Biomedical subjects

Michael L Madigan

Publications and source records attributed to Michael L Madigan.

12 recordsLinked to original sources

PubMed2006

Influence of fatigue time and level on increases in postural sway.

The purpose of this study was to investigate the influence of fatigue time and fatigue level on the increases in postural sway during quiet standing. Centre of pressure-based measures of postural sway were collected both before and after fatiguing participants using three different fatigue levels and two different fatigue times. Results showed increasing fatigue time increased sway velocity and sway area, and increasing fatigue level increased sway velocity. Fatigue time effects are important to consider when applying laboratory-based findings to the field given that the fatigue time can differ substantially between the two. Fatigue level effects imply a dose - response relationship between localized muscle fatigue and risk of falling that can have important implications in work/rest cycle scheduling for occupations at risk of injurious falls.

Accidental Falls↗

PubMed2006

Practicing recovery from a simulated trip improves recovery kinematics after an actual trip.

The goal of this study was to determine if practicing recovery from a simulated trip improved the ability of older adults to recover from an actual trip. Twelve healthy older adults ranging in age from 63 to 83 years were randomly assigned to either a control or an experimental group. Each group performed one trip before and one trip after an intervention. The experimental group received trip recovery training on a modified treadmill while the control group walked on a treadmill for 15 min. Compared to the control group, the experimental group showed greater reduction in maximum trunk angle (p=0.027) and time to maximum trunk angle (p=0.043), as well as increased minimum hip height (p=0.020). Although the results showed beneficial effects of trip recovery training on actual trip recovery, future studies should explore the ability to retain improvements over extended periods.

Accidental Falls↗

PubMed2006

Postural sway and joint kinematics during quiet standing are affected by lumbar extensor fatigue.

The purpose of this study was to investigate changes in postural sway and strategy elicited by lumbar extensor muscle fatigue. Specifically, changes in center of mass (COM), center of pressure (COP), and joint kinematics during quiet standing were determined, as well as selected cross correlations between these variables that are indicative of movement strategy. Twelve healthy male participants stood quietly both before and after exercises that fatigued the lumbar extensors. Whole-body movement and ground reaction force data were recorded and used to calculate mean body posture and variability of COM, COP, and joint kinematics during quiet standing. Three main findings emerged. First, participants adopted a slight forward lean post-fatigue as evidenced by an anterior shift of the COM and COP. Second, post-fatigue increases in joint angle variability were observed at multiple joints including joints distal to the fatigued musculature. Despite these increases, anterior-posterior (AP) ankle angle correlated well with AP COM position, suggesting the body still behaved similar to an inverted pendulum. Third, global measures of sway based on COM and COP were not necessarily indicative of changes in individual joint kinematics. Thus, in trying to advance our understanding of how localized fatigue affects movement patterns and the postural control system, it appears that joint kinematics and/or multivariate measures of postural sway are necessary.

Adult↗

PubMed2006

Effects of fatigue and gender on peroneal reflexes elicited by sudden ankle inversion.

The purpose of this study was to investigate the effects of neuromuscular fatigue and gender on peroneus brevis muscle (PB) and peroneus longus muscle (PL) reflexes elicited by sudden ankle inversion. Sixteen males and fifteen females stood on a "trap-door" platform that suddenly inverted the ankle 20 degrees when released. The resulting movement elicited peroneal reflexes. Reflex measurements were collected both before and after fatiguing the ankle evertors. Reflex delay in the PB and PL was not affected by fatigue, gender, or their interaction. Reflex amplitude in the PL exhibited no main effect of fatigue or gender, but their interaction was significant. Pairwise comparisons revealed PL reflex amplitude decreased by 11.3% in males (p=0.008) and increased 22.1% in females (p=0.003) with fatigue. A similar trend was found in the PB, but was not statistically significant. This opposite effect in females and males may be due to differences in how males and females compensate for fatigue, and may be related to the gender difference in ankle injury rate.

Adolescent↗

PubMed2006

Effect of lumbar extensor fatigue on paraspinal muscle reflexes.

Low back disorders are a frequent medical problem. Altered neuromuscular control of the spine has been associated with low back pain, and may contribute to its occurrence. The purpose of this study was to investigate the effect of lumbar extensor fatigue on reflex delay and amplitude in the paraspinal muscles. Ten healthy males (20-22 years of age) were subjected to an anteriorly-directed perturbation applied at the inferior margin of the scapulae while standing quietly before and after a lumbar extensor fatiguing protocol. The fatiguing protocol consisted of multiple sets of back extensions and intermittent isometric maximum voluntary contraction on a Roman chair for 14 min until 60% of unfatigued lumbar extensor MVC was reached. Reflexes were recorded from the paraspinal muscles at the level of L4. Results indicated the mean reflex delay was 60+/-18 ms and was not affected by fatigue (p=0.278). Reflex amplitude increased 36+/-32% with fatigue (p=0.017). The increase in reflex amplitude may reflect an attempt to compensate for losses in muscle force capacity with fatigue in order to maintain sufficient spinal stability. However, additional studies are necessary to investigate the mechanisms of this fatigue-related change in paraspinal reflex.

Adult↗

PubMed2006

Age-related differences in muscle power during single-step balance recovery.

The purpose of this study was to investigate age-related differences in muscle power during a surrogate task of trip recovery. Participants included 10 healthy young men (19-23 years old) and 10 healthy older men (65-83). The task involved releasing participants from a forward-leaning posture. After release, participants attempted to recover their balance using a single step of the right foot. Muscle power at the hip, knee, and ankle of the stepping limb were determined from the product of joint angular velocity and joint torque. Muscle powers during balance recovery followed a relatively consistent pattern in both young and older men, and showed effects of both lean and age. Interestingly, the effects of age did not always involve smaller peak power values in the older men as expected from the well-documented loss of muscle power with aging. Older men exhibited smaller peak muscle power at the knee and larger peak muscle power at the ankle and hip compared to young men. The increases in muscle power at the ankle and hip may result from a neuromuscular adaptation aimed at improving balance recovery ability by compensating for the age-related loss of muscle function.

Adult↗

PubMed2005

Lumbar extensor fatigue and circumferential ankle pressure impair ankle joint motion sense.

Fatigue of the lumbar extensor muscles has been associated with a degradation of balance, but the mechanism is not well understood. The ankle plays a major role in upright standing, and loss of proprioceptive acuity at the ankle could contribute to a degradation of balance. Therefore, the first objective of this study was to investigate the effect of lumbar extensor fatigue on ankle proprioceptive acuity. The second objective was to investigate the effect of circumferential ankle pressure (CAP) on ankle proprioceptive acuity to evaluate CAP as a potential intervention to mitigate any loss of proprioceptive acuity at the ankle with lumbar extensor fatigue. To address these objectives, ankle joint motion sense was evaluated with and without CAP, both before and after the lumbar extensors were fatigued. Results showed an impairment in joint motion sense with both fatigue and CAP. These results indicate that lumbar extensor fatigue impairs ankle proprioceptive acuity, which may help explain observed increases in postural sway subsequent to lumbar extensor fatigue.

Adaptation, Physiological↗

PubMed2005

Postural strategy changes with fatigue of the lumbar extensor muscles.

The purpose of this study was to investigate the effect of lumbar extensor fatigue on postural strategy in response to a balance perturbation. Anteriorly-directed force perturbations were applied to the upper back with a padded pendulum and attempted to challenge the postural control system without eliciting a stepping response. In three separate sessions, subjects were perturbed both before and after a fatiguing protocol that induced lumbar extensor fatigue to one of three different fatigue levels. Postural strategy was quantified using center of pressure position along with joint angles and joint torques for the ankle, knee, hip, and "low back" joints. Results showed both proactive and reactive changes in postural strategy. Proactive changes involved a slight anterior lean prior to the perturbation, and reactive changes were consistent with a shift toward more of a hip strategy with fatigue. In addition, results suggested that subjects classified as moving mostly at the hip prior to fatigue were more affected by fatigue compared to subjects classified as moving roughly equal amounts at the ankle and hip prior to fatigue. Increasing fatigue level exaggerated some, but not all, of the changes in postural strategy with fatigue. These findings illustrate that neuromuscular fatigue can influence postural strategy in response to a balance perturbation.

Adult↗

PubMed2005

Age and stepping limb performance differences during a single-step recovery from a forward fall.

BACKGROUND: The purpose of this study was two-fold: 1) to evaluate any age-related differences in peak joint velocities of the stepping limb during single-step recovery from a forward fall, and 2) to determine if the ability to recover from a forward fall with a single step differs when stepping with the dominant or nondominant lower limb (LL). METHODS: Ten young (19-23 years old) and ten older (65-83 years old) men were released from forward-leaning positions and attempted to recover their balance with a single step. Lean magnitude was increased until the men failed to recover their balance with a single step. The men performed the experiment twice, once while stepping with the dominant LL and once while stepping with the nondominant LL, to determine if the ability to recover from a forward fall is limb dependent. Peak joint velocities during single-step recoveries were determined. RESULTS: No age-related differences in peak joint velocities were found during recovery from small lean magnitudes, but older men exhibited slower velocities during recovery from maximum lean magnitudes. There was no difference in the maximum lean magnitude achieved by the men when stepping with the dominant or nondominant LL. CONCLUSIONS: The previously reported age-related reduction in stepping speed seems to be due to localized reductions in maximum hip flexion velocity, knee flexion and extension velocity, and ankle plantar flexion velocity. Also, the ability of young and older men to recover from a forward fall with a single step does not seem to be limb dependent.

Accidental Falls↗

PubMed2005

Age-related differences in peak joint torques during the support phase of single-step recovery from a forward fall.

BACKGROUND: Previous studies have reported that older adults have a reduced ability to recover balance with a single step after a forward-induced fall. To better understand the reasons for this reduced ability, this study investigated any age-related differences in peak joint torques during the support phase of a single-step balance recovery from a forward fall. METHODS: Ten young (19-23 years old) and 10 older (65-83 years old) men were released from forward-leaning positions and attempted to recover their balance with a single step. Lean was increased until they failed to recover their balance with a single step. Peak extensor torques were calculated for the support phase of balance recovery and were compared across age groups. RESULTS: A consistent pattern of joint torques emerged during the support phase of balance recovery, suggesting a similar strategy across young and older participants. Despite this similarity, older participants exhibited smaller peak knee extensor torques during the support phase of single-step balance recoveries, and trends toward larger peak extensor torques at the hip and ankle. CONCLUSIONS: The age-related differences found are believed to be the combined result of an age-related reduction in muscle strength and an age-related neuromuscular adaptation to mitigate the effects of muscle strength loss on physical performance capabilities.

Accidental Falls↗

PubMed2003

Changes in landing biomechanics during a fatiguing landing activity.

The objective of this study was to investigate the effects of LE fatigue on ground impact force, LE kinematics, and LE kinetics during landing. Ground reaction force (GRF), kinematic, and electromyogram (EMG) data were collected from 12 male subjects during a fatiguing landing activity (FLA). This activity allowed not only the biomechanical differences between unfatigued and fatigued landings to be determined, but also the time history of multiple biomechanical variables as fatigue progressed. EMG mean frequency analysis using data collected immediately before and after the FLA indicated that subjects experienced fatigue of the quadriceps muscles. Results indicated a decrease in ground impact force and an increase in maximum joint flexion during landing with fatigue. Joint impulse values were consistent with a distal to proximal redistribution of extensor moment production. Potential reasons for this redistribution are discussed. A trend reversal in hip and ankle impulse during the activity suggest a change in landing strategy as fatigue progressed. The data also suggest that the measured changes in landing biomechanics may have been influenced by other factors, in addition to fatigue, such as a neuromuscular protective mechanism to decrease impact force magnitude.

Adult↗

PubMed2002

A muscle temperature compensation technique for EMG fatigue measures.

PURPOSE: The use of electromyogram-based fatigue measurements during high-intensity, dynamic activities is confounded by the accompanying increase in muscle temperature. The purpose of this communication was to demonstrate the use of a muscle temperature compensation technique for electromyogram (EMG) fatigue measurements. METHODS: Subjects were six healthy men (mean age 30.8 +/- 5.6 yr) with no recent history of lower extremity injury. In part 1 of this study, the relationship between muscle temperature and EMG mean power frequency was determined for the vastus lateralis muscle (VL). The VL was heated with diathermy to a temperature of approximately 39 degrees C. Isometric EMG data were collected during the performance of a nonfatiguing protocol as the muscle cooled (39-34 degrees C). In part 2 of this study, the subjects rode a lower-extremity ergometer at workloads of 25%, 50%, and 75% of their VO2max. Isometric EMG and intramuscular temperature data were collected from the VL during intermittent interruptions of the activity. The relationship between muscle temperature and EMG mean power frequency established in part 1 was used with the measured change in muscle temperature to correct for the effect of temperature on the EMG mean power frequency. RESULTS: The results from part 1 revealed a linear relationship between EMG mean power frequency and muscle temperature (N = 5, mean slope = 2.82 +/- 0.27 Hz. degrees C-1, R2 = 0.88 +/- 0.02). The mean slope was used as a muscle temperature compensation factor that quantified the influence of muscle temperature on EMG mean power frequency. For part 2, representative data from a single subject are presented to demonstrate the use of the muscle temperature compensation technique. CONCLUSION: A muscle temperature compensation technique for EMG mean power frequency analysis has been demonstrated. This technique corrects for the detrimental influence of muscle temperature changes on EMG fatigue measurements, thereby improving the efficacy of EMG fatigue measurements during high-intensity, dynamic activities that result in muscle temperature increases.

Electromyography↗