The purpose was to investigate central and peripheral processing mechanisms through the use of electromyography (EMG) to determine differences between the performance of children with and without ADHD on a lower extremity choice response time task. Sixteen children with ADHD were tested on and off medication along with 19 children without ADHD. For premotor time, the comparison group performed significantly faster than children with ADHD. The longer latencies exhibited in central processing of children with ADHD were related to midline crossing inhibition (MCI). Medication improved the speed of processing for children with ADHD, but did not negate MCI.
Search Results
Fractionated Lower Extremity Response Time Performance in Boys with and Without ADHD
Scott J. Pedersen, Paul R. Surburg, Matthew Heath, and David M. Koceja
Lower-Extremity Kinetic Response to Weighted-Vest Resistance during Stepping Exercise in Older Adults
George J. Salem, Sean P. Flanagan, Man-Ying Wang, Joo-Eun Song, Stanley P. Azen, and Gail A. Greendale
Stepping activities when wearing a weighted vest may enhance physical function in older persons. Using 3 weighted-vest resistance dosages, this study characterized the lower-extremity joint biomechanics associated with stepping activities in elders. Twenty healthy community-dwelling older adults, ages 74.5 ± 4.5 yrs, performed 3 trials of forward step-up and lateral step-up exercises while wearing a weighted vest which added 0% body weight (BW), 5% BW, or 10% BW. They performed these activities on a force platform while instrumented for biomechanical analysis. Repeated-measures ANOVA was used to evaluate the differences in ankle, knee, and hip maximum joint angles, peak net joint moments, joint powers, and impulses among both steping activities and the 3 loading conditions. Findings indicated that the 5% BW vest increased the kinetic output associated with the exercise activities at all three lower-extremity joints. These increases ranged from 5.9% for peak hip power to 12.5% for knee extensor impulse. The application of an additional 5% BW resistance did not affect peak joint moments or powers, but it did increase the joint impulses by 4–11%. Comparisons between exercise activities, across the 3 loading conditions, indicated that forward stepping preferentially targeted the hip extensors while lateral stepping targeted the plantar flexors; both activities equally targeted the knee extensors. Weighted-vest loads of 5% and 10% BW substantially increased the mechanical demand on the knee extensors, hip extensors (forward stepping), and ankle plantar flexors (lateral stepping).
Lower Extremity Kinematic and Kinetic Differences in Runners with High and Low Arches
Dorsey S. Williams III, Irene S. McClay, Joseph Hamill, and Thomas S. Buchanan
High- and low-arched feet have long been thought to function differently. The purpose of this study was to investigate the relationship between arch structure and lower extremity mechanics in runners with extreme pes planus and pes cavus. It was hypothesized that low-arched individuals would exhibit an increased rearfoot eversion excursion, eversion/tibial internal rotation ratio, and increased angular velocity in rearfoot eversion when compared to high-arched runners. In addition, it was hypothesized that high-arched runners would exhibit greater vertical loading rates. Twenty high-arched and 20 low-arched runners with histories of running-related injuries were included in this study. Low-arched runners were found to have increased rearfoot eversion excursion, eversion to tibial internal rotation ratio, and rearfoot eversion velocity. High-arched runners had increased vertical loading rate when compared to low-arched runners. These results suggest that arch structure is associated with specific lower extremity kinematics and kinetics. Differences in these parameters may subsequently lead to differences in injury patterns in high-arched and low-arched runners.
Lower Extremity Mechanics During Marching at Three Different Cadences for 60 Minutes
Joseph F. Seay, Peter N. Frykman, Shane G. Sauer, and David J. Gutekunst
During group marches, soldiers must walk in step with one another at the same imposed cadence. The literature suggests that shorter trainees may be more susceptible to injury due to overstriding that can occur when taller recruits dictate marching cadence. This study assessed the effects of fixed cadence simulated marching at cadences above and below preferred step rate (PSR) on lower extremity joint mechanics in individuals who were unaccustomed to marching. During three separate visits, 13 volunteers walked with a 20 kg load on a force-sensing treadmill at self-selected PSR, PSR+15% (shorter strides), and PSR–15% (longer strides) at 1.3 m/s for 60 min. Two-way RM ANOVAs (cadence by time) were performed during the stance phase. Ranges of motion and anteroposterior ground reaction force increased significantly as cadence decreased (P < .03). Knee extension moment increased slightly when step rate decreased from PSR+15% (shortest strides, 0.85 ± 0.2 N m/kg) to PSR (0.87 ± 0.3 N m/kg, 3% increase); however, this increase was substantially greater (20% increase) when cadence was decreased from PSR to PSR–15% (longest strides, 1.09 ± 0.3 N m/kg). Our results indicate that overstriding during fixed-cadence marching is a factor that can substantially increase mechanical stress on lower extremity joints.
Strength Training Affects Lower Extremity Gait Kinematics, Not Kinetics, in People With Diabetic Polyneuropathy
Tom Melai, Nicolaas C. Schaper, T. Herman IJzerman, Paul J.B. Willems, Ton L.H. de Lange, Kenneth Meijer, Aloysius G. Lieverse, and Hans H.C.M. Savelberg
Increased forefoot loading in diabetic polyneuropathy plays an important role in the development of plantar foot ulcers and can originate from alterations in muscle strength, joint moments and gait pattern. The current study evaluated whether strength training can improve lower extremity joint moments and spatiotemporal gait characteristics in patients with diabetic polyneuropathy. An intervention group receiving strength training during 24 weeks and a control group receiving no intervention. Measurements were performed in both groups at t = 0, t = 12, t = 24 and t = 52 weeks at an individually preferred and standardized imposed gait velocity. The strength training did not affect the maximal amplitude of hip, knee and ankle joint moments, but did result in an increase in stance phase duration, stride time and stride length of approximately 5%, during the imposed gait velocity. In addition, both groups increased their preferred gait velocity over one year. Future longitudinal studies should further explore the possible effects of strength training on spatiotemporal gait characteristics. The current study provides valuable information on changes in gait velocities and the progressive lower extremity problems in patients with polyneuropathy.
Lower-Extremity Biomechanics and Maintenance of Vertical-Jump Height During Prolonged Intermittent Exercise
Randy J. Schmitz, John C. Cone, Timothy J. Copple, Robert A. Henson, and Sandra J. Shultz
Context:
Potential biomechanical compensations allowing for maintenance of maximal explosive performance during prolonged intermittent exercise, with respect to the corresponding rise in injury rates during the later stages of exercise or competition, are relatively unknown.
Objective:
To identify lower-extremity countermovement-jump (CMJ) biomechanical factors using a principal-components approach and then examine how these factors changed during a 90-min intermittent-exercise protocol (IEP) while maintaining maximal jump height.
Design:
Mixed-model design.
Setting:
Laboratory.
Participants:
Fifty-nine intermittent-sport athletes (30 male, 29 female) participated in experimental and control conditions.
Interventions:
Before and after a dynamic warm-up and every 15 min during the 1st and 2nd halves of an individually prescribed 90-min IEP, participants were assessed on rating of perceived exertion, sprint/cut speed, and 3-dimensional CMJ biomechanics (experimental). On a separate day, the same measures were obtained every 15 min during 90 min of quiet rest (control).
Main Outcome Measures:
Univariate piecewise growth models analyzed progressive changes in CMJ performance and biomechanical factors extracted from a principal-components analysis of the individual biomechanical dependent variables.
Results:
While CMJ height was maintained during the 1st and 2nd halves, the body descended less and knee kinetic and energetic magnitudes decreased as the IEP progressed.
Conclusions:
The results indicate that vertical-jump performance is maintained along with progressive biomechanical changes commonly associated with decreased performance. A better understanding of lower-extremity biomechanics during explosive actions in response to IEP allows us to further develop and individualize performance training programs.
Temporal Influences of Functional Knee Bracing on Torque Production of the Lower Extremity
Brian Campbell, James Yaggie, and Daniel Cipriani
Context:
Functional knee braces (FKB) are used prophylactically and in rehabilitation to aide in the functional stability of the knee.
Objective:
To determine if alterations in select lower extremity moments persist throughout a one hour period in healthy individuals.
Design:
2X5 repeated measures design.
Setting:
Biomechanics Laboratory.
Subjects:
Twenty subjects (14 male and 6 female, mean age 26.5±7 yrs; height 172.4±13 cm; weight 78.6±9 kg), separated into braced (B) and no brace (NB) groups.
Intervention:
A one-hour exercise program divided into three 20 minute increments.
Main Outcome Measures:
Synchronized three-dimensional kinematic and kinetic data were collected at 20-minute increments to assess the effect of the FKB on select lower extremity moments and vertical ground reaction forces.
Results:
Increase in hip moment and a decrease in knee moment were noted immediately after brace application and appeared to persist throughout a one hour bout of exercise.
Conclusions:
The FKB and the exercise intervention caused decreases in knee joint moments and increases in hip joint moments.
Lower Extremity Strength and Mechanics during Jumping in Women with Patellofemoral Pain
John D. Willson and Irene S. Davis
Context:
Lower extremity (LE) weakness might be associated with altered mechanics during weight bearing in subjects with patellofemoral pain syndrome (PFPS).
Objective:
To analyze LE strength, mechanics, and the association between these variables among women with and without PFPS during a simulated athletic task.
Design:
Case control.
Setting:
Motion-analysis laboratory.
Subjects:
20 women with PFPS and 20 healthy women.
Main Outcome Measures:
Peak isometric lateral trunk-flexion, hip-abduction, hip external-rotation, knee-flexion, and knee-extension strength, as well as hip- and knee-joint excursions and angular impulses during single-leg jumps.
Results:
PFPS subjects produced less hip-abduction, hip external-rotation, and trunk lateral-flexion force than the control group. The PFPS group also demonstrated greater hip-adduction excursion and hip-abduction impulses. The association between the strength measurements and LE mechanics was low.
Conclusions:
Women with PFPS demonstrate specific weaknesses and altered LE mechanics. Weakness is not, however, highly correlated with observed differences in mechanics.
The Influence of Physical Activity, Body Composition, and Lower Extremity Strength on Walking Ability
Elisa Marques, Joana Carvalho, Andreia Pizarro, Flávia Wanderlay, and Jorge Mota
We examined the relationship among objective measures of body composition, lower extremity strength, physical activity, and walking performance and determined whether this interaction differed according to walking ability. Participants were 126 adults ages 60–91 yr. Stepwise multiple regression analysis showed that the 30-s chair stand test (30sCST), appendicular lean mass index (aLMI), body mass index, and age were independent contributors to walking performance, explaining 44.3% of the variance. For slower walkers, appendicular fat mass index (aFMI), moderate to vigorous physical activity (MVPA), 30sCST, and aLMI (r 2 = .49, p < .001) largely explained variance in walking performance. For faster walkers, aFMI and aLMI explained 31.4% (p < .001) of the variance. These data suggest that both fat and lean mass are associated with walking performance in higher- and lower-functioning older adults, whereas MPVA and muscle strength influence walking ability only among lower-functioning older adults.
Lower Extremity Muscle Strength and Risk of Self-Reported Hip or Knee Osteoarthritis
Jennifer M. Hootman, Shannon FitzGerald, Carol A. Macera, and Steven N. Blair
Purpose:
The purpose of this study was to investigate the gender-specific longitudinal association between quadriceps strength and self-reported, physician-diagnosed hip or knee osteoarthritis (OA).
Methods:
Subjects were 3081 community-dwelling adults who were free of OA, joint symptoms and injuries, completed a maximum treadmill exercise test, had isokinetic knee extension and flexion and isotonic leg press strength measurements taken at baseline and returned at least one written follow-up survey. Multivariate logistic regression was used to estimate odds ratios and 95% confidence intervals.
Results:
Women with moderate or high isokinetic quadriceps strength had a significantly reduced risk (55% to 64%) of hip or knee OA. A similar, nonsignificant trend was noted among men. Moderate isotonic leg press strength was protective for hip or knee osteoarthritis among men only.
Conclusions:
These results suggest that quadriceps weakness is an independent and modifiable risk factor for lower extremity OA, particularly among women.
