Appendix 1

Quality assessment
The quality of the articles was assessed with the PEDro scale. The criteria of this scale can be found in Table 3. The questions are given a value of 1 if “yes” can be answered and a value of 0 if “no” can be answered. The total sum of all the values is the final score (range 0-11 points). The questions given a value 1 is the end score, with a minimum value of 0 and a maximum value of 11. The reliability of the PEDro score is considered fair to good [37]. A study is considered to be of high quality when the summed score on questions 2 – 11 has a value equal to 6 or higher [38-40].
Next to the PEDro scale, 5 extra items are scored (see table 4), which can provide some extra insight into the quality of the studies, as they are tailored to studies investigating the effect of exercise in the treatment of RA.

Table 3 Scoring items of the PEDro scale (from Maher et al. [37])

Items of the PEDro scale
External validity
1 / The eligibility criteria were specified.
Internal and statistical validity
2 / The subjects were randomly allocated to groups.
3 / The allocation was concealed.
4 / The groups were similar at baseline on most important prognostic indicators.
5 / There was a blinding of all subjects.
6 / There was blinding of all therapists who administered the therapy.
7 / There was blinding of all assessors who measured at least one key outcome.
8 / Measurements of at least one key outcome were obtained from more than 85% of the subjects initially allocated to groups.
9 / All subjects from whom outcome measures were available received the treatment or control condition as allocated; where this was not the case, data for at least one key outcome were analyzed by “intention to treat”.
10 / The results of between-group statistical comparisons are reported for at least one key outcome.
11 / The study provides both point measurements and measurements of variability for at least one key outcome.
Table 4 Scoring items for this study
Scoring items for this study
1 / Are the hand deformities of the person with RA described?
2 / Is the disease duration described?
3 / Is medication use described?
4 / Are frequency, intensity and duration of the intervention described?
5 / Are functional outcomes included?
6 / Are new techniques / VR applications used in the intervention?

The results of the quality assessment are summarized in Table 5. Four of the 8 studies included in this review had a score higher than 6 on the PEDro scale, indicating a high quality. The other 4 studies scored a 4 or 5, indicating a lower quality. On the scoring items of this study, scores ranged from 1 to 4 out of 5. Descriptions that were particularly lacking according to these additional scoring items, were descriptions about hand deformities, medication used and the inclusion of functional outcomes. No new techniques / VR applications were used in the interventions.

Table 5 Results of the quality assessment

Authors [reference number] / PEDro scalea / Quality score items for this studyc
Buljina [17] / 7 / 3 2, 3, 4
O’Brien et al. [26] / 7 / 4 2, 3, 4, 5
Rapoliene & Krisciunas [28] / 4 / 3 2, 4, 5
Ronningen & Kjeken [16] / 4 / 1 1
Brorsson et al. [30] / 4 / 3 2, 4, 5
Speed & Campbell [29] / 5 / 2 2, 4
Cima [21] / 7 / 1 4
Dogu [27] / 8 / 4 1, 2, 3, 4

a Maximum score is 10. Score excludes the criterium for external validity, on which all articles scored positively.
b The full questions of the scoring items for this study are described in Table 4.
c Total score, with the number of the questions on which was scored positively in superscript. Maximum score is 5.