I have started doin the Parkrun, but I do spend a lot of time sitting at the PC so thought maybe some kind of device, muscle strength is OK but my lungs are like that of a 90 year old man.
when i took up running i was the same. i think i managed 6k in an hour. i was a wreck. had only done weights for 5 years previously and a bit of football here and there.
so i started running twice a day. morning and evening. i did different types of runs to mix it up. like in the morning i might just do a full sprint for 15 minutes. in the evening i would do a slow jog for 90 minutes. basically you want to work on both endurance (long distances over time) and speed (running at a high pace for shorter periods of time) and also inbetween.
i would run for 15 mins (full pelt) or do a 5k or 10k or 15k in my sessions depending on how i was feeling. for the 15 mins run i kept track of distance, how far i could run inside 15 mins this was basically running at a constant fast pace for 15 minutes, you don't want to be slowing down then speeding up but keep at a pace you can maintain for the duration.
i then afterwards either spent 30-45 minutes in the sauna or did some weights. i'd be sipping water constantly. i managed to figure out how to stop getting cramps, etc. how doing different things effected my cardio.
e.g. let's say i ran 5k at a slight incline in 25 minutes. i then went out on the lash that weekend for 1 night. the next time i tried doing 5k it would take me 30 minutes. this is the impact binge drinking had. it then took me 2 weeks to get to back to where i was before so no improvement made for all that hard work because of 1 night out. so i started cutting out all the stuff effecting my improvement.
at the end of it all i think i managed 10k in under an hour on an incline easily. when i started i managed only 6k on my first day on flat.
i got myself a heart rate monitor and i'd been running for about 2 years now. my resting heart rate was around 45-50 bpm which is athlete status. my diet has always been quite good. just overeating and the drinking. cut the drinking right down and upped started running was what made the biggest difference.
i had done my knee ligaments in playing football so i was fine running in straight lines (on a treadmill), twisting and turning is what caused me issues but i managed to build up the muscles around my knee to overcome it somewhat. i then done my ankle ligaments on the opposite leg playing football. i couldn't walk for 2 days, then i was limping for 2 weeks and i've never ran since. put about 20kg back on, i was fit as a fiddle before now my resting heart rate is in the 70's.
i'm going to start running again hopefully this weekend if everything goes to plan.
basically it isn't easy and there are no short cuts. takes time, dedication and ultimately willpower. i honestly think running is the best way to improve cardio for me anyway. i'm not much of a swimmer and i found rowing boring. with running it was easier to track my development as you can see the time and distance on the screen.
when i got back into football at the peak of my cardio, i was literally twice the player i was before. i could take people on with ease. i could pass and move twice as quick. i would be running for the full hour never needing to go in goals for a break. in fact after an hour of football i still felt i could give more whereas before i would be in goals for a break every so often.
if you want something you can do at home cheaply, then it has to be skipping. skip rope £5 off ebay the little thin plastic type ones are best, forget leather with wooden handles, it's not needed. then go into the back garden and do what i like to call boxing training. basically skip for 3 minutes. rest for 1 minute. skip for 3 minutes. rest for 1 minute and see how many rounds you can last. you then want to up the intensity. double skips, tricks, skipping faster as you improve.
ultimately sign of true cardio isn't what you can do, how fast you can do it. it's how fast you recover. this is why when i was playing football i could play a full hour at a high intensity and still be fresh. i was recovering quicker than anybody else on the pitch. so i could keep on going for longer.