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.

The modified massive cuff stitch: functional and structural outcome in massive cuff tears.

BACKGROUND: The massive cuff stitch (MCS) is known to be a strong suture, suitable for rotator cuff repair. We modified this technique for massive cuff tears by employing a horizontal medial mattress suture from an anchor as well as a vertically crossing transosseous suture. METHODS: We included 42 patients with massive cuff tears suitable for repair: 22 were treated with the modified MCS (MCS group), and 20 with a simple transosseous suture (STS group). The range of motion (ROM), muscle strength, visual analog scale, and the Japanese Orthopaedic Association (JOA) scores were evaluated pre-operatively and 12 and 24 months post-operatively. The incidence of post-operative re-tears was examined at least 1 year post-operatively using Sugaya's classification. RESULTS: The ROM, muscle strength, degree of pain, and the JOA scores were much improved after surgery in both groups, and there was no significant intergroup difference throughout the pre- and post-operative periods. In contrast, post-operative MRI revealed a significantly lower re-tear rate in the MCS group than in the STS group (9.1% vs. 40%, P = 0.0296). CONCLUSIONS: The techniques tested were comparable in terms of functional outcome after surgical repair of massive cuff tears; however, the modified MCS repair technique produced superior structural outcomes with a significantly lower re-tear rate.

"Hybrid exercise" prevents muscle atrophy in association with a distinct gene expression pattern.

"Hybrid exercise" utilizing combined electrical stimulation and voluntary muscle contraction has been developed as a muscle exercise method. Although our previous studies have confirmed the effectiveness of the procedure, the mechanisms of its efficacy still remain unclear. In the present study, we identified genes that are specifically expressed in disused muscles, using the semitendinosus muscle from patients who underwent anterior cruciate ligament (ACL) reconstruction. Preoperative exercise was performed by four ACL-injured patients, who were subjected either to hybrid exercise (n=2), electrical stimulation (n=1), or no electrical stimulation (n=1), in addition to standard weight training for 4 weeks. Cross-sectional area (CSA) of the semitendinosus muscle was measured before and after the exercise by magnetic resonance imaging (MRI). A piece of the semitendinosus muscle was isolated during the surgery, and comprehensive analysis of the gene expression in this sample was performed using DNA microarray analysis. CSA increased in size by 4.2 and 14.7%, respectively, after hybrid exercise, and by 1.4% after electrical stimulation. However it shrunk by 7.7% without electrical stimulation. DNA microarray analysis revealed that hybrid exercise was more effective at stimulating the expression of signal transduction-, transcription- and cytoskeleton-related genes in semitendinosus muscles than electrical stimulation alone. In particular, gene ontology analysis revealed that hybrid exercise induced significantly higher expression of eukaryotic translation initiation factor 5A (EIFSA), peroxisomal biogenesis factor 6 (PEX6) and histone cluster 1 H4 (HIST1H4), compared with electrical stimulation alone. The expression of signal transduction-, transcription- and cytoskeleton-related genes may play an important role in muscle bulk increasing mechanisms in hybrid exercise.

Development of a training method for weightless environment using both electrical stimulation and voluntary muscle contraction.

Extreme skeletal muscle atrophy is rampant in astronauts exposed to extended periods of microgravity (muG), and it is one of the main problems in human space exploration. A "Hybrid training" (HYB) method utilizing combined electrical stimulation and voluntary muscle contraction has been developed as a possible solution. A wearable HYB device and a virtual reality (VR) system were developed for use in space, and were verified at muG generated by parabolic flight (PF). A 36-year-old male subject performed HYB of reciprocal flexion and extension as a knee joint exercise training in a seated position at 1G, 2G and muG. The wearable HYB device and VR system developed for the study functioned well during the flight. However knee extension was insufficient at 1G and 2G, and the maximum knee extension angles at 1G and 2G were smaller than at muG. The extension velocity in the latter half of each motion was slower than in the first half at 1G and 2G, but no difference in velocity was observed at muG. The subject could extend the knee joint sufficiently and keep a constant extension velocity, because his legs were weightless at muG. The congruity between the subject's actual joint motions and instructed joint motions during muG was improved, when VR was employed with or without body fixation; accordingly, the subject was able to perform the desired joint motion. The VR system improved HYB exercise performance at muG during PF. HYB is considered a useful training method for future human space exploration.

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.