Biomedical subjects

Joseph Hamill

Publications and source records attributed to Joseph Hamill.

27 records · Page 2Linked to original sources

PubMed2004

The role of selected extrinsic foot muscles during running.

OBJECTIVE: To determine the kinematic, kinetic and EMG responses to perturbations of the foot by running in varus, neutral, and valgus-wedged shoes. DESIGN: Within-subjects study comparing kinematics, kinetics and EMG while running in three different shoe conditions. BACKGROUND: Excessive pronation has been cited as a key contributor to many types of running injuries. However, the roles of the extrinsic foot muscles (those that control motion of the foot) during the stance phase of running have not been adequately identified, which is critical to determining the relationship between pronation and injury. METHODS: Ten males ran in varus, valgus, and neutral-wedged shoes while three-dimensional kinematic and kinetic data and EMG data were collected. Surface EMG data were collected from the tibialis anterior, peroneus longus, medial and lateral gastrocnemius, and soleus. Indwelling EMG was obtained from the tibialis posterior. The net joint moment, power, and total positive and negative work was calculated in the frontal plane. EMG onset, offset, and integrated values were reported. RESULTS: The maximum eversion angle, maximum inversion moment and total negative work done in the frontal plane were greatest while running in the valgus shoe and least in the varus shoe. The greater joint moment was not accompanied by changes in muscle activation patterns, although the tibialis posterior data were inconclusive in this respect. CONCLUSIONS: Greater pronation leads to greater energy absorption in the foot invertor muscles and tendons. While not conclusive, the EMG data suggest that for these muscles there was not a neuromuscular adaptation to the perturbation.

Adult↗

PubMed2004

Orthotic intervention in forefoot and rearfoot strike running patterns.

OBJECTIVE: To compare the differential effect of custom orthoses on the lower extremity mechanics of a forefoot and rearfoot strike pattern. DESIGN: Fifteen subjects ran with both a forefoot and a rearfoot strike pattern with and without orthoses. Lower extremity kinematic and kinetic variables were compared between strike pattern and orthotic conditions. BACKGROUND: Foot orthoses have been shown to be effective in controlling excessive rearfoot motion in rearfoot strikers. The effect of orthotic intervention on rearfoot motion in forefoot strikers has not been previously reported. METHODS: Five trials were collected for each condition. Peak rearfoot eversion, eversion excursion, eversion velocity, peak inversion moment, and inversion work were compared between conditions. Kinematic variables in the sagittal plane of the rearfoot and in the frontal and sagittal plane of the knee were also determined. RESULTS: Increased rearfoot excursions and velocities and decreased peak eversion were noted in the forefoot strike pattern compared to the rearfoot strike pattern. Orthotic intervention, however,did not significantly change rearfoot motion in either strike pattern. Reductions in internal rotation and abduction of the knee were noted with orthotic intervention. CONCLUSIONS: Foot orthoses do not differentially effect rearfoot motion of a rearfoot strike and a forefoot strike running pattern. Orthotic intervention has a larger and more systematic effect on rearfoot kinetics compared to rearfoot kinematics.

Adolescent↗

PubMed2004

Influence of gender on hip and knee mechanics during a randomly cued cutting maneuver.

OBJECTIVE: To investigate gender differences in three-dimensional hip and knee joint mechanics in collegiate athletes during a randomly cued cutting maneuver. DESIGN: Three-dimensional kinematics and kinetics were collected on 24 collegiate soccer players (12 females and 12 males) while each performed the cutting maneuver. In order to create a randomly cued condition, subjects were signaled by a lighted target board that directed them to perform one of three tasks. Hip and knee joint mechanics were compared between genders using one-tailed t-tests. BACKGROUND: Female athletes have an anterior cruciate ligament injury rate that is larger than their male counterparts. Gender differences in hip and knee joint mechanics during a randomly cued cutting maneuver have not been previously reported. METHODS: Five randomly cued cutting trials were included in the analysis. Selected peak hip and knee joint angles and moments were measured during the first 40 degrees of knee flexion across the stance phase. RESULTS: Females demonstrated significantly less peak hip abduction than did males. Otherwise, there were no gender differences in selected peak hip and knee joint kinematics and moments. CONCLUSIONS: Male and female collegiate soccer players demonstrate similar hip and knee joint mechanics while performing a randomly cued cutting maneuver. RELEVANCE: Because it is known that females incur a greater number of anterior cruciate ligament injuries than males, it is of interest to identify gender differences in lower extremity mechanics when performing sport specific tasks. Understanding of these differences will contribute to the development of prevention training programs.

Adolescent↗

PubMed2004

High-arched runners exhibit increased leg stiffness compared to low-arched runners.

Leg stiffness between high-arched (HA) and low-arched (LA) runners was compared. It was hypothesized that high-arched runners would exhibit increased leg stiffness, increased sagittal plane support moment, greater vertical loading rates, decreased knee flexion excursion and increased activation of the knee extensor musculature. Twenty high-arched and 20 low-arched subjects were included in this study. Leg stiffness, knee stiffness, vertical loading rate and lower extremity support moment were compared between groups. Electromyographic data were collected in an attempt to explain differences in leg stiffness between groups. High-arched subjects were found to have increased leg stiffness and vertical loading rate compared to low-arched runners. Support moment at the impact peak of the vertical ground reaction force was related to leg stiffness across all subjects. High-arched subjects demonstrated decreased knee flexion excursion during stance. Finally, high-arched subjects exhibited a significantly earlier onset of the vastus lateralis (VL) than the low-arched runners. Differences exist in leg stiffness and vertical loading rate between runners with different foot types. Differences in lower extremity kinetics in individuals with different foot types may have implications for new treatment strategies or preventative measures.

Adolescent↗

PubMed2004

Kinematic adaptations during running: effects of footwear, surface, and duration.

UNLABELLED: Repetitive impacts encountered during locomotion may be modified by footwear and/or surface. Changes in kinematics may occur either as a direct response to altered mechanical conditions or over time as active adaptations. PURPOSE: : To investigate how midsole hardness, surface stiffness, and running duration influence running kinematics. METHODS: In the first of two experiments, 12 males ran at metabolic steady state under six conditions; combinations of midsole hardness (40 Shore A, 70 Shore A), and surface stiffness (100 kN x m, 200 kN x m, and 350 kN x m). In the second experiment, 10 males ran for 30 min on a 12% downhill grade. In both experiments, subjects ran at 3.4 m x s on a treadmill while 2-D hip, knee, and ankle kinematics were determined using high-speed videography (200 Hz). Oxygen cost and heart rate data were also collected. Kinematic adaptations to midsole, surface, and running time were studied. RESULTS: Stance time, stride cycle time, and maximal knee flexion were invariant across conditions in each experiment. Increased midsole hardness resulted in greater peak ankle dorsiflexion velocity (P = 0.0005). Increased surface stiffness resulted in decreased hip and knee flexion at contact, reduced maximal hip flexion, and increased peak angular velocities of the hip, knee, and ankle. Over time, hip flexion at contact decreased, plantarflexion at toe-off increased, and peak dorsiflexion and plantarflexion velocity increased. CONCLUSION: Lower-extremity kinematics adapted to increased midsole hardness, surface stiffness, and running duration. Changes in limb posture at impact were interpreted as active adaptations that compensate for passive mechanical effects. The adaptations appeared to have the goal of minimizing metabolic cost at the expense of increased exposure to impact shock.

Adaptation, Physiological↗

PubMed2003

Running training and adaptive strategies of locomotor-respiratory coordination.

It has been suggested that stronger coupling between locomotory and breathing rhythms may occur as a result of training in the particular movement pattern and also may reduce the perceived workload or metabolic cost of the movement. Research findings on human locomotor-respiratory coordination are equivocal, due in part to the fact that assessment techniques range in sensitivity to important aspects of coordination (e.g. temporal ordering of patterns, half-integer couplings and changes in frequency and phase coupling). An additional aspect that has not received much attention is the adaptability of this coordination to changes in task constraints. The current study investigated the effect of running training on the locomotor-respiratory coordination and the adaptive strategies observed across a wide range of walking and running speeds. Locomotor-respiratory coordination was evaluated by the strength and variability of both frequency and phase coupling patterns that subjects displayed within and across the speed conditions. Male subjects (five runners, five non-runners) locomoted at seven different treadmill speeds. Group results indicated no differences between runners and non-runners with respect to breathing parameters, stride parameters, as well as the strength and variability of the coupling at each speed. Individual results, however, showed that grouping subjects masks large individual differences and strategies across speeds. Coupling strategies indicated that runners show more stable dominant couplings across locomotory speeds than non-runners do. These findings suggest that running training does not change the strength of locomotor-respiratory coupling but rather how these systems adapt to changing speeds.

Adaptation, Physiological↗

PubMed2003

Limitations in the use and interpretation of continuous relative phase.

Continuous relative phase (CRP), a variable used to quantify intersegmental coordination, is difficult to interpret if care is not taken regarding the assumptions and limitations of the measure. Specifically, CRP is often interpreted as a higher resolution form of discrete relative phase (DRP). DRP, however, yields information regarding the relative dispersion of events in oscillatory signals while CRP describes their relationship in a higher order phase-plane domain. In this paper we address issues surrounding the calculation of CRP and suggest a new interpretation based on the aforementioned methodological issues. Through the use of test signals, with known properties, it was found that the CRP information will be arbitrary if no normalization procedures are used to account for frequency differences in the component oscillators. In addition, signals with non-sinusoidal trajectories will produce patterns in CRP that are not equivalent to discrete relative phase (DRP) measures. The implications of these issues are discussed.

Computer Simulation↗

PubMed2002

Relationship between shock attenuation and stride length during running at different velocities.

The purpose of the study was to investigate the characteristics of shock attenuation during high-speed running. Maximal running speed was identified for each subject [n = 8 males, 25 (SD 4.6) years; 80 (8.9) kg; 1.79 (0.06) m] as the highest speed that could be sustained for about 20 s on a treadmill. During testing, light-weight accelerometers were securely mounted to the surface of the distal antero-medial aspect of the leg and frontal aspect of the forehead. Subjects completed running conditions of 50, 60, 70, 80, 90, and 100% of their maximal speeds with each condition lasting about 20 s. Stride length, stride frequency, leg and head peak impact acceleration were recorded from the acceleration profiles. Shock attenuation was analyzed by extracting specific sections of the acceleration profiles and calculating the ratio of head to leg power spectral densities across the 10-20 Hz frequency range. Both stride length and stride frequency increased across speeds (P < 0.05) and were correlated with running speed (stride length r = 0.92, stride frequency r = 0.89). Shock attenuation increased about 20% per m x s(-1) across speeds (P< 0.05), which was similar to the 17% increase in stride length per m x s(-1). Additionally, shock attenuation was correlated with stride length (r = 0.71) but only moderately correlated with stride frequency (r = 0.40) across speeds. It was concluded that shock attenuation increased linearly with running speed and running kinematic changes were characterized primarily by stride length changes. Furthermore, the change in shock attenuation was due to increased leg not head peak impact acceleration across running speeds.

Acceleration↗

PubMed2002

Characteristics of the vertical ground reaction force component prior to gait transition.

The purpose of the study was to examine the vertical ground reaction force component when approaching the gait transition point from either a walk-to-run or run-to-walk perspective. The vertical ground reaction forces (VGRF) of five steps before gait transitions for both walk-to-run and run-to-walk were collected on a motor driven treadmill with embedded force plates. Transition specific characteristics of the VGRF were observed for both types of gait transition. Running peak force and time to peak force reduced dramatically in a quadratic fashion as approaching to the run-to-walk transition. The walking VGRF first peak increased linearly, and the second peak decreased quadratically prior to walk-to-run transition. Walking VGRF appearing to be more sensitive to acceleration than the running VGRF.

Acceleration↗