Table 2.

Assessment of evidence for the risk of studied outcomes based on Grades of Recommendations, Assessment, Development and Evaluation framework (GRADE)

Risk	Quality of study limitations: ↓	Indirectness of evidence: ↓	Inconsistency: ↓	Imprecision range confidence interval effect size > 2.0: ↓	Publication bias yes: ↓	Effect estimate > 2.0: ↑ > 5.0: ↑↑	Dose-response effect: ↑	Residual confounding: ↑	Overall certainty (high, moderate, low)
Kneeling	yes ↓a	no (−)	no (−)	no (−) 1.66–2.77	no (−)b	yes ↑ 2.14	no (−)	no (−)	moderate
Squatting > 1 h per day	yes ↓a	no (−)	no (−)	no (−) 1.34–3.03	no (−)	yes ↑ 2.01	no (−)	no (−)	moderate
Standing or walking > 2 h per day	yes ↓a	no (−)	no (−)	no (−) 0.91–2.05	no (−)	no (−) 1.37	no (−)	no (−)	low
Walking > 2 miles per day	yes ↓a	no (−)	no (−)	no (−) 0.92–1.97	no (−)	no (−) 1.35	no (−)	no (−)	low
Risk of climbing > 30 flights of stairs per day	yes ↓a	no (−)	no (−)	no (−) 1.58–3.30	no (−)	yes ↑ 2.28	no (−)	no (−)	moderate
Risk of lifting and carrying ≥ 10 kg	no (−)c	no (−)	no (−)	no (−) 1.35–1.96	no (−)	no (−) 1.63	no (−)	no (−)	moderate
Risk of lifting and carrying ≥ 25 kg	yes ↓a	no (−)	no (−)	no (−) 1.08–2.24	no (−)	no (−) 1.56	no (−)	no (−)	low
Risk of playing football	yes ↓a	no (−)	no (−)	yes ↓ 3.24–8.41	no (−)	yes ↑↑ 5.24	no (−)	no (−)	moderate
Risk of mining	yes ↓a	no (−)	no (−)	yes ↓ 2.16–12.69	no (−)	yes ↑↑ 5.23	no (−)	no (−)	moderate
Risk of floor layers	yes ↓a	no (−)	no (−)	no (−) 1.43–2.78	no (−)	no (−) 1.99	no (−)	no (−)	low

^a All studies had a high risk of bias

^b Egger’s test p = 0.04. However, Nauwald et al. 1986 is the reason due to its wide confidence intervals due to the zero for the comparison group

^c 2/3 studies had a high risk of bias, and high risk of bias studied increased the RR (High risk RR = 1.83; 95% CI 1.28–2.62; Low risk RR = 1.56; 95% CI 1.26–1.93), but: low risk of bias studies was statistically significant