the EMG activity was altered. Our results demonstrate that for the hamstring muscles, EMG activity is influenced by knee flexion angle during maximum knee flexion. Our result of the relationship between EMG activity and joint angle differs from those reported by Vredenbregt et al. [28] and Leedham et al. [29], who found that the surface EMG activity is the same at different joint angles under maximum contraction. In both reports, the biceps brachii muscle was used to analyze the EMG and joint angle relationship. When a surface electrode is used

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Fig. 4. Torque-angle and EMG-angle relationships during maximum isokinetic knee flexion in the prone position. a) Torque, b) ST, c) SM, d) BF long, e) BF short.

to detect the EMG signal, the detection volume may be altered with muscle length changes [10]. However, Leedham et al. [29] confirmed the detection volume at different joint angles using the EMG amplitudes obtained during evoked contraction. Thus, we believe that the relationship between EMG and joint angle obtained in the study is reliable. Howard et al. [11] reported that biceps brachii and brachioradialis have different relative activation at different joint angles, and suggested that when an elbow joint flexes with the steady-state EMG level of the biceps brachii muscle, the EMG of the brachioradialis muscle varies as the elbow angle changes. Therefore, in the studies by Vredenbregt et al. [28] and Leedham et al. [29], the EMG activity of

the brachioradialis muscle may have varied as the elbow angle changed. We believe that the relationship between EMG activity and joint angle depends on the muscles examined, and hence our results differ from those of Vredenbregt et al. [28] and Leedham et al. [29]. The EMG activity of BF long was appreciably different to that of the other hamstrings under both isometric and isokinetic conditions. The peak activity of BF long was obtained at a knee angle between 15 and 30°, while the other hamstrings showed the largest activity at a knee angle between 90 and 105°. This result indicates that BF long participates strongly in knee flexion torque at the early stages of knee flexion, whereas the other three muscles bellies participate in flexion torque at a knee

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angle of nearly 90°. Several authors have examined knee flexion torque during harvesting of autogenous semitendinosus tendon for reconstruction of the contralateral anterior cruciate ligament [30–32]. They have suggested that the peak torque value of the hamstring muscles during maximum isokinetic flexion almost reaches the preharvest value. However, Ohkoshi et al. [31] found that the peak torque angle of knee flexion was significantly reduced, and the torque that was obtained in the latter half of the torque curve decreased, after harvest of the semitendinosus tendon in spite of the recovery of the peak torque value. This phenomenon supports our result that the semitendinosus muscle participates in the torque at a knee angle of nearly 90°. Several morphological features of the individual hamstring muscles have been reported and are shown in Table 2. [1–4,33] The hamstring muscles are often classified into bi-articular muscles (ST, SM and BF long) and monoarticular muscle (BF short) or into the medial hamstrings (ST, SM) or lateral hamstrings (BF long and short) according to their anatomical position. The moment arm of the individual hamstring muscle has been investigated by Herzog et al. [3], who reported that the moment arm of ST and BF increases as knee angle increases. On the other hand, the SM moment arm remains constant between 0 and 90° of knee flexion and then decreases as knee angle increases. Other morphological characteristics of the BF long, including variation of muscle weight, pennation angle, muscle volume, physiological cross sectional area (PCSA), and muscle fiber length are not different for the different hamstring muscles [1,2,4]. In addition, there are many factors that could effect EMG activity that are likely to vary as the joint angle changes, including the activity of muscle spindles, Golgi tendon organ, joint capsule receptors and passive and active resistance of antagonist muscle. However, whether the behavior of BF long with respect to these factors behaves differently than the other hamstring muscles is unclear.

Hatze [34] indicated that each elbow flexor reaches optimum length in the active length–tension curve at different joint angles. Herring et al. [35] reported that sarcomere number is regulated in such a way that each sarcomere is at the optimum length at the joint position where most force is exerted on the fiber attachment. Normally this position is that at which the motor units of the muscle are fully recruited. Libet et al. [25] have demonstrated that the motor-unit activation at intermediate muscle length was greater than that at long and short muscle length during maximum contraction. Consequently, each hamstring muscle might reach optimum length in the active length–tension curve at a different knee angle. Namely, the sarcomere length of BF long may be most suitable for producing maximum tension from 15 to 30° knee flexion angle, whereas that of the other three heads of hamstrings may be appropriate from 90 to 105° knee flexion angle in the prone position. Two important findings resulted from this study. One is that the EMG activity of the hamstring muscles varies with knee angle during maximum knee flexion. Therefore, it was considered that the relationship between torque and angle is influenced not only by the sarcomere length and the moment arm but also muscle activation of agonist muscles even if the movement is performed with maximum effort. The other is the exceptional behavior of BF long during knee flexion. Namely, the EMG activity of the BF long is greatest between knee angles of 15 and 30° and then decreases as the knee angle increases. The EMG activity of the other heads of hamstrings increases as knee angle increases and peak EMG activity occurs between knee flexion angles of 90 and 105°. This difference in EMG activity of the hamstrings might be caused by muscle morphological features that are altered by changes in muscle length, however it is uncertain which of these factors is most influential. And the results may also vary at different hip joint angle and may not apply directly to surface electrodes.

Table 2 Morphology of hamstring muscles

Bi/mono-articular Knee rotator Nerve supply Muscle weight (g) 4) Muscle volume (cm3)1) PCSAa (cm2)1) Pennation angle (ⴰ)4) Fiber length (mm)2,4) % type I fibers 33) Sarcomere length Moment arm (cm) during flexion3) a

Physiological cross sectional area

ST

SM

BF long

BF short

BiInternal Tibial N. 76.9 260.1 16.2 5 155.6 – – 0→7

BiInternal Tibial N. 107.5 291.9 44.0 15 63.3 – – 2.5→1

BiExternal Tibial N. 128.4 241.4 29.8 0 80.2 66.9 – 1.5→3

MonoExternal Peroneal N. – 118.1 7.9 23.3 130.3 –

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Acknowledgements The authors are grateful to Dr Serge H Roy (Boston University Neuromuscular Research Center, Boston, MA) for his comments on the manuscript.

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Hideaki Onishi received his MS and PhD in disability science from Tohoku University Graduate School of Medicine, Sendai, Japan, in 1997 and 2000. He gained the Japanese national license of Physical Therapists in 1989. He graduated from the Department of Physical Therapy School of Allied Medical Sciences, Shinshu University in 1989. Between 1989 and 1995, he worked for Meiwa Hospital, Hyogo, Japan, as a Physical Therapists He is presently a lecturer in the Department of Physical Therapy at Niigata University of Health and Welfare, Niigata, Japan. His research interests include focusing on functional anatomy and Kinesiology of the lower limb. He is a member of the International Society of Electrophysiology and Kinesiology, the Japanese Association of Rehabilitation Medicine and the Japanese Association of Physical Therapists.

Ryo Yagi received his M.D. degree (1985) from Shinshu University, Matsumoto, Japan. He graduated from the Faculty of Medicine, Shinshu University in 1973. He was a Director of the Section of Rehabilitation Medicine in the Department of Orthopedic Surgery, Tokyo Koseinenkin Hospital, Tokyo, Japan, from 1990 to 1994. From 1994 to 2000, he was an Associate Professor of the Department of Restorative Neuromuscular Surgery and Rehabilitation, Graduate School of Medicine, Tohoku University, Sendai, Japan. He is presently a Director of the Department of Rehabilitation, Toyohashi City Hospital, Toyohashi, Japan. He is a member of the Japanese Association of Rehabilitation Medicine, the Japanese Orthopaedic Association and the Japan Medical Society of Paraplegia. Mineo Oyama obtained the Japanese national license of Occupational Therapists in 1984 after graduating from Higashinagoya National Hospital Rehabilitation College. He was engaged in hand rehabilitation from 1984 to 1996 at Nagoya Ekisaikai Hospital. In 1998 and 2001 he received his M.S. and PhD in disability science from the Tohoku University Graduate School of Medicine. He is presently a postdoctoral research fellow at the Mayo Clinic. His research interests focus on hand therapy, functional anatomy of the hand and clinical application of functional electrical stimulation for the paralyzed upper extremities. He is a member of the Japanese Association of Occupational Therapists, the Japan Hand Therapy Society and the International Functional Electrical Stimulation Society.

Kiyokazu Akasaka graduated from the School of Allied Medical Professions, Kanazawa University in 1990. He started working as a Licensed Physical Therapist in 1990. He received a BA degree from Wichita State University, Kansas in 1993 and an MS and PhD in disability science from Tohoku University Graduate School of Medicine in 1997 and 2000, respectively. Since 2000, he has been working as a Physical Therapist at Saitama Medical Center, Saitama Medical School. He is a member of the Japanese Association of Physical Therapists, the Japanese Association of Rehabilitation Medicine, the Japanese Society of Clinical Neurophysiology, and the Japanese Society of Electrophysiology and Kinesiology. Kouji Ihashi received his PhD in medical science from Tohoku University in 1995. He received his Japanese national license of Physical Therapy in 1976. From 1976 to 1982, he was engaged in work on physical therapy for SCI and stroke patients. He worked for the Department of Physical Therapy, School of Allied Medical Sciences, Shinshu University from 1983 to 1992 first as an Assistant Professor then as an Associate Professor engaged in work on chest physical therapy and kinesiology. From 1993 to 1998 he worked at Tohoku University Graduate School of Medicine, on FES and TES and also kinesiology. He is currently a Professor of the Department of Physical Therapy, Yamagata Prefectural University of Health Science. Yasunobu Handa received his M.D. and Doctor of medical science degrees from Tohoku University School of Medicine, Sendai, Japan. From 1976 to 1988, he was an Associate Professor of Anatomy at Shinshu University School of Medicine, Matsumoto, Japan. He was a Professor of Anatomy at Tohoku University School of Medicine from 1988 to 1994. From 1994 to 1999, he was a Professor in the Department of Restorative Neuromuscular Surgery and Rehabilitation, Tohoku University Graduate School of Medicine. Since 1999, he has been a Professor in New Industry Creation Hatchery Center Tohoku University. His principal fields of interests are functional and therapeutic electrical stimulation for the paralyzed extremities in stroke, head injury, spinal cord injury and ALS patients and for the paralyzed diaphragm and neurogenic bladder. He is also interested in functional anatomy and Kinesiology of the extremity motion.