Forerunner 735xt

First, a standardized warm-up of 10 min at 100 W was performed; the ramp protocol consisted of increments of 30 W · min^-3 until volitional exhaustion [13 (link)]. The end of the test was considered when the participant was unable to maintain the power output of each final completed stage. During GXT participants were monitored through a gas exchange measurement system/device with breath-by-breath technology and calibrated before each test (Metalyzer 3b, CORTEX Biophysik GmbH, Leipzig, Germany). Each participant used their own bike mounted on a smart training device (Bkool, model Bkool one; Madrid, Spain). The protocol was completed with a PowerTap P1 (PP1), which produced reliable output power readings of 100–500 W, in a seated position (rho ≥ 0.987), and an absolute reliability index (150–500 W; COV = 2.3%; SEM < 1.0 W) [18 ]. The PowerTap during cardiopulmonary tests are more ecologically valid, allowing cyclists to use their own bicycles [18 ]. HR was collected via a HR monitor (HRM-Tri; Garmin Ltd., Olathe, KS, USA). The smart trainer assessed power with internal sensors that were paired to a smartwatch for future analysis (Forerunner 735xt, Garmin, Olathe, KS, USA).

The University of Kansas Medical Center Human Subjects Committee (#00146392) approved this study. Participants provided informed consent after eligibility screening prior to beginning study activities. Child participants were encouraged to provide informed assent when deemed able by their parents. Interested families completed the demographics form, the CSP-2, and the SRS to determine eligibility. A Garmin Forerunner 735XT or 935 watch collected sleep-related data for one week during the first baseline phase (A1). Next, during the first intervention phase (B1), participants wore the Garmin watches and a SmartKnitKids Compresso-T for three weeks. Then, participants removed the Compresso-T for a second week of a baseline phase (A2). To end, participants wore the Compresso-T for a second intervention phase (B2) of two weeks. Caregivers completed the CSHQ and PSI-SF at each phase including before week one, after week one, after week four, after week five, and after week seven.

Test day 2 included four running tests on the treadmill, two venous blood samples, and a 65-km UM. Test day 2 was conducted on three separate occasions due to limitations of equipment and staff capacity, to ensure smooth testing procedures with little to no waiting times (maximum number of six participants per day). For the same reason, RE measurements during the UM could only be conducted at +3% incline. Tests took place in January and February 2018 with comparable outdoor conditions (average temperature + 6°C) for the UM. The UM was designed as a loop course (a total of three laps) starting and finishing at our university department. Each lap measured 21.7 km with a cumulative ascent of 364.4 m and cumulative descent of 364.4 m (Garmin Forerunner 735XT), equating to a total distance of 65 km (±1093 m). The terrain consisted predominately of forest tracks, gravel, and tarmac paths. It contained several uphill and downhill running sections and the average slope measured 3% (positive and negative elevation), which was used as the incline/decline for further tests (uphill/downhill) on the treadmill as outlined below. Participants were allowed to select their own individual running speed during the UM and were allowed to drink and eat ad libitum. During the course, runners were self-sufficient but after each lab food and drink was provided to them at the university.