The Dumbbell Stopgap
It is almost universally accepted that the best way to get stronger or increase lean muscle mass is regular barbell training. Unfortunately, a huge number of gyms have begun avoiding barbells in favor of more cardio equipment. For many people, these watered-down, feel-good globogyms are the only available exercise facilities. Often, in what seems like no more than lip service to strength training, these gyms have racks of relatively light dumbbells for “toning.” These are far from ideal as exercise implements, and both barbell training and bodyweight exercises are generally more useful for building strength.
If you have access to barbells and wish to weight train, Starting Strength is almost universally recommended. It also has a wiki, but it is highly recommended you buy the book. It costs about as much as an average monthly gym membership and will teach you more about lifting than almost any other resource. Check out /r/weightroom for more resources and a wealth of user-generated content, some of which comes from current and/or former world record holders.
If you wish to train in bodyweight exercises, these are also an option. They are excellent for building static strength, maintaining weight while growing stronger, and learning basic and advanced body mechanics. For these, Overcoming Gravity and Building the Gymnastic Body are both excellent resources. Check out /r/bodyweightfitness for more resources and a wealth of user-generated content (including much information from Steven Low, the author of Overcoming Gravity). The only thing you really need for this is access to some sort of horizontal bar and a bit of open space.
If you have the resources to build a home gym, that is an excellent option if your only other gym access is one of the aforementioned mediocre-to-bad gyms. Stronglifts.com (another beginner program akin to Starting Strength) has a good writeup on what you will need or want to buy. This can take time, space, and money, but if you have those three things, you should definitely consider it. A home gym can start as simply as a single kettlebell or be as complex and specialized as a professional strongman’s training facility. If you have a single kettlebell and a place to stand, you have enough of a home gym to get started. Buy Enter the Kettlebell and check out /r/kettlebell.
All that being said, if you are unable to do any of the above things for whatever reason, you can start training with dumbbells UNTIL YOU CAN DO ONE OF THE ABOVE OPTIONS. They are all preferable to dumbbell training for beginners.
What this program is not
This program is not for people with a single pair of fixed-weight dumbbells. This program is not an optimal way to get strong or build muscle mass. This program is not a long-term training program.
What this program is
As the name implies, this program is a stopgap until you can gain access to one of the above options. If you are motivated to grow stronger and want to do so immediately, this program will get you started before your motivation dries up as you wait for equipment or books. This program requires that you have access to a set of dumbbells (meaning a progression of dumbbells, usually at 2.5 or 5 lb intervals) or a pair of adjustable dumbbells. You will be working out 3 times a week. You will probably look silly and do exercises that no one else in your gym is doing. This is okay. The only person judging you in the gym is yourself. If someone in the gym is looking at you funny or giving you dirty looks or even talking about you, they don’t matter. You are in the gym to grow stronger and healthier. Anything else in the gym that doesn’t contribute to these goals is meaningless.
There are 2 workouts: A and B. They will alternate with a one-day gap and have a 2-day gap every weekend. So on the first week, you will do Workout A on Monday, B on Wednesday, and A again on Friday (or whatever 3 days you have chosen). On the second week, you will do Workout B on Monday, A on Wednesday, and B again on Friday. And so on. Start with the lightest dumbbells available to you. These may seem incredibly easy or may be too heavy. If they are easy, start with them anyway so that you can learn proper form. As you increase the weight, they will become more difficult. If the available dumbbells are too heavy, start doing the exercises with empty hands.
Seated shoulder press If you don’t have access to a seat, sit on the floor with your legs outstretched (also called a Savickas Press). The latter is actually preferable, but I can’t find a good video guide to doing it.
For each exercise but the plank, at the lightest weight available (or with empty hands), do as many repetitions (reps) as possible, up to 10. Do this three times (sets) before moving on to the next exercise. Rest for 1 minute between sets. When you can do an exercise for 3 sets of 10 reps each, increase the dumbbell weight by one step next time you do the exercise. You may progress very quickly using this method, but eventually it will take longer to increase the weight. This is okay. If you remain stuck at the same number of reps and the same dumbbell weight for 3 workouts, decrease the dumbbell weight by two steps and try progressing again.
For the plank, do 3 sets held as long as possible. If you can’t do 3 sets when you start out, do as many sets as you can.
If you have access to them, dips and pullups are used by both bodyweight strength trainees and weightlifters. They are excellent exercises and will greatly increase your strength. Do the same as above: 3 sets of as many reps as you can. These sets can go beyond 10 reps and still be effective, so do as many as you can 3 times. If you can do 3 sets of 10 reps, you will most likely be stronger than many people in your gym.
This program has a relatively short shelf life. It runs out when your available dumbbell weights run out. This should be long enough, however, to acquire books, information, and/or equipment to move on to one of the more effective programs mentioned above. If you receive or acquire enough equipment to end this program earlier and move on to more effective training methods, please do so as soon as possible. All of the programs mentioned above were made by experienced fitness professionals. This program was made by a random asshole, who is not a fitness professional, on the internet.
Good luck in your quest to grow stronger, healthier, and more fit!