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Mobility of the Elastic Counterpressure Space Suit Glove Kunihiko Tanaka, Patrick Danaher, Paul Webb, and Alan R. Hargens TANAKA K, DANAHER P, WEBB P, HARGENS AR. Mobility of the elasity and dexterity may be improved compared to that of tic counterpressure space suit glove. Aviat Space Environ Med 2009; the G-glove since it avoids working against expansion 80:890–3. associated with the G-glove. Although grip endurance Introduction: To evaluate the mobility of the current gas-pressurized time with the E-glove is the same as that with the glove of the extravehicular mobility unit (G-glove) and the elastic counterpressure glove (E-glove), we investigated range of motion (ROM) and G-glove (3), we hypothesized that the time course of indices of fatigue during grip endurance with both gloves using a bare fatigue with the E-glove would be different from that hand as a control. Methods: In nine healthy male right-handed subjects, with the G-glove if the mobility was different. In the ROM of the proximal interphalangeal joint of the left middle finger was present study, we evaluated the mobility of the finger measured. The median frequency of electromyography (EMG) of the left flexor carpi radialis during grip with 25% of maximum strength was and fatigue during isometric contraction of the G- and measured with the bare hand, G-glove, and E-glove. Using Borg’s scale, E-gloves, with both compared to a bare-hand control. discomfort was assessed during each grip test. Results: ROM of the E-glove was similar to that of the bare hand (91 6 3° and 97 6 1° for the METHODS E-glove and bare hand, respectively) and significantly higher than that of the G-glove (74 6 2°). The change in the median frequency of the EMG, The protocol was approved by the Institutional which is correlated with Borg’s scale, was significantly smaller using the Review Board at the University of California, San Diego, E-glove at marker time points of 1/4 and 1/2 of the total endurance time and NASA Johnson Space Center. Informed, written (23.5 6 1.5 and 210.4 6 1.2 Hz) compared to thoseby forPublishing the G-glove Technology Delivered to: Guest User (210.1 6 1.1 and 216.7 6 1.9 Hz). Thus, the G-glove had faster onset consent was obtained IP: 76.167.134.242 On: Sat, 15 Mar 2014 23:20:26from all subjects. Nine healthy of fatigue than the E-glove. Conclusion: These results suggest the E-glove male right-handed Copyright: Aerospace Medical Associationsubjects ranging from 22 to 38 yr old, has better mobility and is more suitable for fine motor tasks as compared 178.6 6 1.6 cm in height, and 76.9 6 2.8 kg in bodyweight to the G-glove. (mean 6 SE) volunteered for the present study and were Keywords: handgrip, electromyography, median frequency, range of motion, extravehicular activity. used for measurements. Their left hands were 19.0 6 0.2

T

HE DEMANDS OF extravehicular activity (EVA) will increase for future lunar and Martian exploration missions planned by NASA (1,8). EVA suits should have good mobility for various tasks and should be lightweight for the activity in partial gravity environments (6). Though the gas-pressurized current U.S. EVA glove (G-glove), officially called the extravehicular mobility unit (EMU) glove, is a remarkable achievement in soft material and anthropometrical construction, concerns still exist about flexibility of the suit (7,11). Elastic counterpressure (ECP), formerly known as mechanical counterpressure, is a novel and potentially advantageous concept that applies elastic compression to counteract the vacuum of the space (15). Previously, we demonstrated that an ECP glove (E-glove) and the sleeve can generate the same pressure against the finger, dorsum of the hand, and the wrist as the EMU and the ECP can counteract adverse effects of negative ambient pressure, such as decreased skin blood flow and temperature (12–14). Thus, the ECP can replace gas pressure and theoretically maintain physiologic conditions during situations of highly negative ambient pressure. Furthermore, we previously documented that an E-glove has the same grip strength as the G-glove (3). With the E-glove, mobil890

cm in length and 22.1 6 0.5 cm in palm circumference. The G-glove and arm sleeve assembly, used during EVAs (EMU 4000), were borrowed from NASA Johnson Space Center. A typical cross-section of the G-glove and sleeve consists of a pressure garment (two layers) and the thermal micrometeoroid garment (seven layers). The E-glove system consisted of three layers: 1) the comfort layer, 2) the slip layer that facilitated the donning of the glove, and 3) the final pressure layer that provides the elastic counterpressure (13). These glove layers were then pulled over and attached to the EMU gas-pressurized sleeve. In order to seal the arm of this unit to the E-glove covering the hand, we employed a flexible gel pack around the wrist that kept the sleeve unit airtight while not interfering with compression by the E-glove.

From the Department of Orthopedic Surgery, University of California, San Diego, UCSD Medical Center, San Diego, CA. This manuscript was received for review in April 2009. It was accepted for publication in July 2009. Address reprint requests to: Alan R. Hargens, Ph.D., Department of Orthopedic Surgery, University of California, San Diego, 350 Dickinson St., Suite 121, MC 8894, San Diego, CA 92103; ahargens@ucsd.edu. Reprint & Copyright © by the Aerospace Medical Association, Alexandria, VA. DOI: 10.3357/ASEM.2562.2009

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MOBILITY OF THE ECP GLOVE—TANAKA ET AL. Range of Motion Test A custom-made goniometer was placed on the proximal interphalangeal (PIP) joint of the left middle finger. The goniometer was made of a silicon tube (internal diameter: 1 mm, external diameter: 2 mm) filled with conductive gel and the tube was protected by a stainless spring from compression. The impedance of the meter was changed with lengthening caused by joint movement. The goniometer was connected to a wheat-stone bridge amplifier and the voltage output was calibrated at 30°, 60°, and 90° of the joint for each subject. Maximal range of motion (ROM) of the joint without any glove and at normal ambient pressure was recorded. After donning the G- or E-glove, ROM was recorded with normal ambient pressure (0 mmHg) and 2200 mmHg conditions. So volunteers were subjected to five experimental conditions—bare hand at 0 mmHg, G-glove at 0 mmHg, G-glove at 2200 mmHg, E-glove at 0 mmHg, and E-glove at 2200 mmHg. The order of the experimental conditions was randomized. Endurance Test

where MDF is the median frequency, P(v) is the power spectral density derived by the transformation of the EMG signal, and v is the frequency variable. To analyze the relationship between subjective fatigue and objective fatigue indices, the median frequency was calculated every 30 s and changes in the frequency from the starting point were plotted with Borg’s scale. To compare differences in median frequency between the G- and E-gloves during the grip-endurance test, changes in median frequency were analyzed at marker-time points of 1/4, 1/2, and 3/4, as well as at the end of the grip-endurance test. All data were expressed as means 6 SE. The statistical significance of the differences in the ROM was analyzed by one-way analysis of variance. Correlation between Borg’s scale and the medial frequency of the EMG was analyzed using Spearman’s correlation coefficient by rank. Considering time and type of glove as variable factors, the changes in median frequency were analyzed using repeated measure ANOVA for statistical significance. If statistical significance was found, Tukey’s post hoc test was applied to compare conditions. Significance was set at P , 0.05.

Grip strength and endurance were measured with the RESULTS bare hand, G-, and E-glove. Tests were performed at normal ambient pressure and with both gloves at 2200 Fig. 1 shows summarized data for nine subjects of mmHg, the approximate pressure differential experiROM across the PIP joint with the bare hand in normal enced in a gas-pressurized space suit during EVA (12,13). ambient pressure and with the G- and the E-gloves in Each volunteer was seated in front of the hypobaric normal ambient Delivered by Publishing Technology to: Guestpressure User and at 2200 mmHg pressure chamber with arms at a 90° angle. Grip endurance time conditions. The PIP joint of the bare hand could flex to IP: 76.167.134.242 On: Sat, 15 Mar 2014 23:20:26 at 25% of previously determined maximum bare Medical 97° 6 1° from horizontal extension position in normal Copyright: Aerospace Association handgrip strength was tested. The order of testing of the ambient pressure. With the G- glove, the range was sigbare hand, G-, or E-glove was randomized among subnificantly decreased to 73° 6 2° and 74° 6 2° at normal jects. The volunteers were questioned about their faambient and 2200 mmHg pressure conditions, respectigue level according to Borg’s discomfort scale, tively. The G-glove was expanded and hard to bend in numbered from 0 (resting) to 10 (maximal exertion), evthe 2200 mmHg condition, but no significant difference ery 30 s during the endurance test (4). Surface electrowas observed between the two ambient pressure condimyography (EMG) of the left flexor carpi radialis was tions due to exertion of the volunteers and volume measured continuously and simultaneously. Two EMG change in the G-glove. However, ROM of the E-glove electrodes, 2 cm apart, were placed over the muscle belly and a reference electrode was placed on the dorsum of the right hand. The signal was amplified, monitored, and recorded continuously at a rate of 1024 Hz using an analog-to-digital converter with programming software (LabView 5.0.1, National Instruments, Austin, TX). EMG data were passed through a high-pass filter with a low cut-off frequency of 10 Hz. During a 1-s period, 1024 samples were analyzed with fast Fourier transformation. The sampling rate and the filter was appropriate to calculate median frequency of the EMG signal since usable energy of the EMG is between 70 and 300 Hz (5,10). Median frequency of the EMG was used as an index of local objective muscle fatigue. Median frequency was calculated as the frequency at which the spectrum derived by the transformation was divided into two parts of equal power. It was described accordFig. 1. The range of motion on the proximal interphalangeal joint with the bare hand in normal ambient pressure (0 mmHg) and with ing to following equation (5):

³

MDF

0

P (Z )d Z

³

f

MDF

P (Z )d Z

1 P (Z )d Z 2 ³0 f

the gas-pressurized glove taken from the extravehicular mobility unit (G-glove) and the elastic counterpressure glove (E-glove) in normal ambient pressure and at 2200 mmHg of negative pressure. *P , 0.05 vs. bare hand in the normal ambient pressure condition.

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MOBILITY OF THE ECP GLOVE—TANAKA ET AL. was very close to that of the bare hand, i.e., 93° 6 3° and 91° 6 3° in the normal ambient and 2200 mmHg pressure conditions, respectively. Fig. 2 presents the relationship between Borg’s scale (2 to 10) and changes in the median frequency analyzed every 30 s during the endurance test with the bare hand. The change in median frequency (objective fatigue) was linearly correlated with Borg’s scale (subjective fatigue scale). Thus, median frequency of the EMG was used as a continuous and objective index of local muscle fatigue. Fig. 3 shows changes in median frequency during grip endurance with the G- and E-gloves. The endurance time of each subject was highly variable depending Fig. 3. Changes in median frequency during grip endurance with on the physical attributes of each subject (29 ~120 and 40 the gas-pressurized glove taken from the extravehicular mobility unit ~103 s for G- and E-glove, respectively). Thus the endur(G-glove) and the elastic counterpressure glove (E-glove). The endurance ance time was normalized and total endurance time was time was normalized and the frequency was plotted at 1/4, 1/2, 3/4, and set at one. Median frequency decreased for both with the end of endurance time. *P , 0.05 vs. G-glove. the G- and E-gloves during the grip endurance test. During the early phase (at 1/4 and 1/2 of the endurance the E-glove during the early phase of grip endurance time), the decrease in the median frequency with the compared to that of the G-glove. G-glove was significantly greater than that with the The ROM of the PIP joint of the middle finger with the E-glove. After that, the frequency continued to decrease E-glove is close to that of the bare hand in both normal with the E-glove. However, with the G-glove, the freambient and the hypobaric conditions. ROM is not difquency at 1/2 and 3/4 time points were the same. Fiferent between each condition since the the E-glove has nally, the frequency for both the G- and E-gloves dropped thin layers and does not expand under hypobaric condito 226 and 222 Hz from the starting point of the grip tions (13). ROM is significantly smaller with the G-glove endurance test, respectively, as greater fatigue set in. No compared to that with the E-glove in both normal ambisignificant changes in frequency between the G- and ent and hypobaric conditions. Regardless of the pressure Delivered by at Publishing to: Guest User E-glove were observed in the latter phase, i.e., 3/4 and Technology between the inside and outside of the suit, IP: 76.167.134.242 On: Sat,differential 15 Mar 2014 23:20:26 at the end of the endurance test. ROM ofAssociation the finger is restricted in the G-glove, probably Copyright: Aerospace Medical due to multiple layers for leak prevention and protecDISCUSSION tion from meteoroids. The E-glove does not require such In the present study, we document that 1) ROM of the a hard leak-proof layer for pressurization. Furthermore, PIP joint on the middle finger with the E-glove is similar the E-glove has both retractive force and extensibility to that of the bare hand and significantly greater than due to using spandex yarn (9). The properties support that of the G-glove; 2) a median frequency of EMG is glove deformation along the joint movement and the Elinearly correlated with subjective fatigue scale from the glove bends naturally with little effort. The layers of the early stage to the exhausting endpoint of fatigue; and 3) E-glove used in the present study are aimed for pressurthe median frequency of EMG is significantly lower in ization only, although the G-glove has thermal meteoroid garment layers which protect the body from changing temperature, micrometeorites, and radiation. Further studies are needed if ROM is changed with such additional layers as with the E-glove, but the results encourage the use and study of elastic material for EVA. The median frequency of EMG is used as an index of muscle fatigue (2). In the present study, the median frequency of the muscle flexor carpi is not only decreased with time, but also linearly correlated with subjective discomfort during endurance. The correlation between the highest discomfort scale with a severe task is known (4), but we find that the frequency can be also an index of fatigue during mild discomfort. The median frequency of EMG decreased according to the time of grip endurance with both the G- and E-gloves. Total endurance time was not different between the G- and E-gloves (3), but the decrease in the frequency, an index of fatigue, was significantly smaller with the Fig. 2. Relationship between subjective (Borg’s scale) and change in E-glove during the first half of the endurance test. The objective (median frequency of electromyography) scales during isomethigh ROM and lack of expansion of the E-glove might ric contraction of the bare hand. 892

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MOBILITY OF THE ECP GLOVE—TANAKA ET AL. 4. Fleming SL, Jansen CW, Hasson SM. Effect of work glove and type of muscle action on grip fatigue. Ergonomics 1997; 40:601–12. 5. Georgakis A, Stergioulas LK, Giakas G. Fatigue analysis of the surface EMG signal in isometric constant force contractions using the averaged instantaneous frequency. IEEE Trans Biomed Eng 2003; 50:262–5. 6. Graziosi D, Ferl JG. Performance of an advanced space suit design for international space station and planetary applications. Warrendale, PA: SAE; 1999:1-7. SAE technical paper series 1999-01-1967. 7. Jones JA, Hoffman RB, Buckland DA, Harvey CM, Bowen CK, et al. The use of an extended ventilation tube as a countermeasure for EVA-associated upper extremity medical issues. Acta Astronautica 2008; 63:763–8. 8. Joyce S, Ferguson C, Weinstein P. Public support for Mars missions: the importance of informing the next generation. Acta Astronautica 2009; 64:718–23. ACKNOWLEDGMENT 9. Lee CG. Changes of pulling-out length and shrinkage ratio in This study was supported by NASA grant NAG9–1916, Honeywell polyester/spandex power net warp knitted fabrics. Fibers and contract S00001424, and an unrestricted gift from RORE, Inc. Polymers 2006; 7:51–6. The first author, Kunihiko Tanaka, was a Research Associate at the 10. Najarian K, Splinter R. Electromyogram. In: Najarian K, Splinter University of California, San Diego. R. Biomedical signal and image processing. London: Taylor & Authors and affiliations: Kunihiko Tanaka, M.D., Ph.D., Department Francis; 1995:237–55. of Physiology, Gifu University Graduate School of Medicine, Gifu, 11. Shields N Jr, King LC. Testing and evaluation for astronaut Japan; Patrick Danaher, M.D., and Alan R. Hargens, Ph.D., Department extravehicular activity (EVA) operability. Hum Perf Extrem of Orthopedic Surgery, University of California, San Diego, UCSD Environ 1998; 3:145–9. Medical Center, San Diego, CA; and Paul Webb, M.D., Consultant, 12. Tanaka K, Limberg R, Webb P, Reddig M, Jarvis CW, et al. Yellow Springs, OH. Mechanical counter pressure on the arm counteracts adverse effects of hypobaric exposures. Aviat Space Environ Med 2003; 74:827–32. REFERENCES 13. Tanaka K, Waldie J, Steinbach GC, Webb P, Tourbier D, et al. 1. Aydogan-Cremaschi S, Orcun S, Blau G, Pekny JF, Reklaitis GV. Skin microvascular flow during hypobaric exposure with and A novel approach for life-support-system design for manned without a mechanical counter-pressure space suit glove. Aviat space missions. Acta Astronautica 2009; 65:330–46. Space Environ Med 2002; 73:1074–8. 2. Blackwell JR, Kornatz KW, Heath EM. Effect of grip span on 14. Waldie JM, Tanaka K, Tourbier D, Webb P, Jarvis CW, et al. maximal grip force and fatigue of flexor digitorum superficialis. Compression under a mechanical counter pressure space suit Appl Ergon 1999; 30:401–5. Publishing Technology to:. JGuest User 2002; 9:93–7. glove Gravit Physiol 3. Danaher P, Tanaka K, Hargens AR.Delivered Mechanical by counter-pressure IP: grip 76.167.134.242 On: Sat,15. 15Webb Mar P2014 23:20:26 . The space activity suit: an elastic leotard for extravehicuvs. gas-pressurized spacesuit gloves: and sensitivity. Aviat activity. Aerosp Med 1968; 39:376–83. Space Environ Med 2005; 76:381–4. Copyright: Aerospace MedicallarAssociation

help generate the specified grip strength. The change in frequency was the same as that with the G-glove at the end of the endurance test because subjects were exhausted independently of type of glove. In conclusion, the E-glove has similar ROM to a bare hand and ROM is significantly larger than that of the G-glove. Changes in median frequency of EMG, an objective index of muscle fatigue, is significantly smaller during the early phase of grip endurance. Thus the E-glove is more suitable for fine motor activities of short duration as compared to the G-glove. Further study will be needed with the E-glove, which can protect from micrometeoroids and radiation.

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Mobility of the elastic counterpressure space suit glove  
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