Exercise program design is considered both an art and a science.  The science is a critical part of the process, as prescription of any exercise variable requires an understanding of science-based principles [2]. In resistance training, these variables include: volume, intensity, tempo, rest intervals and frequency.  The successful achievement of a specific training outcome (i.e. hypertrophy, strength, power, muscular endurance) will be largely determined by proper manipulation of these training variables.  This article will provide a brief overview of each training variable and how such variables can be manipulated to achieve the desired training adaptation.

 

Exercise Program Design Variables

Volume

Volume in exercise program design describes the amount of exercise performed within a  specific time period [14].  For example, volume within a training session or over a weekly basis [12, 14]. Volume is defined as either [12, 14]:

(i) Total repetitions (sets x repetitions)
(ii) Volume load (sets x repetitions x resistance)

Repetitions

Training volume in exercise program design is prescribed according to the number of repetitions per set, number of sets per session, and the number of sessions per week [14].  Repetitions can be classified into three approximate ranges [12]:

1. Low (1 to 5)
2. Moderate (6 to 12)
3. High (15 or more)

Low repetitions are shown to be optimal for increasing muscle strength with minimal benefit to muscle hypertrophy [12].  Lifting at low repetition ranges allows for heavier weights to be used and for maximal muscular force and tension to be exerted [12].  Adaptions in muscular strength are associated with an improved response of the nervous system [12].  Motor units, which are individual neurons that innervate muscle fibers, become more synchronised and recruited in greater numbers under heavier loads [12]. Additionally, nerve impulses are stimulated at higher frequencies, all of which contribute to improved muscular strength [12].

Moderate repetitions (6 to 12) are optimal for muscle hypertrophy [2, 6].  This repetition range allows for increased tension to be exerted by the working muscles.  Also, at moderate repetitions, muscle tension is maintained long enough (time-under-tension) to enhance muscle damage and fatigue, both essential for muscle growth [12].

Using higher repetitions (15 or more) is better suited to achieving adaptations in muscular endurance (i.e. muscles ability to work sub maximally over a longer period) [12].  Working at higher repetition ranges requires less maximal force or muscle tension, however time-under-tension is enhanced from lifting over a longer duration [12].  The benefit of increased time-under-tension is an accumulation of metabolites in the blood (i.e. lactate, inorganic phosphate, hydrogen ions) that stimulate muscle protein synthesis and muscle growth [6].

Sets

A set in exercise program design is defined as a group of consecutive repetitions [8].  The literature shows that a single set performed to failure is enough to induce muscle hypertrophy and strength gains in both untrained and trained subjects [5].  However, a larger body of evidence supports the use of multiple sets over single sets for maximising muscle strength and growth.  A recent (2016) systematic review by Schoenfeld and colleagues showed a dose-response relationship whereby higher volumes (more sets per muscle per week) of resistance training resulted in greater hypertrophic gains compared to lower volumes [10].  As a general guideline for exercise program design, Schoenfeld recommends 2-4 sets per exercise, although this is more dependent on program design [12].  For time restricted training, lower volumes (<5 sets per muscle per week) is sufficient to gain muscle [13].  However, for those that can allocate more time to training, more sets (10+) per muscle per week, up to a certain limit, would lead to greater hypertrophy gains [10].

Intensity

Intensity, in the context of this article, is defined by load or the amount of weight lifted.  Among exercise variables, it is found to be the greatest driver of muscle hypertrophy and strength, even  more than volume [7, 12].  Intensity, in exercise program design, can be determined by repetition maximum (RM), defined by the maximum amount of weight lifted with correct technique for given number of repetitions [2].  For example, a 5RM is the maximum amount lifting with correct technique for five repetitions.

Training intensity, should be manipulated in exercise program design according to the desired goal and is generally determined by repetition range [2, 6].  For training goals related to increasing muscular strength, intensities of approximately 90 to 100 percent of 1RM is advocated [2, 12].  Heavier loads allow for maximal muscle force/tension to be generate, which is conducive to increasing muscular strength [12].  For example, someone with a 1RM squat of 50kg would use loads of 45kg to 50kg.  Training intensities for strength are generally applied within repetition ranges of 1 to 5 [12].

For training goals associated with muscle hypertrophy, moderate intensities of 65 to 85 percent 1RM are optimal for muscle development [12].  Moderate intensities allow for an ideal combination of sufficient muscle force/tension and time-under-tension that provide muscle fatigue and damage, both critical for muscle hypertrophy [12].  Repetition ranges of approximately 6 to 12 are associated with these intensities [2, 6, 12].

Lower intensities of approximately 60 percent or less are best suited to endurance related goals with less of an impact on hypertrophy or strength [12].  The build up of metabolites is advantageous for promoting muscle protein synthesis, however, muscle tension is considerably reduced compared with moderate or higher training intensities  [2, 6, 12].  Training intensities for endurance is typically applied to repetitions of 15 or more [12].

Tempo

Tempo or velocity in exercise program design refers to the speed at which repetitions are performed [6].

Tempo is divided into three different contractions [6]:

1. Eccentric (lowering)
2. Isometric (static)
3. Concentric (lifting)

This variable is expressed numerically in seconds and typically represented in four parts.  For example, a tempo of 2-1-0-1, would refer to a two second eccentric lowering, one second isometric hold in the bottom position, zero second concentric raise, and a one second isometric hold in the top position [8, 12].

For training adaptations related to improving strength, faster tempos (<1 second concentric, 1 second eccentric) have been found to be superior to slower tempos (1-2 seconds concentric, 1-2 seconds eccentric) [4,6].  Because force = mass x acceleration, intentionally slowing tempo would lead to reductions in force production as load would need to be lessened to compensate for a slower tempo [6].  Muscular force, particularly during the eccentric phase of a lift, is highly important for muscle hypertrophy, therefore using very slow tempos (i.e. 15 seconds per repetition) is counterproductive to muscle development [12].  Although, some research exists demonstrating that slower tempos can enhance protein synthesis (24-30 hours post workout), provided the lift is taken to failure [3].

As general guidelines for exercise program design, eccentric tempos of 2 to 3 seconds with an explosive concentric phase are beneficial for muscle growth [12].  However, the literature indicates wider ranges of tempos from 0.5 – 8.0 seconds per repetition can be applied for muscle hypertrophy [11].

Applying an isometric hold at either the bottom or top of a lift would increase time-under-tension, provided muscle tension is maintained, which may stimulate increased motor unit recruitment, muscle firing frequency, and force development [1].  Paused isometric holds at the bottom of a lift (i.e. squat or bench press) using high loads (>85 of 1RM) are commonly used to enhance strength gains.  As a general recommendation for exercise program design, maintaining constant tension at the bottom and top of a lift are suggested in contrast to applying longer isometric holds [12].

Rest Intervals

A rest interval in exercise program design is defined as the length of time between the end of one set to the start of another set or exercise [12].  Rest periods greatly influences the adaptive response to resistance training and its length is largely related to intensity (load) applied [6].  Rest intervals can be classified into three approximate ranges [12]:

1. Short – 30-60 seconds or less
2. Moderate – 1-2 minutes
3. Long – 3 minutes or more

Moderate rest intervals are beneficial for muscle hypertrophy and are found to be potent anabolic stimulators [6].  Hypertrophy training that uses moderate-to-heavy loads performed at moderate repetitions (6-12) rely primarily on energy provided by the adenosine triphosphate (ATP)- phosphocreatine (PCr) system and glycolysis [6].  These rest periods allow for metabolite accumulation in the blood (i.e. lactate), stimulation of anabolic hormones (i.e growth hormone, testosterone), and enhanced localised blood flow, all of which help to stimulate muscle growth [6].

Short rest intervals are best when training for muscular endurance [6, 12].  Endurance training that uses light loads performed at high repetitions (15 or more) primarily utilises aerobic metabolism for energy [6].  Training with short rest periods allows for enhanced metabolite accumulation, increased mitochondrial and capillary numbers and improved lactate buffering capacity [6, 12].

Although short and moderate rest intervals are beneficial for muscle endurance and hypertrophy, these rest periods have detrimental effects to strength and power [6].  Strength and power that uses heavy loads performed at low repetitions (1-6) rely on the ATP-PC energy system, which is best replenished with longer rest periods [6].  For strength, 2 minute rest intervals are advocated, while for power training, rest intervals of 4-8 minutes may be necessary to fully recuperate taxed energy systems [9].

Frequency

Training frequency in exercise program design refers to the number of training sessions completed within a specified period (i.e. one week) [2].  The duration between gym sessions is critical for ensuring sufficient muscular and neurological recovery [2].  Another aspect of great importance is selecting training frequencies to maximise protein synthesis [12].  Returning to the gym before the body has recuperated can severely impair protein synthesis as muscle damage persists [12].  Moreover, impairing the body’s recovery will negatively impact force production and the amount of weight that can be lifted in subsequent
training sessions [12].

Amongst the untrained, a training frequency of 1-3 days per week is found to promote muscular adaptations [2].  As training experience increases, research shows that frequencies of 3-4 days per week may be required to elicit further training adaptations [2].  Among advanced weightlifters and bodybuilders, frequencies of 4-6 days or more per week are found to enhance strength and metabolic adaptions [6].  However, the organisation of workouts at higher-frequencies of training become increasingly important to avoid overtraining [2, 6].

Weekly training frequency directly impacts total training volume [12].  For example, if within-session training volume remains constant and the number of training sessions are increased, total training volume will increase.  The danger with increasing frequency under these circumstances is an increased risk of overtraining [12].  Given this, exercise program design, using either split routine or total-body training, should be structured to ensure adequate recovery.

As a general recommendation for exercise program design, Schoenfeld recommends at least 3 training sessions per week to maximise muscle hypertrophy and a minimum of 48 hours between sessions that train the same muscle group [12].

Summary

Exercise program design is a complex process that involves manipulation of multiple variables.  Some of these variables include volume, intensity, tempo, rest intervals, and frequency.  The scientific literature provides highly valuable information as to how these variables should be manipulated to accelerate and maximise the desired training adaptation.  Prior to engaging in resistance training, an individual or personal trainer should consider the desired objective then apply evidence-based guidelines to justify exercise prescription.

 

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References:

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[2] Bird, S. P. 2005. Designing Resistance Training Programmes to Enhance Muscular Fitness. Sports Medicine. Vol. 35, No. 10, pp. 841-851.

[3] Burd, N. A. 2012. Muscle time under tension during resistance exercise stimulates differential muscle protein sub-fractional synthetic responses in men. The Journal of Physiology. January. Vol. 590 (Part 2), pp. 351-362.

[4] Hay, J. G. 1983. Effects of lifting rate on elbow torques exerted during arm curl exercises. Medicine and Science in Sports and Exercise. Vol. 15, No. 1, pp. 63-71.

[5] Kladir, Z. A. 2014. Single- Versus Three-Set Resistance Training on Strength and Power Among Untrained Men. Proceedings of the International Colloquium on Sports Science, Exercise, Engineering and Technology. pp. 177-187.

[6] Kraemer, W. J. 2004. Fundamentals of resistance training: progression and exercise prescription. Medicine and Science in Sports and Exercise. April. Vol. 36, No. 4, pp. 674-688.

[7] McDonagh, M. J. 1984. Adaptive response of mammalian skeletal muscle to exercise with high loads. European Journal of Applied Physiology and Occupational Physiology. Vol. 52, No. 2, pp. 139-155.

[8] Poliquin, C. 1997. The Poliquin Principles. Napa: Daton Writers Group.

[9] Raastad, T. et al. 2000. Hormonal responses to high- and moderate-intensity strength exercise. European Journal of Applied Physiology. May. Vol. 82, No. 1-2, pp. 121-128.

[10] Schenfeld, B. J. 2016. Dose-response relationship between weekly resistance training volume and increases in muscle mass: A systematic review and meta-analysis. Journal of Sports Sciences. July. Vol. 19, pp. 1-10.

[11] Schoenfeld, B. J. 2015. Effect of repetition duration during resistance training on muscle hypertrophy: a systematic review and meta-analysis. Sports Medicine. April. Vol. 45, No. 4, pp. 577-585.

[12] Schoenfeld, B. J. 2013. The M.A.X. Muscle Plan. Leeds: Human Kinetics.

[13] Schoenfeld, B. J. 2013. How Many Sets Do You Need to Perform to Maximize Muscle Gains? [Online]. [viewed on February 20, 2017]. Available from: http://www.lookgreatnaked.com/blog/how-many-sets-do-you-need-to-perform-to-maximize-muscle-gains/.

[14] Tan, B. 1999. Manipulating Resistance Training Variables to Optimise Maximum Strength in Men: A Review. Journal of Strength and Conditioning Research. Vol. 13, No. 3, pp. 289-304.