Table 4 Adapted from Learmonth and Motl (2018) [14]

Process—assesses the feasibility of processes that are key to future studies

Determine recruitment rates; e.g. the response of participants to recruitment strategies, proportion who remain interested/eligible after information and screening.

Determine ease of randomisation

Consent rate 70% (n=46/66)

Progression to recruitment after screening 93%

(n=43/46)

Easy due to random design, so all components completed by all participants.

Resource—assesses time and resource problems that could occur in future studies

Estimate retention of participants in the study e.g. number of participants completing all aspects of the study, number and reason for attrition.

Demonstrate appropriate eligibility criteria e.g. are inclusion/exclusion criteria too relaxed/stringent

Estimate barriers/refusals to participation

Estimate access to/cost of equipment, space, personnel time

Clinician training needs and competence.

100% of participants completed exercise testing on the day of clinic review.

95% (41/43) of the boys returned the accelerometer (1 lost, 1 unaccounted for).]

84% (36/43 boys) were fully compliant with the entire protocol, wearing the accelerometer long enough for valid data analysis of at least 4 days of 9 h [15].

Exclusion criteria included a bleed in the previous 6 weeks. 8 boys were not eligible for approach at clinic review due to a recent bleed. This was not considered too stringent and enhanced safety of exercise testing.

Reasons such as additional time commitment/burden of exercise testing on the day of routine clinic review was too great for 17% (11/66 declined).

Costs covered by study funds, space available for all exercise testing. The approximate cost of equipment: HR monitor with chest strap and Polar watch £260; Reebok step £80; stop watch £10; tape measure £4. All test procedures are free. A corridor of 12m is required for 10-m ISWT. Study completed within proposed timeframe; target of 40 boys in 1 year (43 in 10 months achieved).

Initial training and supervision required for administering physiotherapy assessment protocol.

Management—assess potential human and data management problems.

Estimate equipment usage e.g. ease of availability, equipment malfunction.

Staff annual leave/sickness

Determine processing time for data collection e.g. time to mail data collection materials

Data collection and analysis – software accessibility

Established that accelerometry and heart rate recording equipment would require updating prior to any further studies.

3% (2/66) of interested eligible boys not recruited on days when they could have participated due to researcher unavailability.

Needs were met by at least 8 accelerometers, required for turnaround time of 1 week accelerometry-wear, postage time back to Centre, and subsequent downloading of data onto specialist software, off-site.

Access to SPSS and ActiGraph Firmware was required, available in this research setting.

Scientific—assess the safety, burden, data collection and response to the study

Estimate challenges perceived/experienced by study personnel e.g. skills required to use assessment protocol

Safety to boys of outcome measures

Burden of research

Determine appropriateness of target group

Determine acceptability to participants e.g. participants views on outcomes.

Training and practice required to implement outcome measures. Greater subjectivity in use of the iSTEP compared with the 10-m ISWT, with regard to stopping boys. Strength of tester versus participant, in myometry testing – difficulty resisting muscle activity in older, stronger boys, but intra-rater reliability should remain stable.

Challenges faced by boys in adverse conditions for exercise testing i.e. very high summer temperatures.

No serious adverse events or reactions, but caution required and does not mean that there are no risks i.e. falls and trips.

Significant amount of additional activity, alongside routine clinic review. Potential delayed onset muscle soreness in the days following exercise testing. Pain experienced during testing did not cause undue discomfort or distress.

Time commitment burden of at least 1.5 hours in addition to routine clinic visit, plus 1 week of accelerometry-wear, measuring usual physical activity.

Difficulties for some boys performing the iSTEP: reduced co-ordination, related to younger children in the cohort. Provided awareness of this.

Boys were asked for verbal feedback on preferred exercise test and reasons. Both exercise tests were generally acceptable to participants.