M. Melissa Gross, Ph.D. | Institute of Gerontology

Assistant Research Scientist, IoG
Assistant Professor
Division of Kinesiology

3040D CCRB
Ann Arbor, MI 48109-2214
Tel: (734) 764-9663
Fax: (734) 936-1925
Email: mgross@umich.edu

Dr. Gross engages in research on human movement that relates biomechanics and motor control. Her work focuses on the effects of age-related changes in the musculoskeletal system on movement strategies used by mid-aged women and the elderly.

In recent years Dr. Gross has worked with IoG faculty member Neil Alexander to understand the role of muscle strength in mobility of frail elderly individuals. They studied the effects of an exercise intervention on a variety of chair-rise tasks that challenge both strength and balance. Results showed that the exercise intervention enabled some of the exercise subjects to perform more of the tasks, to get out of the chair more quickly, and to modify their body position during the tasks in a manner that was consistent with the way young adults rise from a chair. Both muscle strength and balance performance were related to the biomechanics of the chair-rise over progressively more difficult chair configurations.

Working with Ph.D. student Huei-Ming Chai, Gross studied self-induced perturbations of dynamic balance in the elderly during reaching tasks. Results of that study indicated that functional reach distance and center of pressure (COP) excursion decreased with age for the forward reach direction, suggesting that age-related differences in initial posture might affect the dynamic balance. Functional reach distance decreased for reaches to the side, but COP excursion did not, suggesting that dynamic balance results for sagittal plane reaches may not apply to other directions. Results also showed that initial posture significantly affected functional reach distance, COP excursion, and safety margin, but not absolute reach distance, indicating that initial posture may confound the age differences in dynamic balance measures. Movement velocity, however, affected functional reach distance and absolute reach distance, but not COP excursion or safety margin. It was concluded that the functional reach distance, COP excursion, and safety margin measure different aspects of dynamic balance.

Currently, Gross is working with MaryFran Sowers in Epidemiology on an NIH-funded project to investigate functional ability in women transitioning the menopause. Clinical assessment of reach, sit-to-stand, lift, stair climb and gait are assessed together with the kinematics of stair climb, lift and gait in women aged 47-52 years. Preliminary results suggest that functional ability is already decreased in some of the mid-aged women, and that the biomechanical measures are sensitive to the changes in functional ability.

Publications:

Gross, M.M., Stevenson, P.J., Charette, S.L., Pyka, G. and Marcus, R. Effect of muscle strength and movement speed on chair-rise biomechanics in young and healthy elderly women. Gait & Posture, 8:175-185, 1998.

Chai, H.-M. Dynamic balance control during maximum reach movements. University of Michigan Dissertation, 2000.

Alexander, N.B., Gross, M.M , Medell, J.M., and Hofmeyer, MR. Effects of functional ability and training on chair-rise biomechanics in older adults. Journal of Gerontology: Medical Sciences, 56A:M538-M547, 2001.