Galinsky 2000.

Methods	Cross‐over RCT. Data were collected over a 16‐week period. The 16‐week period was divided into 4, 4‐week phases in which participants alternated between the conventional (C) and supplementary (S) rest break schedules. Half of the volunteers from each shifts (day and night) were assigned at random to experience the C‐S‐C‐S order of rest break schedules and the other half were assigned at random to experience the opposite (S‐C‐S‐C) order. As a result of attrition, data from just the first 2 phases of the study were sufficient for analyses (i.e. the C‐S phases).
Participants	Data‐entry operators (seasonal employees) working at an Internal Revenue Service Center. The data‐entry task entailed keying mostly numeric data from paper tax forms using a standard keyboard with a right‐sided numeric keypad. A total of 101 data‐entry operators provided written voluntary, informed consent to participate in the study. Each data‐entry operator had been hired as a 'seasonal' employee under an agreement that the job was temporary. The time at which each operator was released from employment was determined by the workload demands of the facility.
Interventions	The study compared supplementary breaks with conventional breaks Control: the conventional break schedule included one 15‐minute break in the middle of the first half of the work shift and one 15‐minute break in the middle of the second half of the work shift. Intervention: the supplementary break schedule included the same 15‐minute breaks, and also included a 5‐minute break during each hour of the work shift that otherwise did not contain a break. For each 8‐hour shift, the supplementary schedule provided 4 extra 5‐minute breaks for a total of 20 extra minutes of break time. Under each schedule, a 30‐minute lunch period, additional to the 8‐hour work and break time, occurred in the middle of the shift.
Outcomes	Primary outcome Musculoskeletal discomfort ratings for several parts of the body, including the neck, shoulders, upper arms, elbows, forearms, wrists, hands, back, buttocks, and legs. Each rating was made using a 5‐point category rating scale in which the whole numbers 1 to 5 indicated ratings of 'none at all', 'a little', 'moderate', 'quite a bit', and 'extreme', respectively. Secondary outcomes Data entry productivity: 2 measures of productivity, keystrokes per hour and the total number of documents entered by each participant on each day of the study. This measure, which was affected by factors such as the length of tax documents entered and the number of hours worked per day, permitted an assessment of work output. Data accuracy: 2 measures of data‐entry accuracy were used for this study. One was the number of errors made per day by each participant. The other was a daily measure of accuracy percentage, which took into account the number of documents entered per day.
Notes	The author kindly provided additional data on mean and standard deviation for the outcomes after the experimental supplementary breaks condition and after the control condition.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	There was no information on sequence generation. The only information available was: "A within‐subjects/repeated measures design was used … Half of the volunteers from each shift (day and night) were assigned at random to experience the C‐S‐C‐S order of rest break schedules, and the other half were assigned at random to experience the opposite (S‐C‐S‐C) order".
Allocation concealment (selection bias)	Unclear risk	There was no information on allocation concealment.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Blinding not possible, but the risk of performance bias was assessed as low as the intervention consisted of a strict protocol. The study participants "...use custom‐made electrical timers, attached to the top of each video display terminal, to automatically signal their scheduled breaks".
Blinding of outcome assessment (detection bias) Musculoskeletal disorders	High risk	The outcome has only subjective symptoms, i.e. musculoskeletal discomfort ratings (feeling state).
Incomplete outcome data (attrition bias) All outcomes	High risk	Out of the 101 people who volunteered to participate in the study only 42 participants were included in the final analysis. Only the data from the first (first cross‐over) of the 2 phases were sufficient for analysis. Data from the second phase (second cross‐over) were not analysed. Loss to follow‐up amounted to 38 participants and the reasons cited were release from employment and resignation from employment. Questionnaires from 21 participants were too incomplete for analyses.
Selective reporting (reporting bias)	Low risk	The outcomes listed in the methods section were reported in the results.
Other bias	Low risk	The authors reported that "to minimize the potential influence of carry‐over effects and 'Hawthorne effects'… Data from the first 2 weeks of each 4‐week phase were excluded from analyses of the feeling state questionnaire items".