( ( ( Most studies ) ( of ( ( ( physical activity ) and ) ( cardiovascular disease ) ) ) ) ( ( have ( dealt ( with men ) ) ) . ) )
(ROOT (S (NP (NP (JJS Most) (NNS studies)) (PP (IN of) (NP (NP (JJ physical) (NN activity)) (CC and) (NP (JJ cardiovascular) (NN disease))))) (VP (VBP have) (VP (VBN dealt) (PP (IN with) (NP (NNS men))))) (. .)))
Most studies of physical activity and cardiovascular disease have dealt with men.
(ROOT (S (NP (NP (NN Smoking) (NN tobaccowould)) (ADJP (RBS most) (JJ likely))) (VP (VBP have) (NP (NP (DT a) (JJ negative) (NN impact)) (PP (IN on) (NP (NP (DT the) (NN ability)) (PP (IN of) (NP (DT an) (ADJP (JJ individual) (S (VP (TO to) (VP (VB succeed) (PP (IN at) (NP (JJ physical) (NNS activities))) (SBAR (IN because) (S (NP (PRP it)) (NP (PRP it)))))))) (NNP decreases) (NN stamina) (CC and) (JJ cardiovascular) (NN efficiency))))))) (. .)))
Smoking tobaccowould  most likely have a negative impact on the ability of an individual to succeed at physical activities because it it decreases stamina and cardiovascular efficiency.