Neural adaptations account for strength and power improvements observed in athletes within the first ~4 weeks of training. This means that despite no increases in muscle mass, the athletes are able to move more weight and move it faster. This is due to improved coordination and synchronization of muscle firing, a greater ability to recruit higher threshold motor units, improved motor control and inhibition of the golgi tendon organ. Beyond the 4 week mark, athletes continue to make improvements in strength and power output due to further neural adaptations in addition to increases in muscle hypertrophy. Generally with novice athletes, strength and power will both increase at first. However, eventually power will need to be trained specifically to illicit further improvements and transfer to the playing field.
Some important considerations must be made when training specifically for power or hypertrophy. For example, variables such as load, set and repetition configuration and rest period all effect which quality you are trying to develop. This point is illustrated nicely in a new study published ahead of print in the Journal of Strength and Conditioning Research. The study investigated the kinetics and kinematics of cluster versus traditional sets of the back squat in twenty-four college aged men. The subjects were first tested on their 1RM back squat to determine percentages for the subsequent experimental training sessions. 72 hours following the 1RM test, subjects were randomly assigned to perform either a cluster set workout or traditional set workout. Subjects performed another workout 72 hours later which involved the opposite protocol than the one they performed previously. The cluster set involved 4 sets of 2×5 clusters. Here, the athletes would perform 1 set of 5, rest 30 seconds, perform another set of 5 and then rest 90 seconds. This was considered one set and would be repeated 3 more times. The traditional sets simply involved 4 sets of 10 reps so that volume was equalized among the groups. The load used for both conditions was 70% of the subjects 1RM. During all sets, force plates and linear position transducers were used to record force, velocity and power.
The results showed that the cluster sets produced significantly higher force and volume load. In addition, velocity reductions were lessened in the cluster sets enabling greater velocity production later on in sets. Traditional sets did however result in greater time under tension. This research supports previous studies that have made similar comparisons. Breaking sets up into clusters enables one to produce higher quality reps, with greater force, velocity and therefore power. In a straight set of 10, these variables begin to decline about midway through the set. So, if performance is your main objective, then it would be worth considering including clusters to generate greater power outputs and reserve the traditional straight sets for when hypertrophy is the main objective.
Oliver, JM, et al. Velocity drives greater power observed during back squat using cluster sets. Journal of Strength and Conditioning Research, Ahead of Print.