▁measure ▁for ▁dec iding ▁exercise ▁intensity ▁for ▁training ▁and ▁racing ▁in ▁end urance ▁sports ▁( e . g ., ▁long ▁distance ▁running , ▁cy cling , ▁row ing , ▁long ▁distance ▁sw imming ▁and ▁cross ▁country ▁ski ing ), ▁but ▁var ies ▁between ▁individuals ▁and ▁can ▁be ▁increased ▁with ▁training . ▁ ▁Inter val ▁training ▁ ▁Inter val ▁training ▁altern ates ▁work ▁and ▁rest ▁periods ▁allowing ▁the ▁body ▁to ▁tempor arily ▁exceed ▁the ▁la ct ate ▁threshold ▁at ▁a ▁high ▁intensity , ▁and ▁then ▁recover ▁( reduce ▁blood - la ct ate ). ▁This ▁type ▁of ▁training ▁uses ▁the ▁ATP - PC ▁and ▁the ▁la ctic ▁acid ▁system ▁while ▁exer cis ing , ▁which ▁provides ▁the ▁most ▁energy ▁when ▁there ▁are ▁short ▁burst s ▁of ▁high ▁intensity ▁exercise ▁followed ▁by ▁a ▁recovery ▁period . ▁Inter val ▁training ▁can ▁take ▁the ▁form ▁of ▁many ▁different ▁types ▁of ▁exercise ▁and ▁should ▁closely ▁rep licate ▁the ▁movements ▁found ▁in ▁the ▁sport ▁being ▁trained ▁for . ▁Inter val ▁training ▁can ▁be ▁adjust ed ▁to ▁the ▁individual , ▁however ▁it ▁is ▁important ▁to ▁consider ▁the ▁intensity ▁of ▁each ▁interval , ▁duration ▁or ▁distance ▁of ▁each ▁interval , ▁length ▁of ▁rest / rec overy , ▁number ▁of ▁repet itions , ▁frequency ▁of ▁training ▁and ▁recovery ▁type . ▁ ▁F art lek ▁training ▁ ▁F art lek ▁and ▁interval ▁training ▁are ▁similar , ▁the ▁main ▁difference ▁being ▁the ▁structure ▁of ▁the ▁exercise . ▁F art lek ▁is ▁a ▁Swedish ▁word , ▁meaning ▁speed ▁play . ▁This ▁type ▁of ▁training ▁is