Here is the design of a clinical trial:

Official Title: Effects of Insoles Adapted in Flip-flop Sandals in People With Heel Pain: a Randomized, Double-blind Clinical, Controlled Study

Included conditions:
- Heel Pain Syndrome
- Heel

Study Armgroups:
- {'label': 'Experimental group', 'type': 'EXPERIMENTAL', 'description': 'Group 1- The intervention group I will receive a customized strip slipper with a 3mm EVA horseshoe piece (Shore A 32). And 2.5mm EVA cover (Shore A 28).', 'interventionNames': ['Other: Insoles adapted in flip-flop sandals']}
- {'label': 'Sham group', 'type': 'SHAM_COMPARATOR', 'description': 'Group 2- The control group will receive a slipper with a 2.5mm EVA cover (Shore A 32) identical to the one used by the intervention group, but without corrective par', 'interventionNames': ['Other: Insoles adapted in flip-flop sandals']}

Interventions:
- {'type': 'OTHER', 'name': 'Insoles adapted in flip-flop sandals', 'description': 'participants of both groups individually received a pair of customized flip-flop sandals, with or without foot pieces, covered with smooth synthetic leather', 'armGroupLabels': ['Experimental group', 'Sham group']}

Primary Outcomes:
- {'measure': 'Change in Numerical pain intensity scale - NPS', 'description': 'Pain intensity will be evaluated with the 10-point Numerical Pain Rating Scale, where 0 is "pain-free" and 10 is "maximum pain.', 'timeFrame': 'baseline, 6 weeks after, 12 weeks after, 16 weeks folow up'}

Please estimate the sample size based on the assumption: 
80% power, 5% significance level, 10% sample loss, estimated SD of 3.2 points
Sample size calculation
        The sample size was calculated based on the NRPS from a previous study.15 The statistical power of 80% was used to detect a mean difference of 1.8 points in pain, based on a difference found between groups in a study by Costa et al.15 Each group will need 36 individuals considering an estimated SD of 3.2 points and a 5% significance level. However, a sample loss of 10% was added, leading to a sample of 40 individuals per group.