Canadian Journal of Neurological Sciences / Journal Canadien des Sciences Neurologiques
Background: To develop a scale to quantify and discriminate orthostatic from non-orthostatic symp... more Background: To develop a scale to quantify and discriminate orthostatic from non-orthostatic symptoms. We present initial validation and reliability of orthostatic and non-orthostatic symptom scores taken from the Orthostatic Discriminate and Severity Scale (ODSS). Methods: Validity and reliability were assessed in participants with and without orthostatic intolerance. Convergent validity was assessed by correlating symptoms scores with previously validated tools (Autonomic Symptom Profile (ASP) and the Orthostatic Hypotension Questionnaire (OHQ)). Clinical validity was assessed by correlating scores against standardized autonomic testing. Test-retest reliability was calculated using an intra-class correlation coefficient. Results:Convergent Validity: Orthostatic (OS) and Non-Orthostatic (NS) Symptom Scores from 77 controls and 67 patients with orthostatic intolerance were highly correlated with both the Orthostatic Intolerance index of the ASP (OS:r=0.903;NS:r=0.651;…
Canadian Journal of Neurological Sciences / Journal Canadien des Sciences Neurologiques
Background: Strokes can cause a variety of cardiovascular complications. The underlying mechanism... more Background: Strokes can cause a variety of cardiovascular complications. The underlying mechanisms are largely unknown but there is evidence that dysautonomia plays a role in stroke induced-heart injury (SIHI) and arrhythmias triggered by damage of specific brain regions involved in the autonomic regulation of cardiac functions. Understanding these mechanisms could aid in preventing these cardiovascular consequences. We hypothesize that compared to -patients with sinus rhythm (SR) or with cardiogenic atrial fibrillation known before the stroke (cKAF) or diagnosed after the stroke (cAFDAS), those with neurogenic AFDAS (nAFDAS) will show a specific pattern of autonomic functioning. Methods: We will prospectively evaluate 200 ischemic stroke patients at the London Health Sciences Center University Hospital. Participants will undergo continuous electrocardiographic monitoring during 14 days. Based on pre-specified criteria, patients with AFDAS will be classified into presumably neurogen...
Canadian Journal of Neurological Sciences / Journal Canadien des Sciences Neurologiques
Background: Neurogenic orthostatic hypotension (NOH), defined as a drop in systolic blood pressur... more Background: Neurogenic orthostatic hypotension (NOH), defined as a drop in systolic blood pressure (SBP) ≥30mmHg on standing or head-up tilt, is associated with autonomic dysfunction. The cortical autonomic network (CAN) is a network of brain regions associated with autonomic function. Our aim was to investigate CAN activation patterns in NOH patients during autonomic testing. Methods: Fifteen controls (61±14 years) and 13 NOH patients (68±6 years;p=0.1) completed: 1)Deep Breathing (DB), 2)Valsalva maneuver (VM) and 3)Lower-body negative pressure (LBNP) during a functional MRI. Blood-oxygen level dependent (BOLD) contrasts were obtained and contrasted. Results: Compared to controls (C), patients (NOH) had significantly smaller heart rate (HR) responses to DB (C:15.3±9.6 vs.NOH:6.0±2.2) and VR’s (C:2.1±0.47…
Neurogenic orthostatic hypotension (NOH) is a cardinal feature of autonomic dysfunction. The cort... more Neurogenic orthostatic hypotension (NOH) is a cardinal feature of autonomic dysfunction. The cortical autonomic network (CAN) is a network of brain regions associated with autonomic function. Therefore, our objective was to investigate whether impairment of CAN structures is involved in the pathophysiology of NOH. Fifteen controls (63 ± 13 yr) and 15 NOH patients (67 ± 6 yr; P = 0.2) with peripheral autonomic dysfunction completed standard tests of parasympathetic [deep breathing (DB)] and sympathetic [Valsalva maneuver (VM)] activation during a functional MRI. Blood-oxygen-level dependent (BOLD) contrasts were obtained and contrasted. Compared with controls, patients had significantly smaller heart rate responses to DB (control: 15.23 ± 9.6 vs. NOH: 5.7 ± 2.1) and Valsalva ratios (control: 2.1 ± 0.47 vs. NOH: 1.2 ± 0.1; P < 0.001). NOH patients had absent adrenergic phases (late phase II and phase IV) during VM as per a qualitative analysis. During VM, controls had greater activ...
It has been hypothesized that ischemic stroke can cause atrial fibrillation. By elucidating the m... more It has been hypothesized that ischemic stroke can cause atrial fibrillation. By elucidating the mechanisms of neurogenically mediated paroxysmal atrial fibrillation, novel therapeutic strategies could be developed to prevent atrial fibrillation occurrence and perpetuation after stroke. This could result in fewer recurrent strokes and deaths, a reduction or delay in dementia onset, and in the lessening of the functional, structural, and metabolic consequences of atrial fibrillation on the heart. The Pathophysiology and Risk of Atrial Fibrillation Detected after Ischemic Stroke (PARADISE) study is an investigator-driven, translational, integrated, and transdisciplinary initiative. It comprises 3 complementary research streams that focus on atrial fibrillation detected after stroke: experimental, clinical, and epidemiological. The experimental stream will assess pre- and poststroke electrocardiographic, autonomic, anatomic (brain and heart pathology), and inflammatory trajectories in an animal model of selective insular cortex ischemic stroke. The clinical stream will prospectively investigate autonomic, inflammatory, and neurocognitive changes among patients diagnosed with atrial fibrillation detected after stroke by employing comprehensive and validated instruments. The epidemiological stream will focus on the demographics, clinical characteristics, and outcomes of atrial fibrillation detected after stroke at the population level by means of the Ontario Stroke Registry, a prospective clinical database that comprises over 23,000 patients with ischemic stroke. PARADISE is a translational research initiative comprising experimental, clinical, and epidemiological research aimed at characterizing clinical features, the pathophysiology, and outcomes of neurogenic atrial fibrillation detected after stroke.
ObjectiveTo develop a scale to quantify and discriminate orthostatic from non-orthostatic symptom... more ObjectiveTo develop a scale to quantify and discriminate orthostatic from non-orthostatic symptoms. In the current study, we present validation and reliability of orthostatic and non-orthostatic symptom scores taken from the orthostatic discriminate and severity scale (ODSS).MethodsValidity and reliability were assessed in participants with and without orthostatic intolerance. Convergent validity was assessed by correlating symptoms scores with previously validated tools [autonomic symptom profile (ASP) and the orthostatic hypotension questionnaire (OHQ)]. Clinical validity was assessed by correlating scores against standardized autonomic testing. Test–retest reliability was calculated using an intra-class correlation coefficient.ResultsConvergent validity: orthostatic (OS) and non-orthostatic (NS) symptom scores from 77 controls and 67 patients with orthostatic intolerance were highly correlated with both the orthostatic intolerance index of the ASP (OS: r = 0.903; NS: r = 0.651; p < 0.001) and the composite score of the OHQ: (OS: r = 0.800; NS: r = 0.574; p < 0.001). Clinical validity: symptom scores were significantly correlated with the total composite autonomic severity score (OS: r = 0.458; NS: r = 0.315; p < 0.001), and the systolic blood pressure change during head-up tilt (OS: r = − 0.445; NS: r = − 0.354; p < 0.001). In addition, patients with orthostatic intolerance had significantly higher symptom scores compared to controls (OS: 66.5 ± 18.1 vs. 17.4 ± 12.9; NS: 19.9 ± 11.3 vs. 10.2 ± 6.8; p < 0.001, respectively). Test–retest reliability: Both orthostatic and non-orthostatic symptom scores were highly reliable (OS: r = 0.956 and NS: r = 0.574, respectively; p < 0.001) with an internal consistency of 0.978 and 0.729, respectively.InterpretationOur initial results demonstrate that the ODSS is capable of producing valid and reliable orthostatic and non-orthostatic symptom scores. Further studies are ongoing to test sensitivity, specificity and symptom severity.
Purpose To assess the ability of the Orthostatic Discriminant and Severity Scale (ODSS) to distin... more Purpose To assess the ability of the Orthostatic Discriminant and Severity Scale (ODSS) to distinguish symptoms of orthostatic intolerance from non-orthostatic symptoms. Methods Clinical evaluations and questionnaire responses were collected in 73 healthy controls and 132 patients referred to the Autonomic Disorders Clinic from September 1, 2016, through April 30, 2018, for queries regarding autonomic dysfunction. A receiver operating characteristic (ROC) curve analysis was used to interpret sensitivity and specificity and to determine cutoff scores for symptom assessment. Inter-item reliability was assessed using Cronbach’s alpha. To calculate positive and negative predictive powers, patient data were collected in a single-blinded fashion where the researcher collecting questionnaire data was blinded to the clinical evaluation and diagnosis. Predictive powers were calculated using a chi-squared cross-tabulation. Results The orthostatic and non-orthostatic symptoms scores produced ROC curves with an area under the curve of 0.89 and 0.79, respectively. The orthostatic scores yielded a positive and negative predictive power value of 73% and 81%, respectively. Combined, the ODSS identified patients with and without orthostatic symptoms with an overall accuracy of 76%. The reliability of the ODSS was significant, with a Cronbach’s alpha of 0.88, and all dichotomous items were deemed worthy of retention following an inter-item reliability assessment. Conclusions The ODSS demonstrated a strong ability to distinguish patients with and without orthostatic intolerance and demonstrated sensitivity and specificity equivalent to that of other standardized measures. Overall, the ODSS produces symptom scores that are both reliable and useful for both research and clinical practice.
OBJECTIVE Compare activation patterns within the cortical autonomic network in patients with neur... more OBJECTIVE Compare activation patterns within the cortical autonomic network in patients with neurogenic orthostatic hypotension (NOH) versus healthy age-matched controls during an orthostatic challenge. METHODS Fifteen health controls and 15 NOH patients performed 3 Valsalva maneuvers, and 5-min of lower-body negative pressure (LBNP) during a functional brain MRI. RESULTS Compared to controls, NOH patients had significantly less activation within the cerebellum during both LBNP and VM. Both groups had significant activation of the bilateral insula and left thalamus during LBNP. No significant differences were found during the recovery phase of LBNP. CONCLUSIONS The cerebellum, which plays an important role in vestibulo-sympathetic reflexes, important for blood pressure adjustments during postural changes, appear to be affected in patients with NOH. The cerebellum also appears to be affected during other baroreflex mediated stressors such as the VM. SIGNIFICANCE Orthostatic reflexes mediated by the cerebellum may be impaired in patients with NOH. The results suggest an additional pathological pathway in patients with autonomic failure.
The underlying factors related to the divergent findings of age-related fatigue for dynamic tasks... more The underlying factors related to the divergent findings of age-related fatigue for dynamic tasks are not well understood. The purpose here was to investigate age-related fatigability and recovery between a repeated constrained (isokinetic) and an unconstrained velocity (isotonic) task, in which participants performed fatiguing contractions at the velocity (isokinetic) or resistance (isotonic) corresponding with maximal power. To compare between tasks, isotonic torque-power relationships were constructed prior to and following both fatiguing tasks and during short-term recovery. Contractile properties were recorded from 9 old (~75 years) and 11 young (~25 years) men during three testing sessions. In the first session, maximal power was assessed, and sessions 2 and 3 involved an isokinetic or an isotonic concentric fatigue task performed until maximal power was reduced by 40 %. Compared with young, the older men performed the same number of contractions to task failure for the isokin...
PURPOSE: To assess and compare the force-velocity-power relationship (F-V-P) using isotonic and i... more PURPOSE: To assess and compare the force-velocity-power relationship (F-V-P) using isotonic and isokinetic knee extensions in 11 younger (19-30y) and 11 older (69-81y) men. METHODS: The construction of the F-V-P curves were attained with each participant performing maximal, explosive knee extensions at 8 different loads (isotonic) and 8 different velocities (isokinetic) on a Cybex HUMAC NORM dynamometer. Maximal voluntary contraction (MVC or Po), maximal shortening velocity (Vmax), maximum power, optimal torque (Popt) and velocity (Vopt) were assessed and compared. RESULTS: The older men were 43% weaker, 18% slower and ~54% less powerful than the younger men for both isotonic and isokinetic contractions. For the older men, Popt was 35% and 38% lower in the isotonic and isokinetic F-V-P relationships, respectively. The Vopt of the older men were 36% and 25% slower, respectively in the isotonic and isokinetic power curves. Interestingly, the Vopt achieved during isokinetic testing was 16% and 36% higher for both younger (400 vs 346°/s) and older (300 vs 221°/s) men, respectively, compared to the isotonic Vopt. CONCLUSION: For the isotonic modality, the weaker and slower knee extensors of the older men contributed equally to lower power whereas for the isokinetic modality, age-related muscle weakness contributed more than velocity to the reduction in power. The muscle behaves differently between modalities, which may explain parts of the results. The isotonic modality better modelled the F-V relationship, with fewer inherent limitations compared to the isokinetic modality.
Canadian Journal of Neurological Sciences / Journal Canadien des Sciences Neurologiques
Background: To develop a scale to quantify and discriminate orthostatic from non-orthostatic symp... more Background: To develop a scale to quantify and discriminate orthostatic from non-orthostatic symptoms. We present initial validation and reliability of orthostatic and non-orthostatic symptom scores taken from the Orthostatic Discriminate and Severity Scale (ODSS). Methods: Validity and reliability were assessed in participants with and without orthostatic intolerance. Convergent validity was assessed by correlating symptoms scores with previously validated tools (Autonomic Symptom Profile (ASP) and the Orthostatic Hypotension Questionnaire (OHQ)). Clinical validity was assessed by correlating scores against standardized autonomic testing. Test-retest reliability was calculated using an intra-class correlation coefficient. Results:Convergent Validity: Orthostatic (OS) and Non-Orthostatic (NS) Symptom Scores from 77 controls and 67 patients with orthostatic intolerance were highly correlated with both the Orthostatic Intolerance index of the ASP (OS:r=0.903;NS:r=0.651;…
Canadian Journal of Neurological Sciences / Journal Canadien des Sciences Neurologiques
Background: Strokes can cause a variety of cardiovascular complications. The underlying mechanism... more Background: Strokes can cause a variety of cardiovascular complications. The underlying mechanisms are largely unknown but there is evidence that dysautonomia plays a role in stroke induced-heart injury (SIHI) and arrhythmias triggered by damage of specific brain regions involved in the autonomic regulation of cardiac functions. Understanding these mechanisms could aid in preventing these cardiovascular consequences. We hypothesize that compared to -patients with sinus rhythm (SR) or with cardiogenic atrial fibrillation known before the stroke (cKAF) or diagnosed after the stroke (cAFDAS), those with neurogenic AFDAS (nAFDAS) will show a specific pattern of autonomic functioning. Methods: We will prospectively evaluate 200 ischemic stroke patients at the London Health Sciences Center University Hospital. Participants will undergo continuous electrocardiographic monitoring during 14 days. Based on pre-specified criteria, patients with AFDAS will be classified into presumably neurogen...
Canadian Journal of Neurological Sciences / Journal Canadien des Sciences Neurologiques
Background: Neurogenic orthostatic hypotension (NOH), defined as a drop in systolic blood pressur... more Background: Neurogenic orthostatic hypotension (NOH), defined as a drop in systolic blood pressure (SBP) ≥30mmHg on standing or head-up tilt, is associated with autonomic dysfunction. The cortical autonomic network (CAN) is a network of brain regions associated with autonomic function. Our aim was to investigate CAN activation patterns in NOH patients during autonomic testing. Methods: Fifteen controls (61±14 years) and 13 NOH patients (68±6 years;p=0.1) completed: 1)Deep Breathing (DB), 2)Valsalva maneuver (VM) and 3)Lower-body negative pressure (LBNP) during a functional MRI. Blood-oxygen level dependent (BOLD) contrasts were obtained and contrasted. Results: Compared to controls (C), patients (NOH) had significantly smaller heart rate (HR) responses to DB (C:15.3±9.6 vs.NOH:6.0±2.2) and VR’s (C:2.1±0.47…
Neurogenic orthostatic hypotension (NOH) is a cardinal feature of autonomic dysfunction. The cort... more Neurogenic orthostatic hypotension (NOH) is a cardinal feature of autonomic dysfunction. The cortical autonomic network (CAN) is a network of brain regions associated with autonomic function. Therefore, our objective was to investigate whether impairment of CAN structures is involved in the pathophysiology of NOH. Fifteen controls (63 ± 13 yr) and 15 NOH patients (67 ± 6 yr; P = 0.2) with peripheral autonomic dysfunction completed standard tests of parasympathetic [deep breathing (DB)] and sympathetic [Valsalva maneuver (VM)] activation during a functional MRI. Blood-oxygen-level dependent (BOLD) contrasts were obtained and contrasted. Compared with controls, patients had significantly smaller heart rate responses to DB (control: 15.23 ± 9.6 vs. NOH: 5.7 ± 2.1) and Valsalva ratios (control: 2.1 ± 0.47 vs. NOH: 1.2 ± 0.1; P < 0.001). NOH patients had absent adrenergic phases (late phase II and phase IV) during VM as per a qualitative analysis. During VM, controls had greater activ...
It has been hypothesized that ischemic stroke can cause atrial fibrillation. By elucidating the m... more It has been hypothesized that ischemic stroke can cause atrial fibrillation. By elucidating the mechanisms of neurogenically mediated paroxysmal atrial fibrillation, novel therapeutic strategies could be developed to prevent atrial fibrillation occurrence and perpetuation after stroke. This could result in fewer recurrent strokes and deaths, a reduction or delay in dementia onset, and in the lessening of the functional, structural, and metabolic consequences of atrial fibrillation on the heart. The Pathophysiology and Risk of Atrial Fibrillation Detected after Ischemic Stroke (PARADISE) study is an investigator-driven, translational, integrated, and transdisciplinary initiative. It comprises 3 complementary research streams that focus on atrial fibrillation detected after stroke: experimental, clinical, and epidemiological. The experimental stream will assess pre- and poststroke electrocardiographic, autonomic, anatomic (brain and heart pathology), and inflammatory trajectories in an animal model of selective insular cortex ischemic stroke. The clinical stream will prospectively investigate autonomic, inflammatory, and neurocognitive changes among patients diagnosed with atrial fibrillation detected after stroke by employing comprehensive and validated instruments. The epidemiological stream will focus on the demographics, clinical characteristics, and outcomes of atrial fibrillation detected after stroke at the population level by means of the Ontario Stroke Registry, a prospective clinical database that comprises over 23,000 patients with ischemic stroke. PARADISE is a translational research initiative comprising experimental, clinical, and epidemiological research aimed at characterizing clinical features, the pathophysiology, and outcomes of neurogenic atrial fibrillation detected after stroke.
ObjectiveTo develop a scale to quantify and discriminate orthostatic from non-orthostatic symptom... more ObjectiveTo develop a scale to quantify and discriminate orthostatic from non-orthostatic symptoms. In the current study, we present validation and reliability of orthostatic and non-orthostatic symptom scores taken from the orthostatic discriminate and severity scale (ODSS).MethodsValidity and reliability were assessed in participants with and without orthostatic intolerance. Convergent validity was assessed by correlating symptoms scores with previously validated tools [autonomic symptom profile (ASP) and the orthostatic hypotension questionnaire (OHQ)]. Clinical validity was assessed by correlating scores against standardized autonomic testing. Test–retest reliability was calculated using an intra-class correlation coefficient.ResultsConvergent validity: orthostatic (OS) and non-orthostatic (NS) symptom scores from 77 controls and 67 patients with orthostatic intolerance were highly correlated with both the orthostatic intolerance index of the ASP (OS: r = 0.903; NS: r = 0.651; p < 0.001) and the composite score of the OHQ: (OS: r = 0.800; NS: r = 0.574; p < 0.001). Clinical validity: symptom scores were significantly correlated with the total composite autonomic severity score (OS: r = 0.458; NS: r = 0.315; p < 0.001), and the systolic blood pressure change during head-up tilt (OS: r = − 0.445; NS: r = − 0.354; p < 0.001). In addition, patients with orthostatic intolerance had significantly higher symptom scores compared to controls (OS: 66.5 ± 18.1 vs. 17.4 ± 12.9; NS: 19.9 ± 11.3 vs. 10.2 ± 6.8; p < 0.001, respectively). Test–retest reliability: Both orthostatic and non-orthostatic symptom scores were highly reliable (OS: r = 0.956 and NS: r = 0.574, respectively; p < 0.001) with an internal consistency of 0.978 and 0.729, respectively.InterpretationOur initial results demonstrate that the ODSS is capable of producing valid and reliable orthostatic and non-orthostatic symptom scores. Further studies are ongoing to test sensitivity, specificity and symptom severity.
Purpose To assess the ability of the Orthostatic Discriminant and Severity Scale (ODSS) to distin... more Purpose To assess the ability of the Orthostatic Discriminant and Severity Scale (ODSS) to distinguish symptoms of orthostatic intolerance from non-orthostatic symptoms. Methods Clinical evaluations and questionnaire responses were collected in 73 healthy controls and 132 patients referred to the Autonomic Disorders Clinic from September 1, 2016, through April 30, 2018, for queries regarding autonomic dysfunction. A receiver operating characteristic (ROC) curve analysis was used to interpret sensitivity and specificity and to determine cutoff scores for symptom assessment. Inter-item reliability was assessed using Cronbach’s alpha. To calculate positive and negative predictive powers, patient data were collected in a single-blinded fashion where the researcher collecting questionnaire data was blinded to the clinical evaluation and diagnosis. Predictive powers were calculated using a chi-squared cross-tabulation. Results The orthostatic and non-orthostatic symptoms scores produced ROC curves with an area under the curve of 0.89 and 0.79, respectively. The orthostatic scores yielded a positive and negative predictive power value of 73% and 81%, respectively. Combined, the ODSS identified patients with and without orthostatic symptoms with an overall accuracy of 76%. The reliability of the ODSS was significant, with a Cronbach’s alpha of 0.88, and all dichotomous items were deemed worthy of retention following an inter-item reliability assessment. Conclusions The ODSS demonstrated a strong ability to distinguish patients with and without orthostatic intolerance and demonstrated sensitivity and specificity equivalent to that of other standardized measures. Overall, the ODSS produces symptom scores that are both reliable and useful for both research and clinical practice.
OBJECTIVE Compare activation patterns within the cortical autonomic network in patients with neur... more OBJECTIVE Compare activation patterns within the cortical autonomic network in patients with neurogenic orthostatic hypotension (NOH) versus healthy age-matched controls during an orthostatic challenge. METHODS Fifteen health controls and 15 NOH patients performed 3 Valsalva maneuvers, and 5-min of lower-body negative pressure (LBNP) during a functional brain MRI. RESULTS Compared to controls, NOH patients had significantly less activation within the cerebellum during both LBNP and VM. Both groups had significant activation of the bilateral insula and left thalamus during LBNP. No significant differences were found during the recovery phase of LBNP. CONCLUSIONS The cerebellum, which plays an important role in vestibulo-sympathetic reflexes, important for blood pressure adjustments during postural changes, appear to be affected in patients with NOH. The cerebellum also appears to be affected during other baroreflex mediated stressors such as the VM. SIGNIFICANCE Orthostatic reflexes mediated by the cerebellum may be impaired in patients with NOH. The results suggest an additional pathological pathway in patients with autonomic failure.
The underlying factors related to the divergent findings of age-related fatigue for dynamic tasks... more The underlying factors related to the divergent findings of age-related fatigue for dynamic tasks are not well understood. The purpose here was to investigate age-related fatigability and recovery between a repeated constrained (isokinetic) and an unconstrained velocity (isotonic) task, in which participants performed fatiguing contractions at the velocity (isokinetic) or resistance (isotonic) corresponding with maximal power. To compare between tasks, isotonic torque-power relationships were constructed prior to and following both fatiguing tasks and during short-term recovery. Contractile properties were recorded from 9 old (~75 years) and 11 young (~25 years) men during three testing sessions. In the first session, maximal power was assessed, and sessions 2 and 3 involved an isokinetic or an isotonic concentric fatigue task performed until maximal power was reduced by 40 %. Compared with young, the older men performed the same number of contractions to task failure for the isokin...
PURPOSE: To assess and compare the force-velocity-power relationship (F-V-P) using isotonic and i... more PURPOSE: To assess and compare the force-velocity-power relationship (F-V-P) using isotonic and isokinetic knee extensions in 11 younger (19-30y) and 11 older (69-81y) men. METHODS: The construction of the F-V-P curves were attained with each participant performing maximal, explosive knee extensions at 8 different loads (isotonic) and 8 different velocities (isokinetic) on a Cybex HUMAC NORM dynamometer. Maximal voluntary contraction (MVC or Po), maximal shortening velocity (Vmax), maximum power, optimal torque (Popt) and velocity (Vopt) were assessed and compared. RESULTS: The older men were 43% weaker, 18% slower and ~54% less powerful than the younger men for both isotonic and isokinetic contractions. For the older men, Popt was 35% and 38% lower in the isotonic and isokinetic F-V-P relationships, respectively. The Vopt of the older men were 36% and 25% slower, respectively in the isotonic and isokinetic power curves. Interestingly, the Vopt achieved during isokinetic testing was 16% and 36% higher for both younger (400 vs 346°/s) and older (300 vs 221°/s) men, respectively, compared to the isotonic Vopt. CONCLUSION: For the isotonic modality, the weaker and slower knee extensors of the older men contributed equally to lower power whereas for the isokinetic modality, age-related muscle weakness contributed more than velocity to the reduction in power. The muscle behaves differently between modalities, which may explain parts of the results. The isotonic modality better modelled the F-V relationship, with fewer inherent limitations compared to the isokinetic modality.
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Papers by Justin Paturel