TY - JOUR
T1 - Functional impairment of skeletal muscle oxidative metabolism during knee-extension exercise after bed rest
AU - Salvadego, Desy
AU - Lazzer, Stefano
AU - Marzorati, Mauro
AU - Porcelli, Simone
AU - Rejc, Enrico
AU - Šimunič, Bostjan
AU - Pišot, Rado
AU - Di Prampero, Pietro Enrico
AU - Grassi, Bruno
PY - 2011
Y1 - 2011
N2 - A functional evaluation of skeletal muscle oxidative metabolism during
dynamic knee extension (KE) incremental exercises was carried out following a 35-day bed rest (BR) (Valdoltra 2008 BR campaign). Nine young male volunteers (age: 23.5 +/- 2.2 yr; mean +/- SD) were
evaluated. Pulmonary gas exchange, heart rate and cardiac output (by
impedance cardiography), skeletal muscle (vastus lateralis) fractional
O2 extraction, and brain (frontal cortex) oxygenation (by near-infrared
spectroscopy) were determined during incremental KE. Values at exhaustion were considered “peak”. Peak heart rate (147 +/- 18 beats/min before vs. 146 +/- 17 beats/min after BR) and peak cardiac
output (17.8 +/- 3.3 l/min before vs. 16.1 +/- 1.8 l/min after BR) were
unaffected by BR. As expected, brain oxygenation did not decrease
during KE. Peak O2 uptake was lower after vs. before BR, both when
expressed as liters per minute (0.99 +/- 0.17 vs. 1.26 +/- 0.27) and when
normalized per unit of quadriceps muscle mass (46.5 +/- 6.4 vs. 56.9 +/-
11.0 ml/min/100 g). Skeletal muscle peak fractional O2 extraction,
expressed as a percentage of the maximal values obtained during
a transient limb ischemia, was lower after (46.3 +/- 12.1%) vs. before
BR (66.5 +/- 11.2%). After elimination, by the adopted exercise protocol, of constraints related to cardiovascular O2 delivery, a decrease in peak O2 uptake and muscle peak capacity of fractional O2 extraction was found after 35 days of BR. These findings suggest a substantial impairment of oxidative function at the muscle level,
“downstream” with respect to bulk blood flow to the exercising muscles, that is possibly at the level of blood flow distribution/O2 utilization inside the muscle, peripheral O2 diffusion, and intracellular oxidative metabolism.
AB - A functional evaluation of skeletal muscle oxidative metabolism during
dynamic knee extension (KE) incremental exercises was carried out following a 35-day bed rest (BR) (Valdoltra 2008 BR campaign). Nine young male volunteers (age: 23.5 +/- 2.2 yr; mean +/- SD) were
evaluated. Pulmonary gas exchange, heart rate and cardiac output (by
impedance cardiography), skeletal muscle (vastus lateralis) fractional
O2 extraction, and brain (frontal cortex) oxygenation (by near-infrared
spectroscopy) were determined during incremental KE. Values at exhaustion were considered “peak”. Peak heart rate (147 +/- 18 beats/min before vs. 146 +/- 17 beats/min after BR) and peak cardiac
output (17.8 +/- 3.3 l/min before vs. 16.1 +/- 1.8 l/min after BR) were
unaffected by BR. As expected, brain oxygenation did not decrease
during KE. Peak O2 uptake was lower after vs. before BR, both when
expressed as liters per minute (0.99 +/- 0.17 vs. 1.26 +/- 0.27) and when
normalized per unit of quadriceps muscle mass (46.5 +/- 6.4 vs. 56.9 +/-
11.0 ml/min/100 g). Skeletal muscle peak fractional O2 extraction,
expressed as a percentage of the maximal values obtained during
a transient limb ischemia, was lower after (46.3 +/- 12.1%) vs. before
BR (66.5 +/- 11.2%). After elimination, by the adopted exercise protocol, of constraints related to cardiovascular O2 delivery, a decrease in peak O2 uptake and muscle peak capacity of fractional O2 extraction was found after 35 days of BR. These findings suggest a substantial impairment of oxidative function at the muscle level,
“downstream” with respect to bulk blood flow to the exercising muscles, that is possibly at the level of blood flow distribution/O2 utilization inside the muscle, peripheral O2 diffusion, and intracellular oxidative metabolism.
KW - atrofia muscolare
KW - microgravity
KW - microgravità
KW - muscle atrophy
KW - atrofia muscolare
KW - microgravity
KW - microgravità
KW - muscle atrophy
UR - http://hdl.handle.net/10807/56990
U2 - 10.1152/japplphysiol.01380.2010
DO - 10.1152/japplphysiol.01380.2010
M3 - Article
SN - 8750-7587
VL - 111
SP - 1719
EP - 1726
JO - Journal of Applied Physiology
JF - Journal of Applied Physiology
ER -