Physical Function Tests (PFTs) were introduced in Visit 5 (1988) and included in each subsequent RBS visit except visit 12. Participants completed performance-based measurements of lower extremity physical function tasks and grip strength. All tests were administered by trained, certified personnel, with consistent administration and scoring across visits.
Grip strength was measured using a handheld dynamometer in each hand twice, and the maximum grip strength (kg) of each hand was recorded. Grip strength was measured with arm bent at a 90 degree angle at the elbow, forearm parallel to the floor, with arm not touching the body. The participant squeezed the dynamometer maximally while lowering the arm on during a 3 second count. The examiner noted if the participant had Heberden’s nodes (hard nodules on distal finger joints) present on two or more fingers.
Single Chair Stand: With arms folded and feet flat on floor, participants were asked to stand up from a seated position in a chair. Ability to complete this move without using their arms was noted.
Time Chair Stand. With arms folded and feet flat on floor, participants were asked to stand up straight from a seated position in a chair five times without using their arms and moving as quickly as possible without stopping. Time to completion was recorded in seconds.
Gait Observation Participants ambulated for an examiner and were assessed with respect to limp, shuffle, arm swing and speed.
Tandem walking. Participants were asked to walk heel to toe in close succession for six steps. Participants were scored based on number of steps successfully performed. If participant initially had difficulty, but was able to perform the test, this was indicated in the scoring.
Timed “Up and Go” Test (3 meter). Participants were asked to stand up from a seated position in an arm chair, walk to specified point 3 meters distance, turn around walk back and sit down. Participants were instructed to walk at their usual pace. Time to complete was scored in seconds. The task was performed twice.
One leg stand. With shoes removed, participants were asked to stand on one leg for 30 seconds, with eyes open. Each leg was tested. Participants were allowed up to 5 attempts for each leg to reach 30 seconds. Number of attempts and longest number of seconds was recorded.
Nottingham Power Rig. Leg extension power (watts) was measured on the Nottingham Power Rig (University of Nottingham, Nottingham, England) on participants younger than 80 years of age. Participants were asked to complete three trials per leg.
6 Meter Usual Pace. Time to complete (sec) and number of steps was measured as participants walked a 6-m course at usual pace. Participants were asked to complete two trials.
20 cm Narrow Walk. Time to complete (sec) and number of steps was measured as participants walked a narrow (20 cm wide) 6-m course at usual pace. The trial was scored as “unable to assess” if the participant stepped on or outside the line more than twice. Participants were allowed three attempts. If the first two attempts were successful (2 or fewer deviations from the marked course), the third trial was not administered.