Table 4 Overview of the general variables determining the hypoxic dose and preliminary synopsis for the application of intermittent hypoxic–hyperoxic exposure (IHHE) interventions

Main variables relevant for a single IHHE session (acute effects)

Intensity of hypoxia

 Level of hypoxemia, typically reported as oxygen saturation of the blood (S_pO₂, internal intensity) or fraction of inspired oxygen (F_iO₂, external intensity)

F_iO₂ = 0.10–0.12

Intensity of hyperoxia

 Fraction of inspired oxygen (F_iO₂, external intensity) during hyperoxic periods

F_iO₂ = 0.30–0.40

Duration of a single hypoxic period

 Time spent in hypoxia before the onset of reoxygenation period (i.e. onset of normoxia or hyperoxia period)

2–6 min

Intra-session frequency

 Number of hypoxic periods that are interspersed with hyperoxic or normoxic periods (cycle) within a single session or day

4–8 cycles

Intra-session density

 Distribution of hypoxic periods across a distinct time interval with regard to reoxygenation time (i.e. duration of normoxia or hyperoxia period) within a single session or day

1–4 min

Main variables relevant for a IHHE training program (chronic effects)

Inter-session frequency

 The number of IHHE sessions across a distinct time interval

3–5 sessions per week

Inter-session density

 Distribution of IHHE sessions across a distinct time interval with regard to recovery time in-between the IHHE sessions

Every second day until daily for 5 days interspersed with 2 days rest

Duration

 IHHE intervention duration

≥ 3 weeks