A run/walk strategy in a marathon doesn't cost meaningful time or add cardiac stress versus continuous running, in the one RCT that's tested it directly
Interpretation
Hottenrott et al.'s randomised trial of 42 non-elite marathoners found no significant finish-time difference between a run/walk strategy and continuous running (4:14:25 vs 4:07:40, p=0.377), and cardiac-stress markers (BNP, CK-MB, myoglobin) rose similarly in both groups before normalising within 4 days. The run/walk group reported significantly less muscle pain and fatigue. This is a single RCT in non-elite marathoners, not Ironman-distance runners specifically — the direction is well-supported, the precise time cost at longer distances is not independently confirmed.
Practical implication
Don't discourage a deliberate run/walk strategy in an Ironman marathon on the assumption it costs significant time or adds cardiac risk — the best available evidence shows neither. Flag that this is extrapolated from marathon, not Ironman-marathon, data.
Sources
1 source, independently verified.
Randomised comparison of a run/walk strategy vs. continuous running in a marathon: finish times were not significantly different (4:14:25 vs 4:07:40, p=0.377); cardiac-stress markers (BNP, CK-MB, myoglobin) rose similarly in both groups and normalised within 4 days; the run/walk group reported significantly less muscle pain and fatigue (p=0.006). No reduction in cardiac load from run/walk, but also no meaningful time cost.