REF-905 · Villarroel López et al., 2025 · Journal of Functional Morphology and Kinesiology, Vol. · Paper · PubMed · Free full text

High Intensity Functional Training in Hybrid Competitions: A Scoping Review of Performance Models and Physiological Adaptations

B-limited, mixed evidenceMeasured on recreational to highly trained athletesWritten before October 2026, being re-checked

A scoping review mapped research on high-intensity functional training (HIFT) as it relates to hybrid competitions such as CrossFit and HYROX. Searching Web of Science, Scopus and PubMed turned up 39 studies published between 2015 and 2025.

According to these studies, HIFT improved aerobic capacity, anaerobic power, muscular strength and fatigue tolerance; commonly reported gains were 8% to 15% in VO2max and 10% to 20% in strength on major lifts, plus better local muscular endurance, power and recovery capacity.

The benefits looked larger in trained people, particularly those doing more resistance training, and more experienced athletes tolerated fatigue better and performed more consistently under stress. The authors back HIFT as a foundation for multi-domain fitness events, without crediting the benefits to any one event.

Participants

39 studies (2015-2025) on HIFT; participant numbers and characteristics are not summarised in the abstract.

Protocol

Arksey and O'Malley scoping framework, PRISMA-ScR reporting.
Systematic search in Web of Science, Scopus and PubMed.
Narrative mapping of physiological and psychobiological determinants; no meta-analysis described.

Key Results

HIFT raised aerobic capacity, anaerobic power, muscular strength and fatigue tolerance; gains commonly reported were 8% to 15% for VO2max and 10% to 20% for strength in major lifts.
Recovery capacity, local muscular endurance and power output also improved.
The benefits looked larger in trained individuals, particularly those with more resistance-training volume.
Psychobiological responses (perceived exertion, cognitive control, motivation) were explored in several studies; more experienced athletes showed higher fatigue tolerance and better performance consistency under stress.
Authors' conclusion: HIFT is a foundational method for multi-domain fitness events, without attributing the benefits to any single competitive event.

Practical Application

To "does CrossFit-style training prepare me for HYROX?": across 39 HIFT studies, this scoping review found functional training improved aerobic capacity (VO2max gains of 8% to 15% commonly reported), strength (10% to 20% in major lifts) and fatigue tolerance — but the authors do not tie these gains to HYROX itself. HIFT builds the general qualities a hybrid race needs; it is not evidence that HIFT is the best way to prepare for HYROX.
For HYROX specifically, the race-data studies point at running as the largest share of time (REF-510, REF-903). Inference, not tested here: use HIFT for station work and general strength on top of a running base, not in place of it.
The ranges are counts of what individual studies reported, not pooled effects; do not quote them as an expected gain for a given athlete.
Not from this paper; the base's own practice: the weekly structure is in SYNTH-71; concurrent-training scheduling in SYNTH-21.

Limitations

Scoping review: no risk-of-bias pooling or meta-analysis; the ranges are as reported by individual studies.
Most included work is on HIFT/CrossFit rather than HYROX; the authors do not attribute findings to any single event.
Heterogeneous populations, programmes and durations; no dose-response can be drawn from the abstract.
Written from the abstract and record metadata only (full text not read).
How this entry was checked and changed
Why this level

scoping review with a systematic search but no pooled estimates; the included studies are on high-intensity functional training broadly (CrossFit-type), and HYROX-specific primary data are scarce, so for HYROX questions it is not above B-