An individual shall be ineligible for benefits, on the basis of wages for any services if substantially all of such services consist of participating in sports or athletic events or training or preparing so to participate, for any week which begins (after December 31, 1977) during the period between two successive sport seasons (or similar periods), if the individual performed such services in the first of such seasons (or similar periods) and there is a reasonable assurance that the individual will perform such services in the later of such seasons (or similar periods).