does a hard cardiovascualr workout build muscle?

any exercise will build muscle to a certain extent,progressive load is the main factor for hypertrophy,so at first you will gain some muscle then you will reach a platue,HIIT or sprint training would probably build more muscle than ss-cardio.

I'll agree it will build some muscle, especially if you start out with skinny legs

Yes. Running will build leg muscle, but as stated above you will hit a platue unless you change your routine regularly.

Will build your heart muscle mostly . If you use the muscle, it will develop.

Probably not in the sense you are asking.

I think the key word here is "HARD cardiovascualr workout".pushing your self crazily on the bike or w/e for an hour or more could even result in you losing muscle due to your body breaking it down for energy(catabolism i think its called).

well 1/2 weeks into my heavy cardio regime, i have definatly rebuild my muscle which i had lost, i am more toned aswell as weight loss, i kinda let myself go and did no workout for awhile, i found my abs had gone and i could feel no muscle.... now there back and strong along with leg muscles, heres what iv done below.

Gym Workout

Tuesday 5th June - walk to gym / 35min on treadmill 5km / 450 cals. / 3x12 latt pulldown 55kg / 3x12 shouler pushup 35kg / 2x12 + 2x12 on sitdown pullback both angles
3x30 benchpress bar only / 8 lengths in pool / steam room / walk home

Wednesday 6th June - 37min jog treadmil 5.37km 460 cals / 15 lengths swimming / steam room

Thursday 7th June - RPM Cycle class / few length in the pool / steam room

Friday 8th June - toned all upper body / steam room / walked home

Saturday 9th June - Long walk round chalton / sale waterpark no gym

Sunday 10th June - 35min run on treadmill 5km 450calls / few lengths in pool / steam room

Monday 11th June - 55min run on treadmill 8.5km 760calls / few length in the pool / steam room

Tuesday 12th June - toned upper body, couldnt do abbs due to pain / few lengths in pool / steam room

Wednesday - 13th June - 55min run on treadmill 8.5km 760calls / few length in the pool / steam room / walk home

also heres my weight

Weight Chart

Tuesday June 5th : 13st 1lb / weighed at gym 12pm - no food

Friday morning 8th June - 12st 12lbs weighed at home around 10/11am - no food

Tuesday morning 12th June - 12st 12/11 lbs - no food

Thursday Morning 14th June - 12st 11/10 lbs - no food