Paula JG Freund and Jared E Reser with GPT 5.6 

Abstract

Cross-training commonly refers to the use of several distinct activities to develop complementary capacities and distribute physical stress. A comparable form of diversification can occur within a single activity through systematic variation of movement geometry, timing, resistance, coordination, environmental conditions, attentional demands, and regulatory state. The term intra-activity cross-training, or cross-training from within, is proposed for this practice. The general task and its goal remain stable while selected features of execution are varied. This approach is grounded in research on motor abundance, optimal feedback control, task-relevant variability, contextual interference, strength specificity, and locomotor adaptation. Anti-rigidity represents a geometric subtype of intra-activity cross-training in which underused, safe movement configurations are explored under low load, progressively controlled, and reintegrated into the complete activity. Its proposed training unit is the movement option: a functional combination of joint configuration, muscle length, force direction, contraction type, timing, sensory expectation, and load tolerance. The framework distinguishes seven domains of intra-activity variation and applies them to walking, running, swimming, and yoga. Available evidence suggests that structured variability can broaden motor exploration, promote adaptation to changing constraints, and increase usable mobility. Its effects depend on the location, magnitude, sequencing, and relevance of the variation. Excessive or poorly targeted variability may interfere with performance and learning. Direct trials of anti-rigidity and intra-activity cross-training are needed to determine their effects on active range of motion, strength across joint angles, transfer, perturbation tolerance, movement confidence, and long-term function.

Keywords: active mobility, anti-rigidity, contextual interference, cross-training, motor learning, motor variability, movement repertoire, task constraints

1. Introduction

Cross-training is usually organized across activities. A runner cycles, a swimmer lifts weights, and a strength athlete practices yoga. Alternating activities can distribute mechanical stress and expose the body to different metabolic, coordinative, and environmental demands. A second form of diversification is available within each activity because familiar activities contain many possible modes of execution.

Walking illustrates the principle clearly. A person can vary pace, cadence, step length, step width, direction, terrain, incline, arm movement, trunk rotation, breathing, attentional focus, and social context while continuing to walk. Earlier descriptions of anti-rigidity and anti-rigidity while walking proposed the deliberate exploration of different movement vectors, muscle lengths, contraction types, and postural configurations during ordinary activity. They also presented walking as a daily carrier for mobility, breathing, posture, attentional, and behavioral training (Reser, n.d.-a, n.d.-b). 

The present framework develops these observations into a general model of intra-activity cross-training. The central hypothesis is that a familiar activity can be used to train a broader functional repertoire when its internal parameters are varied in a purposeful, graded, and recoverable manner. Anti-rigidity occupies a specific place within the framework as a method for increasing active mobility and reconditioning underused muscular contributions within the activity.

2. Activities as Families of Motor Solutions

An activity label refers to a class of related actions. Walking includes every successful coordination that moves the body through an environment while preserving balance and forward progression. Swimming includes many combinations of propulsion, body rotation, breathing, limb sequencing, stroke rate, and orientation. Yoga includes postures and transitions performed with different ranges, support conditions, levels of muscular engagement, visual demands, and breathing patterns.

Motor-control research provides a formal basis for treating an activity as a family of solutions. The body possesses more biomechanical degrees of freedom than are strictly necessary for many task goals. The uncontrolled manifold framework distinguishes variation that changes an important task outcome from variation among component configurations that leaves the outcome stable. Optimal feedback control models similarly propose that the nervous system can tolerate deviations along dimensions that have little effect on task success while correcting deviations that threaten the goal (Scholz & Schöner, 1999; Todorov & Jordan, 2002). 

Skilled performance therefore includes both consistency and flexibility. The task outcome can remain dependable even when the specific joint angles, muscle forces, trajectories, or timing relations vary. A robust walker arrives at the intended location under several surface, speed, and balance conditions. A robust swimmer preserves propulsion and orientation across changes in stroke rate, breathing schedule, and water conditions.

Intra-activity cross-training can be defined as the systematic variation of an activity’s execution or constraints while preserving its general identity and functional goal. Three features distinguish it from ordinary repetition. A parameter is deliberately varied, the variation creates a meaningful change in the control problem, and the resulting skill or capacity is reintegrated into the complete activity. The activity serves as a stable task framework within which multiple solutions are practiced.

3. Repetition, Variability, and Motor Learning

Repetition develops efficiency and reliability under familiar conditions. Repeated exposure can improve timing, reduce unnecessary effort, stabilize useful coordinations, and lower attentional demands. These benefits are often specific to the speeds, joint configurations, contexts, and sensory conditions encountered during practice. A person may therefore become highly efficient within a narrow region of an activity’s solution space.

Movement variability has several possible sources and functions. Some variability reflects measurement error, physiological noise, fatigue, or poor control. Other variability supports exploration by allowing the learner to sample alternative solutions. In experiments involving reaching and redundant motor tasks, task-relevant variability and exploration within joint redundancy have predicted subsequent learning under some conditions (Singh et al., 2016; Wu et al., 2014). Animal research also indicates that motor variability can be regulated according to recent outcomes and task uncertainty, suggesting that exploration is dynamically adjusted during learning (Dhawale et al., 2019). 

The location of variability within the task is consequential. Ranganathan and Newell (2010) manipulated variation at the level of the target and at the level of redundant movement paths. Practice effects depended on which variable was changed and whether the transfer test matched the practice condition. Their results indicate that exposure to multiple execution paths does not automatically produce broad transfer. The induced variability must address the dimensions that will later require adaptation. 

Research on contextual interference offers a related perspective. Random or interleaved practice can make acquisition more difficult while improving retention or transfer in some tasks. Gradually increasing interference may be useful when the learner first needs a stable foundation (Porter & Magill, 2010; Shea & Morgan, 1979). Other experiments have found limited or null differences among different amounts of task variation, particularly when transfer is weak across all conditions (Schmidt et al., 2021). 

Very high variability can also impair learning. Cardis et al. (2018) found that large induced variability hindered performance and learning in a redundant task, including variability along dimensions that did not directly change the immediate task result. The relevant training objective is therefore a controllable range of task-relevant variability. Its usefulness depends on the learner’s skill, the difficulty of the task, the amplitude of the variation, and the outcome for which transfer is desired. 

4. Anti-Rigidity as Geometric Cross-Training

Anti-rigidity was originally described as a method for counteracting the narrow movement geometry produced by repetitive modern behavior. The framework uses the metaphor of “missing corners” to describe joint positions, muscular contributions, and movement vectors that receive little exposure during habitual activity. Proposed practices include low-force contraction in unfamiliar positions, exploration of several directions, use of concentric, eccentric, and isometric actions, and incorporation of these movements into walking and yoga (Reser, n.d.-a). 

A scientific operational definition can be formulated as follows:

Anti-rigidity is the deliberate, low-load exploration and graded strengthening of underused, safe movement configurations, followed by their reintegration into a familiar activity.

This definition places anti-rigidity within the geometric domain of intra-activity cross-training. It varies joint configuration, muscle length, force direction, contraction type, and coordination while the larger activity continues to organize the movement. Its proposed outcome is an expansion of active, load-tolerant mobility.

The appropriate functional unit is a movement option. A movement option consists of a joint configuration, a set of muscle lengths, a direction and magnitude of force, a pattern of contraction, a sensory prediction, and a degree of load tolerance. A muscle may contribute effectively at one joint angle and poorly at another. A person may possess substantial passive range while lacking the strength, confidence, or coordination required to control that range.

Active mobility can therefore be defined as the range a person can voluntarily enter, stabilize, load appropriately, and exit under control. This formulation incorporates muscular capacity and sensorimotor control alongside mechanical range. Full-range resistance training has been shown to increase flexibility in untrained adults, with improvements comparable to those produced by static stretching in the ranges tested. Isometric training studies also demonstrate that strength adaptations can vary across joint angles and muscle lengths (Morton et al., 2011; Noorkõiv et al., 2014). These findings support the graded loading of underused ranges as one potential mechanism of anti-rigidity. 

The term rehabilitation is most precise when an identified impairment or clinical condition is being treated. In general physical training, reconditioning describes the recovery of underused movement options without implying a diagnosis. Anti-rigidity may contribute to rehabilitation when it is incorporated into an appropriately assessed clinical program, although the named method has not yet been tested as a standardized rehabilitation intervention.

5. Proposed Mechanisms

5.1 Exploration of the Motor Solution Space

A familiar activity often converges on a preferred solution because that solution has been repeatedly successful. The preferred pattern becomes fast, economical, and predictable. Continued reliance on it also reduces the frequency with which neighboring solutions are sampled.

Structured variation creates a local search around the preferred pattern. Small changes in cadence, stance, direction, load, or coordination provide information about alternative solutions and their consequences. The learner can compare effort, stability, comfort, and performance across these alternatives. Studies linking task-relevant variability with learning suggest that appropriately directed exploration can help identify useful movement solutions, although the relationship varies by task and learning mechanism (Singh et al., 2016; Wu et al., 2014). 

5.2 Range-Specific Neuromuscular Adaptation

Muscular function depends on joint position, muscle length, contraction type, velocity, and the coordination of surrounding structures. Repeated training through a limited range provides a concentrated stimulus within that region. Exposure to additional safe ranges can distribute practice across a broader portion of the force-angle and length-tension relationships.

Anti-rigidity applies this principle at low intensity within or adjacent to a functional task. An unfamiliar configuration is first entered with limited range or resistance. Isometric, concentric, or eccentric effort is then added while the person maintains control. The new capacity is subsequently tested in the complete activity. Evidence of angle-specific neuromuscular adaptation and flexibility gains from full-range resistance training makes this mechanism plausible, while direct anti-rigidity trials remain necessary (Morton et al., 2011; Noorkõiv et al., 2014). 

5.3 Sensorimotor Calibration Across Contexts

Every variation changes the relationship between motor commands, sensory feedback, and task outcome. A different surface alters foot placement and balance information. A change in speed alters timing, momentum, and force requirements. A new breathing pattern or visual condition changes the information available for regulating the movement.

Locomotion research demonstrates that apparently modest changes can create distinct control problems. Uneven terrain increases step variability, redistributes lower-limb joint work, changes muscle activity, and raises metabolic expenditure during walking. Running over uneven terrain also alters step variability, muscle activity, leg stiffness, and energetic cost (Voloshina et al., 2013; Voloshina & Ferris, 2015). 

Adaptations may remain partly specific to the conditions under which they were learned. In split-belt treadmill experiments, adaptations acquired at one walking speed transferred incompletely to other speeds, suggesting partial separation among the control processes used for faster and slower walking (Vasudevan & Bastian, 2010). These results support practice across several relevant contexts when broad adaptability is the intended outcome. 

5.4 Attentional and Regulatory Flexibility

The information used to regulate an activity can be varied without making a large visible change in its movement pattern. A walker can attend to foot pressure, route landmarks, arm swing, or an external destination. A swimmer can focus on water pressure, the position of the body relative to the lane, or the effect of the hand on propulsion. These shifts create different perceptual control problems.

Attentional-focus experiments have found that directing attention toward the external effects of movement can improve learning in some balance and skill tasks. The distance and content of that external focus can also influence outcomes (McNevin et al., 2003). Internal attention remains useful for detecting tension, symptoms, breathing, and unfamiliar joint configurations, particularly during anti-rigidity practice. Intra-activity cross-training can therefore include the ability to move attention between bodily, environmental, and task-level information according to current demands. 

Breathing can serve as a regulatory scaffold. Slow diaphragmatic breathing may help reduce excessive arousal, discourage breath-holding, and support sustained attention during controlled movement exploration. One randomized study of healthy adults reported improvements in sustained attention and reductions in negative affect and salivary cortisol after an eight-week diaphragmatic breathing intervention (Ma et al., 2017). These findings support a regulatory role for breathing, while the optimal breathing pattern will vary with activity intensity and individual physiology. 

6. Domains of Intra-Activity Cross-Training

Intra-activity variation can be classified according to the aspect of the control problem being changed. The domains overlap in practice, although separating them is useful for programming and research.

Domain

Variables that can be changed

Examples

Principal capacities

Geometric

Joint angles, ranges, stance, stride, grip, posture

Anti-rigidity, altered stance width, active end-range control

Active mobility, positional strength, movement options

Temporal and metabolic

Pace, cadence, rhythm, interval structure, duration

Brisk and slow walking, running intervals, different stroke rates

Timing, pacing, endurance, recovery

Mechanical

Resistance, incline, drag, load direction, buoyancy

Hills, water resistance, different cycling gears

Force production, force absorption, load tolerance

Coordinative

Sequencing, laterality, component contribution, interlimb relations

Bilateral breathing, nondominant-side practice, unilateral drills

Coordination, symmetry of capacity, alternative strategies

Environmental

Surface, route, slope, space, obstacles, water conditions

Trail walking, curves, open-water orientation, variable support

Contextual adaptation, balance, sensory calibration

Perceptual and attentional

Visual targets, bodily cues, external effects, divided attention

Visual scanning, route finding, changes in gaze

Information selection, perceptual flexibility

Regulatory and strategic

Breathing, arousal, tension, decision rules, social context

Paced breathing, competition, partner interaction, route choice

State regulation, decision-making, emotional adaptability

A single variation may engage several domains. Uphill walking changes mechanical resistance, joint geometry, stride timing, energetic demand, and visual orientation. Bilateral breathing in swimming changes respiratory timing, trunk rotation, laterality, and attention. Classification identifies the primary training intention while acknowledging these secondary effects.

The framework also distinguishes intrinsic variations from added tasks. Intrinsic variation changes the activity’s own control problem. A cognitive or social overlay adds navigation, conversation, memory, or decision-making to the activity. Overlays can train divided attention and contextual adaptability, although they may have little effect on active mobility unless they also change movement execution.

7. Practice Architectures

7.1 Parameter Variation

Parameter variation changes one feature of the activity while preserving its basic organization. A walker alters cadence, a runner changes incline, a swimmer changes stroke rate, and a yoga practitioner changes stance width. Isolating one variable at first allows the learner to attribute changes in effort and control to a particular manipulation. Multiple variables can be combined after the individual variations are familiar.

The magnitude of change should be large enough to create a new control demand and small enough to preserve competent execution. Microvariation remains close to the preferred pattern. Larger variations may involve a different surface, stroke, route, or sequence while retaining the activity’s general goal.

7.2 Component Isolation and Reintegration

Complex activities can be decomposed temporarily so that an underdeveloped component receives concentrated practice. A swimmer can emphasize kicking or pulling, a walker can attend to arm swing, and a yoga practitioner can work on the transition into a posture. Isolation increases attention and practice volume for a component that may be difficult to perceive within the complete action.

Transfer requires reintegration. The component is returned to the whole movement, where timing and force must again be coordinated with the other elements. A useful practice cycle consists of whole-task performance, component isolation, variable component practice, recombination, and evaluation of transfer.

7.3 Constraint Manipulation

A temporary rule can prevent immediate reliance on a habitual solution. Examples include swimming with a specified breathing schedule, walking at a stable cadence over gently changing terrain, performing yoga transitions at a controlled speed, or using the less-preferred side during a simple ball-handling drill. The constraint directs exploration toward a selected region of the activity’s solution space.

Constraint difficulty should be progressive. A rule that overwhelms the performer can produce repeated failure or compensatory movement. A well-calibrated constraint preserves the main task while making the preferred solution less available and encouraging a viable alternative.

7.4 Contextual Transfer and Task Overlays

Contextual transfer moves the activity into a different setting. Walking shifts from pavement to grass or a gentle slope. Running shifts from a treadmill to a track or trail. Swimming shifts between pool lengths, lane conditions, and appropriately supervised open water. Yoga shifts between familiar and unfamiliar sequences, support conditions, or social settings.

Task overlays add perceptual, cognitive, or interpersonal demands. Navigation, conversation, visual scanning, partner coordination, or tactical decision-making can be incorporated when the underlying movement is sufficiently stable. The added demand should be reduced when it degrades safety or causes persistent loss of movement quality.

8. Applications

8.1 Walking

Walking provides a high-frequency platform for intra-activity cross-training. Geometric variables include step length, step width, direction, arm swing, trunk rotation, and the relative contributions of the ankle and hip. Temporal and environmental variables include cadence, speed, curves, inclines, grass, pavement, and safely manageable uneven terrain. Breathing, route selection, visual scanning, and conversation introduce regulatory and attentional demands.

A walking session can alternate short periods of variation with ordinary walking. The individual first establishes a comfortable baseline, then changes one parameter for several steps or a brief interval. Normal walking resumes before balance or control deteriorates. The return period reveals whether the variation has altered ease, awareness, mobility, or coordination.

Walking adaptations show meaningful context specificity. Uneven terrain changes joint work and muscular demand, while split-belt and speed studies indicate that locomotor learning can remain partly tied to the practiced condition. A varied walking program can therefore include several ordinary, safe contexts while preserving a dependable default gait (Vasudevan & Bastian, 2010; Voloshina et al., 2013). 

8.2 Running

Running permits variation in pace, cadence, interval structure, incline, surface, route geometry, acceleration, and attentional focus. These manipulations train overlapping capacities while producing distinct mechanical and metabolic demands. A runner may develop endurance through steady pacing, force production through hills, speed regulation through intervals, and environmental adaptability through controlled surface variation.

The forces and time constraints of running justify conservative progression. Early variation can emphasize pace, duration, cadence, and gentle incline. Large deliberate alterations of foot placement, joint position, or stride geometry require greater caution because each step occurs under substantial and rapidly repeated load.

Experimental manipulation of running step rate shows that relatively small cadence changes can alter step length, braking, joint angles, and lower-extremity loading. Uneven terrain similarly changes energetic cost, step variability, muscle activity, and leg stiffness (Heiderscheit et al., 2011; Voloshina & Ferris, 2015). These findings demonstrate that running remains biomechanically diverse even when the broad activity category is unchanged. 

8.3 Swimming

Swimming offers several forms of internal diversification. Stroke selection changes limb sequencing, trunk rotation, propulsion, and breathing. Stroke rate, breathing frequency, breathing side, interval length, turning technique, and visual orientation can be manipulated within each stroke. Pool length, lane conditions, and open-water navigation introduce environmental changes.

Component isolation is especially clear in swimming. Kickboards, pull buoys, fins, and paddles alter the contribution or resistance of selected components. Their training value depends on subsequent reintegration into the full stroke. An isolated improvement in kicking or pulling becomes functionally useful when it can be coordinated with body position, breathing, and the complete propulsion cycle.

Anti-rigidity within swimming can focus on controlled shoulder, trunk, hip, and ankle configurations within comfortable ranges. Stroke variation distributes movement across different coordinations, while low-load water resistance can support gradual exploration. The volume of repeated shoulder movement warrants careful progression, particularly when range or resistance is increased.

8.4 Yoga

Yoga already contains extensive geometric variation. Postures can be performed at different depths, stance widths, support levels, durations, and degrees of muscular engagement. Transitions can be slowed, paused, reversed, or reorganized. Gaze, breathing, balance demand, and use of props add perceptual and regulatory dimensions.

The visible shape of a posture does not fully specify its training effect. A supported posture may emphasize relaxation or passive range. The same general posture performed with active muscular engagement may train positional strength and active mobility. Anti-rigidity practice can use modest changes in angle and force to examine whether newly available ranges remain controllable.

Sequence variation supplies coordinative cross-training. A familiar posture approached from a new transition creates different anticipatory and balance demands. Reversed sequencing, unilateral emphasis, and changes between static and flowing practice broaden the relationships among postures while retaining yoga as the organizing activity.

9. Programming and Dose

A practical intra-activity session can follow six phases. Each phase has a distinct function, and the complete sequence permits the learner to compare the variation with the ordinary activity.

Phase

Function

Implementation

Baseline

Establish the preferred pattern

Perform the activity comfortably and observe effort, range, rhythm, and control

Selection

Define the training target

Choose one geometric, temporal, mechanical, coordinative, environmental, attentional, or regulatory variable

Variation

Create a manageable control problem

Change the selected variable within a range that preserves safety and task success

Active loading

Develop control and tolerance

Add appropriate isometric, concentric, eccentric, rhythmic, or endurance demand

Reintegration

Return the trained option to the whole activity

Resume complete performance and allow the component to coordinate with the rest of the task

Comparison

Evaluate immediate transfer

Compare ease, stability, mobility, effort, precision, and confidence with baseline

Variation dose has several dimensions. Amplitude describes how far the practice departs from the preferred pattern. Frequency describes how often the variation occurs. complexity describes the number of changing parameters, and unpredictability describes how difficult the variation is to anticipate. Duration and recovery determine how long the altered demand is maintained and whether competent control can be restored between exposures.

Beginning practice can use one variable, low amplitude, predictable sequencing, and frequent return to baseline. Progression can increase the range, duration, resistance, environmental complexity, or number of combined variables. Contextual-interference research suggests that gradually increasing practice difficulty may preserve early learning while introducing the reconstructive demands associated with variable practice (Porter & Magill, 2010). 

Fatigue may provide a useful stimulus, particularly when endurance in a neglected position is being trained. It does not need to define every exercise endpoint. Practice can end when positional control, breathing, balance, or movement smoothness begins to deteriorate. The intended dose produces recoverable challenge and leaves the movement option available for successful reintegration.

Repeated and variable practice should remain complementary. Stable repetition consolidates efficient solutions, while variable practice samples alternatives and changing contexts. Programs can alternate periods devoted to technical stability with periods devoted to structured exploration.

10. Safety and Clinical Scope

Anti-rigidity uses unfamiliar ranges and muscular contributions, which creates a need for conservative loading. Range, force, speed, and balance demand can be reduced independently. An unfamiliar configuration can first be explored without resistance, then with gentle isometric effort, and later within a larger functional movement. Extreme positions and abrupt loading provide poor starting conditions for general practice.

A sensation can guide attention without providing a complete diagnosis. Joint cracking, for example, has been associated with rapid cavity formation during joint separation and does not independently identify a displaced joint, restricted muscle, or damaged tissue (Kawchuk et al., 2015). Functional markers such as active range, control, smoothness, compensation, asymmetry, apprehension, and response to light loading provide more useful training information. 

Persistent pain, numbness, weakness, marked instability, or symptoms that radiate along a limb require clinical assessment before further self-directed loading. Existing injuries, neurologic conditions, connective-tissue disorders, recent surgery, and substantial balance impairment also change the appropriate range and dose. The original anti-rigidity chapter includes similar cautions concerning pain, numbness, radiating symptoms, and the possibility of injury during aggressive exploration (Reser, n.d.-a). 

Anti-rigidity remains a conceptual and practical framework awaiting direct empirical validation. Its constituent elements have established counterparts in active mobility training, full-range resistance exercise, isometric training, variable practice, attentional training, and graded exposure to task constraints. Clinical claims should be evaluated using standardized protocols and condition-specific outcome measures.

11. Research Agenda

The first research requirement is operationalization. Studies should quantify variation according to domain, amplitude, frequency, complexity, unpredictability, duration, and recovery. “Variable training” is too broad when these properties are unspecified. The location of variability within the task should also be reported because variation in the task goal can have different effects from variation in redundant execution variables.

Randomized studies could compare constant practice, cross-activity training, intra-activity cross-training, and combined programs while matching total practice time and overall intensity. A walking trial, for example, could compare ordinary walking with a program that varies cadence, terrain, direction, step geometry, and attentional demands. An anti-rigidity condition could add controlled exploration and loading of underused ranges before reintegration into walking.

Outcome measures should extend beyond immediate performance. Relevant measures include active range of motion, strength across several joint angles, balance, movement smoothness, perturbation recovery, metabolic cost, retention, transfer to unfamiliar conditions, confidence, symptoms, and real-world activity. Kinematic analyses should separate task-relevant variability from variation that leaves the task goal stable, following uncontrolled manifold and related approaches.

Longitudinal research can examine whether a broadened repertoire protects function during fatigue, environmental change, aging, or temporary impairment. Individual differences will probably moderate response. People with very narrow movement repertoires may benefit from modest exploratory variation, while people with poor stability may require a longer period of constant practice before variability is increased.

Mechanistic studies can test whether anti-rigidity changes strength-angle relationships, proprioceptive discrimination, anticipatory control, muscle coordination, or transfer across tasks. These studies would help determine whether the intervention produces broad functional adaptation or highly specific improvements confined to the practiced ranges and contexts.

12. Conclusion

Cross-training can be organized within an activity by varying the conditions and solutions through which its goal is achieved. The proposed framework includes geometric, temporal, mechanical, coordinative, environmental, perceptual, attentional, regulatory, and strategic forms of variation. Walking, running, swimming, and yoga each contain enough internal diversity to train several capacities without requiring a change of activity category.

Anti-rigidity provides the geometric branch of this framework. It uses controlled exploration and graded loading to increase access to underused movement options, then returns those options to the complete activity. The scientific rationale draws support from motor abundance, functional variability, range-specific adaptation, and locomotor learning. Evidence also indicates that variation must be relevant, progressive, and compatible with competent control. Intra-activity cross-training offers a testable model for developing movement repertoires that retain an efficient default while remaining adaptable across changing bodily and environmental conditions.

References

Bernstein, N. A. (1967). The coordination and regulation of movements. Pergamon Press.

Cardis, M., Casadio, M., & Ranganathan, R. (2018). High variability impairs motor learning regardless of whether it affects task performance. Journal of Neurophysiology, 119(1), 39–48. 10.1152/jn.00158.2017

Dhawale, A. K., Miyamoto, Y. R., Smith, M. A., & Ölveczky, B. P. (2019). Adaptive regulation of motor variability. Current Biology, 29(21), 3551–3562.e7. 10.1016/j.cub.2019.08.052

Heiderscheit, B. C., Chumanov, E. S., Michalski, M. P., Wille, C. M., & Ryan, M. B. (2011). Effects of step rate manipulation on joint mechanics during running. Medicine & Science in Sports & Exercise, 43(2), 296–302. 10.1249/MSS.0b013e3181ebedf4

Kawchuk, G. N., Fryer, J., Jaremko, J. L., Zeng, H., Rowe, L., & Thompson, R. (2015). Real-time visualization of joint cavitation. PLOS ONE, 10(4), e0119470. 10.1371/journal.pone.0119470

Ma, X., Yue, Z. Q., Gong, Z. Q., Zhang, H., Duan, N. Y., Shi, Y. T., Wei, G. X., & Li, Y. F. (2017). The effect of diaphragmatic breathing on attention, negative affect and stress in healthy adults. Frontiers in Psychology, 8, 874. 10.3389/fpsyg.2017.00874

McNevin, N. H., Shea, C. H., & Wulf, G. (2003). Increasing the distance of an external focus of attention enhances learning. Psychological Research, 67(1), 22–29. 10.1007/s00426-002-0093-6

Morton, S. K., Whitehead, J. R., Brinkert, R. H., & Caine, D. J. (2011). Resistance training vs. static stretching: Effects on flexibility and strength. Journal of Strength and Conditioning Research, 25(12), 3391–3398. 10.1519/JSC.0b013e31821624aa

Newell, K. M. (1986). Constraints on the development of coordination. In M. G. Wade & H. T. A. Whiting (Eds.), Motor development in children: Aspects of coordination and control (pp. 341–360). Martinus Nijhoff.

Noorkõiv, M., Nosaka, K., & Blazevich, A. J. (2014). Neuromuscular adaptations associated with knee joint angle-specific force change. Medicine & Science in Sports & Exercise, 46(8), 1525–1537. 10.1249/MSS.0000000000000269

Porter, J. M., & Magill, R. A. (2010). Systematically increasing contextual interference is beneficial for learning sport skills. Journal of Sports Sciences, 28(12), 1277–1285. 10.1080/02640414.2010.502946

Ranganathan, R., & Newell, K. M. (2010). Motor learning through induced variability at the task goal and execution redundancy levels. Journal of Motor Behavior, 42(5), 307–316. 10.1080/00222895.2010.510542

Reser, J. (n.d.-a). Anti-rigidity therapy: Bring dormant muscle to fatigue. Program Peace.

Reser, J. (n.d.-b). Use optimal posture and anti-rigidity while walking. Program Peace.

Schmidt, M., Kemena, M., & Jaitner, T. (2021). Null effects of different amounts of task variation in both contextual interference and differential learning paradigms. Perceptual and Motor Skills, 128(4), 1836–1850. 10.1177/00315125211022302

Scholz, J. P., & Schöner, G. (1999). The uncontrolled manifold concept: Identifying control variables for a functional task. Experimental Brain Research, 126(3), 289–306. 10.1007/s002210050738

Shea, J. B., & Morgan, R. L. (1979). Contextual interference effects on the acquisition, retention, and transfer of a motor skill. Journal of Experimental Psychology: Human Learning and Memory, 5(2), 179–187. 10.1037/0278-7393.5.2.179

Singh, P., Jana, S., Ghosal, A., & Murthy, A. (2016). Exploration of joint redundancy but not task space variability facilitates supervised motor learning. Proceedings of the National Academy of Sciences of the United States of America, 113(50), 14414–14419. 10.1073/pnas.1613383113

Stergiou, N., Harbourne, R. T., & Cavanaugh, J. T. (2006). Optimal movement variability: A new theoretical perspective for neurologic physical therapy. Journal of Neurologic Physical Therapy, 30(3), 120–129.

Todorov, E., & Jordan, M. I. (2002). Optimal feedback control as a theory of motor coordination. Nature Neuroscience, 5(11), 1226–1235. 10.1038/nn963

Vasudevan, E. V. L., & Bastian, A. J. (2010). Split-belt treadmill adaptation shows different functional networks for fast and slow human walking. Journal of Neurophysiology, 103(1), 183–191. 10.1152/jn.00501.2009

Voloshina, A. S., & Ferris, D. P. (2015). Biomechanics and energetics of running on uneven terrain. Journal of Experimental Biology, 218, 711–719. 10.1242/jeb.106518

Voloshina, A. S., Kuo, A. D., Daley, M. A., & Ferris, D. P. (2013). Biomechanics and energetics of walking on uneven terrain. Journal of Experimental Biology, 216, 3963–3970. 10.1242/jeb.081711

Wu, H. G., Miyamoto, Y. R., Gonzalez Castro, L. N., Ölveczky, B. P., & Smith, M. A. (2014). Temporal structure of motor variability is dynamically regulated and predicts motor learning ability. Nature Neuroscience, 17(2), 312–321. 10.1038/nn.3616