Table 3.

Outlier interventions with explanatory practice and research caveats.

Intervention		Potential Caveats
Author, Year (Population)	Description	Practice	Research
Effective practices incorporating zero core components
Schlatter, 2022 [79] (healthy adults)	5 min of 6 bpm relaxing breathing prior to simulated medical scenario and test	Investigator present during device-guided practice Physiologically trained residents
Ineffective practices that incorporated the following components:
Human-guided training
Meier, 2020 [46] (simulated stress)	30 min guided standing relaxation breathing prior to simulated stress test	Standing still Interrupted practice
Human-guided training, multiple sessions
Kamath, 2017 [44] (simulated stress)	15 min guided ANB prior to simulated public speaking task	Highly technical practice ANB task performance effects may attenuate stress-reducing effects
Ratcliff, 2019 [47] (clinical, acute)	Guided diaphragmatic breathing for 10 min prior to and during breast biopsy	Difficult to execute lying on stomach and remaining still for biopsy	Practice guides not blinded
Human-guided training, multiple sessions, long-term practice
Thomas, 2017 [50] (clinical, chronic)	Guided diaphragmatic breathing with breath holds, guided via DVD		Practices not continued through outcome period Outcomes reported at baseline and 12 mo
	Same as above, delivered by physiotherapist

Outliers defined as effective interventions that incorporated zero core components and ineffective interventions that incorporated ≥1 core component and satisfied both exclusionary components (e.g., avoided both fast-only breathing and sessions <5 min). Caveats report breath practice and study-specific research characteristics that may have increased interventions’ stress-reducing effects in effective outlier interventions and those that may have lessened or diluted these effects in ineffective outlier interventions. ANB, alternate-nostril breathing; bpm, breaths per minute; DVD, digital versatile disc; min, minutes; mo, months; w/o, without.