Dynamic knee extension as model for study of isolated exercising muscle in humans

Andersen, P.; Adams, R. P.; Sjøgaard, Gisela; Thorboe, A.; Saltin, Bengt

doi:10.1152/jappl.1985.59.5.1647

Cited by 348 publications

(388 citation statements)

References 0 publications

Supporting

Mentioning

360

Contrasting

Unclassified

Order By: Relevance

“…The intersection has been reported to be largely consistent with AT and LT determined by expired gas analysis [4][5][6] . As reported previously, the rate of increase in SBP is low with low workload and becomes higher with a workload above a certain intensity, and an excess increase in blood pressure is associated with greater activation of baroreceptors and suppression of sympathetic nerve activity 7) . This indicates that blood pressure increase is inhibited with greater intensity of exercise.…”

Section: Introductionsupporting

confidence: 75%

“…In addition, when subjects had a habit of exercising daily, HR was 75.4% for men and 66.7% for women at DPBP. In general, AT and HR at DPBP are said to be higher for people who exercise daily than for people 7) reported that the blood pressure response is constant at small load and that it begins to increase beyond a threshold load limit. In other words, one could suggest that HR and SBP are controlled by a pressure receptor-a chemical receptor of aortic arch and sinus caroticus-during exercise.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Effect of Incremental Load of Circulatory Response on Double Product Break Point Detection

Ohtsuki

Watanabe²

2007

J Phys Ther Sci

View full text Add to dashboard Cite

Abstract. The purpose of this study was to examine the effect of circulatory response changes on DPBP evaliation. Seventeen healthy males and females who did not perform exercises daily participated in this study. All subjects performed a graded ergometric test that is generally performed on a cycle ergometer. The SBP and HR were measured at 1-min intervals. In healthy subjects who don't exercise daily, the relationship between HR and SBP, was described by a third order regression curve during exercise in males, and a continuously increasing linear equation in females. The relationship between work rate and DP was described by a third order regression curve during exercise in males, while there was no increase in suppression for females, for whom the relationship could be described by a linear equation. At DPBP, HR was 64.4 ± 4% for males and 60.4 ± 5% for females of maximum heart rate. It is possible to detect with DPBP, the increasing pattern of SBP or HR that was expressed as linear or third regression curve against the work load. It was suggested that DP can be compensated even when the increase of SBP (or HR) was low, because DP is the integral number of SBP and HR.

show abstract

Section: Introductionsupporting

confidence: 75%

Section: Discussionmentioning

confidence: 99%

Effect of Incremental Load of Circulatory Response on Double Product Break Point Detection

Ohtsuki

Watanabe²

2007

J Phys Ther Sci

View full text Add to dashboard Cite

show abstract

“…For example, Koga et al (25) directly compared KE and leg cycling exercise and reported a higher V O 2 G during KE (ϳ12 ml⅐min Ϫ1 ⅐W Ϫ1 ) compared with leg cycling exercise (ϳ9 ml⅐min Ϫ1 ⅐W Ϫ1 ), regardless of whether the exercise was performed at the same absolute (i.e., 66 W) or relative intensity (KE, 38 W; leg cycling, 66 W). It is not clear why the V O 2 G is greater in KE than leg cycling exercise; however, muscle work during KE exercise is restricted mainly to the quadriceps muscle group, whereas a number of muscles groups, including muscles of the upper and lower leg, are recruited during leg cycling exercise (1,21,30), and thus differences may relate to the combined metabolic and/or mechanical efficiencies of the muscles used during the different exercise modes.…”

Section: Discussionmentioning

confidence: 99%

Kinetics of O₂uptake, leg blood flow, and muscle deoxygenation are slowed in the upper compared with lower region of the moderate-intensity exercise domain

MacPhee

Shoemaker²,

Paterson³

et al. 2005

Journal of Applied Physiology

110

View full text Add to dashboard Cite

(SD 4)] performed repetitions (6 -8) of twolegged, moderate-intensity, knee-extension exercise during two separate protocols that included step transitions from 3 W to 90% estimated lactate threshold ( L) performed as a single step (S3) and in two equal steps (S1, 3 W to ϳ45% L; S2, ϳ45% L to ϳ90% L). The time constants ( ) of pulmonary oxygen uptake (V O2), leg blood flow (LBF), heart rate (HR), and muscle deoxygenation (HHb) were greater (P Ͻ 0.05) in S2 ( V O2, ϳ52 s; LBF, ϳ 39 s; HR, ϳ42 s; HHb, ϳ33 s) compared with S1 ( V O2, ϳ24 s; LBF, ϳ21 s; HR, ϳ21 s; HHb, ϳ16 s), while the delay before an increase in HHb was reduced (P Ͻ 0.05) in S2 (ϳ14 s) compared with S1 (ϳ20 s). The V O2 and HHb amplitudes were greater (P Ͻ 0.05) in S2 compared with S1, whereas the LBF amplitude was similar in S2 and S1. Thus the slowed V O2 response in S2 compared with S1 is consistent with a mechanism whereby V O2 kinetics is limited, in part, by a slowed adaptation of blood flow and/or O2 transport when exercise was initiated from a baseline of moderate-intensity exercise.oxygen uptake kinetics; femoral arterial blood flow kinetics; Doppler ultrasound; knee-extension exercise; near-infrared spectroscopy ACCOMPANYING A RISE IN EXERCISE intensity, there is a challenge to increase the rate of oxidative phosphorylation to meet the new metabolic demand of the working muscle. To meet this demand, the respiratory and cardiovascular systems must adapt in a coordinated manner to transport O 2 from the atmosphere to the mitochondria of the exercising muscle, thus allowing oxidative phosphorylation to proceed at the required rate. Pulmonary O 2 uptake (V O 2 ) kinetics is an index of the overall efficiency and conditioning of these integrated systems and can provide pertinent information with regard to the various mechanisms regulating O 2 delivery and O 2 utilization by skeletal muscle during exercise.Recently, it was reported (8) that, for a given absolute increase in work rate (WR), the adaptation of V O 2 during leg-cycling exercise was slower and the gain (G) (i.e., ⌬V O 2 / ⌬WR) was greater when exercise was initiated in the upper compared with the lower regions of the moderate-intensity exercise domain. These observations agree with those of Hughson and Morrissey (22,23) and DiPrampero et al. (13), but differ from those of DiPrampero et al. (12) and Diamond et al.(10), who reported either a faster or similar adaptation, respectively, when comparing exercise initiated from either prior moderate-intensity exercise or rest.Brittain et al. (8) attributed the slowing of V O 2 kinetics in the upper region of the moderate-intensity domain to the bioenergetic properties of the newly recruited motor units, which were assumed to be less efficient (i.e., greater O 2 or ATP cost per contraction) with a more slowly adapting V O 2 response than those motor units recruited initially at exercise onset from rest or very light exercise (i.e., lower region of the moderateintensity domain). Hughson and Morrissey (22,23), however, suggested that the sl...

show abstract

“…The arterial catheter was 20 G and 20 cm (Ohmeda, Swindon, UK), and the venous catheter was a radiopack TFE catheter with side holes (Cook, Bjaevershou, Denmark). A thermistor was inserted through the venous catheter for blood flow measurements by the constant infusion thermodilution technique (1). Thirty minutes after placement of the catheters, breath and blood samples were obtained for assessment of background enrichment of breath and blood CO 2 and blood lactate and glucose.…”

Section: Methodsmentioning

confidence: 99%

Similar carbohydrate but enhanced lactate utilization during exercise after 9 wk of acclimatization to 5,620 m

Hall

Calbet

Söndergaard

et al. 2002

American Journal of Physiology-Endocrinology and Metabolism

Self Cite

View full text Add to dashboard Cite

-We hypothesized that reliance on lactate as a means of energy distribution is higher after a prolonged period of acclimatization (9 wk) than it is at sea level due to a higher lactate R a and disposal from active skeletal muscle. To evaluate this hypothesis, six Danish lowlanders (25 Ϯ 2 yr) were studied at rest and during 20 min of bicycle exercise at 146 W at sea level (SL) and after 9 wk of acclimatization to 5,260 m (Alt). Whole body glucose R a was similar at SL and Alt at rest and during exercise. Lactate R a was also similar for the two conditions at rest; however, during exercise, lactate R a was substantially lower at SL (65 mol ⅐ min Ϫ1 ⅐ kg body wt Ϫ1 ) than it was at Alt (150 mol ⅐ min Ϫ1 ⅐ kg body wt Ϫ1 ) at the same exercise intensity. During exercise, net lactate release was ϳ6-fold at Alt compared with SL, and related to this, tracer-calculated leg lactate uptake and release were both 3-or 4-fold higher at Alt compared with SL. The contribution of the two legs to glucose disposal was similar at SL and Alt; however, the contribution of the two legs to lactate R a was significantly lower at rest and during exercise at SL (27 and 81%) than it was at Alt (45 and 123%).In conclusion, at rest and during exercise at the same absolute workload, CHO and blood glucose utilization were similar at SL and at Alt. Leg net lactate release was severalfold higher, and the contribution of leg lactate release to whole body lactate R a was higher at Alt compared with SL. During exercise, the relative contribution of lactate oxidation to whole body CHO oxidation was substantially higher at Alt compared with SL as a result of increased uptake and subsequent oxidation of lactate by the active skeletal muscles.glucose; isotopes; [1-13 C]lactate CARBOHYDRATE AND LACTATE METABOLISM is altered by hypoxia. Carbohydrate oxidation under hypoxic conditions has been suggested to be the preferable metabolic pathway during exercise, because it provides the highest ATP yield per mole of oxygen (3,15,16). Thus any increase in the percentage of energy derived from carbohydrate sources will result in a more economical use of oxygen. Indeed, results from studies in high-altitude natives (17) and lowlanders exposed to high altitude (5, 27) show a shift toward increased blood glucose utilization relative to normoxic conditions. However, McClelland et al. (23) reported that rats acclimatized to severe hypoxia did not increase carbohydrate utilization compared with normoxic conditions. Moreover, women acclimatized for 10 days to 4,300 m had a tendency for a lower contribution of carbohydrate oxidation to total energy expenditure during exercise, and they had a similar blood glucose disposal compared with sea level (2). In addition, Young et al. (35) suggested that, after chronic hypoxia exposure, increased mobilization and use of free fatty acids during exercise resulted in sparing of muscle glycogen. Thus there is no consensus in the literature with regard to metabolic fuel selection under hypoxic conditions. Some of the differences ob...

show abstract

Dynamic knee extension as model for study of isolated exercising muscle in humans

Cited by 348 publications

References 0 publications

Effect of Incremental Load of Circulatory Response on Double Product Break Point Detection

Effect of Incremental Load of Circulatory Response on Double Product Break Point Detection

Kinetics of O₂uptake, leg blood flow, and muscle deoxygenation are slowed in the upper compared with lower region of the moderate-intensity exercise domain

Similar carbohydrate but enhanced lactate utilization during exercise after 9 wk of acclimatization to 5,620 m

Contact Info

Product

Resources

About

Dynamic knee extension as model for study of isolated exercising muscle in humans

Cited by 348 publications

References 0 publications

Effect of Incremental Load of Circulatory Response on Double Product Break Point Detection

Effect of Incremental Load of Circulatory Response on Double Product Break Point Detection

Kinetics of O2uptake, leg blood flow, and muscle deoxygenation are slowed in the upper compared with lower region of the moderate-intensity exercise domain

Similar carbohydrate but enhanced lactate utilization during exercise after 9 wk of acclimatization to 5,620 m

Contact Info

Product

Resources

About

Kinetics of O₂uptake, leg blood flow, and muscle deoxygenation are slowed in the upper compared with lower region of the moderate-intensity exercise domain