We investigated lower-extremity isometric tremor Approximate Entropy (irregularity), torque steadiness and rate of force development (RFD) and their associations to muscle activation strategy during isometric knee extensions in patients with Parkinson’s disease (PD). Thirteen male patients with idiopathic PD and 15 neurologically healthy matched controls performed isometric maximal contractions (extension/flexion) as well as steady submaximal and powerful isometric knee extensions. The patients with PD showed decreased isometric tremor irregularity. Torque steadiness was reduced in PD and the patients had increased muscle coactivation. A markedly lower RFD was found in PD and the decreased RFD correlated with reduced agonist muscle activation. Furthermore, patient RFD correlated with the Movement-Disorder-Society-Unified-Parkinson’s-Disease-Rating-Scale 3 (motor part) scores. We concluded that both knee isometric tremor Approximate Entropy and torque steadiness clearly differentiate between patients with PD and healthy controls. Furthermore, severely compromised RFD was found in patients with PD and was associated with decreased agonist muscle activation.
Martin H. Rose, Annemette Løkkegaard, Stig Sonne-Holm and Bente R. Jensen
Michelle R. Tanel, Tyler B. Weaver and Andrew C. Laing
-static balance control) by maintaining our center of mass (COM) within our base of support. Common metrics of quasi-static balance control (ie, postural steadiness) can be derived from underfoot center of pressure (COP) measures during quiet standing, 8 and different stance configurations (ie, double leg
Fernando Klitzke Borszcz, Artur Ferreira Tramontin and Vitor Pereira Costa
Maximal lactate steady state (MLSS) is defined as the highest constant intensity of exercise that can be maintained for a longer period without continuous increase in blood lactate concentration ([La − ]), and it is the gold-standard parameter for aerobic evaluation. 1 – 3 MLSS determination is
Rebecca L. Krupenevich, Nick Murray, Patrick M. Rider, Zachary J. Domire and Paul DeVita
Since vision is used in studies of muscle force control, reduced muscle force control might be related to reduced visual ability. We investigated relationships between steadiness in eye movements and quadriceps muscle torque (a surrogate for force) during isometric contractions of constant and varying torques. Nineteen young adults with an average age of 20.7 years and 18 old adults with an average age of 71.6 years performed three vision tasks, three vision and torque tasks at 40% maximal voluntary contraction (MVC), and three vision and torque tasks at 54 nm. Age groups had identical torque steadiness (CV) in 40%-MVC and 54-nm conditions (p > .05). Old had similar vertical (p > .05) but decreased horizontal visual steadiness (SD) (p < .05) compared with young. Correlations between visual steadiness and muscle torque steadiness failed to show a significant relationship (p > .05). We were unable to identify a substantial relationship between muscle torque steadiness and eye movement, as a component of visual steadiness, and conclude that reduced visual steadiness does not contribute to reduced muscle torque steadiness.
Christine M. Tallon, Ryan G. Simair, Alyssa V. Koziol, Philip N. Ainslie and Alison M. McManus
), but not moderate-intensity steady-state exercise (MISS) on a cycle ergometer in adults and adolescents, with subsequent vasodilatory upregulation or normalization resulting in an increase in blood flow one or more hours after the cessation of HIIE, but not MISS ( 2 , 5 ). Recently shear stress was
Ralph Beneke, Volker Schwarz, Renate Leithäuser, Matthias Hütler and Serge P. von Duvillard
Maximal lactate steady state (MLSS) corresponds to the prolonged constant workload whereby the kinetics of blood lactate concentration clearly increases from steady state. Different results of MLSS in children may reflect specific test protocols or definitions. Three methods corresponding to lactate time courses during 20 min (MLSS I), 16 min (MLSS II), and 8 min (MLSS III) of constant submaximal workload were intraindividually compared in 10 boys. At MLSS I, lactate, V̇O2peak, heart rate, and workload were higher (p < .05) than at MLSS II and at MLSS III. The differences between MLSS I, MLSS II, and MLSS III reflect insufficient contribution to lactate kinetics by testing procedures, strongly depending on the lactate time courses during the initial 10 min of constant workload. Previously published divergent results of MLSS in children seem to reflect a methodological effect more than a metabolic change.
Erin Calaine Inglis, Danilo Iannetta, Louis Passfield and Juan M. Murias
, the boundary separating tolerable and nontolerable exercise) and is often identified by measures including the maximal lactate steady state (MLSS) or critical power (CP). 3 Although the accuracy for determining this intensity is best obtained in a laboratory setting, this is not always feasible due to cost
Erin Calaine Inglis, Danilo Iannetta, Daniel A. Keir and Juan M. Murias
The highest rate of muscle metabolism that can be maintained by the oxidative system in steady-state conditions without continual blood lactate accumulation and progressive depletion of high-energy phosphates sets the upper limit of tolerable intensity. Identification of this “critical intensity
Ralph Beneke, Hermann Heck, Helge Hebestreit and Renate M Leithäuser
The value of blood lactate concentration (BLC) measured during incremental load tests in predicting maximal lactate-steady-state (MLSS) workload has rarely been investigated in children. In 17 children and 18 adults MLSS was 4.1 ± 0.9mmol 1.1. Workload at BLC of 3.0mmol 1.1 determined during an incremental load test explained about 80% of the variance (p < .001) and best predicted MLSS workload independent of age. This was despite the increase in power per time related to maximum incremental load test power being higher (p < .001) in children than in adults. The BLC response to given exercise intensities is faster in children without affecting MLSS.
Joseph P. Stitt and Karl M. Newell
This paper presents the stochastic modeling of isometric force variability in the steady-state time series recorded from the index finger of young adults in the act of attempting to hold different levels of constant force. The isometric force time series were examined by assuming that the stochastic (random) models were linear. System identification techniques were employed to estimate the parameters of each linear model. Once the models were parameterized, the values of the estimated parameters were compared to determine if a single linear time-invariant model was applicable across the entire isometric force range. Although the overall random models were found to be nonlinear functions of the target force level, within a fixed target level, linear modeling provided adequate estimates of the underlying processes thus enabling the use of well-known linear system identification algorithms.