| Variation in methodology | Studies n | First author [ref.] | Effect on 6MWD |
| Hallway versus treadmill | 2 | Stevens [14] de Almeida [15] | 13–20% less on treadmill |
| Indoors versus outdoors | 1 | Brooks [16] | 4 m (1%) more outside |
| Circular versus straight track | 2 | Bansal [17] Sciurba [18] | 13–19 m (3–5%) more on circular track |
| Track length | 2 | Sciurba [18] Beekman [19] | No statistically significant difference in 6MWD from tracks of 15–121 m 50 m more on 30-m track compared to 10-m track |
| Wheeled walking aid versus no aid | 6 | Gupta [20] Honeyman [21] Probst [22] Roomi [23] Solway [24] Vaes [25] | Weighted mean 6.2% more with wheeled walker Range 2–46 m more with wheeled walker 83 m more with modern draisine compared to wheeled walker |
| With versus without oxygen | 4 | Davidson [26] Fujimoto [27] Rooyackers [28] Jolly [29] | 12–59 m more with oxygen |
| Oxygen versus compressed air | 2 | Jolly [29] McDonald [30] | 17–109 m more with oxygen |
| Carry oxygen versus oxygen in wheeled cart | 1 | Crisafulli [31] | 23 m more with wheeled cart |
| Patient carries oxygen versus tester carries oxygen | 1 | Woodcock [32] | 24 m versus 35 m improvement |
| Encouragement | 1 | Guyatt [33] | 30.5 m more with encouragement |
| Instructions | 1 | Weir [34] | 53 m further when asked to walk as “fast” as possible, rather than as “far” as possible |