TY JOUR TI Development of punch stiffness in qualified boxers at the special preparatory stage KW boxing KW special physical training KW sports biomechanics KW speed-strength training KW boxing technique JO Scientific notes of P. F. Lesgaft University AU Sinicyn, D.K. AU Shamrai, L.V. PY 2026 IS 0 PB National State University of Physical Education, Sports and Health named after P.F. Lesgaft