Determining Optimum Repetition Number
©Copywrite 2003 David Woodhouse
Research and practical experience suggest that a certain threshold of intensity (percentage of 1RM) must be breached in order to stimulate an increase in strength. There is however disagreement on the value of that threshold. Certainly, novice strength athletes can improve strength using loads as low as 60% whilst conversely, some bulgarian coaches do not log training loads below 90%!
The relationship between intensity and load is subject to wide inter-individual variation. Athletes with extremely high percentages of fast twitch fibres may only be able to perform 3 repetitions with an 80% load. Conversely, endurance athletes may be able to perform more than 30 repetitions at the same intensity. The relationship also varies for different muscle groups within the body due to differences in fibre composition*. The hamstrings for example have a higher proportion of fast twitch fibres than the quadriceps and hence greater reps are possible at 80% when performing knee extensions than when performing knee flexions (curls!). Finally, training itself can influence muscle fibre ratios hence the relationship is variable over time.
Consider 80% to be the threshold for improvements in strength.
V = No. of reps possible at 80% 1RM
Knowledge of an individuals V value (set:rep pyramid) is vital when selecting number of reps per set. If an athlete performs 5 reps at 80% then the repetition number should be <5 since the training threshold is 80% and 5 repetitions at 80% would constitute a set to failure. For a discussion of why this should be avoided please see my ‘Buffering’ article.
Test Limitations
Total time under tension is reduced by an increase in the speed of the eccentric action. This reduces the cumulative fatigue caused by each repetition and hence permits higher numbers of reps. It is necessary therefore that the exercise is performed strictly and that ‘cheat’ methods are eliminated.
Certain exercises do not safely allow the test because stabilising muscles fatigue before the prime movers. For example in pulling movements, the spinal erectors fatigue before the hip extensors.
Exercises that have a high skill component (e.g. Olympic lifts) are rarely performed in sets of greater than three reps. Fatigue negatively effects motor control and hence causes a break down in technique that increases risk of injury. Additionally performing reps under fatigue is detrimental to the development of optimum inter and intra muscular coordination. When performing exercises that limit the number of repetitions per set, decreasing recovery time and increasing the number of sets is a method of raising density (Tonnage / Training Time).
Common Fallacies
- Low reps cause overtraining
It is prolonged periods of high intensity (>90%) that cause overtraining. Low repetitions do not necessarily imply high intensities. Westside powerlifters for example, perform doubles at intensities as low as 60%. Also, as discussed previously; some athletes may have a 3RM of only 80%!
- Low reps do not cause hypertrophy
Low reps can induce significant hypertrophy providing total time under tension (TTUT) is sufficient. Consider the following two workouts:
- 3x8r @ 75% (180s recovery)
- 8x3r @ 85% (120s recovery)
The greater load in Workout 2 increases TTUT (due to slower movement velocities) and average muscle tension. Although training density (i.e. Tonnage divided by total time to complete sets), depending on recovery time, will be lower I would expect Workout 2 to provide the greater stimulus for hypertrophy.
- ‘Pyramiding’ is an effective training scheme
Pyramid training is at best an inefficient training scheme. The early high repetition sets fatigue the lifter prior to the heavier sets that require the most recruitment, stabilisation and motor control. Additionally, if the range in intensity is too great (>10%) there is insufficient volume at any one intensity to stimulate optimum adaptation. Finally, as mentioned previously, the relationship between intensity and the maximum repetitions possible is not linear, i.e. the increments between repetition maximums increase as the number of repetitions decreases (see above graph). The priority focus when designing programs should be to control intensity to protect against overtraining by using a ‘Buffer’ (see separate article). When using multiple rep patterns within the same workout, determining the magnitude of the buffer for each set becomes unnecessarily complicated. (the buffer also needs to increase as reps decrease)
- I recognise that the terms ‘fast’ and ‘slow’ twitch fibres is a significant simplification