Table 1. Baseline Participant Demographic Characteristics and Health-Related Variables.
| Characteristic | Health-related variable, No. (%) | |||||||
|---|---|---|---|---|---|---|---|---|
| Total (n = 1194) | Weekly strenuous PA trajectory subgroup (n = 1194) | Extensive sitting trajectory subgroup (n = 1194) | ||||||
| Persistently no | Low, slightly improving | Moderate, declining | High, improving | High frequency | Moderate frequency | Low frequency | ||
| No. (%) | 594 (49.7) | 354 (29.6) | 151 (12.6) | 95 (8.0) | 121 (10.1) | 386 (32.3) | 687 (57.5) | |
| Age, mean (SD), y | 58.4 (8.9) | 59.4 (9.0) | 57.2 (8.8) | 58.5 (9.2) | 56.3 (7.5) | 61.1 (8.9) | 59.6 (9.2) | 57.3 (8.6) |
| Women | 697 (58.4) | 357 (60.1) | 218 (61.6) | 84 (55.6) | 38 (40.0) | 64 (52.9) | 214 (55.4) | 419 (61.0) |
| Race/ethnicity (white/Caucasian) | 1014 (84.9) | 475 (80.0) | 318 (89.8) | 134 (88.7) | 87 (91.6) | 99 (81.8) | 319 (82.6) | 596 (86.8) |
| Educational level, ≥college graduate | 789 (66.1) | 333 (56.1) | 257 (72.6) | 121 (80.1) | 78 (82.1) | 71 (58.7) | 246 (63.7) | 472 (68.7) |
| BMI, mean (SD) | 26.8 (4.5) | 27.2 (4.6) | 26.6 (4.5) | 26.0 (4.3) | 25.7 (4.0) | 28.0 (5.0) | 27.1 (4.6) | 26.4 (4.3) |
| Comorbidities, mean (SD), No. | 0.3 (0.8) | 0.4 (0.8) | 0.3 (0.8) | 0.2 (0.6) | 0.2 (0.6) | 0.6 (1.1) | 0.4 (1.0) | 0.2 (0.5) |
| Depressive symptoms, yesa | 98 (8.2) | 66 (11.1) | 18 (5.1) | 6 (4.0) | 8 (8.4) | 14 (11.6) | 30 (7.8) | 54 (7.9) |
| Gait speed, mean (SD), m/s | 1.4 (0.2) | 1.3 (0.2) | 1.4 (0.2) | 1.4 (0.2) | 1.4 (0.2) | 1.3 (0.2) | 1.4 (0.2) | 1.4 (0.2) |
| WOMAC pain, mean (SD)b | 2.3 (2.9) | 2.9 (3.4) | 1.8 (2.3) | 1.7 (2.0) | 1.2 (1.8) | 3.0 (3.6) | 2.3 (2.8) | 2.1 (2.8) |
| WOMAC function, mean (SD)c | 6.5 (9.2) | 8.4 (10.8) | 4.7 (6.9) | 4.8 (6.7) | 3.6 (6.8) | 9.1 (11.6) | 6.7 (9.2) | 5.9 (8.7) |
| Knee extensor strength, mean (SD), N | 324 (123) | 312 (124) | 323 (117) | 334 (119) | 393 (129) | 308 (119) | 320 (123) | 329 (123) |
| History of knee injury, yes | 393 (32.9) | 188 (31.6) | 110 (31.1) | 60 (39.7) | 35 (36.8) | 46 (38.0) | 124 (32.1) | 223 (32.5) |
| History of knee surgery, yes | 110 (9.2) | 45 (7.6) | 32 (9.0) | 19 (12.6) | 14 (14.7) | 9 (7.4) | 37 (9.6) | 64 (9.3) |
| Hip pain, yes | 285 (23.9) | 158 (26.6) | 80 (22.6) | 31 (20.5) | 16 (16.8) | 35 (28.9) | 99 (25.6) | 151 (22.0) |
| Ankle pain, yes | 72 (6.0) | 51 (8.6) | 15 (4.2) | 4 (2.6) | 2 (2.1) | 8 (6.6) | 27 (7.0) | 37 (5.4) |
| Foot pain, yes | 89 (7.5) | 51 (8.6) | 26 (7.3) | 8 (5.3) | 4 (4.2) | 10 (8.3) | 28 (7.3) | 51 (7.4) |
| Lack of knee confidence, yes | 167 (14.0) | 102 (17.2) | 39 (11.0) | 16 (10.6) | 10 (10.5) | 24 (19.8) | 59 (15.3) | 84 (12.2) |
| Modified lifestyle to avoid knee-damaging PA, yes | 244 (20.4) | 134 (22.6) | 73 (20.6) | 22 (14.6) | 15 (15.8) | 28 (23.1) | 87 (22.5) | 129 (18.8) |
| Restless sleep, yes | 673 (56.4) | 349 (58.8) | 186 (52.5) | 85 (56.3) | 53 (55.8) | 81 (66.9) | 211 (54.7) | 381 (55.5) |
Abbreviations: BMI, body mass index (calculated as weight in kilograms divided by height in meters squared); N, newton; PA, physical activity; WOMAC, Western Ontario and McMaster Universities Osteoarthritis Index.
a
Center for Epidemiologic Studies Depression scale score 16 or greater.
b
WOMAC pain subscale score range: 0-20, with high scores indicating more severe pain.
c
WOMAC function subscale score range: 0-68, with high scores indicating worse function.