( ( When ( you ( begin ( high ( intensity exercise ) ) ) ) ) ( ( ( the ( primary source ) ) ( of energy ) ) ( ( is ( ( ( adenosine triphosphate ) ( -LRB- ( ATP -RRB- ) ) ) ( in ( your muscles ) ) ) ) . ) ) )
(ROOT (S (SBAR (WHADVP (WRB When)) (S (NP (PRP you)) (VP (VBP begin) (NP (JJ high) (NN intensity) (NN exercise))))) (NP (NP (DT the) (JJ primary) (NN source)) (PP (IN of) (NP (NN energy)))) (VP (VBZ is) (NP (NP (NP (JJ adenosine) (NN triphosphate)) (PRN (-LRB- -LRB-) (NP (NNP ATP)) (-RRB- -RRB-))) (PP (IN in) (NP (PRP$ your) (NNS muscles))))) (. .)))
When you begin high intensity exercise the primary source of energy is adenosine triphosphate (ATP) in your muscles.
(ROOT (S (NP (DT The) (NN coenzyme) (NN atp) (CC or) (NN adenozine) (NN triphosphate)) (VP (VBZ is) (VP (VBN used) (PP (IN in) (NP (NP (DT the) (NN transfer)) (PP (IN of) (NP (NN energy))))) (PP (IN in) (NP (NNS muscles))))) (. .)))