Lower extremity kinematics of a single-leg squat with an orthotic in male and female collegiate athletes.

Kinematic differences have been linked to the gender discrepancies seen in knee injuries. A medially posted orthotic decreases frontal and transverse plane motions in the lower extremity during ambulation, squatting and landing. This study investigated the effect of a medial post on amount and timing of lower extremity motions during a single-leg squat in male and female athletes. We hypothesized there would be differences in these kinematic variables dependent upon sex and post conditions. Twenty male and female athletes performed single-leg squats with and without a five degree full-length medial post. Maximum joint angles were analyzed using a two-way, repeated-measures analysis of variance to determine if the differences created by post condition were statistically significant, whether there were gender differences, or interactions. Differences in maximum motion values and the time at which they occurred were found between men and women at the hip, knee and ankle. The post decreased all frontal plane measures in both sexes and resulted in earlier attainment of maximum ankle eversion and delayed maximum knee valgus. A medially posted orthotic may be beneficial not only in limiting motion, but in affecting the time in which stressful motions occur.

Age-Related Differences in Postural and Goal-Directed Movements During Medial-Lateral Rhythmic Stepping.

Lateral stability and weight transfer are important for successful stepping and are associated with falls in older adults (OAs). This study assessed the influence of step pacing frequency during medial-lateral stepping in place on body center of mass and lower limb movement in young adults, middle-aged adults, and OAs. Medial-lateral center of mass and stepping limb motion and lower limb loading data were collected. Center of mass motion decreased with increasing pacing frequency and increased to a lesser extent with decreasing pacing frequency. Step length was relatively resistant to changes in pacing frequency. OAs exhibited reductions in whole body and stepping motion compared with younger adults. OAs exhibited greater support limb loading. OAs adapt both postural and stepping strategies to successfully step under time-critical conditions.

Lateral rhythmic unipedal stepping in younger, middle-aged, and older adults.

PURPOSE: Voluntary and protective stepping performance changes with age. This has implications for the problem of falls in older adults. The purpose of this study was to examine the influence of metronome paced stepping practice on self-selected preferred rhythmic unipedal stepping performance in the medial-lateral direction among younger, middle-aged and older adults. METHODS: Thirty-two healthy adult subjects (0 younger, 0 middle-aged, 2 older) participated. They performed rhythmic lateral stepping with their dominant limb at their preferred pace before and after 6 trials of metronome-paced stepping. RESULTS: Older subjects had longer stride periods than young and middle-aged subjects prior to metronome pacing. Older subjects exhibited a 25% decrease in preferred stride period between pre- and postpacing trials. This is compared to a 5% and 11 % decrease exhibited by middle-aged and younger subjects respectively. Preferred stride period was similar for older subjects as compared to younger and middle-aged subjects after paced practice. Modification of the stride period occurred mainly during the stance phase of rhythmic stepping. CONCLUSIONS: Comparable stride periods across groups after pacing suggest stepping performance is modifiable. Brief intervals of paced stepping may offer older adults a short-term benefit to stepping performance.

Intrinsic and imposed hamstring length influence posterior pelvic rotation during hip flexion.

BACKGROUND: The contribution of posterior tilt of the pelvis (pelvic rotation) to hip flexion has been described for individuals who are standing, supine, and suspended. The effects of intrinsic and imposed hamstring length on the motion have not been investigated in a controlled manner. This study investigated the influence of intrinsic and imposed hamstring length on pelvic rotation during bilateral active hip flexion. METHODS: Intrinsic hamstring length was characterized by the maximal active straight leg raise angle. Hamstring length was imposed by immobilizing the knees in 0 degrees, 45 degrees, and 90 degrees of flexion. Pelvic and thigh segments were marked with reflective spheres. Subjects' saggital plane motion was captured using computerized motion analysis during bilateral hip flexion while both knees were immobilized in three positions. Multifactorial analysis of variance was employed to show the effect of intrinsic and imposed hamstring length on pelvic rotation. FINDINGS: Pelvic rotation occurred throughout the hip flexion range of motion. Pelvic rotation was influenced significantly by hip flexion angle, knee position, the interaction between hip flexion angle and knee position, and the interaction between hip flexion angle, knee position, and active straight leg raise angle. INTERPRETATION: Both intrinsic and imposed hamstring length influence pelvic rotation during bilateral hip flexion. These influences should be considered by clinicians who have individuals engage in hip flexion maneuvers.

Pelvifemoral rhythm during unilateral hip flexion in standing.

OBJECTIVE: To quantify pelvifemoral rhythm during unilateral hip flexion in standing subjects, under different degrees of resistance. DESIGN: Descriptive and correlational. BACKGROUND: Pelvic rotation contributes to the change in hip flexion angle while individuals are supine. Degree of contribution in standing has not been described. METHODS: Pelvic and femoral motions, relative to vertical, were documented while 14 subjects performed three trials of standing unilateral hip flexion, both with and without a 4.53 kg ankle weight. Pelvic and thigh segments were marked with reflective spheres, and motion was captured by video analysis. RESULTS: Pelvic rotation contributed 18.1% of the change in hip flexion angle. Pelvic rotation occurred throughout the movement. Neither presence of external resistance nor direction of movement significantly changed this contribution. CONCLUSIONS: A strong relationship exists between pelvic rotation and hip flexion in standing subjects. RELEVANCE: Hip flexion, while standing, is a common element of many functional activities. Knowledge of the pelvic contribution increases our understanding of hip and lumbar spine motion during standing activities.

Pelvic and femoral contributions to bilateral hip flexion by subjects suspended from a bar.

OBJECTIVE: To quantify the contribution of the pelvis and femur to active bilateral hip flexion conducted while subjects are suspended by their hands from a bar. DESIGN: Descriptive and experimental. BACKGROUND: Voluntary hip flexion while in a suspended position is used in abdominal strengthening regimens and is required for certain athletic activities. The degree to which pelvic rotation contributes to this maneuver has not been established. METHODS: Pelvic and femoral motions were documented in 14 subjects who performed bilateral hip flexion while they hung by their hands from a bar. A supporting board as well as the trunk, pelvis and thigh were marked with reflective spheres; motion of the pelvis and thigh relative to the board was captured by video analysis. Ratios of pelvic to femoral motion were calculated and the influence of hamstring length (<78 degrees vs >78 degrees of straight leg raising) and knee position (flexed vs extended) on the ratio was determined. RESULTS: The mean pelvifemoral ratio ranged from 0.131 to 0.355, depending on hamstring length and knee position. Pelvic rotation therefore contributed a mean 13.1-35.5% of the observed hip flexion. A 2 x 2 mixed-model analysis of variance showed that the ratio was influenced significantly by each of these two independent variables. The largest pelvic contribution occurred during hip flexion with the knee in the extended position among subjects with shorter hamstrings. CONCLUSIONS: Pelvic motion is an integral part of hip flexion conducted while subjects are suspended their hands from a bar. The pelvic contribution depends on knee position and hamstring length. RELEVANCE: During suspended activities involving hip flexion (e.g. gymnastics), pelvic rotation plays an integral role throughout the range. Inherent or imposed differences in hamstring length can alter the contribution of the pelvis to the motion. Hip flexion, therefore, might be influenced by conditions affecting the ability of the pelvis to rotate (e.g. spinal fusion), or the femur to move on the pelvis (e.g. degenerative joint disease), or be altered by hamstring tension.

Kinematics of the double-leg-lowering test for abdominal muscle strength.

STUDY DESIGN: Prospective descriptive study. OBJECTIVE: To investigate the kinematics of the double-leg-lowering (DLL) test of abdominal muscle strength. BACKGROUND: Adequate strength of the abdominal muscles is necessary for many household, occupational, and sports activities. Therapists, therefore, need valid measures of abdominal muscle strength. METHODS AND MEASURES: A convenience sample of 17 subjects (7 women, 10 men) was tested. Using reflective spheres to identify specific body segments, subjects were videotaped while performing DLL under 2 conditions: attempting (controlled) prevention of anterior pelvic tilting versus not attempting (uncontrolled) prevention of anterior pelvic tilting. Videotape was analyzed using the PEAK 5 2-dimensional system. RESULTS: The pelvis tilted anteriorly by the time the extremities were lowered a mean 3.6 degrees, regardless of condition. No significant difference in anterior pelvic tilting was associated with the 2 DLL conditions (F = 2.95, P = 0.105) but pelvic tilting did increase significantly as the lower extremities were lowered from vertical (F = 98.41, P < 0.001). CONCLUSIONS: There appears to be a natural tendency for the pelvis to tilt anteriorly from very early in the DLL maneuver. As healthy young subjects do not appear able to prevent the tilting, the scoring system associated with the DLL test should be questioned.

Effect of added mass on human unipedal hopping at three frequencies.

Although more commonly done by children, hopping appears to be a rich source of neuromuscular and biomechanical information on adults. Given prior research on the independent effects of hopping frequency and added mass, this study assessed whether these would interact to affect vertical stiffness, contact duration, and lower extremity kinematics during unipedal hopping. Vertical force and two-dimensional kinematics were measured in 10 healthy males hopping at three frequencies: their preferred hopping frequency and frequencies 20% higher and 20% lower, in two conditions with added mass (body mass+10% and body mass+20%). Vertical stiffness was directly related to hopping frequency, while hip flexion, knee flexion, and ankle dorsiflexion were inversely related to hopping frequency. Additional mass significantly increased ankle dorsiflexion and contact duration but did not significantly affect hip flexion, knee flexion, or vertical stiffness. The differential response of vertical stiffness to hopping frequency and added mass was consistent with predictions based on a mass-spring model. The interactive effect of frequency and added mass on the kinematics of the lower extremity and contact period were consistent with earlier studies of the independent effects of hopping frequency and added mass.

Effect of added mass on human unipedal hopping.

Although hopping is considered a children's activity, it can be used to provide insight into the neuromuscular and biomechanical performance of adults. This study investigated whether mass added during unipedal hopping altered the vertical stiffness, hopping period, and angular kinematics of the lower extremity of adults. Measures of two-dimensional kinematics and vertical force were made from 10 healthy men during hopping at a preferred period under three conditions: Body Mass, Body Mass+10%, and Body Mass+20%. Adding mass significantly increased hopping period and hip flexion without significantly affecting vertical stiffness, ankle dorsiflexion, or knee flexion. Overall, the findings agreed with predictions based on a simple-mass spring model. The results indicate unique kinetic and kinematic responses to increased mass during hopping may have potential application in neuromuscular assessment and training for the lower extremities.

Effect of frequency on human unipedal hopping.

All mature forms of locomotion involve periods of unilateral stance. Unipedal hopping may provide useful information about the neuromuscular and biomechanical capabilities of a single lower extremity in adults. This study investigated whether hopping influenced vertical stiffness and lower extremity angular kinematics during human unipedal hopping. Vertical force and two-dimensional kinematics were measured in 10 healthy males hopping at three frequencies: preferred, +20%, and -20%. At +20%, compared to preferred, vertical stiffness increased 55% as hip flexion, knee flexion, and ankle dorsiflexion decreased, while at -20% vertical stiffness decreased 39.4% as hip flexion, knee flexion, and ankle dorsiflexion increased. As in bipedal hopping, the force-displacement relationship was more springlike at the preferred rate and +20% than at -20%. Given the prevalence of unilateral stance during walking, running, and skipping, findings related to unipedal hopping may be useful in the rehabilitation or conditioning of lower extremities.

Knee valgus during drop jumps in National Collegiate Athletic Association Division I female athletes: the effect of a medial post.

BACKGROUND: Female athletes land from a jump with greater knee valgus and ankle pronation/eversion. Excessive valgus and pronation have been linked to risk of anterior cruciate ligament injury. A medially posted orthosis decreases component motions of knee valgus such as foot pronation/eversion and tibial internal rotation. HYPOTHESIS: We hypothesized a medial post would decrease knee valgus and ankle pronation/eversion during drop-jump landings in NCAA-I female athletes. STUDY DESIGN: Controlled laboratory study. METHODS: Knee and ankle 3-dimensional kinematics were measured using high-speed motion capture in 10 National Collegiate Athletic Association Division I female athletes during a drop-jump landing with and without a medial post. Analysis of variance was used to determine differences in posting condition, t tests were used to determine dominant-nondominant differences, and the Pearson correlation coefficient was used to determine relationships between variables. RESULTS: Significant differences were found for all measures in the posted condition. A medial post decreased knee valgus at initial contact (1.24 degrees , P < .01) and maximum angle (1.21 degrees , P < .01). The post also decreased ankle pronation/eversion at initial contact (0.77 degrees , P < .01) and maximum angle (0.95 degrees , P = .039). CONCLUSION: The authors have demonstrated a significant decrease in knee valgus and ankle pronation/eversion during a drop jump with a medial post placed in the athletes' shoes. CLINICAL RELEVANCE: A medial post may be a potential means to decrease risk of anterior cruciate ligament injury.

The effects of ten weeks of lower-body unstable surface training on markers of athletic performance.

Initially reserved for rehabilitation programs, unstable surface training (UST) has recently grown in popularity in strength and conditioning and general exercise scenarios. Nonetheless, no studies to date have examined the effects of UST on performance in healthy, trained individuals. The purpose of this study was to determine the effects of 10 weeks of lower-body UST on performance in elite athletes. Nineteen healthy, trained members (ages 18-23 years) of a National Collegiate Athletic Association Division I collegiate men's soccer team participated. The experimental (US) group (n = 10) supplemented their normal conditioning program with lower-body exercises on inflatable rubber discs; the control (ST) group (n = 9) performed the same exercises on stable surfaces. Bounce drop jump (BDJ) and countermovement jump (CMJ) heights, 40- and 10-yard sprint times, and T-test (agility) times were assessed before and after the intervention. The ST group improved significantly on predicted power output on both the BDJ (3.2%) and CMJ (2.4%); no significant changes were noted in the US group. Both groups improved significantly on the 40- (US = -1.8%, ST = -3.9%) and 10-yard sprint times (US = -4.0%, ST = -7.6%). The ST group improved significantly more than the US group in 40-yard sprint time; a trend toward greater improvement in the ST group was apparent on the 10-yard sprint time. Both groups improved significantly (US = 2.9%, ST = -4.4%) on T-test performance; no statistically significant changes were apparent between the groups. These results indicate that UST using inflatable rubber discs attenuates performance improvements in healthy, trained athletes. Such implements have proved valuable in rehabilitation, but caution should be exercised when applying UST to athletic performance and general exercise scenarios.

Effects of treatment with a cetylated fatty acid topical cream on static postural stability and plantar pressure distribution in patients with knee osteoarthritis.

The purpose of the present investigation was to examine the effects of 30 days of treatment with a topical cream consisting of cetylated fatty acids on static postural stability and plantar pressures in patients with osteoarthritis (OA) of one or both knees. Forty patients diagnosed with knee OA were randomly assigned to 1 of 2 topical treatment groups: (a) cetylated fatty acid (CFA; N = 20; age = 62.7 +/- 11.7 years); or (b) placebo (P; N = 20; age = 64.6 +/- 10.5 years). Patients were tested on 2 occasions: (a) baseline (T1), and (b) following a 30-day treatment period consisting of cream application twice per day (T2). Assessments included 20- and 40-second quiet standing protocols on a force plate to measure center of pressure (COP) total excursion length, COP velocity, and rearfoot and forefoot plantar pressure distribution. In the CFA group, a significant reduction in the COP excursion length and velocity were observed at T2, whereas no significant differences were observed in the P group. No significant differences in mean forefoot, rearfoot, or rearfoot-to-forefoot plantar pressure ratios were observed in either group at T2. However, in a subgroup of participants designated to be right- or left-side dominant, improvements in the right-to-left forefoot plantar pressure ratios were observed in both groups. These data indicate that 30 days of treatment with a topical cream consisting of cetylated fatty acids improves static postural stability in patients with knee OA presumably due to pain relief during quiet standing. Such over-the-counter treatment may help improve the exercise trainability of people with OA.

A cetylated fatty acid topical cream with menthol reduces pain and improves functional performance in individuals with arthritis.

This investigation was an extension of a previous study conducted in our laboratory in which we showed that 1 month of treatment with a topical cream (Celadrin) consisting of cetylated fatty acids was effective for reducing pain and improving functional performance in individuals with osteoarthritis (OA) of the knee (Kraemer et al., Journal of Rheumatology, 2004). We wanted to verify that the addition of menthol to the compound would produce a similar percentage of improvement in therapeutic effects. We used a single treatment group with a pre-post experimental design to examine % treatment changes. Individuals diagnosed with OA of the knee (N = 10; age, 66.4 +/- 11.5 years) and severe pain (e.g., OA, rheumatoid arthritis) of the elbow (N = 8; age, 59.1 +/- 18.2 years) and wrist (N = 10; age, 60.3 +/- 16.8 years) were tested for pain and functional performance before and after 1 week of treatment with a topical cream consisting of cetylated fatty acids and menthol applied twice per day. In individuals with knee OA, significant improvements in stair-climbing ability (about 12%), "up-and-go" performance (about 12%), balance and strength (about 16.5%), and range of motion (about 3.5%) were observed, as were reductions in pain. In individuals with severe pain of the elbow and wrist, significant improvements in dynamic (about 22 and 24.5%, respectively) and isometric (about 33 and 42%, respectively) local muscular endurance were observed, as was a reduction in pain. Neither group demonstrated significant changes in maximal grip strength or maximal force production. One week of treatment with a topical cream consisting of cetylated fatty acids and menthol was similarly effective for reducing pain and improving functional performance in individuals with arthritis of the knee, elbow, and wrist. The % changes were consistent with our prior work on the compound without menthol. Further work is needed to determine the impact of menthol in such a cream. Nevertheless, our data support the use of a topical cream consisting of cetylated fatty acids (with or without menthol) for enhancing the potential for exercise training in this population.

Effect of a cetylated fatty acid topical cream on functional mobility and quality of life of patients with osteoarthritis.

OBJECTIVE: To examine the effect of a topical cream consisting of cetylated fatty acids on functional performance in patients diagnosed with osteoarthritis (OA) of one or both knees. METHODS: Forty patients diagnosed with knee OA were randomly assigned to one of 2 topical treatment groups: (1) cetylated fatty acid (CFA) (n = 20; age 62.7 +/- 11.7 yrs); or (2) placebo group (n = 20; age 64.6 +/- 10.5 yrs). Patients were tested on 3 occasions: (1) baseline (T1), (2) 30 min after initial treatment (T2), and (3) after 30-day treatment of cream application twice per day (T3). Assessments included knee range of motion (ROM), timed "up-and-go" from a chair and stair climbing, medial step-down test, and the unilateral anterior reach. RESULTS: For stair climbing ability and the up-and-go test, significant decreases in time were observed at T2 and T3 compared to T1 in the CFA group only. These differences were significant between groups. Supine ROM of the knees increased at T2 and T3 in CFA group, whereas no difference was observed in the placebo group. For the medial step-down test, significant improvement was observed at T2 and T3 compared to T1 in CFA group. For the unilateral anterior reach, significant improvement was observed for both legs in CFA group and in only the left leg in the placebo group. However, the improvements observed in CFA group were significantly greater than placebo group for both legs. CONCLUSION: Use of a CFA topical cream is an effective treatment for improving knee ROM, ability to ascend/descend stairs, ability to rise from sitting, walk and sit down, and unilateral balance.