<!-- just use textAlign="center" -->
<Table>
<Thead>
<Tr>
<Th />
<Th>First name</Th>
<Th>Last name</Th>
<Th textAlign="center">Participation</Th>
</Tr>
</Thead>
<Tbody>
{participationData.map((participation, i) => (
<Tr>
<Td>{i}</Td>
<Td>{participation.firstName}</Td>
<Td>{participation.lastName}</Td>
<Td textAlign="center">{participation.participation}</Td>
</Tr>
))}
</Tbody>
</Table>