Movement variability refers to the natural variations in motor performance across multiple task repetitions. Unlike traditional training models emphasizing rote repetition (repetitive repetition with no variation) and technical rehearsal to achieve movement automation, research shows that learning and performance are nonlinear processes (Caldeira et al., 2023).
This means repeatedly practicing the same way does not linearly provide better results. Movement variability allows individuals to explore different motor solutions to achieve task goals, leading to more adaptable and resilient movement patterns, better performance, and injury resilience.
The Constraints-Led Approach in Training
A constraints-led approach (CLA) provides an effective method for integrating movement variability into training. This framework emphasizes:
- Encouraging self-organization of movement under constraints
- Inducing movement pattern variability (strategic and execution variability)
- Promoting the coupling of information and movement as skills develop
- Empowering athletes to explore solutions (Caldeira et al., 2023)
Trainers can help clients develop robust movement patterns that remain effective under different conditions by adjusting environmental, task, or individual constraints.
Self-Organization of Movement Under Constraints
Scenario: Split Squat with Load Variability
A personal trainer works with a client who struggles with lower-body stability and strength, particularly in lunges and single-leg movements. Instead of over-coaching every aspect of form, the trainer applies a constraints-led approach to encourage self-organization.
Setup & Constraints:
The client performs a rear-foot elevated split squat (Bulgarian split squat). The trainer provides different load placements (e.g., dumbbell in one hand, both hands, goblet position, or overhead) and other balance aid options (e.g., PVC pipe in one hand, holding onto a squat rack, holding onto an anchored resistance band, having a hand hover over a plyo box, etc).
The client must adjust their posture, balance, and movement strategy based on the load’s position and the balance aid used.
Why This Works:
- Task Constraint: Changing load placement and balance aids force clients to self-organize their posture and control naturally.
- Environmental Constraint: It further encourages real-time stability adjustments if performed on a slightly uneven or soft surface (like a mat).
- Individual Constraint: The trainer can limit verbal feedback, allowing clients to discover their most stable stance and weight distribution.
Execution:
The trainer asks the client to hold a dumbbell only in the right hand for one set, then switch to the left for another. The client has a PVC pipe in the non-dumbbell hand during this set. The trainer progressively moves to a goblet hold and then an overhead hold without giving explicit instructions on adjusting, letting the client figure it out through movement.
The trainer can ask exploratory questions like:
- “What do you notice about your balance?”
- “Which stance feels most stable?”
- “How does shifting the weight change your control?”
Outcome:
The client automatically refines their stability strategies by responding to the changing constraints rather than being given rigid instructions. This improves motor learning, adaptability, and strength in a way that carries over to real-world movements.
Inducing Movement Pattern Variability
Scenario: Reactive Lateral Hurdle Step with Unpredictable Targets
A personal trainer works with a client to improve lower-body agility, coordination, and resilience against injury. Instead of repeating the same movement pattern, the trainer applies strategic (planning) and execution (motor control) variability to encourage adaptive movement solutions.
Setup & Constraints:
- Place several low hurdles in a line.
- The trainer holds up colored cones or numbers randomly to signal where the client should move next.
- The client reacts in real-time, stepping laterally over the hurdles in different directions based on the trainer’s cues.
Why This Works:
- Strategic Variability – The client must adjust their decision-making by responding to the trainer’s unpredictable cues rather than repeating a pre-planned movement.
- Execution Variability – The movement changes slightly each time due to variations in foot placement, speed, and body positioning, preventing over-reliance on a single pattern.
Execution:
- The trainer signals “Left – Blue!” The client quickly moves over the hurdle toward the left, stepping onto a blue marker.
- The trainer changes cues randomly, requiring constant movement variation.
- The trainer occasionally adjusts hurdle spacing or height mid-session to induce variability further.
- The client is encouraged to experiment with different step lengths, landing positions, and upper-body coordination.
Outcome:
- The client learns multiple ways to complete the same task, which improves adaptability in real-world movements.
- This builds movement resilience, reducing injury risk by exposing the body to diverse movement patterns.
- The client improves their ability to react and adjust dynamically rather than relying on repetitive, robotic execution.
Practical Application for Personal Trainers:
- Modify task constraints such as equipment, surface, or environmental conditions to challenge movement adaptability.
- Introduce multi-planar movements to enhance strategic and execution variability.
- Use open-ended drills where clients must find multiple solutions to a given task, reinforcing adaptability.
Balancing Movement Consistency and Variability for Performance and Injury Prevention
While movement variability is essential for adaptability, excessive variability can lead to acute injury, whereas too little variability increases overuse injury risk. This relationship follows an inverted-U shape where optimal variability exists between these two extremes (Cowin et al., 2022). In other words, too little or too much movement can be sub-optimal.
Examples:
- Too little variability: A volleyball athlete who repeatedly lands from jumps with the same mechanics may develop overuse injuries due to localized tissue strain.
- Too much variability: A sprinter with excessive variability in step width may experience balance issues, increasing fall risk.
Practical Application for Personal Trainers:
- Monitor and assess clients’ movement patterns to identify overly rigid or erratic movement tendencies.
- Implement controlled variations in exercise execution to maintain optimal variability, such as changing grip position during pulling movements.
- Educate clients on adjusting their movement strategies based on fatigue and environmental constraints.
Movement Variability and Fatigue
Fatigue can influence movement variability by either increasing or restricting adaptability. Research has shown muscle fatigue induces variability across subjects performing repetitive tasks (Savin et al., 2021). In sports, elite athletes demonstrate variability adjustments to maintain performance despite fatigue, such as modifying jumping mechanics to sustain jump height (Cowin et al., 2022).
Practical Application for Personal Trainers:
- To help clients maintain effective movement patterns under stress, incorporate fatigue-resistant training methods, such as progressive endurance drills.
- Teach clients to recognize and adjust for fatigue-induced variability to avoid compromised form.
- Use interval-based training to allow movement adaptations without excessive fatigue accumulation.
Movement Variability in Rehabilitation and Pain Management
Individuals with chronic non-specific low back pain (CNSLBP) exhibit altered movement variability during functional tasks, though research findings on the direction of variability change are inconsistent (Alsubaie et al., 2023). This suggests that movement variability is critical in pain management and rehabilitation.
Clients may believe that they should not do a particular movement or exercise because of their experience with pain. From the client’s perspective, it is easy to write off ever doing an exercise again that hurts. However, many clients don’t understand that subtle, essential variations in the painful exercise can drastically change the experience.
It’s up to the personal trainer to lead the client through variations of an exercise to help them find their entry point back into the pain-provoking movement. For example, a client with knee arthritis may experience pain while squatting or performing leg exercises. However, their trainer can help them explore strategic and execution variability through different modifications, such as:
- Range of motion
- Proximal joint initiation
- Loading position
- Assistance
- Foot position
- Tempo
- Co-contraction
Practical Application for Personal Trainers:
- Work with healthcare professionals to assess and modify movement strategies for clients with chronic pain.
- Encourage controlled variability in movement to avoid excessive rigidity, which can contribute to discomfort.
- Implement corrective exercises that promote gradual movement adaptability while ensuring stability and control.
Conclusion
Movement variability is a critical component of effective personal training. By understanding and applying the principles of movement variability, personal trainers can:
- Enhance skill acquisition through a constraints-led approach
- Reduce injury risk by balancing movement consistency and variability
- Improve resilience and adaptability in performance
- Support rehabilitation efforts through controlled movement variability
- Help clients develop multiple movement strategies for task success
By implementing these principles, personal trainers can create more effective, adaptable, and injury-resistant training programs that align with modern research on motor learning and performance.
References
- Caldeira, P., Paulo, A., Veloso, A., Infante, J., Davids, K., & Araújo, D. (2023). How functional movement variability facilitates successful skill adaptation during the volleyball attack. International Journal of Sports Science & Coaching, 19(2), 668-676. https://doi.org/10.1177/17479541231168012
- Cowin, J., Nimphius, S., Fell, J., Culhane, P., & Schmidt, M. (2022). A proposed framework to describe movement variability within sporting tasks: A scoping review. Sports Med Open, 8(1), 85. https://doi.org/10.1186/s40798-022-00473-4
- Alsubaie, A. M., Mazaheri, M., Martinez-Valdes, E., & Falla, D. (2023). Is movement variability altered in people with chronic non-specific low back pain? A systematic review. PLoS One, 18(6), e0287029. https://doi.org/10.1371/journal.pone.0287029
- Moreno, F. J., Caballero, C., & Barbado, D. (2023). Editorial: The role of movement variability in motor control and learning, analysis methods, and practical applications. Front Psychol, 14, 1260878. https://doi.org/10.3389/fpsyg.2023.1260878
- Savin, J., Gaudez, C., Gilles, M. A., Padois, V., & Bidaud, P. (2021). Evidence of movement variability patterns during a repetitive pointing task until exhaustion. Appl Ergon, 96, 103464. https://doi.org/10.1016/j.apergo.2021.103464
