Comparison of the cardiac force-time integral with energetics using a cardiac muscle model

1993 ◽  
Vol 26 (10) ◽  
pp. 1217-1225 ◽  
Author(s):  
Tad W. Taylor ◽  
Yoichi Goto ◽  
Katsuya Hata ◽  
Toshiyuki Takasago ◽  
Akio Saeki ◽  
...  
Keyword(s):  
Cardiac Muscle ◽  
Muscle Model ◽  
Time Integral ◽  
Force Time ◽  
Force Time Integral

Regulation of energy consumption in cardiac muscle: analysis of isometric contractions

1999 ◽  
Vol 276 (3) ◽  
pp. H998-H1011 ◽  
Author(s):  
Amir Landesberg ◽  
Samuel Sideman
Keyword(s):  
Energy Consumption ◽  
Cardiac Muscle ◽  
Feedback Mechanism ◽  
Isometric Contractions ◽  
Cross Bridge ◽  
Time Integral ◽  
Length Relationship ◽  
Cross Bridges ◽  
Force Time ◽  
Force Time Integral

The well-known linear relationship between oxygen consumption and force-length area or the force-time integral is analyzed here for isometric contractions. The analysis, which is based on a biochemical model that couples calcium kinetics with cross-bridge cycling, indicates that the change in the number of force-generating cross bridges with the change in the sarcomere length depends on the force generated by the cross bridges. This positive-feedback phenomenon is consistent with our reported cooperativity mechanism, whereby the affinity of the troponin for calcium and, hence, cross-bridge recruitment depends on the number of force-generating cross bridges. Moreover, it is demonstrated that a model that does not include a feedback mechanism cannot describe the dependence of energy consumption on the loading conditions. The cooperativity mechanism, which has been shown to determine the force-length relationship and the related Frank-Starling law, is shown here to provide the basis for the regulation of energy consumption in the cardiac muscle.

scholarly journals Force-time integral decreases with ejection despite constant oxygen consumption and pressure-volume area in dog left ventricle.

1987 ◽  
Vol 60 (6) ◽  
pp. 797-803 ◽  
Author(s):  
H Suga ◽  
Y Goto ◽  
T Nozawa ◽  
Y Yasumura ◽  
S Futaki ◽  
...  
Keyword(s):  
Oxygen Consumption ◽  
Left Ventricle ◽  
Time Integral ◽  
Force Time ◽  
Force Time Integral

The Effect of Muscle Lentgh on Force-Time Integral in Relation to Energy-Rich Phosphate Consumption

1985 ◽  
pp. 605-610 ◽  
Author(s):  
A. De Haan ◽  
J. E. Van Doorn ◽  
P. A. Huijing ◽  
R. D. Woittiez ◽  
H. G. Westra
Keyword(s):  
Time Integral ◽  
Force Time ◽  
Force Time Integral

Preload does not influence nonmechanical O2 consumption in isolated rabbit heart

1994 ◽  
Vol 266 (3) ◽  
pp. H1047-H1054 ◽  
Author(s):  
A. Higashiyama ◽  
M. W. Watkins ◽  
Z. Chen ◽  
M. M. LeWinter
Keyword(s):  
Energy Consumption ◽  
Diastolic Pressure ◽  
Rabbit Heart ◽  
Left Ventricular ◽  
Energetic Cost ◽  
O2 Consumption ◽  
Time Integral ◽  
Force Time ◽  
Whole Heart ◽  
Force Time Integral

Myocardial energy consumption for nonmechanical activity (excitation-contraction coupling) has been shown to be length dependent in isolated muscle studies but no more than minimally affected by preload in the whole heart. However, unloaded O2 consumption (VO2, which is used to estimate nonmechanical VO2 in whole heart) may not be accurate for quantifying nonmechanical energy consumption, because it contains VO2 for residual cross-bridge cycling. To more accurately determine the influence of left ventricular (LV) diastolic volume on nonmechanical VO2 in whole heart, we employed a new method for quantifying nonmechanical VO2, using the drug 2,3-butanedione monoxime (BDM). We measured VO2 and force-time integral during infusion of BDM (< or = 5 mM) at high (VH) and low LV volumes (VL) in 16 excised isovolumically contracting red blood cell-perfused rabbit ventricles. LV end-diastolic pressure was 9.7 +/- 4.6 and 3.8 +/- 2.8 (SD) mmHg at VH and VL, respectively. Nonmechanical VO2, estimated as the VO2-axis intercept of the linear VO2-force-time integral relation obtained during BDM infusion, did not differ significantly between VH and VL (0.0137 +/- 0.0083 and 0.0132 +/- 0.0090 ml O2.beat-1 x 100 gLV-1, P = 0.702). A multiple linear regression analysis for the pooled data confirmed this finding (P = 0.361). We conclude that, in the rabbit heart, LV diastolic volume does not importantly affect nonmechanical energy consumption over a physiological range of LV end-diastolic pressure. This indicates that length-dependent activation does not have an energetic cost in whole rabbit heart and suggests that its predominant mechanism is increased Ca2+ affinity for the contractile proteins.

scholarly journals Stimulation Pattern That Maximizes Force in Paralyzed and Control Whole Thenar Muscles

2002 ◽  
Vol 87 (5) ◽  
pp. 2271-2278 ◽  
Author(s):  
Lisa Griffin ◽  
Sharlene Godfrey ◽  
Christine K. Thomas
Keyword(s):  
Short Interval ◽  
Motor Units ◽  
Muscle Stiffness ◽  
Peak Force ◽  
Single Motor Units ◽  
Time Integral ◽  
Cord Injury ◽  
Force Time ◽  
And Control ◽  
Force Time Integral

The pattern of seven pulses that elicited maximal thenar force was determined for control muscles and those that have been paralyzed chronically by spinal cord injury. For each subject group ( n = 6), the peak force evoked by two pulses occurred at a short interval (5–15 ms; a “doublet”), but higher mean relative forces were achieved in paralyzed versus control muscles (41.4 ± 3.9% vs. 22.7 ± 2.0% maximal). Thereafter, longer intervals evoked peak force in each type of muscle (mean: 35 ± 1 ms, 36 ± 2 ms, respectively). With seven pulses, paralyzed and control muscles reached 76.4 ± 5.6% and 57.0 ± 2.6% maximal force, respectively. These force differences resulted from significantly greater doublet/twitch and doublet/tetanic force ratios in paralyzed (2.73 ± 0.08, 0.35 ± 0.03) compared with control muscles (2.07 ± 0.07, 0.25 ± 0.01). The greater force enhancement produced in paralyzed muscles with two closely spaced pulses may relate to changes in muscle stiffness and calcium metabolism. Peak force-time integrals were also achieved with an initial short interpulse interval, followed by longer intervals. The postdoublet intervals that produced peak force-time integrals in paralyzed and control muscles were longer than those for peak force, however (77 ± 3 ms, 95 ± 4 ms, respectively). These data show that the pulse patterns that maximize force and force-time integral in paralyzed muscles are similar to those that maximize these parameters in single motor units and various whole muscles across species. Thus the changes in neuromuscular properties that occur with chronic paralysis do not strongly influence the pulse pattern that optimizes muscle force or force-time integral.

Energetics of the Frank-Starling effect in rabbit myocardium: economy and efficiency depend on muscle length

2002 ◽  
Vol 283 (1) ◽  
pp. H324-H330 ◽  
Author(s):  
Jeffrey W. Holmes ◽  
Mark Hünlich ◽  
Gerd Hasenfuss
Keyword(s):  
Oxygen Consumption ◽  
Muscle Length ◽  
Published Data ◽  
Average Force ◽  
Time Integral ◽  
Rabbit Myocardium ◽  
Efficiency Increase ◽  
Butanedione Monoxime ◽  
Force Time ◽  
Force Time Integral

We tested the hypothesis that economy and efficiency are independent of length in intact cardiac muscle over its normal working range. We measured force, force-time integral, force-length area, and myocardial oxygen consumption in eight isometrically contracting rabbit right ventricular papillary muscles. 2,3-Butanedione monoxime was used to partition nonbasal oxygen consumption into tension-independent and tension-dependent components. Developed force, force-time integral, and force-length area increased by factors of 2.4, 2.7, and 4.8, respectively, as muscle length was increased from 90% to 100% maximal length, whereas tension-dependent oxygen consumption increased only 1.6-fold. Economy (the ratio of force-time integral to tension-dependent oxygen consumption) increased significantly with muscle length, as did contractile efficiency, the ratio of force-length area to tension-dependent oxygen consumption. The average force-length area-nonbasal oxygen consumption intercept was more than the twice tension-independent oxygen consumption. We conclude that economy and efficiency increase with length in rabbit myocardium. This conclusion is consistent with published data in isolated rabbit and dog hearts but at odds with studies in skinned myocardium.

Effect of rearfoot posts in reducing forefoot forces. A single-subject design

1992 ◽  
Vol 82 (7) ◽  
pp. 371-374 ◽  
Author(s):  
MW Cornwall ◽  
TG McPoil
Keyword(s):  
Varus Deformity ◽  
Single Subject ◽  
Foot Orthoses ◽  
Single Subject Design ◽  
Time Integral ◽  
Subject Design ◽  
Force Time ◽  
Foot Orthosis ◽  
Force Time Integral

The purpose of this study was to assess the effectiveness of a semirigid foot orthosis with a varus wedge on forefoot vertical forces in a 24-year-old female with a compensated rearfoot varus deformity. The results of this study indicate that the use of total contact semirigid foot orthoses reduces the forefoot force-time integral during walking, whether a rearfoot varus wedge was or was not used. The authors recommend that total contact construction of the foot orthoses be considered when a reduction of the forces acting on the forefoot is the goal of treatment.

Plantar Loading Characteristics During Walking in Females With and Without Patellofemoral Pain

2015 ◽  
Vol 105 (1) ◽  
pp. 1-7 ◽  
Author(s):  
John D. Willson ◽  
Eric D. Ellis ◽  
Thomas W. Kernozek
Keyword(s):  
Contact Area ◽  
Patellofemoral Pain ◽  
Peak Force ◽  
First Metatarsal ◽  
Time Integral ◽  
Foot Pronation ◽  
Force Time ◽  
Arch Index ◽  
Plane Joint ◽  
Force Time Integral

Background Patellofemoral pain (PFP) is a common injury, particularly in females. Foot pronation may promote knee and hip transverse plane joint kinematics during gait thought to contribute to PFP. Greater knowledge of plantar loading characteristics in females with PFP may be valuable to provide a basis for clinical decisions regarding footwear and foot orthoses. The purpose of this study was to compare plantar loading distribution in females with and without PFP during gait. Methods Plantar pressure during walking was recorded from 19 females with PFP and 20 females without PFP. Contact area, peak force, and force-time integral were evaluated in ten plantar areas. Arch index was also calculated from contact area data during gait. Results Contact area in females with PFP was 9% smaller in the first metatarsal region (P = .039) and 20% smaller in the midfoot region (P = .042) than in females without PFP. Peak force was 31% lower in the midfoot region for females with PFP (P = .027) and 13% lower in the first metatarsal region (P = .064). Force-time integral was 18% lower in the first metatarsal region in females with PFP (P = .024). Females with PFP demonstrated a lower arch index (suggesting a higher arch) (P = .028). Conclusions Decreased medial forefoot loading and decreased midfoot contact suggest decreased foot pronation during gait in females with PFP relative to females without PFP. Decreased foot pronation may foster increased patellofemoral joint loading rates. These data contribute to rationale for footwear modifications to modify plantar loading characteristics in people experiencing PFP.

scholarly journals Changes in Plantar Loading Based on Shoe Type and Sex During a Jump-Landing Task

2013 ◽  
Vol 48 (5) ◽  
pp. 601-609 ◽  
Author(s):  
Justin C. DeBiasio ◽  
Mary E. Russell ◽  
Robert J. Butler ◽  
James A. Nunley ◽  
Robin M. Queen
Keyword(s):  
Contact Area ◽  
Stress Fractures ◽  
Maximum Force ◽  
Lower Extremity Injury ◽  
Jump Landing ◽  
Time Integral ◽  
Running Shoes ◽  
History Of ◽  
Force Time ◽  
Force Time Integral

Context: Metatarsal stress fractures are common in cleated-sport athletes. Previous authors have shown that plantar loading varies with footwear, sex, and the athletic task. Objective: To examine the effects of shoe type and sex on plantar loading in the medial midfoot (MMF), lateral midfoot (LMF), medial forefoot (MFF), middle forefoot (MidFF), and lateral forefoot (LFF) during a jump-landing task. Design: Crossover study. Setting: Laboratory. Patients or Other Participants: Twenty-seven recreational athletes (14 men, 13 women) with no history of lower extremity injury in the last 6 months and no history of foot or ankle surgery. Main Outcome Measure(s): The athletes completed 7 jumping trials while wearing bladed-cleat, turf-cleat, and running shoes. Maximum force, contact area, contact time, and the force-time integral were analyzed in each foot region. We calculated 2 × 3 analyses of variance (α = .05) to identify shoe-condition and sex differences. Results: We found no shoe × sex interactions, but the MMF, LMF, MFF, and LFF force-time integrals were greater in men (P &lt; .03). The MMF maximum force was less with the bladed-cleat shoes (P = .02). Total foot and MidFF maximum force was less with the running shoes (P &lt; .01). The MFF and LFF maximum forces were different among all shoe conditions (P &lt; .01). Total foot contact area was less in the bladed-cleat shoes (P = .01). The MMF contact area was greatest in the running shoes (P &lt; .01). The LFF contact area was less in the running shoes (P = .03). The MFF and LFF force-time integrals were greater with the bladed-cleat shoes (P &lt; .01). The MidFF force-time integral was less in the running shoes (P &lt; .01). Conclusions: Independent of shoe, men and women loaded the foot differently during a jump landing. The bladed cleat increased forefoot loading, which may increase the risk for forefoot injury. The type of shoe should be considered when choosing footwear for athletes returning to activity after metatarsal stress fractures.

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