( Smoking ( ( ( ( ( reduces ( ( the ability ) ( of ( the blood ) ) ) ) ( to ( carry oxygen ) ) ) and ) ( increases ( ( ( ( ( the ( heart rate ) ) and ) ( basal ( metabolic rate ) ) ) , ) ( thus ( counteracting ( ( ( ( the benefits ) ( of ( physical activity ) ) ) , ) ( including ( cardiovascular fitness ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NN Smoking)) (VP (VP (VBZ reduces) (NP (NP (DT the) (NN ability)) (PP (IN of) (NP (DT the) (NN blood)))) (S (VP (TO to) (VP (VB carry) (NP (NN oxygen)))))) (CC and) (VP (VBZ increases) (NP (NP (DT the) (NN heart) (NN rate)) (CC and) (NP (JJ basal) (JJ metabolic) (NN rate)) (, ,) (S (ADVP (RB thus)) (VP (VBG counteracting) (NP (NP (DT the) (NNS benefits)) (PP (IN of) (NP (JJ physical) (NN activity))) (, ,) (PP (VBG including) (NP (JJ cardiovascular) (NN fitness))))))))) (. .)))
Smoking reduces the ability of the blood to carry oxygen and increases the heart rate and basal metabolic rate, thus counteracting the benefits of physical activity, including cardiovascular fitness.
(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.