When can you train again after tearing a hamstring?

Short answer

It depends on how deep the tear is. In studies, full training took 18.6 days on average, and 34-48 days when the tendon inside the muscle was hurt. Starting rehab early, built around lengthening exercises, brought people back faster than resting.

When can you train again after tearing a hamstring?
'Rest completely until it's fully healed' — is that the answer?
The hamstrings, at the back of the thigh, are the muscles most often torn during exercise. You hear both 'rest until it's fully healed' and 'get moving early.' We checked return times against the research.
How deep the tear went set the return time
6 days on average, 34-48 days if the tendon was hurt
Tracking 70 hamstring injuries over 4 years, full training took 18.6 days on average. When the tendon inside the muscle was hurt, it took 34 days, and 48 days for bigger tears. In a study of 56 people, damage to the tendon at the end of the muscle pushed return from 31 to 73 days.
Moving early cost nothing in recovery
50 people: no difference in strength or muscle recovery
50 people with severe thigh or calf muscle tears were split into early-rehab and delayed-rehab groups. Over 6 months, strength and muscle recovery showed no difference between groups, and the researchers concluded the early group returned faster.
Lengthening exercises brought people back sooner
28 vs 51 days, 49 vs 86 days
75 people did rehab built around exercises that load the muscle while it lengthens. They returned faster than with standard strength rehab (28 vs 51 days). In 56 people it was 49 vs 86 days. Reinjuries within a year totaled 1-2 across both groups.
But rushing did not make it faster
90 people: 23 vs 33 days, no meaningful difference
90 people started lengthening exercises either right after injury or only once they could run fairly well. Return took 23 vs 33 days, with no meaningful difference, and reinjury within 1 year did not differ. Skipping steps saved no time.
Bearable pain did not delay return
15 vs 17 days, with 15% more strength recovered
43 people did rehab either only in a completely pain-free range or allowing bearable pain. Return took 15 vs 17 days, with no difference, and the group that allowed pain recovered 15% more strength.
The risk is higher after you return
A recent injury means 4.8 times the risk
An analysis of 78 studies covering 71,324 people found that any past hamstring injury meant 2.7 times the risk of another, and a recent one meant 4.8 times. In a study of 41 people, a tendon not fully healed on MRI at return was not linked to reinjury within 1 year (20%).
Bottom line: rehab progress, not the calendar, sets your return
About 3 weeks if mild, 5-7 weeks if the tendon is involved
Full training took 18.6 days on average, and 34-48 days when the tendon was hurt. Starting rehab early, built around lengthening exercises, was faster than resting, and bearable pain did not slow return. Even after returning, the risk of another injury stays 2.7 times higher.