Eight weeks of core training raised plank endurance, but running economy did not differ from the control group
The reported improvement is a within-group change without a group × time interaction
Key Findings
Running economy did not differ between core training and control: no group × time interaction for oxygen uptake, heart rate, lactate or perceived exertion after 8 weeks.
21 male college athletes (core training 11, control 10; 4 dropped out injured). Three extra core sessions a week for 8 weeks, progressing from crunch, back bridge, plank and side plank to unstable surfaces and anti-rotation work (Pallof press, mountain climber).
Core endurance (plank test) in the training group: 193.5 ± 71.9 s to 241.5 ± 98.9 s.
Oxygen uptake at the fastest treadmill stage in the training group: 52.4 ± 3.5 to 50.0 ± 2.9 mL/kg/min (p = 0.019).
No group × time interaction for oxygen uptake, heart rate, lactate or perceived exertion; for the plank test the interaction was p = 0.076.
Practical Application
This trial does not show that core training improves running economy: the change did not differ from doing nothing extra. Do not cite its title as evidence.
Together with a small trial showing faster 5000 m but unchanged mechanics (Sato & Mokha 2009, DOI 10.1519/JSC.0b013e31818eb0c5, 20 completers) and one showing no change in economy (Stanton 2004, 18 adolescents), the honest summary is: core training reliably improves core tests; transfer to endurance performance is weak and inconsistent.
Limitations
Small, men only, mixed sports; the gas analyser was replaced during the study; no performance test.
Full text was read; the plank result differs slightly between the abstract and the full text.