Few pull-ups and lots of pushups may not be caused by a strength imbalance.
Pushups and pull-ups are two popular bodyweight exercises for training the chest, shoulders, arms and back. They are both challenging, effective at building strength and endurance and require little or no equipment. These similarities may cause some people to be distressed when they discover than they can do far fewer repetitions of pull-ups than of pushups. This discrepancy may seem like a strength imbalance. Although that assumption is often erroneous, it is important to consider the factors that determine the difficulty of each exercise and how you can train to ensure a healthy balance between muscle groups.
Just because you cannot perform as many pull-ups as you can pushups doesn't mean you have a strength imbalance. During pull-ups, you have to lift your entire weight against gravity, whereas during pushups your body weight is distributed between your hands and feet. This makes standard pushups easier because, according to an article in the Journal of Strength and Conditioning Research, you are only lifting about 64 percent of your body weight. This means that you can do more pushups before reaching exhaustion. This is why physical standard tests, such as those used by the military, require a higher number of pushups than pull-ups.
The mismatch between the average pushup and pull-up repetitions is usually not a cause for concern because they are not directly antagonistic, or opposed. What this means is that the muscles used in pushups, namely the pectoralis major, anterior deltoids and triceps brachii, are not designed to produce force in the opposite direction to those used in pull-ups -- the lattissimus dorsii, teres major, rhomboid and biceps. A more detrimental example is the common imbalance between an overdeveloped chest and a weaker upper back in the trapezii and deltoids, which tends to round the shoulders forward and produce bad posture.
Certain exercises will allow you to stress the same muscles used in pushups or pull-ups while producing higher or lower repetitions. To get a better picture of the strength in your pectorals, shoulders and triceps versus your back and biceps, you can try bench pressing your own body weight, which should produce lower repetitions that are more comparable to the number of pull-ups you can do. Similarly, you can use an assisted pull-up machine to add repetitions. Setting the machine to negate about a third of your body weight should allow you to perform reps closer to your number of pushups.
If there is still a large discrepancy in the strength of one muscle group or another, you can incorporate exercises that re-target those groups in ways that are antagonistic, which will help you to create balance and increased power production by training them together. For instance, declined pushups shift the weight to your hands and increase force requirements. The higher your feet go, the more you will engage muscles like the upper trapezius and medial deltoid, which are antagonists to pull-up muscles. Similarly, inverted rows work the upper back and rear deltoids, which are antagonists to pushup muscles.