Operation Everest II: muscle energetics during maximal exhaustive exercise

1989 ◽  
Vol 66 (1) ◽  
pp. 142-150 ◽  
Author(s):  
H. J. Green ◽  
J. Sutton ◽  
P. Young ◽  
A. Cymerman ◽  
C. S. Houston
Keyword(s):  
Vastus Lateralis ◽  
Lactate Concentration ◽  
Blood Lactate Concentration ◽  
Creatine Phosphate ◽  
Exhaustive Exercise ◽  
Muscle Lactate ◽  
Muscle Energetics ◽  
Metabolic Basis ◽  
Fructose 1,6 Bisphosphate ◽  
Male Subjects

To investigate the metabolic basis for the reduction in peak blood lactate concentration that occurs with maximal exercise after acclimatization to altitude, eight male subjects [maximal O2 uptake of 51.2 +/- 3.0 (SE) ml.kg-1.min-1] were acclimated to progressive hypobaria over a 40-day period. Before decompression (SL-1), at 380 and 282 Torr, and on return to sea level (SL-2) the subjects performed progressive cycle exercise to exhaustion. Analysis of muscle samples obtained from the vastus lateralis before exercise and at exhaustion indicated a pronounced reduction (P less than 0.05) in muscle lactate concentration (mmol/kg dry wt) at 282 Torr (39.2 +/- 11) compared with SL-1 (113 +/- 9.7), 380 Torr (94.6 +/- 18), and SL-2 (92.7 +/- 22). For the other glycolytic intermediates studied (glucose 1-phosphate, glucose 6-phosphate, fructose 6-phosphate, fructose 1,6-bisphosphate, and pyruvate) only the increase in glucose 1-phosphate, glucose 6-phosphate, and fructose 6-phosphate were blunted (P less than 0.05) at 282 Torr. The reduction in muscle glycogen concentration during exercise was similar (P less than 0.05) for all environmental conditions. Although exercise resulted in reductions (P less than 0.05) in ATP and creatine phosphate averaging 30 and 51%, respectively, the magnitude of the change was not dependent on the degree of hypobaria. Inosine monophosphate was elevated (P less than 0.05) approximately 11-fold with exercise at both SL-1 and SL-2. These findings support the hypothesis that the lower lactate concentration observed at 282 Torr after exhaustive exercise is due to a reduction in anaerobic glycolysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of previous exercise with arms or legs on metabolism and performance in exhaustive exercise

1975 ◽  
Vol 38 (5) ◽  
pp. 763-767 ◽  
Author(s):  
J. Karlsson ◽  
F. Bonde-Petersen ◽  
J. Henriksson ◽  
H. G. Knuttgen
Keyword(s):  
Blood Lactate ◽  
Vastus Lateralis ◽  
Lactate Concentration ◽  
Blood Lactate Concentration ◽  
Exercise Bout ◽  
Creatine Phosphate ◽  
The Body ◽  
Exhaustive Exercise ◽  
Leg Exercise ◽  
Muscle Groups

The ability of additional muscles to perform after certain other muscles of the body had been exercised to exhaustion was studied in three male subjects. Exhaustive exercise was performed in two series: series L-A, a bout of leg exercise preceded a bout of arm exercise; series A-L, arm preceded leg (6-min recovery between bouts). Biopsies were taken during the course of each experiment from both the deltoideus and vastus lateralis muscles for determination of ATP, creatine phosphate, lactate, and pyruvate. Exhaustive exercise led to marked elevations in lactate and decreases in ATP and CP in exercised muscle and marked increases in blood lactate concentration. Similar changes, especially in lactate, were observed during and after the first exercise bout in nonexercised muscle. When arm or leg exercise was performed as the second bout, decreases in performance time were observed as compared to performance as the initial bout. It is suggested that the performance potential of muscle is decreased because of internal changes elicited by elevated blood lactate and/or blood H+ concentrations brought about by other muscle groups previously exercised to exhaustion.

Altitude acclimatization and energy metabolic adaptations in skeletal muscle during exercise

1992 ◽  
Vol 73 (6) ◽  
pp. 2701-2708 ◽  
Author(s):  
H. J. Green ◽  
J. R. Sutton ◽  
E. E. Wolfel ◽  
J. T. Reeves ◽  
G. E. Butterfield ◽  
...  
Keyword(s):  
Prolonged Exercise ◽  
Vastus Lateralis ◽  
Acute Hypoxia ◽  
Lactate Concentration ◽  
Absolute Intensity ◽  
Muscle Lactate ◽  
Arterial Lactate ◽  
Metabolic Adaptations ◽  
Exercise Challenge ◽  
Male Subjects

To determine whether the working muscle is able to sustain ATP homeostasis during a hypoxic insult and the mechanisms associated with energy metabolic adaptations during the acclimatization process, seven male subjects [23 +/- 2 (SE) yr, 72.2 +/- 1.6 kg] were given a prolonged exercise challenge (45 min) at sea level (SL), within 4 h after ascent to an altitude of 4,300 m (acute hypoxia, AH), and after 3 wk of sustained residence at 4,300 m (chronic hypoxia, CH). The prolonged cycle test conducted at the same absolute intensity and representing 51 +/- 1% of SL maximal aerobic power (VO2 max) and between 64 +/- 2 (AH) and 66 +/- 1% (CH) at altitude was performed without a reduction in ATP concentration in the working vastus lateralis regardless of condition. Compared with rest, exercise performed during AH resulted in a greater increase (P < 0.05) in muscle lactate concentration (5.11 +/- 0.68 to 22.3 +/- 6.1 mmol/kg dry wt) than exercise performed either at SL (5.88 +/- 0.85 to 11.5 +/- 3.1) or CH (5.99 +/- 0.88 to 12.4 +/- 2.1). These differences in lactate concentration have been shown to reflect differences in arterial lactate concentration and glycolysis (Brooks et al. J. Appl. Physiol. 71: 333–341, 1991). The reduction in glycolysis at least between AH and CH appears to be accompanied by a tighter metabolic control. During CH, free ADP was lower and the ATP-to-free ADP ratio was increased (P < 0.05) compared with AH.(ABSTRACT TRUNCATED AT 250 WORDS)

Metabolic adaptations to training precede changes in muscle mitochondrial capacity

1992 ◽  
Vol 72 (2) ◽  
pp. 484-491 ◽  
Author(s):  
H. J. Green ◽  
R. Helyar ◽  
M. Ball-Burnett ◽  
N. Kowalchuk ◽  
S. Symon ◽  
...  
Keyword(s):  
Citrate Synthase ◽  
Vastus Lateralis ◽  
Lactate Concentration ◽  
Succinic Dehydrogenase ◽  
Training Model ◽  
Muscle Lactate ◽  
Before And After ◽  
Glycogen Utilization ◽  
Male Subjects ◽  
Mitochondrial Capacity

To determine whether increases in muscle mitochondrial capacity are necessary for the characteristic lower exercise glycogen loss and lactate concentration observed during exercise in the trained state, we have employed a short-term training model involving 2 h of cycling per day at 67% maximal O2 uptake (VO2max) for 5–7 consecutive days. Before and after training, biopsies were extracted from the vastus lateralis of nine male subjects during a continuous exercise challenge consisting of 30 min of work at 67% VO2max followed by 30 min at 76% VO2max. Analysis of samples at 0, 15, 20, and 60 min indicated a pronounced reduction (P less than 0.05) in glycogen utilization after training. Reductions in glycogen utilization were accompanied by reductions (P less than 0.05) in muscle lactate concentration (mmol/kg dry wt) at 15 min [37.4 +/- 9.3 (SE) vs. 20.2 +/- 5.3], 30 min (30.5 +/- 6.9 vs. 17.6 +/- 3.8), and 60 min (26.5 +/- 5.8 vs. 17.8 +/- 3.5) of exercise. Maximal aerobic power, VO2max (l/min) was unaffected by the training (3.99 +/- 0.21 vs. 4.05 +/- 0.26). Measurements of maximal activities of enzymes representative of the citric acid cycle (succinic dehydrogenase and citrate synthase) were similar before and after the training. It is concluded that, in the voluntary exercising human, altered metabolic events are an early adaptive response to training and need not be accompanied by changes in muscle mitochondrial capacity.

Relative effects of glycogen depletion and previous exercise on muscle force and endurance capacity

1990 ◽  
Vol 69 (4) ◽  
pp. 1276-1282 ◽  
Author(s):  
R. K. Grisdale ◽  
I. Jacobs ◽  
E. Cafarelli
Keyword(s):  
Vastus Lateralis ◽  
Lactate Concentration ◽  
Creatine Phosphate ◽  
Voluntary Contraction ◽  
Endurance Capacity ◽  
Glycogen Depletion ◽  
Experimental Protocol ◽  
Muscle Lactate ◽  
Emg Amplitude ◽  
Static Contractions

Endurance capacity of human vastus lateralis muscles was observed 24 h after hard exercise followed by either a carbohydrate-restricted or a carbohydrate-loaded diet (depletion and repletion conditions). In a control condition the subjects did no previous exercise and ate their normal diet. Each of these conditions was followed by an experimental protocol in which the five male subjects made a series of alternating 25-s static contractions of each leg at 50% maximal voluntary contraction until one leg failed to achieve the required force (Tlim). Glycogen concentration before the experimental protocol in both legs was significantly lower in the depletion than in the repletion condition. Muscle lactate and creatine phosphate concentrations were within normal limits before the static contractions. The number of contractions the repleted (12.7 +/- 2.2) and depleted (10.3 +/- 1.5) legs could sustain before Tlim were not different from each other, but both were 35% (P less than 0.05) fewer than the control (17.6 +/- 3.0). Surface electromyogram (EMG) amplitude was higher in depleted than in repleted or control muscles. At Tlim, EMG amplitude was maximal, creatine phosphate was 50-70% depleted, and lactate increased fourfold. Average glycogen utilization per contraction in both the repletion and depletion conditions was 5.8 mmol/kg dry wt, but postexercise lactate concentrations were lower in depleted (14.4 +/- 3.6 mmol/kg dry wt) than in repleted (43.2 +/- 7.4) muscles. The EMG frequency distribution shifted downward in all conditions during the experimental protocol and was independent of muscle lactate concentration.(ABSTRACT TRUNCATED AT 250 WORDS)

Which common NIRS variable reflects muscle estimated lactate threshold most closely?

2006 ◽  
Vol 31 (5) ◽  
pp. 612-620 ◽  
Author(s):  
Lixin Wang ◽  
Takahiro Yoshikawa ◽  
Taketaka Hara ◽  
Hayato Nakao ◽  
Takashi Suzuki ◽  
...  
Keyword(s):  
Lactate Threshold ◽  
Near Infrared ◽  
Ventilatory Threshold ◽  
Lactate Concentration ◽  
Blood Lactate Concentration ◽  
Oxygenation Index ◽  
Muscle Lactate ◽  
Tissue Oxygenation Index ◽  
The Mean ◽  
Tissue Hemoglobin

Various near-infrared spectroscopy (NIRS) variables have been used to estimate muscle lactate threshold (LT), but no study has determined which common NIRS variable best reflects muscle estimated LT. Establishing the inflection point of 2 regression lines for deoxyhaemoglobin (ΔHHbi.p.), oxyhaemoglobin (ΔO2Hbi.p.), and tissue oxygenation index (TOIi.p.), as well as for blood lactate concentration, we then investigated the relationships between NIRS variables and ventilatory threshold (VT), LT, or maximal tissue hemoglobin index (nTHImax) during incremental cycling exercise. ΔHHbi.p. and TOIi.p. could be determined for all 15 subjects, but ΔO2Hbi.p. was determined for only 11 subjects. The mean absolute values for the 2 measurable slopes of the 2 continuous linear regression lines exhibited increased changes in 3 NIRS variables. The workload and VO2 at ΔO2Hbi.p. and nTHImax were greater than those at VT, LT, ΔHHbi.p., and TOIi.p.. For workload and VO2, ΔHHbi.p. was correlated with VT and LT, whereas ΔO2Hbi.p. was correlated with nTHImax, and TOIi.p. with VT and nTHImax. These findings indicate that ΔO2Hb strongly corresponds with local perfusion, and TOI corresponds with both local perfusion and deoxygenation, but that ΔHHb can exactly determine deoxygenation changes and reflect O2 metabolic dynamics. The finding of strongest correlations between ΔHHb and VT or LT indicates that ΔHHb is the best variable for muscle LT estimation.

scholarly journals Time required for the restoration of normal heavy exercise V̇o2 kinetics following prior heavy exercise

2006 ◽  
Vol 101 (5) ◽  
pp. 1320-1327 ◽  
Author(s):  
Mark Burnley ◽  
Jonathan H. Doust ◽  
Andrew M. Jones
Keyword(s):  
Blood Lactate ◽  
Priming Effect ◽  
Slow Component ◽  
Lactate Concentration ◽  
Blood Lactate Concentration ◽  
Heavy Exercise ◽  
Cycle Exercise ◽  
V̇o2 Kinetics ◽  
Time Required ◽  
Male Subjects

Prior heavy exercise markedly alters the O2 uptake (V̇o2) response to subsequent heavy exercise. However, the time required for V̇o2 to return to its normal profile following prior heavy exercise is not known. Therefore, we examined the V̇o2 responses to repeated bouts of heavy exercise separated by five different recovery durations. On separate occasions, nine male subjects completed two 6-min bouts of heavy cycle exercise separated by 10, 20, 30, 45, or 60 min of passive recovery. The second-by-second V̇o2 responses were modeled using nonlinear regression. Prior heavy exercise had no effect on the primary V̇o2 time constant (from 25.9 ± 4.7 s to 23.9 ± 8.8 s after 10 min of recovery; P = 0.338), but it increased the primary V̇o2 amplitude (from 2.42 ± 0.39 to 2.53 ± 0.41 l/min after 10 min of recovery; P = 0.001) and reduced the V̇o2 slow component (from 0.44 ± 0.13 to 0.21 ± 0.12 l/min after 10 min of recovery; P < 0.001). The increased primary amplitude was also evident after 20–45 min, but not after 60 min, of recovery. The increase in the primary V̇o2 amplitude was accompanied by an increased baseline blood lactate concentration (to 5.1 ± 1.0 mM after 10 min of recovery; P < 0.001). Baseline blood lactate concentration was still elevated after 20–60 min of recovery. The priming effect of prior heavy exercise on the V̇o2 response persists for at least 45 min, although the mechanism underpinning the effect remains obscure.

Glucose uptake in rat soleus: effect of acute unloading and subsequent reloading

1988 ◽  
Vol 64 (4) ◽  
pp. 1428-1432 ◽  
Author(s):  
E. J. Henriksen ◽  
M. E. Tischler
Keyword(s):  
Maximum Voluntary Contraction ◽  
Lactate Concentration ◽  
Creatine Phosphate ◽  
Voluntary Contraction ◽  
Gradual Decline ◽  
Muscle Lactate ◽  
Generating Capacity ◽  
Target Force ◽  
Muscle Biopsies ◽  
Contractile Failure

Contractile failure during various types of exercise has been attributed to intramuscular metabolic changes. We examined the temporal changes in force-generating capacity and metabolic state during intermittent isometric contractions in humans. One-legged quadriceps contractions at 30% maximum voluntary contraction (MVC) were executed for 6 s, with 4 s of rest between. The decrease in force-generating capacity was tested from brief MVC's and short bursts of 50-Hz stimulation applied at 5-min intervals. After 1 min of exercise, the MVC force declined linearly and in parallel to the 50-Hz stimulation force, indicating that the contractile failure was due to intramuscular processes. After 30 min of exercise the MVC force had declined by approximately 40% compared with the value obtained after 1 min. In separate experiments the same contraction protocol was followed, but two-legged contractions were used. Muscle biopsies taken after 5, 15, and 30 min of exercise showed only minor changes in the concentrations of glycogen, lactate, creatine phosphate (CrP), and ATP. However, at exhaustion, defined as loss of ability to sustain the target force, the concentrations of CrP and glycogen were reduced by 73 and 32%, and muscle lactate concentration had increased to 4.8 mmol/kg wet wt. Thus the gradual decline in force-generating capacity was not due to lactacidosis or lack of substrates for ATP resynthesis and must have resulted from excitation/contraction coupling failure, whereas exhaustion was closely related to phosphagen depletion, without significant lactacidosis.

Lactic acid infusion in dogs: effects of varying infusate pH

1983 ◽  
Vol 54 (5) ◽  
pp. 1254-1260 ◽  
Author(s):  
L. B. Gladden ◽  
J. W. Yates
Keyword(s):  
Lactic Acid ◽  
Blood Lactate ◽  
Muscle Blood Flow ◽  
Lactate Concentration ◽  
Blood Lactate Concentration ◽  
Weak Acid ◽  
Muscle Lactate ◽  
Acid Infusion ◽  
Arterial Blood ◽  
Arterial Ph

This study had two purposes: 1) to determine the effects of varying the pH of lactic acid infusion solutions on the acid-base status of anesthetized dogs, and 2) to determine the effect of elevated blood lactate concentration on muscle lactate concentration. The experiments were performed on the in situ gastro cnemius-plantaris muscle group in 14 mongrel dogs. The infusions increased the arterial blood lactate concentration to 11.0 +/- 0.5 (SE) mM after 20 min. Above an infusate pH of 4.4, the arterial pH increased by 0.118–0.167 during infusion; the arterial pH was unchanged when the infusate pH was between 3.4 and 4.0; and the arterial pH decreased as infusate pH decreased below 3.0. The effect of lactic acid infusion on blood pH appears to be the result of two opposing effects: 1) an acidifying effect due to its weak acid properties, and 2) an alkalinizing effect due to the metabolism of sodium lactate. The estimated ratio between intracellular muscle lactate and venous plasma water lactate averaged 0.647 +/- 0.038, indicative of a substantial gradient between blood and muscle. The infusion produced a significant change from lactate output to lactate uptake by the muscles. The infusion also transiently increased muscle blood flow and oxygen uptake.

Effect of endurance training on activators of glycolysis in muscle during exercise

1994 ◽  
Vol 76 (2) ◽  
pp. 846-852 ◽  
Author(s):  
C. Duan ◽  
W. W. Winder
Keyword(s):  
Endurance Training ◽  
Blood Lactate ◽  
Lactate Concentration ◽  
Lactate Production ◽  
Blood Lactate Concentration ◽  
Quadriceps Muscle ◽  
Muscle Lactate ◽  
Cyclic Monophosphate ◽  
Lactate Levels ◽  
Exercise Induced

Endurance training attenuates exercise-induced increases in blood lactate at the same submaximal work rate. Three intramuscular compounds that influence muscle lactate production were measured in fasted non-trained (NT) and endurance-trained (T) rats. The T rats were subjected to a progressive endurance-training program. At the end of the program (11 wk), they were running 2 h/day at 31 m/min up a 15% grade 5 days/wk. NT and T rats were fasted for 24 h and then anesthetized (pentobarbital, iv) at rest or after running for 30 min at 21 m/min (15% grade). Blood lactate levels were significantly lower in the T rats than in the NT rats after 30 min of running (2.3 +/- 0.2 vs. 3.9 +/- 0.2 mM). The lower blood lactate concentration was accompanied by lower plasma epinephrine (2.8 +/- 0.4 vs. 6.0 +/- 0.8 nM), adenosine 3′, 3′,5′-cyclic monophosphate (0.36 +/- 0.02 vs. 0.50 +/- 0.03 pmol/mg), mg), glucose 1,6-diphosphate (26 +/- 2 vs. 40 +/- 5 pmol/mg), and fructose 2,6-diphosphate (3.2 +/- 0.2 vs. 4.3 +/- 0.3 pmol/mg) in white quadriceps muscle in T than in NT rats. Red quadriceps muscle glucose 1,6-diphosphate and adenosine 3′,5′-cyclic monophosphate were also lower in T than in NT rats. These adaptations may be responsible in part for the lower exercise-induced blood lactate in fasted rats as a consequence of endurance training.

Association Between Deoxygenated Hemoglobin Breaking Point, Anaerobic Threshold, and Rowing Performance

2019 ◽  
Vol 14 (8) ◽  
pp. 1103-1109
Author(s):  
Tiago Turnes ◽  
Rafael Penteado dos Santos ◽  
Rafael Alves de Aguiar ◽  
Thiago Loch ◽  
Leonardo Trevisol Possamai ◽  
...  
Keyword(s):  
Heart Rate ◽  
Anaerobic Threshold ◽  
Power Output ◽  
Vastus Lateralis ◽  
Lactate Concentration ◽  
Blood Lactate Concentration ◽  
Breaking Point ◽  
Vastus Lateralis Muscle ◽  
Incremental Test ◽  
Deoxygenated Hemoglobin

Purpose: To compare the intensity and physiological responses of deoxygenated hemoglobin breaking point ([HHb]BP) and anaerobic threshold (AnT) during an incremental test and to verify their association with 2000-m rowing-ergometer performance in well-trained rowers. Methods: A total of 13 male rowers (mean [SD] age = 24 [11] y and  = 63.7 [6.1] mL·kg−1·min−1) performed a step incremental test. Gas exchange, vastus lateralis [HHb], and blood lactate concentration were measured. Power output, , and heart rate of [HHb]BP and AnT were determined and compared with each other. A 2000-m test was performed in another visit. Results: No differences were found between [HHb]BP and AnT in the power output (236 [31] vs 234 [31] W; Δ = 0.7%), 95% confidence interval [CI] 6.7%), (4.2 [0.5] vs 4.3 [0.4] L·min−1; Δ = −0.8%, 95% CI 4.0%), or heart rate (180 [16] vs 182 [12] beats·min−1; Δ = −1.6%, 95% CI 2.1%); however, there was high typical error of estimate (TEE) and wide 95% limits of agreement (LoA) for power output (TEE 10.7%, LoA 54.1–50.6 W), (TEE 5.9%, LoA −0.57 to 0.63 L·min−1), and heart rate (TEE 2.4%, LoA −9.6 to 14.7 beats·min−1). Significant correlations were observed between [HHb]BP (r = .70) and AnT (r = .89) with 2000-m mean power. Conclusions: These results demonstrate a breaking point in [HHb] of the vastus lateralis muscle during the incremental test that is capable of distinguishing rowers with different performance levels. However, the high random error would compromise the use of [HHb]BP for training and testing in rowing.

Sign in / Sign up

Export Citation Format

Share Document