Table 1. Summary of Training, Support, and Monitoring for Physical Activity Coaches.

	Time	Description
Initial training	6-h training session for all site staff, including coaches with individualized 1.5-h training	• Delivered by either trial PI or the intervention coordinator
		• Review of coach's manual, with explicit, session-by-session guide
		• Familiarized the coaches with the specific challenges of working with patients with HD
		• Offered a background to the intervention's SDT framework
Ongoing support	Minimum 2 discussions, others as needed	• Before first visit, coaches had video discussion with the intervention coordinator to assist them in interpreting a participant's baseline assessment scores
		• After the first or second home visit, coaches had a further discussion with the intervention coordinator to discuss goal setting and address any concerns or issues
		• Coaches were further encouraged to contact the intervention coordinator if they had any questions about the home visits as the intervention progressed, either by e-mail or videoc-onferencing

Abbreviations: HD, Huntington disease; PI, principal investigator; SDT, self-determination theory.