This is an excerpt from Dumbbell Training by Allen Hedrick.
Training with dumbbells provides a variety of advantages. Some of the advantages are practical and some are physiological, but without a doubt, dumbbells will be a good addition to your training program.
Practical Advantages of Dumbbells
Let's start by looking at the practical advantages. One significant benefit of training with dumbbells is their relative low cost and adaptability in comparison with other modes of training. Most exercise machines are expensive and typically can be used to perform only one exercise.
Dumbbells, on the other hand, provide a huge range of exercises. And nearly every barbell exercise you can think of can also be performed with dumbbells. But that is not the end of the list. Add all the exercise variations that are possible with dumbbells that are not possible with barbells (e.g., single-arm and alternating-arm exercises) and you quickly see that the number of potential dumbbell exercises is quite large.
Another benefit of dumbbell training over machine training is that most machines do not lend themselves well to explosive training, the importance of which is discussed in chapter 7. Dumbbells are well suited to explosive training, which is the focus of most of the dumbbell exercises my athletes perform.
While barbells and weight plates are less expensive than exercise machines, they cost more than dumbbells. Further, many exercises performed with barbells require specialized equipment, such as a bench press or squat rack or, in the case of the Olympic lifts, an Olympic lifting bar, bumpers, and a platform that creates a safe area on which to perform the exercises. In contrast, most dumbbell exercises require only an open space for training, a rubber mat or piece of plywood to protect the floor, and an adjustable exercise bench.
Another practical benefit of dumbbell training is that little training space is required, both for storing the dumbbells and for exercising with them. Compare this to machine training, where multiple machines are required to train the entire body, and barbell training, where training occurs with an 8-foot-long (2.4 m) barbell and a recommended 2-foot (61 cm) cushion of space on either end of the barbell. Because of their small size, dumbbells require very little space during training. While you do want a safe buffer around an athlete training with dumbbells, it is possible to train more athletes in a smaller area than could train on either machines or with barbells. Because of the small space requirement during dumbbell training, several athletes can train simultaneously and efficiently with minimal risk of injury. For example, it is possible to have 20 to 25 athletes training with dumbbells in a relatively small area (i.e., 500 square feet) during a training session (broken into groups of two, with one athlete lifting and a partner spotting while waiting to perform a set).
A relatively small number of dumbbells is required to train the entire body. For most people, a weight range from 5 pounds (9.1 kg) to 70 pounds (31.7 kg) in 5-pound (2.3 kg) increments will provide the resistance required to perform most exercises, although some advanced male athletes may need dumbbells 125 pounds (56.7 kg) or heavier. With this limited number of dumbbells it is possible to train all of the major muscle groups of the body performing only dumbbell exercises. For fixed-weight dumbbells (nonadjustable), a weight range from 5 pounds to 70 pounds would require 14 pairs of dumbbells with the weight increasing at 5 pound increments. For adjustable-weight dumbbells, having six 10-pound plates, two 5-pound plates, and two 2 1/2-pound plates would be sufficient to cover a weight range of 5 to 70 pounds (the exact combination would depend on the weight of both the handle and the clamps).
Another benefit of dumbbells is that they are safer than barbells when performing certain exercises, such as one-leg squats or lateral box crossovers because dumbbells are easier to drop safely than a barbell. Say you are performing one-leg squats and you lose your balance—it is easy to safely drop dumbbells held at arm's length in either hand to regain your balance. However, with a barbell across your back, it is more difficult to drop the barbell safely without risking injury to yourself or to someone standing nearby or damaging the equipment.
Dumbbell training also makes it easier for people with injuries to continue to train without aggravating the injury site. An athlete with an arm or shoulder injury would not be able to train the upper body using a barbell. However, it is possible to perform one-arm dumbbell training using the uninjured arm and continue to train. Similarly, a lower-body injury would prevent athletes from performing Olympic lifts with a barbell. However, by using just one dumbbell, stabilizing the body by holding onto something stable with the opposite hand, and lifting the injured leg off the floor, athletes can adapt the Olympic lifts to accommodate one leg.
A final practical benefit of dumbbell training is that, generally, dumbbell exercises are easier to teach than barbell exercises. For example, most strength and conditioning coaches agree that on average it is much easier to teach someone how to correctly catch a dumbbell clean than to teach that same person how to catch a barbell clean. This means you can get through the teaching process and on to productive training more rapidly when training with dumbbells. This is especially important when working with large groups.
Physiological Advantages of Dumbbells
Several physiological advantages of dumbbell training make it effective. Because barbell training is much more common than dumbbell training, the belief exists that barbell training is superior. A study comparing muscle activation while performing barbell bench press and dumbbell bench press found that the pectoralis major appeared to reach approximately the same peak activation level during the lifting phase of these two chest exercises. While greater muscle recruitment was not demonstrated in the dumbbell movement as compared with the barbell movement as has been suggested by some, this may have occurred because of the low number of repetitions and the low weight used in the study (subjects performed three repetitions with a resistance representing a six-repetition maximum) did not result in fatiguing contractions in the recruited muscles (Welsch et al. 2005).
Perhaps one of the most significant benefits to dumbbell training is that you have to control two independent implements rather than controlling a barbell with both arms simultaneously. This makes dumbbell training a more complex motor activity when performing many exercises.
Because you are working with two independent implements, you have the opportunity to perform either alternating movements (e.g., alternating bench press, with one arm pressing a dumbbell up while the opposite arm is lowering a dumbbell) or single-arm movements (e.g., one-arm bench press, doing all the repetitions with the same arm). For many athletes, alternating-arm exercises and single-arm exercises provide a more sport-specific way to train because many activities in sports involve single-arm movements (e.g., throwing a punch, spiking a volleyball, swinging a racket) rather than both arms moving simultaneously through the same movement pattern (Behm et al. 2011). Further, athletes rarely apply force against a balanced resistance during competition. Both alternating and single-arm movements provide a unique training stimulus compared with typical barbell training (Lauder and Lake 2008).
Learn more about Dumbbell Training.