Research has shown one type of muscle contraction is most effective at increasing muscle strength and size...the eccentric contraction. Rather than focusing on "lifting" weights, the emphasis should be on lowering them.
If performed correctly, you may even be able to reduce your time at the gym. Exercisers who only "lower" weight will see the same improvements as those who "raise" and "lower" weights, despite only performing half the number of repetitions!
Focusing on "eccentric" muscle contractions, in which activated muscles are lengthened, is more important to increasing strength and size of muscles, rather than the volume.
Research has proven that just one eccentric muscle contraction a day can increase muscle strength if it is performed five days a week, even if it's only three seconds a day. However, "concentric" (lifting a weight) or isometric muscle contraction (holding a weight) does not provide such an effect.
You can be far more efficient and still see significant results by focusing on eccentric muscle contractions.
For example, in the case of a dumbbell curl, many people may believe the lifting action provides the most benefit, or at least some benefit, but research shows concentric muscle contractions contribute little to the training effects.
Crunching the numbers
One such study consisted of three groups who performed dumbbell curls twice a week for five weeks, plus a control group who did nothing.
Of the training groups, one performed eccentric-only muscle contractions (lowering weight), another concentric-only muscle contractions (lifting weight) and another performed both concentric and eccentric muscle contractions (lifting and lowering weight alternatively).
All three saw improvements in concentric strength, but this was the only improvement for the concentric-only group. The eccentric-only and concentric-eccentric groups also saw significant improvements in isometric (static) strength and eccentric strength.
Most interestingly, despite the eccentric-only group doing half as many reps as those lifting and lowering weights, the gains in strength were very similar and the eccentric-only group also saw a greater improvement in muscle thickness, an indicator of muscle hypertrophy: 7.2% compared to the concentric-eccentric group's 5.4%.
Understanding the benefits of eccentric-focused training can allow people to spend their time exercising more efficiently.
Putting it into practice
So how can we put this knowledge to use in the gym?
Grab a dumbbell, use two hands to help with the concentric (lifting weight) phase, before using one arm for the eccentric phase (lowering weight), when performing exercises such as:
Using leg weight machines:
Chair sit: From a half-squatting position, sit down slowly on a chair in three seconds, (narrower and wider stances will create different effects). If this is easy, try to sit down with one leg.
Chair recline: Sit on the front of a chair to make a space between your back and the backrest, recline back slowly in three seconds (arms can be crossed at the chest or hold at the back of a head).
Uneven squat: Stand behind a chair, lean to one side to put more weight on one leg, then squat down in three seconds.
Heel down: Still behind a chair, lean forward and raise your heels. Then, lift one leg off the ground and lower the heel of the other leg in three seconds.
Wall kiss: Lean against a wall with both arms fully extended. Bend the elbow joint slowly over three seconds until your face gets close to the wall.
Front lunge: Place one leg in front of the other and bend the knees deeper over three seconds.
Adapted from: 'Comparison between concentric-only, eccentric-only and concentric-eccentric resistance training of the elbow flexors for their effects on muscle strength and hypertrophy' (European Journal of Applied Physiology.)