Isometric Contraction of Arm Flexor Muscles as a Method of Evaluating Cardiac Vagal Tone in Man

1997 ◽  
Vol 92 (2) ◽  
pp. 175-180 ◽  
Author(s):  
M. Al-Ani ◽  
K. Robins ◽  
A. H. Al-Khalidi ◽  
J. Vaile ◽  
J. Townend ◽  
...  
Keyword(s):  
Heart Rate ◽  
Isometric Contraction ◽  
Maximum Voluntary Contraction ◽  
Young Male ◽  
Vagal Tone ◽  
Voluntary Contraction ◽  
Respiratory Cycle ◽  
Cardiac Vagal Tone ◽  
Flexor Muscles ◽  
Voluntary Contractions

1. We have previously shown that brief voluntary isometric contractions of upper arm flexor muscles performed for one respiratory cycle elicit a significant decrease in the R—R interval. The present study was designed to determine if similar changes are produced by non-voluntary electrically evoked contractions and, if so, to establish the consistency and repeatability of the associated changes in the R—R interval. 2. The heart rate (R—R interval) response to voluntary or non-voluntary brief isometric contraction equivalent to 40% of the maximum voluntary contraction was studied in 10 healthy young male subjects during controlled ventilation at supine rest. 3. The absolute values of R—R intervals occurring in any one of 10 arbitrary phases of a respiratory cycle were measured and plotted by a computer. 4. Both voluntary and non-voluntary contractions elicited similar changes in heart rate and R—R interval, which were greater during expiration than during inspiration. 5. This confirms our previous finding that the magnitude of the R—R interval changes, with brief isometric contraction, is positively related to the degree of cardiac vagal tone. 6. Analysis of the variability between repeated tests initiated in either inspiration or expiration revealed that there was significantly less variability with the electrically induced contraction. 7. It was concluded that electrically induced contractions of 40% maximal voluntary contraction are a viable alternative to voluntary contractions and provide a more controllable means of measuring cardiac vagal withdrawal.

Changes of muscular sound during sustained isometric contraction up to exhaustion

1989 ◽  
Vol 66 (4) ◽  
pp. 1593-1598 ◽  
Author(s):  
C. Orizio ◽  
R. Perini ◽  
A. Veicsteinas
Keyword(s):  
Isometric Contraction ◽  
Exercise Intensity ◽  
Maximum Voluntary Contraction ◽  
Isometric Exercise ◽  
Surface Emg ◽  
Voluntary Contraction ◽  
Biceps Muscle ◽  
Output Force ◽  
Contact Transducer ◽  
Four Levels

The sound (SMG) generated by the biceps muscle during isometric exercise at 20, 40, 60, and 80% of maximum voluntary contraction (MVC) up to exhaustion has been recorded by a contact transducer and integrated (iSMG), together with the surface electromyogram (EMG) in eight young untrained men. At the onset of exercise, iSMG and integrated surface EMG (iEMG) amplitude increased linearly with exercise. iSMG remained constant for 253 +/- 73 (SD), 45 +/- 16, 21 +/- 5, and 0 s at the four levels of contraction. Then iSMG increased linearly at 20% MVC, fluctuated at 40% MVC, and decreased exponentially at 60 and 80% MVC. iSMG exhaustion-to-onset ratio was 5.0 at 20%, 1.0 at 40%, and 0.2 at 60 and 80% MVC. On the contrary, independently of exercise intensity, iEMG increased with time, being 1.4 higher at exhaustion than at the onset. The nonunivocal iSMG changes with time and effort of exercise suggest that the sound may be a useful tool to acquire different information to EMG and output force during muscle contraction up to fatigue.

FORCE SUMMATION AND TWITCH POTENTIATION CAPACITY IN HUMAN ANKLE PLANTAR- AND DORSI-FLEXOR MUSCLES

2014 ◽  
Vol 17 (04) ◽  
pp. 1450015
Author(s):  
Yoichi Ohta ◽  
Kengo Yotani
Keyword(s):  
Muscle Function ◽  
Pulse Train ◽  
Maximum Voluntary Contraction ◽  
Voluntary Contraction ◽  
Twitch Potentiation ◽  
Flexor Muscles ◽  
Human Ankle ◽  
Before And After ◽  
Isometric Torque ◽  
Plantar Flexor Muscles

Purpose: The present study aimed to clarify inter-individual correlation between the magnitudes of force summation and the post-activation potentiation (PAP), in human ankle plantar- and dorsi-flexor muscles. Methods: We analyzed 10 male participants plantar-flexor muscles and the 12 male participants dorsi-flexor muscles using a database from a previous study. Before and after maximum voluntary contraction, we measured the amount of isometric torque evoked by a single, double- and triple-pulse train stimulus. Results: The magnitude of PAP was significantly positively correlated with the magnitude of force summation in both the plantar- and dorsi-flexor muscles. Conclusions: The present study confirmed the correlation between the magnitudes of force summation and PAP in human ankle plantar- and dorsi-flexor muscles. This suggests that muscle characteristics affecting the force summation capacity depend on the PAP, to some degree. These results suggest that the combination of both parameters might enhance the usefulness of evaluating changes in muscle function using intrinsic contractile properties.

Lesser vagal withdrawal during isometric exercise with age

1995 ◽  
Vol 79 (3) ◽  
pp. 805-811 ◽  
Author(s):  
J. A. Taylor ◽  
J. Hayano ◽  
D. R. Seals
Keyword(s):  
Heart Rate ◽  
Arterial Pressure ◽  
Respiratory Rate ◽  
High Frequency ◽  
Isometric Exercise ◽  
Vagal Tone ◽  
Cardiac Vagal Tone ◽  
Age Related ◽  
Lower Baseline ◽  
Vagal Withdrawal

The tachycardia that accompanies isometric exercise decreases with age in humans; however, the mechanism of this decline is unknown. To determine whether less cardiac vagal withdrawal is associated with the age-related decrease in this response, we assessed high-frequency R-R interval variability (0.15–0.40 Hz), an index of cardiac vagal tone, before (control) and during isometric exercise to exhaustion in healthy young (21–29 yr; n = 12) and older (61–72 yr; n = 11) men. During control, the two groups did not differ in respiratory rate, mean arterial pressure, or heart rate, although the older subjects had a lower high-frequency amplitude (12.2 +/- 1.1 vs. 29.4 +/- 4.6 ms/Hz; P < 0.05). During isometric exercise, the respiratory rate and arterial pressure responses did not differ; however, the older men had a lower absolute heart rate and a smaller increase in heart rate, and only the young men demonstrated a significant decline in high-frequency amplitude. The heart rate responses to exercise were correlated with the declines in high-frequency amplitude (initial, r = -0.808; midpoint, r = -0.714; peak, r = -0.632; all P < 0.005), which were, in turn, correlated with the control high-frequency amplitude (initial, r = -0.727; midpoint, r = -0.643; peak, r = -0.610; all P < 0.01). Thus smaller declines in high-frequency amplitude, related to lower baseline amplitude, corresponded to smaller increases in heart rate throughout isometric exercise. Therefore, we conclude that the smaller tachycardiac response to isometric exercise in older humans is associated with an inability to decrease cardiac vagal tone below an already reduced baseline level.

scholarly journals Associations between Acoustic Features of Maternal Speech and Infants' Emotion Regulation following a Social Stressor

2021 ◽  
Author(s):  
Jacek Kolacz ◽  
Elizabeth B daSilva ◽  
Gregory F Lewis ◽  
Bennett I Bertenthal ◽  
Stephen W Porges
Keyword(s):  
Heart Rate ◽  
Social Engagement ◽  
Vagal Tone ◽  
Fast Fourier Transformation ◽  
Acoustic Features ◽  
Sinus Arrhythmia ◽  
Cardiac Vagal Tone ◽  
Gaze Aversion ◽  
Maternal Speech ◽  
Electrocardiogram Ecg

Caregiver voices may provide cues to mobilize or calm infants. This study examined whether maternal prosody predicted changes in infants' biobehavioral state during the Still Face, a stressor in which the mother withdraws and reinstates social engagement. Ninety-four dyads participated in the study (infant age 4-8 months). Infants' heart rate and respiratory sinus arrhythmia (measuring cardiac vagal tone) were derived from an electrocardiogram (ECG). Infants' behavioral distress was measured by negative vocalizations, facial expressions, and gaze aversion. Mothers' vocalizations were measured with spectral analysis and spectro-temporal modulation using a two-dimensional fast Fourier transformation of the audio spectrogram. High values on the maternal prosody composite were associated with decreases in infants' heart rate (β=-.26, 95% CI: [-.46, -.05]) and behavioral distress (β=- .20, 95% CI: [-.38, -.02]), and increases in cardiac vagal tone in infants whose vagal tone was low during the stressor (1 SD below mean β=.39, 95% CI: [.06, .73]). High infant heart rate predicted increases in the maternal prosody composite (β=.18, 95% CI: [.03, .33]). These results suggest specific vocal acoustic features of speech that are relevant for regulating infants' biobehavioral state and demonstrate mother-infant bi-directional dynamics.

scholarly journals Circulating Inflammatory Markers Are Inversely Associated with Heart Rate Variability Measures in Type 1 Diabetes

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Anne-Marie L. Wegeberg ◽  
Tina Okdahl ◽  
Tina Fløyel ◽  
Christina Brock ◽  
Niels Ejskjaer ◽  
...  
Keyword(s):  
Heart Rate ◽  
Heart Rate Variability ◽  
Type 1 Diabetes ◽  
Adhesion Molecules ◽  
Autonomic Neuropathy ◽  
Vagal Tone ◽  
Cardiovascular Autonomic Neuropathy ◽  
Intercellular Adhesion Molecule ◽  
Cardiac Vagal Tone

Introduction. A neuroimmune communication exists, and compelling evidence suggests that diabetic neuropathy and systemic inflammation are linked. Our aims were (1) to investigate biomarkers of the ongoing inflammation processes including cytokines, adhesion molecules, and chemokines and (2) to associate the findings with cardiovascular autonomic neuropathy in type 1 diabetes by measuring heart rate variability and cardiac vagal tone. Materials and Methods. We included 104 adults with type 1 diabetes. Heart rate variability, time domain, and frequency domains were calculated from a 24-hour Holter electrocardiogram, while cardiac vagal tone was determined from a 5-minute electrocardiogram. Cytokines (interleukin- (IL-) 1α, IL-4, IL-12p70, IL-13, IL-17, and tumor necrosis factor- (TNF-) α), adhesion molecules (E-selectin, P-selectin, and intercellular adhesion molecule- (ICAM-) 1), and chemokines (chemokine (C-C motif) ligand (CCL)2, CCL3, CCL4, and C-X-C motif chemokine (CXCL)10) were assessed using a Luminex multiplexing technology. Associations between concentrations of inflammatory biomarkers and continuous variables of heart rate variability and cardiac vagal tone were estimated using multivariable linear regression adjusting for age, sex, disease duration, and smoking. Results. Participants with the presence of cardiovascular autonomic neuropathy had higher systemic levels of IL-1α, IL-4, CCL2, and E-selectin than those without cardiovascular autonomic neuropathy. IL-1α, IL-4, IL-12, TNF-α, and E-selectin were inversely associated with both sympathetic and parasympathetic heart rate variability measures (p>0.01). Discussion. Our results show that several pro- and anti-inflammatory factors, believed to be involved in the progression of diabetic polyneuropathy, are associated with cardiovascular autonomic neuropathy, suggesting that these factors may also contribute to the pathogenesis of cardiovascular autonomic neuropathy. Our findings emphasize the importance of the neuroimmune regulatory system in the pathogenesis of neuropathy in type 1 diabetes.

Dynamic changes in cardiac vagal tone as measured by time-series analysis

1990 ◽  
Vol 258 (3) ◽  
pp. H896-H902 ◽  
Author(s):  
G. E. Billman ◽  
J. P. Dujardin
Keyword(s):  
Heart Rate ◽  
Time Series ◽  
Time Series Analysis ◽  
Rate Control ◽  
Vagal Tone ◽  
Heart Rate Control ◽  
Dynamic Changes ◽  
Sinus Arrhythmia ◽  
Cardiac Vagal Tone ◽  
Series Analysis

A time-series analysis of heart rate variability was evaluated as a marker of cardiac vagal tone using well-characterized autonomic interventions. Heart period (R-R interval) was recorded in 14 mongrel dogs from which the amplitude of the respiratory sinus arrhythmia (0.24-1.04 Hz) was determined. Exercise elicited significant (P less than 0.01) reductions in the index of vagal tone (control 6.3 +/- 0.3 ln ms2 vs. exercise 2.4 +/- 0.4 ln ms2) that were accompanied by significant (P less than 0.01) increases in heart rate (control 123.1 +/- 5 vs. exercise 201.0 +/- 7.7 beats/min). The vagal tone index remained greater than 0 throughout exercise. After propranolol HCl pretreatment, the vagal tone index rapidly decreased toward zero (control 6.2 +/- 0.5; exercise 0.7 +/- 0.3 ln ms2), despite significantly lower increases in heart rate (control 109.3 +/- 4.2; exercise 178.0 +/- 7.6 beats/min). Atropine given during exercise evoked significantly greater increases in heart rate in the control (+48.7 +/- 7.9 beats/min) vs. propranolol (+14.2 +/- 6.7 beats/min) conditions. These data suggest that 1) high levels of cardiac vagal tone remain during exercise; 2) vagal withdrawal is largely responsible for the heart rate increase after beta-adrenergic receptor blockade; and 3) time-series analysis of the R-R interval can provide a dynamic and noninvasive index of cardiac vagal tone.

Increased ventilation does not impair maximal voluntary contractions of the elbow flexors

2008 ◽  
Vol 104 (6) ◽  
pp. 1674-1682 ◽  
Author(s):  
Janette L. Smith ◽  
Jane E. Butler ◽  
Peter G. Martin ◽  
Rachel A. McBain ◽  
Janet L. Taylor
Keyword(s):  
Exercise Performance ◽  
Voluntary Contraction ◽  
Elbow Flexor ◽  
Voluntary Activation ◽  
Neural Drive ◽  
Flexor Muscles ◽  
Elbow Flexor Muscles ◽  
Muscle Groups ◽  
Voluntary Contractions ◽  
Limb Exercise

Exercise performance is impaired by increased respiratory work, yet the mechanism for this is unclear. This experiment assessed whether neural drive to an exercising muscle was affected by cortically driven increases in ventilation. On each of 5 days, eight subjects completed a 2-min maximal voluntary contraction (MVC) of the elbow flexor muscles, followed by 4 min of recovery, while transcranial magnetic stimulation tested for suboptimal neural drive to the muscle. On 1 day, subjects breathed without instructions under normocapnia. During the 2-min MVC, ventilation was ∼3.5 times that at rest. On another day, subjects breathed without instruction under hypercapnia. During the 2-min MVC, ventilation was ∼1.5 times that on the normocapnic day. On another 2 days under normocapnia, subjects voluntarily matched their breathing to the uninstructed breathing under normocapnia and hypercapnia using target feedback of the rate and inspiratory volume. On a fifth day under normocapnia, the volume feedback was set to each subject's vital capacity. On this day, ventilation during the 2-min MVC was approximately twice that on the uninstructed normocapnic day (or ∼7 times rest). The experimental manipulations succeeded in producing voluntary and involuntary hyperpnea. However, maximal voluntary force, fatigue and voluntary activation of the elbow flexor muscles were unaffected by cortically or chemically driven increases in ventilation. Results suggest that any effects of increased respiratory work on limb exercise performance are not due to a failure to drive both muscle groups optimally.

ATP synthesis and proton handling in muscle during short periods of exercise and subsequent recovery

2003 ◽  
Vol 94 (6) ◽  
pp. 2391-2397 ◽  
Author(s):  
David Bendahan ◽  
Graham J. Kemp ◽  
Magali Roussel ◽  
Yann Le Fur ◽  
Patrick J. Cozzone
Keyword(s):  
Maximum Voluntary Contraction ◽  
Lactate Production ◽  
Atp Synthesis ◽  
Voluntary Contraction ◽  
Intracellular Water ◽  
Resonance Spectroscopy ◽  
Proton Production ◽  
Finger Flexion ◽  
Flexor Muscles ◽  
Finger Flexor Muscles

We used31P-magnetic resonance spectroscopy to study proton buffering in finger flexor muscles of eight healthy men (25–45 yr), during brief (18-s) voluntary finger flexion exercise (0.67-Hz contraction at 10% maximum voluntary contraction; 50/50 duty cycle) and 180-s recovery. Phosphocreatine (PCr) concentration fell 19 ± 2% during exercise and then recovered with half time = 0.24 ± 0.01 min. Cell pH rose by 0.058 ± 0.003 units during exercise as a result of H+ consumption by PCr splitting, which (assuming no lactate production or H+ efflux) implies a plausible non-Pi buffer capacity of 20 ± 3 mmol · l intracellular water−1 · pH unit−1. There was thus no evidence of significant glycogenolysis to lactate during exercise. Analysis of PCr kinetics as a classic linear response suggests that oxidative ATP synthesis reached 48 ± 2% of ATP demand by the end of exercise; the rest was met by PCr splitting. Postexercise pH recovery was faster than predicted, suggesting “excess proton” production, with a peak value of 0.6 ± 0.2 mmol/l intracellular water at 0.45 min of recovery, which might be due to, e.g., proton influx driven by cellular alkalinization, or a small glycolytic contribution to PCr resynthesis in recovery.

Maximum Voluntary Contraction as a Function of Upper Extremity Posture in Females

2000 ◽  
Vol 44 (30) ◽  
pp. 5-441-5-444
Author(s):  
Kurt T. Hegmann ◽  
Arun Garg
Keyword(s):  
Perceived Exertion ◽  
Selection Process ◽  
Maximum Voluntary Contraction ◽  
Shoulder Girdle ◽  
Voluntary Contraction ◽  
Ratings Of Perceived Exertion ◽  
Job Tasks ◽  
Shoulder Flexion ◽  
Pain Ratings ◽  
Voluntary Contractions

Background: Little has been published on the maximum strength of the shoulder girdle as a function of varying postures. Such information may help aid in job design by better assessing the capabilities of workers. Methods: Female subjects (n=12) were required to hold a weight in place for 4 seconds in one of 6 different functional postures: 0/90 (shoulder flexion angle = 0° and included elbow angle = 90°), 30/90, 60/90, 90/120, 120/150 and 150/180. Postures and weights were chosen at random and measurements were repeated. Final weight adjustments were in increments of 0.1 lb. At least 3 minutes of rest between lifts was provided. Maximum voluntary contractions (MVCs) were required to be reproduced within 2 lbs. Dynamic lifting of the weight and holding in place MVCs (“lift and hold”), as well as only holding the weight in place MVCs (“hold only”) were assessed separately. Maximum voluntary torques were also computed and adjusted for arm weight. Ratings of perceived exertion (Borg CR-10) and pain ratings (0–10 scale) were obtained. Results: Maximum voluntary contractions varied greatly, with the strongest to weakest measurements approximating 2:1 ratios. For the 90/120 posture, lift and hold MVC was 14.6±3.0 lb. (range 9.5–19.0). The hold only MVC for 90/120 was 18.1±2.9 lb. (range 13.5–25.3). Similar variability occurred in all postures. Adjusted for arm weight, MVC for lift and hold at 90/120 was 18.1±3.3 lb, while hold only was 21.7±3.2 lb. Across all postures, hold only MVCs were greater than lift and hold MVCs by 4.3 lb. (26%). Lift and hold MVC torque at 120/150 was 217.2±39.3 in-lb. (range 157.5–266.8), while hold only was 280.6±38.0 in-lb. Across all postures, hold only maximum voluntary torques were greater than lift and hold torques by 25%. Except for the 0/90 and 150/180 postures, posture had little effect on hold only maximum voluntary torques. Borg CR-10 ratings averaged 6.6 for lift and hold and 6.9 for hold only (p>0.05). Posture had no effect on pain ratings, which averaged 0.8. Conclusions: Variability in female shoulder girdle lifting strength is substantial. Removing the lifting portion of job tasks likely substantially increases the percentage of workers capable of performing the tasks. Weakest postures are 90/120 and 120/150 and the female lift and hold MVC for those postures is 15 lb. (hold only 19 lb.). 30/90, 60/90 and 150/180 postures are equally strong; MVCs for lift and hold in those postures are 18 lb. (hold only 23 lb.). When overhead work is required, 150/180 posture appears preferable to 90/120 or 120/150. Some screening or selection process may be necessary on some jobs due to the degree of variability in strength.

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