Brief Answer:
inosine is a maybe.

Detailed Answer:
It at least 1) has a rationale, nearly all the performance enhancing drugs are ToTal CRAP (creatine, the partial beta agonist used in poultry, whey--which is inferior to chicken with or without the beta agonist in them, etc.). Inosine is used by muscle to make mRNA and DNA which is used in making protein and making cells grow in number and size. Frankly a normal diet probably is good enough. and 2) because it is a normal dietary ingredient, it isn't banned nor tested for. It is extremely unlikley to be bad for you.

Here's are two. Ok, for me they make all the difference.
https://www.ncbi.nlm.nih.gov/pubmed/0000
Reduced prostaglandins promote muscle growth. There are hundreds of articles about this fact. It has been WELL-established for a decade. Prostaglandin inhibitors are aspirin like drugs. They need to be there while you exercise. I'm not 100% on aspirin. BUT naproxen at prescription levels Does Work. Furthermore, it is OBVIOUS that lowering the PAIN from lactic acid but not it's production (which is the stimulus for muscle building) will not only make barbells far, far more pleasant but also more effective.
here's the downside. The stimulus for muscle building is higher in me--middle aged guy--than in you--20 year old. BUT obviously, your performance is better. This is because the muscle breakdown pathways are basically not there at age 20. If you stop doing exercise for 6 months your tone will be crap BUT you will not lose 50% of the built up muscle mass which occurs in middle aged people who stop exercise for 6 months. The pathways of muscle breakdown are shut down by aspirin like drugs. Very important for me; might not matter for you. Still, there is the strongest data for them of anything but illegal stuff.

Next, viagra opens up lung circulation. It will help in sprints and other physical situations where being winded is the limiting factor. It's Going To Get Banned. well, at least for female atheletes.

More information can be got. BUT it depends on the specific function you want. Cross training has been known to be plain stupid for most of a century. It has never been advocated by Am Soc. Sports Med. There's white meat (fast muscles involved in rapid movement and power and body building) and dark meat (endurance). White meat is how muscle grows, but it is turned (mostly irreversibly) into dark meat by endurance exercise. You can get one or the other but if you try both you get sort of neither. "MUSCLE CONFUSION".

Therefore, for more specific recommendations it requires knowing exactly what you want otherwise I'm going to give possibly the exact wrong advice.

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Brief Answer:
Very good input

Detailed Answer:
First, on the lungs. There are a lot of physiological processes that kick in with exercise. The lung vessel dilation is the main one which then gets more blood through the lung, etc. This is why with exercising for a while, you run better. Nasal dilation is another effect that is seen. It is called "warm ups". You need it. It might be 20 min on a treadmill at low to moderate levels or less. It also lowers resistance in other vessels, dilates circulation to the extremities, moves blood away from areas not involved with exercise (digestion) and many other effects. THere are nasal strips in the pharmacy. They are worth the 5 to 10 dollars to try.

Then, naproxen is an easy answer. The detectable amount is a lot lower than the amount that is needed to do something. 6 hrs of active effect is a pessimistic number 10 hrs is overly optimistic. Cannot predict in your particular case which number it is closer to but you can probably feel it and knwow.

On muscle growth, you have a big problem. Tendons and cartilege grow far slower than muscle. If I give you exercises to grow muscle they are GUARANTEED to hurt the dislocated shoulder. So, I can refer you to
http://www.acsm.org/public-information/acsm-journals/guidelines
and there's a lot of good info there. There is a LOT.

Ok, for core and lower limb it's fairly easy because the shoulders can be isolated OUT from the exercise. They can be for biceps, but it would take a personal trainer or physical therapist to devise very specific exercise to NOT work on the shoulders.

Let us assume there is a "magic pill". It still wouldn't be magic for you.
1) even illegal steroids require exercise to work and that is a problem with shoulder tendons in you and worse 2) they build muscle far more than they build tendons and then you unbalance the shoulder and the tendons get torn more.

Sports teams cannot take the time for the tendons to properly heal so they pretty much always get it wrong. My patients with tendon issues go through about a full year of work to build up the tendons working at extremely LOW weights and building up. It hasn't been looked at, and, the NSAIDS probably matter a lot on this because tendons are very susceptible to inflammation induced damage and deterioration.

Now, aspirin like drugs are notorious for stomach irritation. If I am recommending a lot of them for about a year, then warnings about stomach irritation and bleeding are important. Furthermore, this is usually not noticeable as pain and it is somewhat preventable by taking them with food or with proton pump inhibitors but probably needs physician monitoring.

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