Freeze or Flop: Rethinking the Terminology and Sequence of the Stress Response

Abstract

The widely used phrase ‘fight, flight, or freeze’ has long shaped our understanding of the stress response. However, this tripartite model oversimplifies the dynamic and multi-layered nature of human defensive behaviours. Drawing from evolutionary biology, trauma theory, and autonomic neuroscience, this conceptual paper proposes a refined vocabulary: ‘fright’ (initial orienting alertness) and ‘flop’ (collapsed immobility) are added to the sequence, while ‘freeze’ is reframed to refer specifically to the hypertonic rigidity of tonic immobility. These adaptations, closely aligned with the defence cascade outlined by Kozlowska et al. (2015), aim to improve clinical clarity for manual therapists who encounter patients with stress-related autonomic dysregulation.

Introduction

The stress response is a fundamental adaptive process that enables organisms to respond to both threats and demands. In evolutionary terms, these demands were often immediate and life-threatening, requiring rapid mobilisation of physiological and behavioural resources. Today, many modern stressors – while not directly life-threatening – still trigger the same ancient systems, creating a mismatch between biology and environment.

Traditionally summarised as “fight, flight, or freeze,” the stress response has become part of common language. Yet this simplification conceals important distinctions between different states of defensive activation and immobilisation. As Kozlowska et al. (2015) demonstrated, the human defence response is better understood as a branching, context-dependent cascade that includes multiple forms of immobility, each with distinct neurophysiological features. 

This paper proposes a refinement of this model by:

• Introducing fright as the initial orienting response to a potential threat or demand;
• Reserving freeze for tonic immobility (a hypertonic state);
• Using flop to describe collapsed immobility (a hypotonic, parasympathetic-dominant state).
• Noting fawn as a behaviourally learned appeasement response with distinct features.

From Cannon to Kozlowska: An Evolving Model

Walter Cannon (1915) laid the foundation for modern stress theory by describing the fight-or-flight response. Later, the idea of a “freeze” response was added to account for immobility under threat – popularised through trauma research (van der Kolk, 2014) and survival literature (Levine, 1997). Yet over time, “freeze” became a catch-all term, blurring the distinction between immobilised states driven by muscle tension and those marked by flaccidity and shutdown.

Kozlowska et al. (2015) clarified this confusion by identifying six distinct stages of the defence cascade:

1. Arousal – heightened alertness and orientation,
2. Fight or Flight – active sympathetic mobilisation,
3. Freezing – motor inhibition with high muscle tone,
4. Tonic Immobility – involuntary rigid stillness, often with dissociation,
5. Collapsed Immobility – hypotonic, flaccid state linked to dorsal vagal dominance.
6. Quiescent Immobility – a state of restorative stillness after threat passes.

In this paper, we reframe “arousal” as fright, “tonic immobility” as freeze, and “collapsed immobility” as flop to better reflect both clinical experience and pedagogical clarity. Fawn is also mentioned as an additional behaviourally conditioned state.

The Updated Sequence: Fright, Fight or Flight, Freeze or Flop (Fawn and Quiescent)

Fright - The initial orienting phase – marked by high alertness, vigilance, and activation of the amygdala and periaqueductal grey – is what we propose to call fright (Fanselow, 1994). This precedes active responses and prepares the organism to assess risk or respond.

Fight or Flight - When escape or resistance is possible, sympathetic activation drives either mobilisation (flight) or confrontation (fight) (Cannon, 1915). This state is metabolically expensive and linked to increased heart rate, blood pressure, and muscle perfusion.

Freeze – Freeze, as redefined here, refers to tonic immobility – a state of motor inhibition with sustained high muscle tone. Though the body appears still, it is physiologically braced, often with co-activation of sympathetic and parasympathetic systems (Roelofs, 2017). Clinically, this may appear as rigid posture, holding patterns, or internal “stuckness.”

Flop – When neither escape nor defence is viable, the system may enter flop – a parasympathetic-dominant, hypotonic state akin to collapsed immobility. This is mediated by the dorsal vagal complex and often presents as limp, passive, unresponsive behaviour. While a patient muscles feel relaxed, it reflects a profound state of autonomic withdrawal and disconnection (Marx et al., 2008; Kozlowska et al., 2015).

Fawn - A behavioural defence strategy characterised by appeasement, people-pleasing, or compliance in response to perceived threat or relational instability (Walker, 2013). It reflects a learned psychological adaptation that may mask underlying autonomic dysregulation, though this remains under-researched. 
Quiescent Immobility – The sixth stage, quiescent immobility, reflects a post-threat restorative state, promoting healing and integration. This state is mentioned here for completeness but is not the focus of this paper.

Clinical Relevance: Freeze ≠ Flop

From a clinical standpoint, freeze and flop may appear similar but represent very different states. A patient in a freeze state may still function outwardly, but internally experience immobilisation and rigidity. Their muscles feel tense, their breath may be held, and they report being “stuck.”

In contrast, patients in a flop state may walk and talk, yet present with hypotonic muscles, poor responsiveness, and symptoms of resignation, hopelessness, fatigue, or depression. This can be easily misinterpreted as relaxation, when in fact it reflects parasympathetic dominance and loss of adaptive capacity.

Recognising this difference is critical. Manual therapists must move beyond the false assumption that softness equals relaxation and that all is well. Tense muscles may reflect a defensive brace (freeze), while soft ones may signal autonomic withdrawal (flop). Misreading these states can lead to inappropriate treatment strategies.

Implications for Manual Therapists and Body-Centred Practitioners

For osteopaths, physiotherapists, and other body-centred therapists, this refined terminology helps bridge psychophysiological theory with hands-on practice. The Reaset Approach (Meyers, 2014, 2019), for example, prioritises autonomic regulation – recognising that structural and functional interventions have limited effect when the nervous system is dysregulated.

Understanding the differences between fright, freeze, and flop allows practitioners to:

• Better assess the patient’s underlying autonomic state,
  
• Avoid mistaking parasympathetic collapse for relaxation,
• Tailor interventions to support recovery from dysregulation,
• And restore a sense of safety before structural correction.

Conclusion

The classical model of “fight, flight, or freeze” no longer suffices to capture the complexity of human stress responses. By refining the vocabulary to include fright and flop, and by clarifying the definitions of freeze and collapse, we move towards a more accurate, clinically useful framework. These distinctions are not just academic – they are essential for effective diagnosis, communication, and care.

As our understanding of autonomic regulation deepens, so too must the language we use to describe it. A clear, precise vocabulary helps clinicians align interventions with the patient’s true physiological state – improving outcomes and restoring balance where it begins: in the body.

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References

• Cannon, W. B. (1915). Bodily changes in pain, hunger, fear and rage. New York: Appleton.
  
• Fanselow, M. S. (1994). Neural organization of the defensive behavior system responsible for fear. Psychonomic Bulletin & Review, 1(4), 429–438. https://doi.org/10.3758/BF03210947
  
• Gallup, G. G. (1977). Tonic immobility: The role of fear and predation. The Psychological Record, 27(1), 41–61.
• Kozlowska, K., Walker, P., McLean, L., & Carrive, P. (2015). Fear and the Defense Cascade: Clinical Implications and Management. Harvard Review of Psychiatry, 23(4), 263–287. https://doi.org/10.1097/HRP.0000000000000065
  
• Marx, B. P., Forsyth, J. P., Gallup, G. G., Fusé, T., & Lexington, J. M. (2008). Tonic immobility as an evolved predator defence: Implications for sexual assault survivors. Clinical Psychology: Science and Practice, 15(1), 74–90.
  
• Meyers, T. (2014). The effect of the Reaset Approach on the autonomic nervous system, state-trait anxiety and musculoskeletal pain in patients with work-related stress: A pilot study [BSc thesis]. Dresden: Dresden International University in cooperation with Osteopathie Schule Deutschland. Available from: https://drive.google.com/file/d/19P_mKjKx4YG0p6VijTnl6wHXaUGknvVm/view
  
• Meyers, T. (2019). The effect of the “Reaset Approach” on the autonomic nervous system, neck-shoulder pain, state-trait anxiety and perceived stress in office workers: A randomised controlled trial [MSc thesis]. Dresden: Dresden International University in cooperation with Osteopathie Schule Deutschland. Available from: https://drive.google.com/file/d/14ElvJBLRwAbZvQm20ydg9X5oEWRJD_0E/view
  
• Porges, S. W. (2011). The polyvagal theory: Neurophysiological foundations of emotions, attachment, communication, and self-regulation. W. W. Norton & Company.
• Roelofs, K. (2017). Freeze for action: Neurobiological mechanisms in animal and human freezing. Philosophical Transactions of the Royal Society B, 372(1718), 20160206. https://doi.org/10.1098/rstb.2016.0206
  
• van der Kolk, B. (2014). The body keeps the score: Brain, mind, and body in the healing of trauma. Penguin Books.
• Walker, P. (2013). Complex PTSD: From surviving to thriving: A guide and map for recovering from childhood trauma. Azure Coyote. 

This article was written by Tom Meyers with the assistance of ChatGPT, blending personal insights and advanced AI support to create a compelling and impactful message.

Image Reference
© 2021 The National Institute for the Clinical Application of Behavioral Medicine

I took the freedom in line of the article to replace "COLLAPSE" with "FLOP" but full credits go to NICABM https://www.nicabm.com/how-the-nervous-system-responds-to-trauma/