Active Isolated Stretching (AIS)
Active Isolated Stretching (AIS) is a dynamic stretching method that leverages voluntary muscular activation of agonists and synergists to actively move joints through an increasing range of motion, simultaneously facilitating relaxation of the target (antagonist) muscle through reciprocal inhibition (Mattes, 1995). This technique, pioneered by Aaron Mattes, integrates principles from neuromuscular physiology, biomechanics, and motor control to enhance flexibility in a controlled, functional, and performance-supportive manner.
Unlike passive stretching, AIS requires active neuromuscular engagement throughout the movement arc, making it both a flexibility and a motor control intervention. This dual effect makes AIS particularly valuable for strength and conditioning coaches, physical therapists, athletic trainers, and clinicians working with athletic populations.
Neurophysiological Mechanisms Behind AIS
AIS operates through a combination of reflexive neuromuscular pathways and biomechanical principles that work synergistically to improve flexibility without overstretching tissues or compromising neuromuscular readiness.
| Mechanism | Explanation | Effect on Stretch |
|---|---|---|
| Reciprocal Inhibition | Contraction of agonist muscle activates Ia afferents → spinal interneurons → inhibits alpha motor neuron of antagonist | Allows antagonist to relax and lengthen during movement |
| Short Hold Prevents Stretch Reflex | Stretch reflex (myotatic reflex) via muscle spindle activation occurs with sustained lengthening (>~6 sec) (Magnusson et al., 1996) | Short holds (<2 sec) avoid triggering this reflex |
| Dynamic Neuromuscular Rehearsal | Repeated active contractions through increasing ROM improve motor unit recruitment patterns | Enhances neuromuscular coordination at new ROM |
| Proprioceptive Desensitization | Progressive exposure reduces protective muscle guarding through CNS recalibration | Increases tolerance to stretch over multiple reps |
Key insight: AIS takes advantage of the brief period where antagonist inhibition and stretch reflex suppression overlap, creating a neurological “window” for safer, deeper range of motion improvements.
AIS vs Other Stretching Methods
A critical distinction of AIS is that it does not rely on prolonged passive tissue elongation or strong external forces; instead, it emphasizes active movement into the end range, under neuromuscular control.
| Feature | AIS | Static Stretching | Dynamic Stretching | PNF Stretching |
|---|---|---|---|---|
| Muscle Activity | Active (agonist contraction) | Passive | Active | Active/Passive |
| Hold Time | 1–2 seconds | 15–60 seconds | None (continuous movement) | 6–10 seconds contraction |
| Neurophysiologic Mechanism | Reciprocal inhibition | Viscoelastic creep | Neural potentiation | Autogenic inhibition |
| Stretch Reflex Involvement | Avoided | May be triggered | Avoided | May be triggered |
| Performance Impact (Acute) | Maintains force/power output | Temporary decrease in force/power | Enhances neural drive | Temporary decrease |
Implication: AIS is better suited than static stretching for pre-activity flexibility enhancement when maintaining neuromuscular performance is essential (Behm & Chaouachi, 2011).
Biomechanical Considerations
AIS emphasizes joint-specific and plane-specific movement control. Each stretch moves the limb along its anatomical plane, minimizing compensatory movements and isolating target muscles more precisely than passive methods.
Key biomechanical principles include:
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Isolated joint movement: AIS requires segmental control to avoid multi-joint compensation (e.g., pelvic tilting in hamstring stretch).
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Controlled velocity: Movement is slow enough to avoid ballistic momentum but active enough to recruit agonist musculature.
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Progressive ROM: Each repetition seeks incremental gains through neurophysiological desensitization rather than tissue creep.
Coaching cue: Watch for accessory joint motion—encourage stabilization of adjacent joints to prevent energy leaks or compensatory strategies.
Execution Protocol for Coaches and Trainers
The standard AIS protocol includes:
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Position client to stabilize non-moving joints (e.g., supine with opposite leg bent to prevent lumbar extension).
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Instruct active contraction of agonist muscle (e.g., hip flexors during hamstring stretch).
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Move limb actively into end range without external force.
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Hold stretch 1–2 seconds—avoid longer holds to prevent stretch reflex.
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Return limb to starting position in controlled manner.
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Repeat for 8–12 repetitions, gradually progressing end range.
Example: Active Isolated Hamstring Stretch
| Step | Description |
|---|---|
| Start Position | Supine, opposite knee bent, hip neutral |
| Movement | Actively lift straight leg into hip flexion |
| End Range | Stop just before discomfort/tension; hold 1–2 sec |
| Return | Lower leg back under control |
| Repetition | Perform 10 reps, progressing slightly each time |
Coaching focus: Ensure pelvis remains neutral to avoid posterior tilt; cue core engagement for lumbo-pelvic stability.
Applications of AIS in Strength & Conditioning
AIS can be integrated strategically into different phases of training:
| Phase of Training | Use of AIS |
|---|---|
| Pre-Training Warm-up | Enhance active ROM without loss of power |
| Movement Prep | Improve movement-specific flexibility (e.g., overhead athletes) |
| Corrective Exercise | Address mobility restrictions affecting movement quality |
| Rehabilitation | Restore flexibility without overstressing healing tissue |
| Cool-down | Reduce mild post-exercise tone without overstretching |
Contraindications: Avoid AIS in acute inflammation, post-surgical tissues lacking tensile integrity, or clients unable to actively contract target musculature.
Benefits and Challenges of AIS
| Benefits | Challenges |
|---|---|
| Reduces neural inhibition without reducing strength | Requires motor control and body awareness |
| Prevents overstretch injury due to client-controlled force | Harder to learn without coaching supervision |
| Promotes neuromuscular control alongside flexibility | May be insufficient alone for connective tissue remodeling |
| Useful across warm-up, corrective, rehab contexts | Limited evidence for chronic tissue adaptation vs. static methods |
AIS is an optimal choice for flexibility improvements where motor control and performance integrity are priorities.
Scientific Rationale and Supporting Research
AIS aligns with motor control-based models of flexibility, emphasizing neural factors (e.g., stretch tolerance, reciprocal inhibition) over purely mechanical tissue properties (Weppler & Magnusson, 2010).
Research supports the premise that short-duration active stretching avoids neural inhibition and strength loss commonly seen with static stretching:
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Magnusson et al. (1996) found prolonged static stretching increased muscle compliance but reduced neural drive acutely.
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Behm & Chaouachi (2011) reported dynamic and active stretching better preserved neuromuscular performance pre-exercise.
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Sharman et al. (2006) highlighted reciprocal inhibition as a key mechanism in flexibility improvements during active stretching protocols.
Interpretation: AIS’s short, active holds exploit a neurophysiological “sweet spot” for flexibility enhancement without acute performance compromise.
Key Coaching Points for AIS Implementation
- Always cue agonist activation first; movement should be initiated by the client, not passively assisted.
- Maintain neutral alignment and joint stabilization to isolate target tissues.
- Avoid compensatory movement patterns (e.g., pelvic tilt, lumbar extension) that reduce stretch specificity.
- Limit hold duration to 1–2 seconds; extending hold negates neurological benefit and may activate stretch reflex.
- Integrate gradual progression across repetitions rather than forcing range on initial attempts.
References
Behm, D. G., & Chaouachi, A. (2011). A review of the acute effects of static and dynamic stretching on performance. European Journal of Applied Physiology, 111(11), 2633–2651. https://doi.org/10.1007/s00421-011-1879-2
Magnusson, S. P. (1998). Passive properties of human skeletal muscle during stretch maneuvers: A review. Scandinavian Journal of Medicine & Science in Sports, 8(2), 65–77. https://doi.org/10.1111/j.1600-0838.1998.tb00171.x
Magnusson, S. P., Simonsen, E. B., Aagaard, P., Sørensen, H., & Kjaer, M. (1996). A mechanism for altered flexibility in human skeletal muscle. The Journal of Physiology, 497(1), 291–298. https://doi.org/10.1113/jphysiol.1996.sp021768
Mattes, A. R. (1995). Active isolated stretching: The Mattes method. Aaron Mattes.
Moore, M. A., & Kukulka, C. G. (1991). Depression of Hoffman reflexes following voluntary contraction and implications for proprioceptive neuromuscular facilitation therapy. Physical Therapy, 71(4), 321–329. https://doi.org/10.1093/ptj/71.4.321
Sharman, M. J., Cresswell, A. G., & Riek, S. (2006). Proprioceptive neuromuscular facilitation stretching: Mechanisms and clinical implications. British Journal of Sports Medicine, 40(1), 63–68. https://doi.org/10.1136/bjsm.2005.018051
Weppler, C. H., & Magnusson, S. P. (2010). Increasing muscle extensibility: A matter of increasing length or modifying sensation? Physical Therapy, 90(3), 438–449. https://doi.org/10.2522/ptj.20090012