Muscle co-contraction during gait in individuals with articular cartilage defects in the knee

Publication date: July 2016
Source:Gait & Posture, Volume 48
Author(s): Louise M. Thoma, Michael P. McNally, Ajit M. Chaudhari, David C. Flanigan, Thomas M. Best, Robert A. Siston, Laura C. Schmitt
Increased muscle co-contraction during gait is common in individuals with knee pathology, and worrisome as it is known to amplify tibiofemoral compressive forces. While knees with articular cartilage defects (ACD) are more vulnerable to compressive forces, muscle co-contraction has never been reported in this population. The purpose of this study was to evaluate the extent to which individuals with ACDs in the knee demonstrate elevated quadriceps to hamstrings muscle co-contraction on the involved limb during gait compared to the uninvolved limb and to healthy controls. We also explored the impact of participant characteristics and knee impairments on co-contraction. Twenty-nine individuals with full-thickness knee ACDs (ACD group) and 19 healthy adults (control group) participated in this study. Participants performed five gait trials at self-selected speed, during which activity of the quadriceps and hamstrings muscles were collected with surface electromyography. Three-dimensional motion capture was used to define phases of gait. Quadriceps strength and self-reported outcomes were also assessed in the same session. There were no differences in quadriceps: hamstrings co-contraction between the ACD and control groups, or between the involved and uninvolved limb for the ACD group. For both ACD and control groups, co-contraction was highest in early stance and lowest in late stance. Quadriceps strength was consistently the strongest predictor of muscle co-contraction in both the ACD and the control groups, with individuals with lower strength demonstrating greater co-contraction. Further study is needed to understand the effect of increased muscle co-contraction on joint compressive forces in the presence of varied quadriceps strength.



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Muscle co-contraction during gait in individuals with articular cartilage defects in the knee

Publication date: July 2016
Source:Gait & Posture, Volume 48
Author(s): Louise M. Thoma, Michael P. McNally, Ajit M. Chaudhari, David C. Flanigan, Thomas M. Best, Robert A. Siston, Laura C. Schmitt
Increased muscle co-contraction during gait is common in individuals with knee pathology, and worrisome as it is known to amplify tibiofemoral compressive forces. While knees with articular cartilage defects (ACD) are more vulnerable to compressive forces, muscle co-contraction has never been reported in this population. The purpose of this study was to evaluate the extent to which individuals with ACDs in the knee demonstrate elevated quadriceps to hamstrings muscle co-contraction on the involved limb during gait compared to the uninvolved limb and to healthy controls. We also explored the impact of participant characteristics and knee impairments on co-contraction. Twenty-nine individuals with full-thickness knee ACDs (ACD group) and 19 healthy adults (control group) participated in this study. Participants performed five gait trials at self-selected speed, during which activity of the quadriceps and hamstrings muscles were collected with surface electromyography. Three-dimensional motion capture was used to define phases of gait. Quadriceps strength and self-reported outcomes were also assessed in the same session. There were no differences in quadriceps: hamstrings co-contraction between the ACD and control groups, or between the involved and uninvolved limb for the ACD group. For both ACD and control groups, co-contraction was highest in early stance and lowest in late stance. Quadriceps strength was consistently the strongest predictor of muscle co-contraction in both the ACD and the control groups, with individuals with lower strength demonstrating greater co-contraction. Further study is needed to understand the effect of increased muscle co-contraction on joint compressive forces in the presence of varied quadriceps strength.



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Muscle co-contraction during gait in individuals with articular cartilage defects in the knee

Publication date: July 2016
Source:Gait & Posture, Volume 48
Author(s): Louise M. Thoma, Michael P. McNally, Ajit M. Chaudhari, David C. Flanigan, Thomas M. Best, Robert A. Siston, Laura C. Schmitt
Increased muscle co-contraction during gait is common in individuals with knee pathology, and worrisome as it is known to amplify tibiofemoral compressive forces. While knees with articular cartilage defects (ACD) are more vulnerable to compressive forces, muscle co-contraction has never been reported in this population. The purpose of this study was to evaluate the extent to which individuals with ACDs in the knee demonstrate elevated quadriceps to hamstrings muscle co-contraction on the involved limb during gait compared to the uninvolved limb and to healthy controls. We also explored the impact of participant characteristics and knee impairments on co-contraction. Twenty-nine individuals with full-thickness knee ACDs (ACD group) and 19 healthy adults (control group) participated in this study. Participants performed five gait trials at self-selected speed, during which activity of the quadriceps and hamstrings muscles were collected with surface electromyography. Three-dimensional motion capture was used to define phases of gait. Quadriceps strength and self-reported outcomes were also assessed in the same session. There were no differences in quadriceps: hamstrings co-contraction between the ACD and control groups, or between the involved and uninvolved limb for the ACD group. For both ACD and control groups, co-contraction was highest in early stance and lowest in late stance. Quadriceps strength was consistently the strongest predictor of muscle co-contraction in both the ACD and the control groups, with individuals with lower strength demonstrating greater co-contraction. Further study is needed to understand the effect of increased muscle co-contraction on joint compressive forces in the presence of varied quadriceps strength.



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On Older Listeners' Ability to Perceive Dynamic Pitch

Purpose

Natural speech comes with variation in pitch, which serves as an important cue for speech recognition. The present study investigated older listeners' dynamic pitch perception with a focus on interindividual variability. In particular, we asked whether some of the older listeners' inability to perceive dynamic pitch stems from the higher susceptibility to the interference from formant changes.

Method

A total of 22 older listeners and 21 younger controls with at least near-typical hearing were tested on dynamic pitch identification and discrimination tasks using synthetic monophthong and diphthong vowels.

Results

The older listeners' ability to detect changes in pitch varied substantially, even when musical and linguistic experiences were controlled. The influence of formant patterns on dynamic pitch perception was evident in both groups of listeners. Overall, strong pitch contours (i.e., more dynamic) were perceived better than weak pitch contours (i.e., more monotonic), particularly with rising pitch patterns.

Conclusions

The findings are in accordance with the literature demonstrating some older individuals' difficulty perceiving dynamic pitch cues in speech. Moreover, they suggest that this problem may be prominent when the dynamic pitch is carried by natural speech and when the pitch contour is not strong.

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On Older Listeners' Ability to Perceive Dynamic Pitch

Purpose

Natural speech comes with variation in pitch, which serves as an important cue for speech recognition. The present study investigated older listeners' dynamic pitch perception with a focus on interindividual variability. In particular, we asked whether some of the older listeners' inability to perceive dynamic pitch stems from the higher susceptibility to the interference from formant changes.

Method

A total of 22 older listeners and 21 younger controls with at least near-typical hearing were tested on dynamic pitch identification and discrimination tasks using synthetic monophthong and diphthong vowels.

Results

The older listeners' ability to detect changes in pitch varied substantially, even when musical and linguistic experiences were controlled. The influence of formant patterns on dynamic pitch perception was evident in both groups of listeners. Overall, strong pitch contours (i.e., more dynamic) were perceived better than weak pitch contours (i.e., more monotonic), particularly with rising pitch patterns.

Conclusions

The findings are in accordance with the literature demonstrating some older individuals' difficulty perceiving dynamic pitch cues in speech. Moreover, they suggest that this problem may be prominent when the dynamic pitch is carried by natural speech and when the pitch contour is not strong.

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On Older Listeners' Ability to Perceive Dynamic Pitch

Purpose

Natural speech comes with variation in pitch, which serves as an important cue for speech recognition. The present study investigated older listeners' dynamic pitch perception with a focus on interindividual variability. In particular, we asked whether some of the older listeners' inability to perceive dynamic pitch stems from the higher susceptibility to the interference from formant changes.

Method

A total of 22 older listeners and 21 younger controls with at least near-typical hearing were tested on dynamic pitch identification and discrimination tasks using synthetic monophthong and diphthong vowels.

Results

The older listeners' ability to detect changes in pitch varied substantially, even when musical and linguistic experiences were controlled. The influence of formant patterns on dynamic pitch perception was evident in both groups of listeners. Overall, strong pitch contours (i.e., more dynamic) were perceived better than weak pitch contours (i.e., more monotonic), particularly with rising pitch patterns.

Conclusions

The findings are in accordance with the literature demonstrating some older individuals' difficulty perceiving dynamic pitch cues in speech. Moreover, they suggest that this problem may be prominent when the dynamic pitch is carried by natural speech and when the pitch contour is not strong.

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On the performance and flow characteristics of jet pumps with multiple orifices

The design of compact thermoacoustic devices requires compact jet pump geometries, which can be realized by employing jet pumps with multiple orifices. The oscillatory flow through the orifice(s) of a jet pump generates asymmetric hydrodynamic end effects, which result in a time-averaged pressure drop that can counteract Gedeon streaming in traveling wave thermoacoustic devices. In this study, the performance of jet pumps having 1–16 orifices is characterized experimentally in terms of the time-averaged pressure drop and acoustic power dissipation. Upon increasing the number of orifices, a significant decay in the jet pump performance is observed. Further analysis shows a relation between this performance decay and the diameter of the individual holes. Possible causes of this phenomenon are discussed. Flow visualization is used to study the differences in vortex ring interaction from adjacent jet pump orifices. The mutual orifice spacing is varied and the corresponding jet pump performance is measured. The orifice spacing is shown to have less effect on the jet pump performance compared to increasing the number of orifices.

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