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Chris Hopkins

Declining physical function is common among aging adults; however, physical activity may decrease the rate of functional loss among adults with or at risk of developing osteoarthritis. Previous studies on this topic used subjective measures of physical activity and were subject to higher selection bias. This study employed propensity score matching techniques to reduce selection bias when measuring the association between objectively measured physical activity and future physical function. Participants (n = 687) of the Osteoarthritis Initiative were included in either a physically active group (n = 280) or a physically inactive group (n = 407) according to baseline accelerometer data. Participants’ performance on functional tests 4 years later was compared using both ordinary least squares linear regression and average treatment effects from propensity score matching. Analysis revealed physical activity to be associated with significantly better performance on a 400-m walk test, but not 20-m gait speed or chair stand tests.

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Marie A. Johanson, Megan Armstrong, Chris Hopkins, Meghan L. Keen, Michael Robinson, and Scott Stephenson


Stretching exercises are commonly prescribed for patients and healthy individuals with limited extensibility of the gastrocnemius muscle.


To determine if individuals demonstrate more dorsiflexion at the ankle/rear foot and less at the midfoot after a gastrocnemius-stretching program with the subtalar joint (STJ) positioned in supination compared with pronation.


Randomized controlled trial.


Biomechanical laboratory.


22 volunteers with current or recent history of lower-extremity cumulative trauma and gastrocnemius tightness (10 women and 4 men, mean age 28 y) randomly assigned to stretching groups with the STJ positioned in either pronation (n = 11) or supination (n = 11).


3-wk home gastrocnemius-stretching program using a template to place the subtalar joint in either a pronated or a supinated position.

Main Outcome Measures:

A 7-camera Vicon motion-analysis system measured ankle/rear-foot dorsiflexion and midfoot dorsiflexion of all participants during stretching with the STJ positioned in both pronation and supination before and after the 3-wk gastrocnemius-stretching program.


A 2-way mixed-model ANOVA revealed a significant interaction (P = .019). At posttest, the group who performed the 3-week stretching program with the STJ positioned in pronation demonstrated more increased ankle/rear-foot dorsiflexion when measured with the STJ in pronation than the group who performed the 3-wk stretching program with the STJ positioned in supination. No significant main effect of stretching group or interaction for dorsiflexion at the midfoot was detected (P = .755 and P = .820, respectively).


After a 3-wk gastrocnemius-stretching program, when measuring dorsiflexion with the STJ positioned in supination, the participants who completed a 3-wk gastrocnemius stretching program with the STJ positioned in pronation showed more increased dorsiflexion at the ankle/rear foot than participants who completed the stretching program with the STJ positioned in supination.