A recent meta-analysis had a look on benefits of melatonin in different populations. Whereas athletes were not part of those, some uf us suffer from insomnia or jet lag.
The use of melatonin by healthy adults shows promise to prevent phase shifts from jet lag and improvements in insomnia, but to a limited extent. For the initiation of sleep and sleep efficacy, the data cannot yet confirm a positive benefit. However, no recommendation can be proposed for the use of melatonin in shift workers. Melatonin has a very low side effect profile and limited evidence of habituation and tolerance.
The dosing question was not fully answered, as all ranges of dosing was used.