For example,
a narrow hand placement will result in significantly greater tricep activation than a wide base hand placement.
Indeed, Cogley et al. (2005) reported that
narrowing the hand placement from shoulder width to thumbs touching increases Pectoralis major EMG amplitude from 63 to 86 % of MVC.
Not exact matches
You can target different muscle groups by adjusting your
hands placement: the wide grip is great for stressing the pecs, while a
narrower grip works the triceps better.
Now, your arms certainly won't explode if you decide to use a wider or more
narrow grip (
hand placement) when doing chin - ups.