The phrase "most helpful in" is correct and can be used in written English.
Example: Learning new vocabulary words is most helpful in improving my understanding of the text.
If needed, trying different vaping products can help smokers identify which are most helpful in getting them to end smoking.
"The governor can be most helpful in building the base, grass-roots organization, helping to raise funds, as I did in 2000".
Most helpful in its discussion of character formation.
It's been most helpful in terms of how I engage the schools we work with".
You're 100percentt right — rest is most helpful in overcoming muscle soreness.
Which CS classes were most helpful in putting this project together?
Your article was most helpful in explaining what was going on.
Have your students try another self-observation about the interventions that are most helpful in falling asleep.
Reviewing course requirements for different fields with counselors was probably the most helpful in narrowing her interests, she says.
What experiences at Harvard do you look back on as having been most helpful in your career?
Such guidelines generally include recommendations about which markers are likely to be most helpful in given circumstances.
