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Table 1 Selected studies: summary of studies in order of level of evidence, with extracted data

From: The effectiveness of a chair intervention in the workplace to reduce musculoskeletal symptoms. A systematic review

Author (ref) Country Design n Population Intervention Measures Outcomes Conclusion Notes
Wang et al. 2008[17] USA RCT 293 (subset of operators with Rempel 2007 with lower p) Group n= (111;84;98) Sewing machine operators with back /hip pain Gp 1: control Pre and post monthly for 4/12: Pain symptoms- intensity (1-5) and frequency Mean pain Improv’t gp 2 vs 1: 0.25(95%CI: 0.16, 0.34);GP3 vs 1: 0.43 (0.34-0.51) per month. Adjustable, swivelling chairs offer advantage (reduction in LB/Hip pain) for workers in seated/UL occupations; flat pan superior to curved? Obtain means and sd for pain scores for each group (presented graphically in Fig 5A) at 4/12f/u
Gp2: curved pan chair
Gp 3: flat seat pan chair (all received misc items, chairs hgt adjustable)
Remple et al. 2008[19] USA RCT 277 (subset with upper p) Group n pain (105;72;100) Sewing machine operators with neck/ shoulder pain Gp 1: control Gp2: curved pan chair Gp 3: flat seat pan chair (all received miscel items; intervention chairs hgt adjustable) Pre and post monthly for 4/12: Pain symptoms- intensity (1-5) and frequency Mean pain Improv’t gp 2 vs 1: 0.34 (95% CI: 0.28, 0.41); GP3 vs 1: 0.14 (.07-.022) per month. Adjustable, swivelling chairs offer advantage (reduction in Cx/shoulder pain) for workers in seated/ UL occupations; curved pan superior to flat? Obtain means and sd for pain scores for each group (presented graphically in Fig 5A) at 4/12f/u
Amick et al. 2003[4] USA RCT (assigned according to office location) 192(87;52;S3) Office workers (>4hrs per day at computer;>6 hrs per day sitting) Gp1: adjustable chair + training Pre (2xmonthly) and post intervention (3x over 1 year). Musculo- skeletal symptoms-1. Growth over workday 2. Average pain over workday Symptom growth over workday: Gp 1<gp2/3 at 12/12f/u (p=0.012). Ave pain levels: Reduced for both Gp 1+2 compared to Gp3 Highly adjustable chairs plus training resulted in less end of day pain and reduced average pain (largest reduction in neck/shoulder, followed by upper and lower back) Cant separate chair as sole intervention but clear that chair + info is superior to info alone or nothing.
Gp2: training only
Gp3: no intervention
Herbert et al. 2001 [20 USA Pre and post test 36 Garment workers (“spooling” task), female Adjustable chairs and training in their use MS symptom survey prior to and 6/12 after introduction. Joint position in sitting via video (subgroup only). Upper limbs only. Baseline pain report89% of group; post 63.9% (p=0.007); Reduction in severity at 10/11 anatomic sites after intervention. Only modest declines in awkward posture (small n) Reduction in people with pain and reduction in severity overall at upper limb anatomical sites. Inconclusive posture change findings.  
Gadge et al. 2007[18] Australia Sungle case, multiple baseline (ABAB) 4 University students (sitting “most of the time”) Standard office chair (adjustable) vs “saddle” seat (dis) Comfort (VAS); Production (typing task speed and accuracy); Posture (videotape) Multiple measures across 4 phases. Discomfort in lower back increased over time in both chairs but less so in the saddle; discomfort was significantly worse in lower limbs in saddle chair; Productivity no change; Greater trunk to thigh angles in saddle. Some benefits for lower back discomfort and posture in saddle but also issues (lower limb discomfort).