In training forearms are weaker than can not always reach full fatigue, so that the use of handles to help eliminate the problem enough yet to be developed impede the natural strength of the muscles in that region; think there is a general rule that appointment should be avoided to maximize the use of straps and try to catch the weights naturally to force the development of movement and consequently maximize hypertrophy and strength in the forearms.
Many friends sent us comments which cited that unfortunately happens in some exercises force imbalance to the point of getting up a load far superior to that achieved with hand catch, for example is very common in the deadlift or shrinkage where the imbalance can to limit the gains as long forearms fail before the target muscle and only in such cases the use of the handles is recommended providing the benefits of a workout.
The problem is that some people create a dependency on the use of handles and fail to train without them, but this unnecessary use further increases the strength imbalance between forearms and other muscles including reaching an important asymmetry noted that ultimately destroys the harmony the body and can lead to injuries.
Experts of cite that handles are not aesthetic accessories for use inside the gym as it happens with the belt (that can also be used in specific occasions but we see people parading with them inside the gym); the straps should be used only when there is no other way out, even should avoid using them when the situation is difficult and the weight is escaping almost hand in hand but manages to finish the series.
The recommendation is to use the handles on the latest series of training, which will probably be using the increased load, it is also ideal to use those that were manufactured with reinforced and resistant fabric to achieve optimal grip on shrugs, in rowing, in the deadlift, or performing exercises longer series.