Twenty spinal injured wheelchair bound individuals were tested to peak VO2 on a wheelchair ergometer. Sixteen subjects were paraplegics (5 females, 11 males) and four were quadriplegic (2 females, 2 males). The level of injury ranged from C4-5 to L2-3. The mean age of the subjects was 29.9 years, with a mean weight of 63.66 kg. Prior to the peak VO2 and during the rest immediately after peak VO2, each subject was tested for the ability to discriminate touch over the skin of the thigh, leg, and foot. A chi square statistical technique was used to test for differences between pre- and postexercise sensitivity. The chi square was significant at the .003 level of significance. Because the increase in sensitivity was short, it was theorized that under peak exercise stress the body may recruit pathways that have been dormant, but not injured, explaining the increase in sensitivity.
Lee N. Burkett, Jack Chisum, Jack Pierce and Kent Pomeroy
Keith R. Williams, Rebecca Snow and Chris Agruss
This study investigated changes in kinematics with fatigue during intercollegiate competition, a noncompetitive track run, and a constant speed treadmill run. To account for changes in kinematics resulting from speed differences, regression equations for each individual generated from nonfatigue data were used to predict rested kinematics for speeds matching those of the fatigue conditions. A factor analysis procedure grouped 29 kinematic variables into sets of independent factors, and both factor variables and individual variables were analyzed for changes with fatigue, which were minimal. Only one significant difference was found in the factor variables between nonfatigue and fatigue states. Comparisons of specific kinematic variables showed a significant increase in step length with fatigue, an increased maximal knee flexion angle during swing, and an increased maximal thigh angle during hip flexion. While fatigue did not result in marked changes in kinematics for the group as a whole, changes for individuals were at times large.
Jonisha P. Pollard, William L. Porter and Mark S. Redfern
Euler angle decomposition and inverse dynamics were used to determine the knee angles and net forces and moments applied to the tibia during kneeling and squatting with and without kneepads for 10 subjects in four postures: squatting (Squat), kneeling on the right knee (One Knee), bilateral kneeling near full flexion (Near Full) and bilateral kneeling near 90° flexion (Near 90). Kneepads affected the knee flexion (p = .002), medial forces (p = .035), and internal rotation moments (p = .006). Squat created loading conditions that had higher varus (p < .001) and resultant moments (p = .027) than kneeling. One Knee resulted in the highest force magnitudes and net moments (p < .001) of the kneeling postures. Thigh-calf and heel-gluteus contact forces decreased the flexion moment on average by 48% during Squat and Near Full.
Scott Ross, Kevin Guskiewicz, William Prentice, Robert Schneider and Bing Yu
T o determine differences between contralateral limbs’ strength, proprio-ception, and kinetic and knee-kinematic variables during single-limb landing.
Hip, knee, and foot isokinetic peak torques; anterior/posterior (AP) and medial/lateral (ML) sway displacements during a balance task; and stabilization times, vertical ground-reaction force (VGRF), time to peak VGRF, and knee-flexion range of motion (ROM) from initial foot contact to peak VGRF during single-limb landing.
The kicking limb had significantly greater values for knee-extension (P = .008) and -flexion (P = .047) peak torques, AP sway displacement (P = .010), knee-flexion ROM from initial foot contact to peak VGRF (P < .001), and time to peak VGRF (P = .004). No other dependent measures were significantly different between limbs (P > .05).
The kicking limb had superior thigh strength, better proprioception, and greater knee-flexion ROM than the stance limb.
Lise Kronborg, Thomas Bandholm, Henrik Palm, Henrik Kehlet and Morten Tange Kristensen
Early mobilization following hip fracture surgery reduces medical complications and mortality, but may increase the risk of falling. The aim was to objectively measure the physical activity (time spent upright) the first week after hip fracture surgery and relate it to functional performance and fear of falling at discharge. The 24-hr upright time was measured for a median of six days using a thigh-worn accelerometer in 37 patients (mean 80 years ± 8.4) and increased from median 13 (IQR 6–31) min to 46 (11–107) min at day 7. More upright time at discharge was associated with less fear of falling (r = –.48, p = .01, n = 27), which also was associated with fast gait speed (r = –.50, p = .02, n = 23) and a faster Timed Up and Go test time (r = .54, p < .01, n = 22), indicating a need for further studies on motivation and limitations for more physical activity following hip fracture surgery.
Scott J. Black, Michael L. Woodhouse, Stephen Suttmiller and Larry Shall
The effects of hip position on thigh electromyographic (EMG) activity and knee torque were evaluated. Twenty-four recreational athletes (12 males and 12 females) volunteered to participate. Subjects were tested isokinetically at 30°/s in sitting and supine positions both concentrically and eccentrically during knee flexion and extension. Gravity-corrected torques (N·m) were obtained for all tests. EMG amplitude (mV) was collected via surface electrodes. Torque values were significantly greater (p<.05) for knee flexion in the sitting position when compared to the supine. EMG activity did not change relative to hip position but typically increased (p<.05) during concentric trials. Knee extension torque and EMG activity did not change during sitting or supine positions. Results indicated that the sitting position had statistically significant advantages over the supine position for producing greater hamstring torque and maintaining similar levels of EMG output during isokinetic knee flexion.
Ursula Barrett and Drew Harrison
This study examined the force-velocity and power-velocity relationships of the quadriceps muscles of children and adults. Measurements of muscle function were collected using the Con-Trex isokinetic dynamometer. Twenty adults and twenty children performed maximal effort knee extensions at nine different velocities. The mean force-velocity curves of children and adults revealed obvious differences between the groups. The curves remained different following corrections of torque for CSA and velocity for length. ANOVA revealed significant differences in the uncorrected values of power between the two groups. When power values were corrected for lean thigh muscle volume, no significant differences were found between the groups. These findings suggest that differences in muscle strength between children and adults are a function of muscle size and imply that muscle function remains relatively unchanged from childhood to early adulthood.
Ugo H. Buzzi and Beverly D. Ulrich
The purpose of this study was to examine the dynamic stability of two groups of children with different dynamic resources in changing contexts. The stability of the lower extremity segments of preadolescent children (8–10 years old) with and without Down syndrome (DS) was evaluated as children walked on a motorized treadmill at varying speeds. Tools from nonlinear dynamics, maximum Lyapunov exponent, and approximate entropy were used to assess the behavioral stability of segmental angular displacements of the thigh, shank, and foot. Our results suggest that children with DS show decreased dynamic stability during walking in all segments and that this might be a consequence of inherently different subsystem constraints between these groups. Differences between groups also varied, though not uniformly, with speed, suggesting that inherent differences could further constrain the behavioral response to changing task demands.
Kenneth G. Holt, Suh Fang Jeng and Linda Fetters
Preferred stride frequency (PSF) of adult human walking has been shown to be predictable as the resonant frequency of a force driven harmonic oscillator (FDHO). The purpose of this study was to determine whether the PSF of 9-year-old children was predictable using the same resonance formula as that of adults. Subjects walked around a gymnasium at a rate at which they felt comfortable. Stride frequency was measured as the time for 20 strides and the stride period was calculated. The best-fit prediction based on resonance was then calculated using the overall center of mass of three segments (foot, shank, thigh) to determine the simple pendulum equivalent (SPE) length. Results indicated that a constant of 2 applied to the gravitational constant of the resonance formula, the same formulation used for adults, can be used to predict the cadence of children.
Yukio Urabe, Mitsuo Ochi and Kiyoshi Onari
To investigate changes in muscle strength in the lower extremity after ACL reconstruction.
Prospective case series.
Isokinetic muscle strength measured in 6 movements (hip extension/flexion, hip adduction/abduction, knee extension/flexion) and circumference of the thigh/calf.
Clinic and home.
44 (24 men, 20 women) between the ages of 16 and 47 years with an ACL rupture. All underwent reconstruction via a semitendinosus autograft.
Main Outcome Measures:
The peak torque for each joint movement was recorded. Repeated-measures ANOVA and power analysis were conducted to detect significant interaction effects.
The decline of muscle strength after ACL reconstruction remained not only in the knee extensors and flexors but also in the hip adductors.
Rehabilitation programs that address the behavioral patterns and physiological characteristics of an ACL injury will benefit the athlete’s whole body and lead to a full recovery.