Training Variation Part 1: An Introduction

By: Cody Haun, PhD, MA, CSCS

Have you ever wondered how often you should change up your routine or exercise selection to maximize results? Practically, being able to identify when better results can be obtained through a different training strategy is critical to the optimal training process. Although not always easy, select evidence and strategies can be used to improve the likelihood that training is varied at the appropriate time so that progress can continue. Some of the most common questions I’ve been asked over the years about training programming, and a thought experiment I regularly conduct myself, revolves around this topic and understandably so. Larger scale training variation is certainly important and deserves adequate attention, but the nature of training variation dictates its application at the level of individual training sessions and where I’ve found it most frequently misapplied. Considering this, I wanted to write a series of blog posts on the concept of variation but begin with this short post establishing a definition and some of the important underpinning concepts. So we’re on the same page, I’d first like to define training variation and organize it into three levels so this series is more practically beneficial. Training variation can be defined as an intentional alteration in training parameters aimed at eliciting a specific adaptation. To be clear, training variation is not the same thing as exercise variation. Exercise variation is only one method of training variation. For example, changing the number of reps per set or number of working sets completed for an exercise or group of exercises is an additional type of training variation. Moreover, alterations in training frequency, rest periods, and movement velocity are additional methods of training variation.

With this in mind, variation can be organized into macrocycle-level variation, mesocycle-level variation, and microcycle-level variation. An example of macrocycle-level variation is the organization and alteration in the overall focus of training for longer-term training periods on the order of months to years with intent to achieve a specific adaptive outcome. For example, planning a hypertrophy training phase seeking to enhance muscular size prior to a phase focused on enhancing maximum strength with the overall intention of the macrocycle being to increase maximum strength. Mesocycle-level variation is an alteration in the configuration of microcycle (e.g., 1-2 weeks) structures on the order of months to promote specific physiological responses in these timeframes again aimed at a specific longer-term adaptive outcome. Stated differently, mesocycle-level variations consider the structure and overarching nature of microcycles that make up a mesocycle (e.g., session emphasis, microcycle session number, etc). For example, planning 4 weeks of progressive increases in training volume by adding an additional training session each week prior to a week of deloading where training stress is reduced to promote recovery-adaptation. Microcycle-level variation occurs within individual training sessions and considers appropriate variation strategies on the order of days. Microcycle-level variations are essentially the “means to the end” of the overall training process. This is the level of the training process where direct programming of exercises, sets, reps, etc occur and where training variation must be carefully applied.

First, it’s important to understand that training should not be varied for the sake of variation alone and that the overarching point of variation is to maximize progress. In fact, there are times when very little variation is required to continue making progress so long as the principle of specificity and overload are being appropriately applied (which aren’t exclusive of the principle of variation). The intent of training variation is to maximize progress over time, not to “confuse the muscles” (since muscles don’t have brains) or some other posited reason. The principles of specificity and overload denote that training should be specific to the goal of the training program and that training stress should be increased over time in an appropriate manner. Variation of training in different forms allows this to occur. Stated differently, training variation should be directed or targeted toward the overarching goal of the training process and adhere to the principles of specificity and overload. An obvious example of training variation with intent to adhere to these principles is simply increasing the volume and/or intensity of effort during a training cycle to better ensure desired adaptations. Using this strategy, and altering the selection of exercises at the appropriate time, is based on two additional concepts discussed below.

One of the most well-established adaptive phenomena in the field of exercise physiology is the “Repeated Bout Effect”. To put it simply, the repeated bout effect denotes that the repetition of the same or very similar training bout after adaptation to the bout occurs (e.g., typically after a few days to one week) results in a dampened muscle damage response. This has been demonstrated at multiple levels of analysis, with one of the more simple examples being a reduction in or non-existence of perceived muscle soreness if the same bout of training is repeated within a short time-frame. As pointed out by McHugh, this protective adaptive response involves neural, mechanical, and cellular factors. This concept, and other reasoning, underpins what Zatsiorsky and Kraemer referred to as the “Law of Accommodation”. Louie Simmons has also adamantly supported this concept in his years as an elite powerlifting coach. These authors posit that accommodation is a decrease in the adaptive response of the body to a specific stimulus. Generally speaking, I think we’d all agree that once you’ve lifted a load during a specific exercise, it’s often notably easier to lift the same load in a proximal time frame (assuming no extreme alterations in lifestyle or behavioral factors and that the lift wasn’t a eye-bulging, bloody-nose max effort). What is less clear is to what extent one should increase the load the next training session for the same exercise or how training should be specifically varied to avoid accommodation. For example, should the load be increased by 5kg, 5%, 10kg, or 10 %, etc.? Should the exercise be changed on a weekly basis to avoid accommodation? More on this in later posts. To conclude this post, I’d like to highlight some of the physiological occurrences that support the concepts of the repeated bout effect and the law of accommodation that will help set the stage for the next post on variation, and provide some helpful strategies in the meantime. Readers are encouraged to consult McHugh’s review for more details, as the points below are based on central tenants of the review article.

As mentioned prior, with repeated training bouts adaptations within the nervous systems (i.e., central and peripheral) and at the structural and biochemical level of muscle and connective tissue contribute to a blunted adaptive response. These alterations persuade the eventual variation of training for continued progression. I’ll highlight some of these below and future posts will focus on practical implications and strategies for using variation to your advantage. To be clear, the adaptations highlighted below theoretically occur in the short-term after a single bout of a specific training stimulus and have been or would likely be observed if the bout is repeated in a proximal training bout.

Neural adaptations: 1) an increased recruitment of slower-twitch motor units, and 2) increased activation of larger motor units.
Mechanical adaptations: 1) increased dynamic muscle stiffness, and 2) increased passive muscle stiffness.
Cellular adaptations: 1) parallel and/or longitudinal addition of sarcomeres to existing myofibrils and therefore larger, hypothetically stronger muscle fibers, 2) a reduced inflammatory response, and 3) molecular alterations favoring a more effective contractile response upon excitation of a motor nerve.

These adaptations to a single bout of training involve different timeframes and appropriate programming should take this into account. Practically, these occurrences point to the concept that training should be varied enough in a subsequent bout to spur similar adaptations so that one becomes even stronger over time or continues to realize increases in muscle size. Theoretically, these adaptations will not occur if training isn’t appropriately varied through an increase in training stress or other method of variation. These adaptations are primarily thought to occur as a protective effect to avoid injury, but can obviously contribute to improvements in strength and/or muscle size. Paradoxically, it seems the only way to continually and confidently realize these adaptations is to disrupt the current state of neural and cellular factors to an extent that can be recovered from and adapted to without overdoing it. This is the nature of appropriately applying overload and specificity through training variation over time. To be clear, this information serves as the foundation of varying training so that continued adaptive responses from training can occur. If training stress isn’t sufficiently increased or maintained at an appropriate frequency through variation methods, these adaptations will dissipate; albeit at different rates (more on this in later posts). As promised, some practical implications follow with the plan moving forward to delve into some of the nuances of these processes in future posts.

Variation can be viewed as a principle beneath the umbrella of the principles of specificity and overload, and viewed as a strategy to appropriately apply specificity and overload rather than an exclusive principle altogether. For example, increasing the number of challenging sets completed for an exercise from week to week during a training cycle is a form of training variation and is useful for applying progressive overload. I recently provided an example of this form of variation in another blog post if you’re curious. I’m defining an exercise as a movement performed in context of a training session with the intention of improving a specific fitness characteristic or skill. The principle of specificity dictates that specific adaptations occur to specific stimuli. For example, regular back squatting is very likely to improve back squatting ability. Conversely, random training and exercise selection promotes random adaptations. Expecting back squatting ability to improve from a random combination of lower-body exercises decided upon while walking into the gym is unwise. Immediately, it is apparent that exercise selection should be based on the specific goal of the training process considering both the short and long-term. If whole-body muscle hypertrophy is the goal and in terms of efficiency, one is hard-pressed to find movements better than complete range of motion, technically-proficient barbell squatting, pressing, and pulling. To avoid semantics, the basic reasoning for this is due to the fact that these exercises require the recruitment and action of the largest number of muscles across the majority of their lengths per unit time. Similarly, if strength is defined as one’s ability to produce force, one is equally hard-pressed to find movements that better develop this ability from a whole-body perspective. Dumbbell, machine, and other exercise variations can certainly still promote hypertrophy and strength adaptation but should be carefully considered and included for best results. Selection and variation of exercise and training parameters really boils down to the principle of specificity and the direction in which one would like to aim training. Let’s assume we agree that barbell or multi-joint exercises should compose the majority of exercises in a microcycle for maximum strength and/or hypertrophic benefits based on the brief reasoning provided above and consider some additional aspects of selection and variation.

For strength and hypertrophy, exercise selection should consider: a) movement emphasis, b) muscle emphasis, c) connective tissue stress, and d) nervous system stress. Exercise selection and variation should involve the careful consideration of which muscles are being emphasized and to what extent, and how selection could affect subsequent exercises or sessions in the microcycle so that the best overall outcome of the training cycle can be realized rather than focusing on an individual session alone. Furthermore, recent historical training must be contemplated along with the aim of the subsequent training phase. For competitive strength or physique athletes, having set competition dates helps provide clarity for when certain exercises should be emphasized or deemphasized and when training should be varied and to what extent. As a prelude to future posts, a couple of research examples of relevance can help capture the importance of exercise selection and training variation. Differences in adaptive outcomes of machine-based exercises and barbell exercises are apparent in as short as 8 weeks of duration. For example, Wirth et al showed significantly greater improvements in the squat jump and countermovement jump and numerically greater improvements in maximum isometric peak forces of the left and right legs after 8 weeks of barbell back squatting compared to the machine leg press exercise. This example points to the importance of realizing that short-term training decisions can have significant and obvious effects on performance and that, for best results, random exercise selection and variation is suboptimal. Another cool study by Fonseca et al showed that varying exercises and/or intensity of effort over the course of 12 weeks compared to constant programmed intensities of effort and/or exercises tended to result in significantly greater improvements in 1RM. Since most training studies only span 8-12 weeks in duration, it’s difficult to assert when adaptations would dampen and when variation is crucial. However, we have enough evidence at this point (both practical and empirical) that allows strategic, intelligent variation to be applied. The next post in the series will focus on variation of training through increasing training stress over the course of a mesocycle or block of training and how appropriate manipulations can lead to more pronounced adaptations.


The Importance of Load During Resistance Training: Part 1 | The Aplyft Blog

“I am a scientist first and a coach second. I have a passion for positively impacting the lives of people through providing critically thought-out, data-driven, scientifically-sound nutrition and training programming services that equip individuals to successfully achieve their performance and/or physique goals. I seek to offer the best service within my power and I am confident, given my background, education, experience, and relentless pursuit of knowledge pertaining to human physiology and the training process, that I can provide you with programming to realize great results. Feel free to contact me with any questions.”


Cody Haun, PhD(c), MA, CSCS
-APLYFT Science Consultant