Role of skeletal muscles impairment and brain oxygenation in limiting oxidative metabolism during exercise after bed rest

Bowen TS, Cannon DT, Murgatroyd SR, Birch KM, Witte KK, Rossiter HB. The intramuscular contribution to the slow oxygen uptake kinetics during exercise in chronic heart failure is related to the severity of the condition. J Appl Physiol 112: 378 -387, 2012. First published October 27, 2011 doi:10.1152/japplphysiol.00779.2011The mechanism for slow pulmonary O2 uptake (V O2) kinetics in patients with chronic heart failure (CHF) is unclear but may be due to limitations in the intramuscular control of O2 utilization or O2 delivery. Recent evidence of a transient overshoot in microvascular deoxygenation supports the latter. Prior (or warm-up) exercise can increase O2 delivery in healthy individuals. We therefore aimed to determine whether prior exercise could increase muscle oxygenation and speed V O2 kinetics during exercise in CHF. Fifteen men with CHF (New York Heart Association I-III) due to left ventricular systolic dysfunction performed two 6-min moderate-intensity exercise transitions (bouts 1 and 2, separated by 6 min of rest) from rest to 90% of lactate threshold on a cycle ergometer. V O2 was measured using a turbine and a mass spectrometer, and muscle tissue oxygenation index (TOI) was determined by near-infrared spectroscopy. Prior exercise increased resting TOI by 5.3 Ϯ 2.4% (P ϭ 0.001), attenuated the deoxygenation overshoot (Ϫ3.9 Ϯ 3.6 vs. Ϫ2.0 Ϯ 1.4%, P ϭ 0.011), and speeded the V O2 time constant (V O2; 49 Ϯ 19 vs. 41 Ϯ 16 s, P ϭ 0.003). Resting TOI was correlated to V O2 before (R 2 ϭ 0.51, P ϭ 0.014) and after (R 2 ϭ 0.36, P ϭ 0.051) warm-up exercise. However, the mean response time of TOI was speeded between bouts in half of the patients (26 Ϯ 8 vs. 20 Ϯ 8 s) and slowed in the remainder (32 Ϯ 11 vs. 44 Ϯ 16 s), the latter group having worse New York Heart Association scores (P ϭ 0.042) and slower V O2 kinetics (P ϭ 0.001). These data indicate that prior moderate-intensity exercise improves muscle oxygenation and speeds V O2 kinetics in CHF. The most severely limited patients, however, appear to have an intramuscular pathology that limits V O2 kinetics during moderate exercise. muscle oxygenation; near-infrared spectroscopy; prior exercise CHRONIC HEART FAILURE (CHF) is a syndrome characterized by exercise intolerance due to breathlessness and fatigue in the presence of cardiac dysfunction. A treadmill or cycle-based symptom-limited peak exercise test, with pulmonary gas exchange measurement to determine peak O 2 uptake (V O 2peak ), is the most widely used measure of physiological limitation in CHF and provides objective information on aerobic capacity, symptomatology, and prognosis (35). However, activities of daily living rarely occur at or around V O 2peak . Therefore, the rate at which aerobic energy transfer adapts [O 2 uptake (V O 2 ) kinetics] to changing energy demands may provide an assessment that is more appropriate to daily exercise limitations in CHF than traditional measures (1, 52). Accordingly, initial evidence indicates that V O 2 kinetics are more strongly correlated to disease s...

mentioning

confidence: 81%

The intramuscular contribution to the slow oxygen uptake kinetics during exercise in chronic heart failure is related to the severity of the condition

Bowen

Cannon²,

Murgatroyd³

et al. 2012

“…A portable NIR continuous-wave photometer (PortaMon, Artinis, The Netherlands) was utilized. Specific details on the method can be found in recent papers by our group (32,37). (18).…”

Section: Measurementsmentioning

confidence: 99%

Skeletal muscle oxidative function in vivo and ex vivo in athletes with marked hypertrophy from resistance training

Salvadego

Domenis

Lazzer

et al. 2013

Self Cite

Oxidative function during exercise was evaluated in 11 young athletes with marked skeletal muscle hypertrophy induced by long-term resistance training (RTA; body mass 102.6 Ϯ 7.3 kg, mean Ϯ SD) and 11 controls (CTRL; body mass 77.8 Ϯ 6.0 kg). Pulmonary O2 uptake (V O2) and vastus lateralis muscle fractional O2 extraction (by near-infrared spectroscopy) were determined during an incremental cycle ergometer (CE) and one-leg knee-extension (KE) exercise. Mitochondrial respiration was evaluated ex vivo by high-resolution respirometry in permeabilized vastus lateralis fibers obtained by biopsy. Quadriceps femoris muscle cross-sectional area, volume (determined by magnetic resonance imaging), and strength were greater in RTA vs. CTRL (by ϳ40%, ϳ33%, and ϳ20%, respectively). V O2peak during CE was higher in RTA vs. CTRL (4.05 Ϯ 0.64 vs. 3.56 Ϯ 0.30 l/min); no difference between groups was observed during KE. The O2 cost of CE exercise was not different between groups. When divided per muscle mass (for CE) or quadriceps muscle mass (for KE), V O2 peak was lower (by 15-20%) in RTA vs. CTRL. Vastus lateralis fractional O2 extraction was lower in RTA vs. CTRL at all work rates, during both CE and KE. RTA had higher ADP-stimulated mitochondrial respiration (56.7 Ϯ 23.7 pmol O2·s Ϫ1 ·mg Ϫ1 ww) vs. CTRL (35.7 Ϯ 10.2 pmol O2·s Ϫ1 ·mg Ϫ1 ww) and a tighter coupling of oxidative phosphorylation. In RTA, the greater muscle mass and maximal force and the enhanced mitochondrial respiration seem to compensate for the hypertrophy-induced impaired peripheral O2 diffusion. The net results are an enhanced whole body oxidative function at peak exercise and unchanged efficiency and O 2 cost at submaximal exercise, despite a much greater body mass. skeletal muscle hypertrophy; mitochondrial respiration; oxidative metabolism during exercise RESISTANCE TRAINING PROGRAMS have been developed with the aim of improving variables of muscle function such as strength, power, speed, local muscular endurance, coordination, and flexibility (21). Resistance training is now considered an important part of training and rehabilitation programs for healthy subjects and for various types of patients, such as cardiac patients (45), patients with pulmonary diseases (10), patients undergoing prolonged bed-rest periods (2), or elderly subjects (28). In these populations, the combination of resistance training with the more conventional endurance exercise improves the patients' outcomes and quality of life (45).An increase in the cross-sectional area of skeletal muscle fibers and a shift of fiber-type distribution toward type 2 fibers are typical adaptations induced by resistance training; these adaptations enhance the muscle force-generating potential (12) but could represent an impairment to skeletal muscle oxidative metabolism. On the other hand, muscles with higher maximal force would need to recruit a lower number of motor units, and therefore more oxidative (and more efficient) muscle fibers (20,26). According to other authors, strength training may increas...

“…Pulmonary ventilation [(VE) expressed in BTPS], V O2, and CO2 output (V CO2), both expressed in STPD, were determined breath by breath by a computerized metabolic cart (SensorMedics Vmax29c, Bilthoven, The Netherlands). For details on this standard method, see Porcelli et al (37). Gas exchange ratio was calculated as V /V O2.…”

Section: Cycloergometric Exercise Protocolsmentioning

confidence: 99%

“…The actual amplitude of the slow component (A= s) was estimated as the difference between the average V O2 value obtained during the last 20 s of CLE and the asymptotic value of the fundamental component (25). The percent contribution of the slow component to the total amplitude (Atot) of the response (A= s/Atot) was also calculated (37).…”

Section: Cycloergometric Exercise Protocolsmentioning

confidence: 99%

Lack of functional effects of neuromuscular electrical stimulation on skeletal muscle oxidative metabolism in healthy humans

Porcelli

Marzorati

Pugliese

et al. 2012

Self Cite

-A recent study has demonstrated that neuromuscular electrical stimulation (NMES) determines, in vitro, a fast-to-slow shift in the metabolic profile of muscle fibers. The aim of the present study was to evaluate if, in the same subjects, these changes would translate, in vivo, into an enhanced skeletal muscle oxidative metabolism. Seven young men were tested (cycle ergometer) during incremental exercises up to voluntary exhaustion and moderate and heavy constant-load exercises (CLE). Measurements were carried out before and after an 8-wk training program by isometric bilateral NMES (quadriceps muscles), which induced an ϳ25% increase in maximal isometric force. Breathby-breath pulmonary O2 uptake (V O2) and vastus lateralis oxygenation indexes (by near-infrared spectroscopy) were determined. Skeletal muscle fractional O2 extraction was estimated by near-infrared spectroscopy on the basis of changes in concentration of deoxygenated hemoglobin ϩ myoglobin. Values obtained at exhaustion were considered "peak" values. The following functional evaluation variables were unaffected by NMES: peak V O2; gas exchange threshold; the V O2 vs. work rate relationship (O2 cost of cycling); changes in concentration of deoxygenated hemoglobin ϩ myoglobin vs. work rate relationship (related to the matching between O2 delivery and V O2); peak fractional O2 extraction; V O2 kinetics (during moderate and heavy CLE) and the amplitude of its slow component (during heavy CLE). Thus NMES did not affect several variables of functional evaluation of skeletal muscle oxidative metabolism. Muscle hypertrophy induced by NMES could impair peripheral O2 diffusion, possibly counterbalancing, in vivo, the fast-to-slow phenotypic changes that were observed in vitro, in a previous work, in the same subjects of the present study. strength training; muscle hypertrophy; near-infrared spectroscopy; gas exchange kinetics NEUROMUSCULAR ELECTRICAL STIMULATION (NMES) (26, 28) is widely utilized as a complement to voluntary exercise in athletes (27) and in patients, such as those with heart failure (46), chronic obstructive pulmonary disease (34), or cancer (6). NMES represents an obligatory choice for training in patients who cannot perform voluntary contractions, such as those with spinal cord lesions (10), or in patients immobilized for fractures or following ligament reconstruction surgery (42). It is well established that NMES leads to significant increases in muscle mass and maximal voluntary strength (13,26,39).The effects of NMES on oxidative metabolism appear rather controversial. At molecular level, Perez et al. (36) reported a higher succinic dehydrogenase activity after NMES training, whereas both citrate synthase and phosphofructokinase activities were unchanged. Kim et al. (21) reported, after a NMES training program, no changes in citrate synthase activity and number of capillaries. Nuhr et al. (35) showed an increase in the activity of citrate synthase associated with a decrease in the activity of glyceraldehyde phosphate dehydrogenase. Int...