Range of Motion (ROM) - Fundamental Terminology to Enhance Understanding and Improve the Application of ROM for Physiological Adaptations Posted on 24 Jan 14:06

First, I want to personally thank everyone for their positive feedback regarding the initial series of hypertrophy articles (Foundational Concepts for Understanding Hypertrophy, Theoretical Framework for Optimizing Training Periodization and Programming, and Hypertrophy Periodization and Programming – Programming Variables – Part 1 and Part 2). Since numerous individuals had questions regarding various topics throughout the articles, I will dedicate the following articles to explaining specific areas of interest that pertain to their questions. The first topic I would like to present and thoroughly explain is range of motion (ROM).  


On the surface, a discussion on ROM may seem basic and straight to the point. However, a vast array of thoughts and considerations come to light under the surface. In comparison, a simple description of what most individuals see as they sit on the beach would be the sand under their feet that reaches into the crashing waves, an ocean that transcends into the horizon, and potentially a beautiful sky. The previous sentence described three incredibly complex topics in one sentence: sand, ocean, and sky. Suppose we present a scientific explanation of the ocean from this person's view. In that case, it could take weeks or months to thoroughly describe what is under the ocean's surface (i.e., the variety of aquatic life and how it survives). Fortunately, it will not take weeks or months to explain ROM thoroughly, but it will require some cognitive effort.  


While most athletes and trainers think they understand ROM, they do not. Unfortunately, this may sound insulting, but they literally cannot develop a solid understanding of ROM. Yes, in the literal sense, most individuals do not have the prerequisite academic knowledge about skeletal muscle physiology to form an understanding of ROM. However, this is understandable because being an exercise physiologist or sport scientist specializing in understanding the mechanisms of hypertrophy or physique transformation is only relevant to some careers. Even in the field of exercise, there have been many financially successful trainers with insufficient scientific knowledge and overall intelligence. While these trainers may not enhance the individual's physique or improve their resilience significantly, they can provide the motivation necessary for individuals to show up and train consistently. Typically, these individuals progress little, but they do not get worse, and eventually, as long as clients do not quit, the trainer will develop a large clientele base. There have also been countless champion bodybuilders that are entirely clueless about muscle physiology, exercise technique, and ROM. The individuals that can win IFBB bodybuilding competitions with horrific exercise form and terrible execution are obviously genetically gifted (i.e., wide clavicles, narrow waist, small joints, excessively round muscle bellies, proportion, symmetry) and are hyper-responsive to positive effects of performance-enhancing drugs (PEDs) while being hyper-resilient to the adverse effects of the PEDs.  


Why am I pointing out these two examples of poor arguments? Because I have overheard countless conversations from lesser-educated individuals claiming science-based information is useless because Insta-Trainer or IFBB Pro Bodybuilder does not use full ROM or proper form, and they built incredible physiques. Unfortunately, many individuals are unaware of their lack of general intelligence, critical thinking skills, and logical fallacy use. Hopefully, pointing out these apparent fallacies (appeal to authority, hasty generalization, red herring, and bandwagon fallacy) will prevent an individual from falling prey to these idiotic ideas.  


 I understand that most people do not care to learn to intricacies of ROM as it pertains to skeletal muscle hypertrophy. Therefore, I kept my initial description of ROM brief in a previous article (Hypertrophy Periodization and Programming – Programming Variables – Part 2) to encourage individuals to use their largest active ROM (or full ROM) for a majority of their resistance training. Then implement partial ROM as needed for specific goals or issues (i.e., intensification technique, occlusion training methods, orthopedic issues, or specialization cycles). That basic description may satisfy the curiosity of ROM for most individuals' resistance training efforts. However, the number of questions I have received indicates a need for a thorough explanation of ROM pertaining to Hypertrophy and Hypertrophy Training.


Since humans think in words or specific language, understanding the appropriate terminology is vital. An individual needs to know the accurate definition of a term or word to form proper thoughts about the subject. Please do not rush through this article and apply a studious effort to comprehend the following terminology.   


  Range of Motion (ROM) 


Range of Motion (ROM) is generally defined as the degree of movement that occurs at a joint. [1.] Again, the degree of movement that occurs at a joint. This definition does not include information regarding muscle length or tension. Therefore, the general definition of ROM is focused on the joint, not the muscle length or exercise. However, in resistance training, the term can be applied to specific exercises and used to communicate form or execution. i.e., barbell bench press ROM, preloading ROM with the words barbell bench press constrains the concept of ROM to the specific exercise pattern of barbell bench press. While performing a barbell bench press with a traditional straight bar, the individual may not achieve a full stretch and a full squeeze of the pectoralis fibers. However, if they can guide the barbell down to their chest and back up to the fully locked-out position, they can achieve a full ROM for the barbell bench press exercise. Modifying the context in which ROM is used may satisfy the need for a quick exercise explanation, but it needs to provide more information to help an individual understand the potential influence of ROM on hypertrophic outcomes. Technically, ROM is the degree of movement that occurs at a joint. However, I would like to present a few subcategories of ROM that I have used to improve my understanding and application of ROM to enhance physiological adaptations.


  Full ROM (fROM) vs. Partial ROM (pROM) 


I want to start with the two most common subcategories of ROM that I hear in discussions of resistance exercise. Full ROM and Partial ROM are regularly used to communicate exercise form or technique. Similar to ROM, these terms satisfy the need for a quick explanation but lack the necessary details to paint the complete picture of physiological adaptations. Once an individual understands the definition of ROM, the terms Full ROM (fROM) and Partial ROM (pROM) should be self-explanatory. When used to describe exercise execution, fROM symbolizes performing the predetermined ROM for the patterned exercise, and pROM represents performing less than the predetermined fROM for the patterned exercise or training through a limited degree of excursion [2.]. These terms are straightforward and easy to understand but used without proper context, and these simple terms can become quite confusing and leave room for various questions. 


For example, if someone says, "I performed fROM during my workout today.", then I would think, "fROM of what… the monoarticular muscle groups, biarticular muscle groups, movement patterns, compound exercises, isolation exercises, loaded exercises, unloaded exercises, internal training, external training...". Therefore, it is best to keep the use of these terms within the specific context of explaining exercise execution. If someone says, "I performed fROM on the preacher curl machine," I would know that they performed the maximum concentric elbow flexion and eccentric elbow extension possible in the specific degree of shoulder flexion provided by that preacher curl machine. Providing accurate and descriptive context also applies to pROM. When discussing pROM, it may be more beneficial to include an additional term to describe the degree of pROM. For example, if a trainer instructs their client to perform a pROM dumbbell bench press, they will not know what degree of motion to perform the pROM dumbbell bench press. Potentially, the trainer could have meant the lengthened pROM (Initial ROM), mid-range pROM, and shortened pROM (Final ROM). Hopefully, these examples explain why terminology is vital for reliable communication. In an effort to provide a thorough explanation of pROM, I will provide additional terminology that may be beneficial for hypertrophic endeavors.


The concept of performing specific exercises with a Partial ROM to bias more tension toward specific tissue is a training mode that has been used for decades. While most individuals have no idea what they are doing and perform the worst version of pROM for hypertrophic outcomes, a select few implement these techniques with precision and reap positive benefits. If we want to discuss using pROM, we must develop a language to adequately describe our thoughts, examine the variables, and consider the potential consequences. First, develop a pROM language to describe our thoughts on the specific exercise or movement execution. Foundationally, the pROM of an exercise or movement can be described as Lengthened pROM, Mid-Range pROM, or Shortened pROM. Lengthened pROM is the bottom third or bottom half of an exercise's movement pattern. Mid-Range pROM is performed by cutting off the lengthened and shortened positions of the exercise's movement pattern and focusing tension on the middle third or middle half. Shortened pROM is the top third or top half of the exercise's movement pattern, also known as the squeeze. These three terms are adequate for discussing potential physiological adaptations related to the training with pROM.   


  Lengthened ROM (Lengthened ROM) 


Lengthened ROM begins in the exercise's movement pattern stretch or lengthened tissue end range and stops at the mid-range or slightly above the middle range of the movement pattern.


  Mid-Range ROM (Mid-Range ROM) 


Mid-Range ROM describes the middle portion of the exercise's movement pattern that is performed without the fully lengthened and fully shortened positions.  


  Shortened ROM (Shortened ROM) 


Shortened ROM begins in the mid-range or slightly below the exercise's movement pattern and stops at the squeeze or shortened tissue end range of the movement pattern.


  Active ROM vs. Passive ROM   


Similar to the externally constrained exercise movement pattern ROM terms, there are internally constrained ROM terms. The expressions Active ROM and Passive ROM are typically used in orthopedic and physical therapy settings. However, I regularly use these terms performing Functional Range Assessments (FRA) and communicating Internal Training vs. External Training information.  


Passive ROM is simply defined as a movement performed without internal tension, but it is produced by an external force (gravity, machine, therapist, stretch strap). For example, when performing an FRA, the certified specialist will move the client's joint through their Passive ROM to assess the articular potential before asking the client to perform the same ROM actively.  


Active ROM is the individual's capacity to internally stabilize their joint and move it through a ROM without external assistance. For example, during an FRA exam, after the certified specialist performs the Passive ROM test, they will ask the client to attempt the same ROM without the practitioner's help. Usually, the Active ROM is ~ 85% of the Passive ROM, but if there is a large discrepancy between Passive ROM and Active ROM, then the trainer can modify the individual's periodization and programming to address the issues.


I know most trainers and athletes do not have the educational background to identify the biological and neurological information provided by the proper application of these terms. Since this article is primarily dedicated to defining ROM, providing a lengthy description of Internal Training vs. External Training may distract from the topic of ROM. Therefore, I will address the topic of Internal Training vs. External Training in a separate article.


For example, suppose an individual's shoulder joint has inadequate Passive ROM for the overhead shoulder flexion used in their programmed shoulder press exercise. In that case, they will be unable to train their overhead shoulder flexion tissue with that exercise sufficiently. Instead of setting up in the correct posture and position to stimulate the desired overhead shoulder flexion tissue, the individual will hyper-extend their spine, lean back, and perform a pROM incline press. On the surface, it may look like a shoulder press exercise. However, their spine is at a 45° to 60-degree angle instead of 80° to 90° degrees. The incorrect posture and position of the spine change the position of the scapulae and shoulder joints. When the individual begins to perform the shoulder press exercise, the load will place tension on the fibers in line with the force. This individual can only achieve a pROM for overhead shoulder flexion musculature with their modified posture (position described above). Therefore, the individual will not provide an adequate shoulder press stimulus to achieve the desired adaptations. Eventually, training with poor posture and positions may lead to the accumulation of shoulder joint injuries, loss of mobility, and poor development of the target tissues. Then the individual will be forced to re-evaluate the movement capacity and prioritize Internal Training, quit training, or spend thousands of dollars a year for multiple years on medical or physiotherapy interventions. In summary, Passive ROM and Active ROM provide quality information that can be used to enhance the individual's periodization and programming. 


  Muscle ROM vs. Motor Unit ROM 


At last, the two ROM terms that were created to help an individual understand the specific physiological adaptations provided by specific resistance training exercises. Muscle ROM and Motor Unit ROM help explain the specific and regional adaptations of skeletal muscle to various stimuli. Unfortunately, most people think that if they perform an exercise, then they are contracting the entire muscle they are trying to stimulate. However, this is not the case, and their misunderstanding of the all-or-none principle of muscle physiology can create lackluster results from training. The all-or-nothing principle states that the neurological discharge to a particular motor unit causes the entire motor unit to contract, not the entire muscle group. The motor unit is the motoneuron, its connected muscle fibers, and the neuromuscular junctions linking the neuron and fibers. Therefore, understanding this basic freshman-level muscle physiology makes it easy to understand how specific ROM training can cause regional adaptations in skeletal muscle. However, without proper knowledge of this terminology, it would be impossible to accurately discuss the ROM mechanisms related to specific or regional adaptations.  


The word Muscle in Muscle ROM represents the individual muscle with a distinct origin and insertion being discussed. For example, Muscle ROM describes the individual muscles of the quadriceps (rectus femoris, vastus lateralis, vastus medialis, vastus intermedius, tensor of the vastus intermedius), not the quadriceps as a whole. While all quadriceps muscles merge into the quadriceps femoris tendon, they have different origins, which could change their function. Therefore, assigning the specific term of Muscle ROM to each of these muscles may improve the accuracy of thought and depth of ROM understanding. Muscle ROM describes the path from maximally lengthened or stretched to maximal shortened or squeezed. Obviously, the Muscle ROM is directly influenced by the number of joints crossed and the movement capacity of the individual articulations (joints). Muscle ROM is similar to a term used in therapeutic exercise textbooks, functional excursion. Functional excursion is defined as the path of maximal stretch to maximal concentric contraction with consideration of the joint or joints crossed. [3.] Since Muscle ROM and functional excursion are very similar, some may use the terms interchangeably. Overall, these terms provide the foundation of information regarding the potential ROM of muscle actions necessary for skeletal muscle hypertrophy. 


The concept of Motor Unit ROM is necessary for understanding specific physiological adaptations, especially regional hypertrophy. The number of muscle fibers that connect to a motor unit can vary significantly between muscles. For example, motor units in the eye may be connected to ten or fewer muscle fibers for precise movement, and motor units in the rectus femoris may be connected to thousands of muscle fibers for gross motor movement. Motor units are generally connected to the same fiber types (fast, intermediate, slow) within the muscle tissue. On average, most humans have a mix of fast, slow, and intermediate fibers, but this can vary significantly due to genetics and epigenetics. The neurological drive that recruits motor units activates specific motor units based on stimulus to the system. Therefore, if the specific stimulus recruits fast twitch fibers, it will activate fast twitch motor units, providing a stimulus to the specific motor unit's muscle fibers. However, various factors can modify the motor units being activated. Evolutionarily, humans have developed escalating and rotating recruitment patterns to meet the excessive demands of the environment.   


Suppose the stimulus originally recruits smaller motor units with slow and intermediate fibers, but the stimulus is repeated to fatigue or failure. In that case, a neurological recruitment pattern known as Henneman's Size Principle takes effect, and the larger, stronger, and faster motor units are recruited. Since each resistance training exercise provides a specific mechanical tension stimulus throughout its ROM, it is easy to understand how specific ROM within each exercise can translate into more mechanical tension for the recruited and activated motor units. If specific motor units are recruited and activated more than other motor units, they will experience greater physiological adaptation. The greater stimulus and adaptation to specific motor units are the foundation for regional hypertrophy. While each muscle may have thousands of motor units, the motor units receiving the largest mechanical tension stimulus from the ROM performed will experience the greatest adaptations. In clinical studies, researchers have suggested that training specific ROM in biceps exercises has the potential effect of regional hypertrophy. [4.][5.] In my opinion, this is why some individuals never develop well-rounded physiques. If an individual does not put tension on specific regions of motor units, then they will not grow or develop those specific regions of muscle tissue. Overall, it is important to periodize and program exercises or movements in training to place adaptive force or tension on the desired muscle tissue.


In summary, ROM is the degree of movement that occurs at a joint, not a muscle or exercise. However, in the context of communicating exercise form or technique, a specific exercise name ROM can be used to help paint the picture for proper execution. Then the terms specific exercise names Full ROM, Lengthened Partial ROM, Mid-Range Partial ROM, and End-Range Partial ROM can be used to increase the detail of the specific exercises target ROM. Also, understanding Active ROM and Passive ROM for proper testing and assessing an individual's needs analysis may help the periodization and programming of Internal Training and External Training to enhance physiological adaptations and reduce the likelihood of injuries. Finally, visualizing the differences between Muscle ROM and Motor Unit ROM should shed light on the possibilities for specific physiological adaptations and regional hypertrophy. Please understand that this is a brief summary of a few points to consider when discussing the topic of ROM. Hopefully, it will add clarity and accuracy to your philosophical conversations regarding Range of Motion (ROM).



[1.] Haff GG and Triplett NT. Essentials of strength training and conditioning. 4th ed. Champaign, IL: Human Kinetics, 2015. 

[2.] Newmire DE and Willoughby DS. Partial compared with full range of motion resistance training for muscle hypertrophy: a brief review and an identification of potential mechanisms. J Strength Cond Res 32: 2652-2664, 2018

[3.] {Ref 2_32.} Kisner, C, Colby, LA, and Borstad, J. Introduction. In: Therapeutic Exercise: Foundations and Techniques. Philadelphia, PA: F.A Davis, 2017. 

[4.] Pinto RS, Fomes N, Radaellik R, Botton CE, Brown LE, and Bottaro M. Effect of range of motion on muscle strength and thickness. J Strength Cond Res 26: 2140-2145, 2012.

[5.] Sato S, Yoshida R, Ryosuke K, Yahata K, Yadaka K, Nunes JP, Nosaka K, and Nakamura M. Elbow joint angles in elbow flexor unilateral resistance exercise training determine its effects on muscle strength and thickness of trained and non-trained arms. Front Physiol 12: 734509, 2021