TY JOUR TI JUMPING EXERCISES EFFICIENCY AT YOUNG MIDDLE DISTANCES’ RUNNERS KW young runners KW middle-distance running KW sports result KW physical fitness KW performance gains KW training factor JO Scientific notes of P. F. Lesgaft University AU Kashenkov, Y.B. AU Odintsova, M.O. AU Starostin, S.D. AU Bekmansurov, R.K. PY 2023 IS 0 PB National State University of Physical Education, Sports and Health named after P.F. Lesgaft