An upper arm model for simulated weightlessness

Allen C. Parcell, S. W. Trappe, M. P. Godard, David L. Williamson, IV, W. J. Fink, D. L. Costill

Research output: Contribution to journalArticle

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Abstract

This investigation examined the effects of 4 weeks of non-dominant arm unloading on the functional and structural characteristics of the triceps brachii muscle of six normo-active college-age males (age: 23 ± 1 years, height: 176 ± 4 cm, weight: 76 ± 6 kg). The primary intention of this study was to determine if arm unloading is an effective analogue for simulating the effects of weightlessness on human skeletal muscle. Subjects were tested 2-3 days preceding unloading in a standard arm sling and following removal of the sling. The sling was worn during waking hours to unload the arm. Subjects were allowed to remove the sling during sleep and bathing. Torque production (Nm) during maximal isometric extension at 90°significantly declined (P < 0.05) in response to unloading (53.93 ± 5.07 to 47.90 ± 5.92; 12%). There was no significant change (P > 0.05) in the force-velocity attributes of the triceps over the other measured velocities (1.05, 1.57, 2.09, 3.14, 4.19, 5.24 rad s-1). Cross-sectional muscle area (CSA) of the upper arm was smaller (44.3 ± 2.7 to 42.4 ± 2.5 cm2; 4%) following 4 weeks of unloading (P < 0.05). Histochemical analysis of individual muscle fibres demonstrated reductions in fibre CSA of 27 and 18% for type I and type II fibres, respectively. However, these changes were not statistically significant. Electrophoretic analysis of muscle samples revealed a significant increase (40 ± 7 to 58 ± 4%, pre- and post-, respectively) in myosin heavy chain (MHC) type II isoforms following unloading. Reductions in type I MHC isoform composition failed to reach statistical significance (P < 0.08). Amplitude of the integrated electromyographic (IEMG) signal during maximal isometric contraction of the long head of the triceps decreased by 21% in response to the 4-week unloading period (P < 0.05). The changes in triceps, muscle structure and function found with arm unloading are similar in magnitude and direction to data obtained from humans following exposure to real and simulated weightlessness. These findings demonstrate that arm unloading produces some of the effects seen in response to weightlessness in muscles of the upper arm and provides potential for an additional model to simulate the effects of microgravity on human skeletal muscle.

Original languageEnglish (US)
Pages (from-to)47-54
Number of pages8
JournalActa Physiologica Scandinavica
Volume169
Issue number1
DOIs
StatePublished - 2000

Fingerprint

Weightlessness Simulation
Arm
Weightlessness
Muscles
Myosin Heavy Chains
Protein Isoforms
Skeletal Muscle
Isometric Contraction
Torque
Sleep

All Science Journal Classification (ASJC) codes

  • Physiology

Cite this

Parcell, A. C., Trappe, S. W., Godard, M. P., Williamson, IV, D. L., Fink, W. J., & Costill, D. L. (2000). An upper arm model for simulated weightlessness. Acta Physiologica Scandinavica, 169(1), 47-54. https://doi.org/10.1046/j.1365-201X.2000.00689.x
Parcell, Allen C. ; Trappe, S. W. ; Godard, M. P. ; Williamson, IV, David L. ; Fink, W. J. ; Costill, D. L. / An upper arm model for simulated weightlessness. In: Acta Physiologica Scandinavica. 2000 ; Vol. 169, No. 1. pp. 47-54.
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abstract = "This investigation examined the effects of 4 weeks of non-dominant arm unloading on the functional and structural characteristics of the triceps brachii muscle of six normo-active college-age males (age: 23 ± 1 years, height: 176 ± 4 cm, weight: 76 ± 6 kg). The primary intention of this study was to determine if arm unloading is an effective analogue for simulating the effects of weightlessness on human skeletal muscle. Subjects were tested 2-3 days preceding unloading in a standard arm sling and following removal of the sling. The sling was worn during waking hours to unload the arm. Subjects were allowed to remove the sling during sleep and bathing. Torque production (Nm) during maximal isometric extension at 90°significantly declined (P < 0.05) in response to unloading (53.93 ± 5.07 to 47.90 ± 5.92; 12{\%}). There was no significant change (P > 0.05) in the force-velocity attributes of the triceps over the other measured velocities (1.05, 1.57, 2.09, 3.14, 4.19, 5.24 rad s-1). Cross-sectional muscle area (CSA) of the upper arm was smaller (44.3 ± 2.7 to 42.4 ± 2.5 cm2; 4{\%}) following 4 weeks of unloading (P < 0.05). Histochemical analysis of individual muscle fibres demonstrated reductions in fibre CSA of 27 and 18{\%} for type I and type II fibres, respectively. However, these changes were not statistically significant. Electrophoretic analysis of muscle samples revealed a significant increase (40 ± 7 to 58 ± 4{\%}, pre- and post-, respectively) in myosin heavy chain (MHC) type II isoforms following unloading. Reductions in type I MHC isoform composition failed to reach statistical significance (P < 0.08). Amplitude of the integrated electromyographic (IEMG) signal during maximal isometric contraction of the long head of the triceps decreased by 21{\%} in response to the 4-week unloading period (P < 0.05). The changes in triceps, muscle structure and function found with arm unloading are similar in magnitude and direction to data obtained from humans following exposure to real and simulated weightlessness. These findings demonstrate that arm unloading produces some of the effects seen in response to weightlessness in muscles of the upper arm and provides potential for an additional model to simulate the effects of microgravity on human skeletal muscle.",
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Parcell, AC, Trappe, SW, Godard, MP, Williamson, IV, DL, Fink, WJ & Costill, DL 2000, 'An upper arm model for simulated weightlessness', Acta Physiologica Scandinavica, vol. 169, no. 1, pp. 47-54. https://doi.org/10.1046/j.1365-201X.2000.00689.x

An upper arm model for simulated weightlessness. / Parcell, Allen C.; Trappe, S. W.; Godard, M. P.; Williamson, IV, David L.; Fink, W. J.; Costill, D. L.

In: Acta Physiologica Scandinavica, Vol. 169, No. 1, 2000, p. 47-54.

Research output: Contribution to journalArticle

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T1 - An upper arm model for simulated weightlessness

AU - Parcell, Allen C.

AU - Trappe, S. W.

AU - Godard, M. P.

AU - Williamson, IV, David L.

AU - Fink, W. J.

AU - Costill, D. L.

PY - 2000

Y1 - 2000

N2 - This investigation examined the effects of 4 weeks of non-dominant arm unloading on the functional and structural characteristics of the triceps brachii muscle of six normo-active college-age males (age: 23 ± 1 years, height: 176 ± 4 cm, weight: 76 ± 6 kg). The primary intention of this study was to determine if arm unloading is an effective analogue for simulating the effects of weightlessness on human skeletal muscle. Subjects were tested 2-3 days preceding unloading in a standard arm sling and following removal of the sling. The sling was worn during waking hours to unload the arm. Subjects were allowed to remove the sling during sleep and bathing. Torque production (Nm) during maximal isometric extension at 90°significantly declined (P < 0.05) in response to unloading (53.93 ± 5.07 to 47.90 ± 5.92; 12%). There was no significant change (P > 0.05) in the force-velocity attributes of the triceps over the other measured velocities (1.05, 1.57, 2.09, 3.14, 4.19, 5.24 rad s-1). Cross-sectional muscle area (CSA) of the upper arm was smaller (44.3 ± 2.7 to 42.4 ± 2.5 cm2; 4%) following 4 weeks of unloading (P < 0.05). Histochemical analysis of individual muscle fibres demonstrated reductions in fibre CSA of 27 and 18% for type I and type II fibres, respectively. However, these changes were not statistically significant. Electrophoretic analysis of muscle samples revealed a significant increase (40 ± 7 to 58 ± 4%, pre- and post-, respectively) in myosin heavy chain (MHC) type II isoforms following unloading. Reductions in type I MHC isoform composition failed to reach statistical significance (P < 0.08). Amplitude of the integrated electromyographic (IEMG) signal during maximal isometric contraction of the long head of the triceps decreased by 21% in response to the 4-week unloading period (P < 0.05). The changes in triceps, muscle structure and function found with arm unloading are similar in magnitude and direction to data obtained from humans following exposure to real and simulated weightlessness. These findings demonstrate that arm unloading produces some of the effects seen in response to weightlessness in muscles of the upper arm and provides potential for an additional model to simulate the effects of microgravity on human skeletal muscle.

AB - This investigation examined the effects of 4 weeks of non-dominant arm unloading on the functional and structural characteristics of the triceps brachii muscle of six normo-active college-age males (age: 23 ± 1 years, height: 176 ± 4 cm, weight: 76 ± 6 kg). The primary intention of this study was to determine if arm unloading is an effective analogue for simulating the effects of weightlessness on human skeletal muscle. Subjects were tested 2-3 days preceding unloading in a standard arm sling and following removal of the sling. The sling was worn during waking hours to unload the arm. Subjects were allowed to remove the sling during sleep and bathing. Torque production (Nm) during maximal isometric extension at 90°significantly declined (P < 0.05) in response to unloading (53.93 ± 5.07 to 47.90 ± 5.92; 12%). There was no significant change (P > 0.05) in the force-velocity attributes of the triceps over the other measured velocities (1.05, 1.57, 2.09, 3.14, 4.19, 5.24 rad s-1). Cross-sectional muscle area (CSA) of the upper arm was smaller (44.3 ± 2.7 to 42.4 ± 2.5 cm2; 4%) following 4 weeks of unloading (P < 0.05). Histochemical analysis of individual muscle fibres demonstrated reductions in fibre CSA of 27 and 18% for type I and type II fibres, respectively. However, these changes were not statistically significant. Electrophoretic analysis of muscle samples revealed a significant increase (40 ± 7 to 58 ± 4%, pre- and post-, respectively) in myosin heavy chain (MHC) type II isoforms following unloading. Reductions in type I MHC isoform composition failed to reach statistical significance (P < 0.08). Amplitude of the integrated electromyographic (IEMG) signal during maximal isometric contraction of the long head of the triceps decreased by 21% in response to the 4-week unloading period (P < 0.05). The changes in triceps, muscle structure and function found with arm unloading are similar in magnitude and direction to data obtained from humans following exposure to real and simulated weightlessness. These findings demonstrate that arm unloading produces some of the effects seen in response to weightlessness in muscles of the upper arm and provides potential for an additional model to simulate the effects of microgravity on human skeletal muscle.

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