Biomedical subjects

Mark D Grabiner

Publications and source records attributed to Mark D Grabiner.

21 records · Page 2Linked to original sources

PubMed2002

Influence of lower extremity strength of healthy older adults on the outcome of an induced trip.

OBJECTIVES: To determine whether decreased lower extremity strength contributes to trip-related falls in older adults. DESIGN: A cross-sectional sample of older adults were safety-harnessed and tripped while walking using a concealed, mechanical obstacle. Lower extremity strength was compared between trip outcome groups. SETTING: A biomechanics research laboratory. PARTICIPANTS: Seventy-nine healthy, community-dwelling adults aged 65 and older (50 women). MEASUREMENTS: Ankle, knee, and hip flexion and extension strength were measured isometrically and isokinetically. Measured strengths were subjected to a factor analysis. Strength factor scores were compared between those who recovered from the trip and those who fell by three previously identified mechanisms: during-step, after-step, and elevating-response falls. RESULTS: Seven common factors, one associated with each direction of exertion at each joint and one with the time rate of moment increase, explained 88% of the variance in measured strength. The during-step (n=5) fallers were significantly stronger in the ankle extension (plantarflexion), knee flexion, overall extension, and total strength factors than those who successfully recovered using a similar, lowering strategy (n=26). The elevating-response faller (n=1) was stronger in the plantarflexion and overall extension factors than most of those who recovered using a similar, elevating strategy (n=11). Two of three after-step fallers were among the weakest subjects tested. CONCLUSION: Weak older adults and the strongest older adults may be at greater risk of falling from a trip, although by different mechanisms. High strength may increase the likelihood of a during-step or elevating-response fall; decreased strength may increase the likelihood of an after-step fall.

Accidental Falls↗

PubMed2002

Can fall-related hip fractures be prevented by characterizing the biomechanical mechanisms of failed recovery?

Unintentional injuries are the seventh leading cause of death in adults ages 65 and older, and the greatest number of these deaths results from fall-related injuries. In addition to the startling mortality, the morbidity associated with fall-related injuries, particularly hip fractures, has become a research imperative. This article reviews a series of studies that was undertaken to determine the biomechanical reasons that older adults are unable to recover from very large postural perturbations that are applied during locomotion that, if not corrected, can lead to a fall. Our protocol involves causing older adults to trip unexpectedly while walking normally in the laboratory. The results from this series of experiments were used to design an experiment that characterized the biomechanical similarities between recovery biomechanics after an induced trip and those following a large postural perturbation delivered by a motorized treadmill. Collectively, we have been able to document different recovery strategies and categories of falls by older adults following an induced trip; the biomechanical causes of these falls by older adults; and the very rapid motor adaptations that occur with repeated exposure to large perturbations that may be protective against falls from tripping and, therefore, reduce the substantial fall-related morbidity and mortality in older adults.

Accidental Falls↗

PubMedDate not supplied

Motor control of the vastus medialis oblique and vastus lateralis muscles is disrupted during eccentric contractions in subjects with patellofemoral pain.

BACKGROUND: Inappropriate control of the vastus medialis oblique and vastus lateralis muscles by the central nervous system can contribute to maltracking of the patella. HYPOTHESIS: The activation timing and amplitude of the vastus medialis oblique and vastus lateralis muscles will be different between normal subjects and patients with patellofemoral pain. STUDY DESIGN: Controlled laboratory study. METHODS: Subjects with patellofemoral pain and asymptomatic control subjects performed maximum voluntary knee extension contractions initiated from a flexed and an extended position. The activation timing and amplitude of the vastus lateralis and vastus medialis oblique muscles were quantified from the recorded electromyographic signals. RESULTS: There were no between-group differences in activation timing. The activation amplitude of the vastus medialis oblique and vastus lateralis muscles of the patellofemoral pain subjects was altered to the greatest extent during eccentric contractions and differed significantly from that of control subjects. CONCLUSIONS: The activation amplitudes of the vastus medialis oblique and vastus lateralis muscles of subjects with patellofemoral pain are consistent with a laterally tracking patella during eccentric contractions. CLINICAL RELEVANCE: The findings suggest the clinical importance of determining whether altered activation patterns are sensitive to rehabilitation, and, if so, if subjective reports of knee joint pain and function parallel changes in the activation patterns as a result of rehabilitation.

Adult↗