Are All Reps Made Equal? Discussing Range of Motion, Repetition Velocity & Time Under Tension.

Some of the less experienced lifters out there may believe that it is relatively straightforward to lift a weight and to put it down, once you have learned to the correct technique. To a certain extent this is true, and for many novice lifters, simply performing repetitions with correct form at a moderate speed is sufficient to make significant muscle and strength gains. Many personal trainers preach that this is method is optimal for the majority of trainees, and again this may be true for those who are new to the weight room and where the major objectives of their training are to learn the proper technique for each lift whilst gradually increasing the weight and minimising the risk of injury.

However, many bodybuilders and strength athletes successfully utilise partial ranges of motion and a range of repetition speeds regularly within their training. ‘Speed days’ have become an essential part of a powerlifters training arsenal and the famous bicep peaks of Arnold were not built by the rudimentary 3 sets of 8-12 reps of bicep curls every week! This is not to say that incorrect form should be encouraged, only that there are a variety of factors involved in a single repetition that can be manipulated by more experienced lifters to take their training to the next level…and bad form is not one of them!

Firstly, we will explore the evidence for and against the use of various repetition velocities within your training. Although this is subject is a contentious one, it is generally accepted that the speed at which a repetition is performed can affect metabolic, neural and hypertrophic responses to training¹. The widely accepted gold standard for the speed at which a repetition is performed is a moderate velocity, with a 2 second concentric contraction, a 1 second pause and a 4 second eccentric portion of the repetition². It has been hypothesised that utilising this speed format maximises muscular tension and therefore induces greater strength and hypertrophy gains². In comparison to alternative repetition formats, a moderate velocity has been demonstrated to carryover into the greatest strength increases in comparison to other velocities³ as well as across all velocities⁴, and has been shown to enhance muscular performance (i.e. number of reps, work and power output, volume, and increases in strength gains)¹.

Although, a moderate repetition velocity is most frequently recommended, the utilisation of intentionally slow velocity repetitions may be beneficial in the improvement of local muscular endurance and hypertrophy¹. However, the overwhelming majority of studies have found that the intentional use of slow velocities may be suboptimal for strength, improvements in 1RM, and hypertrophy^1,5. This may be due to lower neural activation, the recruitment of fewer motor units, and a lower training load due to the use of submaximal loads⁶.

In contrast to intentionally slow repetition velocities, a number of benefits of the utilisation of fast velocities have been identified, particularly in advanced training. The premise behind the advantage of rapid repetition velocity training, especially for power training, is that power production is increased when the same amount of work is performed over a shorter period of time¹. This method also allows the use of heavier loads, compared to slow velocities, and is often practiced in order to reduce ‘sticking points’ in a lift by providing increased momentum¹. High velocity repetition training has also been shown to increase strength and hypertrophy through increased recruitment of high threshold motor units^7,8. Training with rapid velocity repetitions has also been found to contribute to increased local muscular endurance⁹ and increased hormonal response to training¹⁰. When performed rapidly, the eccentric portion of repetitions has also been found to result in greater hypertrophy than slow eccentric contractions, although this is only the case in exercises performed against gravity (e.g. the bench press)¹¹.

However, fast velocity repetition training is not without its disadvantages, and it has been noted that the deceleration phase of a repetition, towards the end of a repetition before completion, increases as velocity increases¹² and therefore power increases may be more specific to the beginning of a repetition¹. Injury may also be more frequent when this training method is utilised¹³.

From the literature, it can therefore be concluded that training across all velocities may be important to improve force production, local muscle endurance and hypertrophy. Although currently there is a lack of consensus, and often conflicting results, regarding repetition velocity¹⁴, it seems logical to vary the repetition velocities you use in your training and to ensure that you correctly utilise the eccentric portion of a repetition.

Another aspect of a repetition which can be manipulated is the range of motion used, and this can generally be divided into full range of motion (ROM), where the movement is performed throughout the entire range, and partial ROM, where the movement is performed only through a portion of range. It is generally recommended that a full ROM is used for each of the repetitions performed, however Drinkwater and colleagues¹⁵ recently demonstrated that peak power produced was highest in subjects who performed to partial ROM repetitions with heavy loads, which may be a useful tool for improving strength. This strategy may also be useful for athletes who have reached a plateau in full range ROM training¹⁶. However, recently, a substantial amount of evidence supporting the use of full ROM repetitions has been published, with Pinto and colleagues¹⁷ demonstrating that full ROM increased strength to a greater extent that partial ROM training. In an initial study by Massey et al¹⁸, no difference in strength gains between groups who performed repetitions using full ROM, partial ROM or a combination of the two were observed. However, as a result of a follow-up study by the same research group¹⁹, in which athletes performed bench press sessions using full, partial, or a combination of ROMs over a number weeks, it was demonstrated that each of the groups gained bench press strength and that lifting through the full ROM was superior to performing repetitions using partial or a combination of ROMs. Therefore, it should be recommended that athletes utilise a full ROM for most of their training, although partial repetitions may be useful in breaking plateaus and training to failure.

Time under tension during a repetition or set is another factor that may affect strength and hypertrophy gains, and this is commonly believed to be crucial in weight training. Increased time under tension (TUT) has been associated with improvements in local muscle endurance¹ as well as increased protein synthesis²⁰. Increased TUT can be achieved through two strategies, which include the performance of a moderate number of repetitions using intentionally slow velocities, or the performance of a high number of repetitions using moderate to fast velocities. It has also been demonstrated that an increased TUT results in greater fatigue²¹. The authors therefore hypothesised that, if neuromuscular fatigue is an important variable in the development of strength and hypertrophy, that the utilisation of greater TUT may yield greater muscle and strength gains so long as the training load is not compromised. However, to date no study has yet found a direct correlation between TUT and gains in strength or hypertrophy.

In conclusion, although significant evidence exists supporting the variation of repetition velocities, range of motion, and time under tension within your training, the majority of evidence would suggest that performing conventional repetitions at a moderate velocity, through a full range of motion, will yield the greatest increase in strength and hypertrophy over time. However, in order to maximise strength, hypertrophy, neural adaptations and muscular endurance it may be beneficial to frequently incorporate such training variables in the form of ‘speed days’, forced repetitions or sets with increased TUT. It must be stressed, however, that the inclusion of these training variables should not come at the expense of your training progression.

References

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