Table 3. Baseline and Adjusted Secondary and Post Hoc Outcomes at the 18-Month Follow-up in a Study of the Effect of High-Intensity Strength Training on Knee Pain and Knee Joint Compressive Forces Among Patients With Knee Osteoarthritisa.
| Outcomes | Intensity | Control | Mean difference (95% CI) | P valuea | |
|---|---|---|---|---|---|
| High | Low | ||||
| Prespecified secondary outcomes | |||||
| WOMAC function (0-68) | |||||
| Baseline, mean (SD) | 25.5 (10.3) | 26.6 (10.7) | 25.0 (10.3) | ||
| 18 mo, adjusted means (95% CI)b | 17.8 (15.9 to 19.7) | 14.9 (13.0 to 16.8) | 16.4 (14.4 to 18.4) | ||
| No. | 88 | 89 | 88 | ||
| High intensity vs control | 1.4 (−1.3 to 4.1) | .32 | |||
| High intensity vs low intensity | 2.9 (0.2 to 5.6) | .03 | |||
| Low intensity vs control | −1.5 (−4.3 to 1.2) | .27 | |||
| 6-Minute walk distance, m | |||||
| Baseline, mean (SD) | 466 (91) | 479 (90) | 490 (92) | ||
| 18 mo, adjusted means (95% CI) | 508 (492 to 525) | 514 (497 to 530) | 515 (497 to 532) | ||
| No. | 73 | 75 | 67 | ||
| High intensity vs control | −6 (−31 to 18) | .62 | |||
| High intensity vs low intensity | −5 (−29 to 18) | .67 | |||
| Low intensity vs control | −1 (−25 to 23) | .94 | |||
| Knee extensor strength, Nm | |||||
| Baseline, mean (SD) | 72.6 (31.2) | 75.1 (30.2) | 75.9 (32.8) | ||
| 18 mo, adjusted means (95% CI) | 98.5 (94.2 to 102.8) | 93.2 (88.9 to 97.6) | 88.5 (84.0 to 93.0) | ||
| No. | 79 | 78 | 75 | ||
| High intensity vs control | 10.0 (3.8 to 16.2) | .002 | |||
| High intensity vs low intensity | 5.3 (−0.8 to 11.4) | .09 | |||
| Low intensity vs control | 4.7 (−1.5 to 10.9) | .13 | |||
| Hip abductor strength, Nm | |||||
| Baseline, mean (SD) | 62.8 (22.7) | 66.9 (25.4) | 64.7 (22.6) | ||
| 18-mo, adjusted means (95% CI) | 74.6 (71.5 to 77.6) | 74.6 (71.6 to 77.6) | 69.5 (66.5 to 72.6) | ||
| No. | 74 | 77 | 73 | ||
| High intensity vs control | 5.0 (0.7 to 9.3) | .02 | |||
| High intensity vs low intensity | −0.0 (−4.3 to 4.2) | .99 | |||
| Low intensity vs control | 5.0 (0.8 to 9.3) | .02 | |||
| Thigh muscle volume, cm3 | |||||
| Baseline mean (SD) | 662 (183) | 685 (188) | 661 (171) | ||
| 18 mo, adjusted means (95% CI) | 672 (657 to 687) | 679 (664 to 694) | 670 (655 to 685) | ||
| No. | 73 | 76 | 75 | ||
| High intensity vs control | 2 (−20 to 23) | .89 | |||
| High intensity vs low intensity | −8 (−29 to 13) | .48 | |||
| Low intensity vs control | 9 (−12 to 30) | .39 | |||
| Thigh fat volume, cm3 | |||||
| Baseline, mean (SD) | 736 (367) | 712 (351) | 750 (342) | ||
| 18 mo, adjusted means (95% CI) | 712 (683 to 740) | 721 (693 to 749) | 709 (681 to 737) | ||
| No. | 73 | 76 | 75 | ||
| High intensity vs control | 3 (−37 to 42) | .89 | |||
| High intensity vs low intensity | −10 (−49 to 30) | .63 | |||
| Low intensity vs control | 12 (−27 to 51) | .54 | |||
| Log IL-6c | |||||
| Baseline, mean (SD) | 1.0 (0.7) | 0.9 (0.6) | 0.9 (0.7) | ||
| 18 mo, adjusted means (95% CI) | 0.9 (0.8 to 1.0) | 0.9 (0.8 to 1.0) | 0.9 (0.8 to 1.0) | ||
| No. | 88 | 93 | 85 | ||
| High intensity vs control | 0.0 (−0.1 to 0.2) | .88 | |||
| High intensity vs low intensity | 0.0 (−0.1 to 0.2) | .58 | |||
| Low intensity vs control | −0.0 (−0.2 to 0.1) | .70 | |||
| Joint space width, mm | |||||
| Baseline, mean (SD) | 3.1 (1.3) | 3.0 (1.5) | 3.0 (1.4) | ||
| 18 mo, adjusted means (95% CI) | 2.9 (2.8 to 3.1) | 2.8 (2.7 to 2.9) | 2.8 (2.6 to 2.9) | ||
| No. | 83 | 84 | 81 | ||
| High intensity vs control | 0.2 (−0.0 to 0.4) | .054 | |||
| High intensity vs low intensity | 0.1 (−0.0 to 0.3) | .12 | |||
| Low intensity vs control | 0.0 (−0.1 to 0.2) | .68 | |||
| Post hoc outcome | |||||
| Knee flexor strength, Nm | |||||
| Baseline mean (SD) | 35.0 (20.1) | 38.2 (20.3) | 38.1 (22.5) | ||
| 18 mo, adjusted means (95% CI) | 51.5 (48.7 to 54.3) | 52.6 (49.7 to 55.4) | 43.8 (40.9 to 46.8) | ||
| No. | 79 | 78 | 75 | ||
| High intensity vs control | 7.6 (3.6 to 11.7) | <.001 | |||
| High intensity vs low intensity | −1.1 (−5.1 to 2.9) | .59 | |||
| Low intensity vs control | 8.7 (4.7 to 12.7) | <.001 | |||
Abbreviation: WOMAC, Western Ontario and McMaster Universities Osteoarthritic Index.
a
Pairwise treatment group comparisons performed at the .05 significance level for testing 18-month effect.
b
The model-adjusted outcomes used only participants with complete follow-up data and were adjusted for sex, baseline BMI, and baseline outcome values. Sensitivity analyses were conducted to multiply impute data for participants with missing data under the assumption that data were missing at random (eTable 2 in Supplement 2).
c
Log-transform data presented because IL-6 data in pg/mL do not meet the assumption of normality. This aligns with the statistical comparisons that were based on the log-transformed data.