When splitting a sample into exercisers and non-exercisers, it appears that exercise as a pre-requisite precedes a higher range of activity. Inactive people tend to be on the lower end of creatine kinase activity and relatively clustered in magnitude, while exercise generally increases activity, but also introduces a larger range of possible activity.[56]
Healthy sources of fat include: cold water oily fish (such as salmon, mackerel, and sardines), extra-virgin olive oil, peanuts (unsalted), avocado, pecans, almonds, hazelnuts, walnuts or flaxseed. Nuts (any sort, just make sure they are unsalted) are a great food to snack on if you're having trouble gaining weight, as they are not only high in calories, but they contain monounsaturated fats, a good source of protein, fibre and contain a number of essential minerals that are needed for health. For those not consuming any oily fish, you may want to consider taking a fish oil supplement, such as cod liver oil or flaxseeds.

Duchenne’s Muscular Dystrophy (DMD) is associated with a reduction in intracellular creatine stores[554] known to only affects males. It is an X-linked progressive myopathy associated with abnormalities in the dystrophin gene.[555] The standard therapy at this moment involves corticosteroids such as prednisone.[556][557] Creatine is thought to be therapeutic since the known targetable abnormalities in DMD (impairment in protein synthesis associated with oxidative stress and increased protein breakdown) is a property of creatine and supplementation showed promise in the first case study[558] and benefit in a group of mixed dystrophinopathies.[559]

I learned from this to focus on the body weight exercises. I never understood why I could lift a lot of weight, but felt weak when it came to dips, pull ups, push ups etc. Normally I spend 2 hours in a gym: 20 min jogging, 80 min lifting, 20 min jogging, 5 days a week. After reading this I’m excited to incorporate HIIT training in addition to mobility training on my off days, because I think I was wasting a lot of time and effort. I can push way harder on lifting days without the jog beforehand, so I’ll also be able to make the most of 60 minutes…
Overload: The first thing you need to do to build lean muscle tissue is use more resistance than your muscles are used to. This is important because the more you do, the more your body is capable of doing, so you should increase your workload to avoid plateaus. In plain language, this means you should be lifting enough weight that you can only complete the desired number of reps. You should be able to finish your last rep with difficulty, but also with good form.
Translation: your muscles are going to have more energy. The process of accessing that energy is so complicated, you almost need an organic chemistry degree to totally understand it. Yes, it’s complicated, but completely necessary for biochemical reactions like muscle contractions. And the more your muscle works, the more ATP is depleted and needs to be replaced for you to make progress toward your goals. With creatine supplementation, you can enhance your ATP regeneration and thus delay onset of muscle fatigue and work more intensely for a longer period of time. Little goes a long way in the pursuit of muscle gains.
Besides the high-quality protein content of casein/whey, the newer formulations have little or no lactose (i.e., milk sugar), which some people have negative reactions to. The native milk proteins also provide a host of smaller proteins called peptides, many of which, such as lactoferrin, have vital health benefits. The rich cysteine content of whey acts as a precursor of glutathione, a primary endogenous antioxidant and liver detoxifier in the body.
Collectively the above investigations indicate that creatine supplementation can be an effective strategy to maintain total creatine pool during a rehabilitation period after injury as well as to attenuate muscle damage induced by a prolonged endurance training session. In addition, it seems that creatine can act as an effective antioxidant agent after more intense resistance training sessions.