why runners should avoid gloves, straps and belts in the weight room

Weight lifting is a great cross training exercise for runners. Training with weights helps you build muscle in ways that aren’t stressed enough as a runner, which can lead to a healthier and less injury prone body that can run faster and farther.
Weight training doesn’t have to be complex. As a runner, you will usually want to stick to body weight exercises or simple moves with dumbbells or barbells. There’s no need to start out with expensive equipment such weight gloves, wrist straps or weight belts, which can be bad for you and should be avoided except in limited circumstances.
First, what are they?

Weight lifting gloves are padded gloves that usually have the fingers cut off, much like bicycling gloves, that help you maintain your grip on a bar.
Wrist straps are pieces of rope or leather that you wrap around your wrists and then wrap around a bar to help support heavy weights and to make it so that you do not have to rely upon your grip to keep from dropping the bar.
Weight belts are belts that you wear around your stomach and lower back. They are not used to hold your shorts up; instead, they are used to support your back so that you are less likely to contort it into a potentially dangerous position. All three items should be used when you are lifting heavy weights at or near your maximum where there is a good possibility of not being able to maintain your grip or keep your back straight. In fact, in some cases it would be foolish not to use them.

However, for the average runner, recreational weight lifter or even the serious athlete that is not a power lifter, they should not be necessary.
Instead, you should concentrate more on building a base and lifting weights that you can handle.
I recommend my athletes that are cross training in the weight room to avoid using gloves, straps or belts for the following reasons:

They discourage good form. By relying on a foreign implement, you are not learning how to support your own back or wrists. In most situations outside of a gym, you will not have gloves, straps, or a weight belt available (or you will not think to use them if you do) and can easily hurt yourself if you are used to having extra support that is not there. Moving a heavy box, or playing outside with your kids can be a lot less pleasurable after throwing your back out.
They make exercises easier. By helping to support the weight, you are not getting the same benefits. You will not develop a better grip by supporting the bar with straps or with gloves. Your back will not get as strong if it doesn’t have to do all the work of keeping a bar from moving.
They can encourage lifting too much weight. Since exercises are made easier, it can be tempting to lift more weight than you are ready for. This is especially dangerous for inexperienced weight lifters who are not really sure what they are capable of and have not perfected the proper form. They just are not ready to push their limits yet.
You only have two hands. I think that carrying a water bottle around with you at the gym is much more important than carrying extra implements, and you should carry a memo pad or other journal where you can record your workouts as well. You do not want to have to keep track of a few extra items on top of those. Granted, you could wear them from exercise to exercise, but there is no reason to wear them for exercises where they would do no good under any circumstances.
Deadlifts and squats can be safely done without a weight belt. Despite the common assertion that your back requires the extra support, people were picking things up off of the floor long before weight belts were invented. The trick is to learn good form, and to remember to use that good form while exercising. It also doesn’t hurt to lift manageable and realistic weights. For near maximum weight lifts, then you would want to use a weight belt. Every tool has its place, but for a recreational weight lifter I do not see the need for gloves, straps, or belts. For somebody just getting into weight lifting, learn the proper form and method for each exercise and try to do it without extra support. In fact, you may even want to try getting rid of your shoes while lifting to help strengthen your feet. Your muscles are meant to be used in unison, not in isolation.

A good rule of thumb is that if you can do five or more repetitions in an exercise, then you probably do not need to use gloves, straps or a weight belt. For recreational or novice weight lifters, and for most athletes, there is often little reason to need to lift weights heavy enough that you can not lift them a half dozen times per set, and so little reason to run out to purchase something you don’t need before you go to the gym for the first time.