Recently, studies are coming out that show a general decline in testosterone levels of men in the United States and around the world. The trend is across the board and doesn’t appear to be caused simply by a decline in health, aging or an increase in obesity rates. It could be caused because of chemicals or environmental factors. In any case, low levels of testosterone can affect many areas of your health, including your ability to build muscle. If you suspect that you have low testosterone levels, you can ask your doctor to test you for it. In addition to traditional hormone therapies, there are also many natural ways to boost your levels including through supplements, some of which will be discussed later in this article.
Safety. Excess quantities of antioxidants may produce a ‘pro-oxidant’ effect, which is the opposite of what you would take these supplements for. The Australian Institute of Sport recommends that antioxidant vitamin supplements only be taken for a period of a few weeks while the body adjusts to stressful circumstances. Excess vitamin C may promote excess iron absorption, which may not be healthy for everyone.
A: Let your symptoms be your guide. A slight sore throat or runny nose may require you to back off for a day or two but don’t confine yourself to your bed and assume the worst. However, you must also remember that prolonged, intense exercise can decrease immune function and make you more susceptible to bacterial and viral based sickness so it's equally as important to listen to your body and respond accordingly.
“There is a lot of mixed research on creatine’s ability to improve muscle strength,” the government website says. “However, analyses of this research show that creatine seems to modestly improve upper body strength and lower body strength in both younger and older adults.” Creatine has also been shown to improve athletes’ performance in rowing, soccer, and jumping height.
It is suggested [16,37] that another mechanism for the effect of creatine could be enhanced muscle glycogen accumulation and GLUT4 expression, when creatine supplementation is combined with a glycogen depleting exercise. Whereas it has been observed [38] that creatine supplementation alone does not enhance muscle glycogen storage. Hickner et al [15] observed positive effects of creatine supplementation for enhancing initial and maintaining a higher level of muscle glycogen during 2 hours of cycling. In general, it is accepted that glycogen depleting exercises, such as high intensity or long duration exercise should combine high carbohydrate diets with creatine supplementation to achieve heightened muscle glycogen stores [39].
In regard to practical interventions, concurrent glycogen loading has been noted to increase creatine stores by 37-46% regardless of whether the tissue was exercised prior to loading phase.[176] It is important to note, however, that creatine levels in response to the creatine loading protocol were compared in one glycogen-depleted leg to the contralateral control leg, which was not exercised.[176] This does not rule out a possible systemic exercise-driven increase in creatine uptake, and the increase in creatine noted above[176] was larger than typically seen with a loading protocol (usually in the 20-25% range). Consistent with an exercise-effect, others have reported that exercise itself increases creatine uptake into muscle, reporting 68% greater creatine uptake in an exercised limb, relative to 14% without exercise.[153]
One pilot study using 150mg/kg creatine monohydrate for a five day loading phase followed by maintenance (60mg/kg) for the remainder of the five weeks noted that supplementation was associated with fewer muscle symptoms and complaints alongside improved muscular function,[572] yet a later trial trying to replicate the obsevations using 150mg/kg daily for five weeks noted the opposite, that creatine supplementation exacerbated symptoms.[573] 
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