Introducing the Yielding Phase and New Metrics in ForceDecks

Announcements, Expert Insights

ForceDecksJumps/Test Types

Available in:

 EN 
Introducing the Yielding Phase and New Metrics in ForceDecks

About the Authors

Dr. Daniel Cohen is the co-founder of ForceDecks and has over 20 years of experience as a consultant and researcher evaluating healthy and injured elite athletes using force platforms. He currently works with teams across the English Premier League, NBA, NFL and NHL. He is also an Adjunct Associate Professor in Human Performance and Innovation at the University of Limerick’s School of Education.

Dr. Gavin Lenton is a lead product manager at VALD, where he has spent the past five years helping ensure its technologies remain at the forefront of human measurement. He holds a PhD in Biomechanics from Griffith University and is an Adjunct Research Fellow at Macquarie University, bridging the gap between research and product innovation.

The latest ForceDecks iOS update introduces the yielding eccentric sub-phase and other new eccentric countermovement jump (CMJ) metrics, further enhancing the granularity of the CMJ assessment. These additions are informed by research and applied practice, and respond to a growing interest in the eccentric phase among performance and rehabilitation practitioners using ForceDecks.

Origins of ForceDecks Terminology

The CMJ is divided into four distinct phases of movement – eccentric, concentric, flight and landing – some of which include sub-phases that reflect specific performance qualities and associated metrics.

When ForceDecks was developed…its terminology was established based on the landmark literature of the time.

When ForceDecks was developed from 2011 to 2015, its terminology was established based on the landmark literature of the time. This foundational work set the precedent for ForceDecks terminology and phase delineation:

  • Cormie et al. (2009, 2007) introduced a range of eccentric and concentric phase metrics derived from the force, power, velocity and displacement-time curves.
  • Jakobsen et al. (2012) described the impact of resistance training on CMJ force-time constrained metrics.
  • Gathercole et al. (2015, 2013) reported fatigue and training-related responses in jumping performance, specific to phases and durations.

The phases were complemented by metrics and terminology used in applied practice at the English Institute of Sport (from whom the braking phase was adopted), forming the original ForceDecks terminology. However, much like other terminology noted within strength and conditioning literature, these phase and sub-phase terms are not consistent across the field, creating confusion for some force plate users.

Balancing Accuracy and Clarity

For continuity, ForceDecks maintains the eccentric and concentric framework, even though, during the “eccentric phase” (start of movement to maximal countermovement depth), muscles are not exclusively lengthening.

…ForceDecks maintains the eccentric and concentric framework, even though, during the “eccentric phase,” muscles are not exclusively lengthening.
ForceDecks phase terminology alongside foundational research that informed phase labels.

ForceDecks phase terminology alongside foundational research that informed phase labels.

With thousands of clients running automated data pipelines, renaming phases risks creating more confusion than clarity. Instead, the focus is on education: explaining the origins of these definitions, highlighting their value in profiling and monitoring and showing how they map to movement or other frameworks within literature and contemporary practice.

New Terms and Metrics

Research has introduced new layers of nuance, with Harry et al. (2020) defining another eccentric sub-phase: “yielding.” This phase begins at minimum eccentric force, when force begins to increase and precedes ForceDecks’ deceleration phase, when downward velocity starts to decrease.

Research has introduced new layers of nuance, with Harry et al. (2020) defining another eccentric sub-phase: “yielding.”

In ForceDecks, the yielding and deceleration sub-phases together make up the eccentric braking phase. Note that in some research, the ForceDecks eccentric deceleration phase is referred to as the “braking phase.”

VALD continues to evolve with research and practice. That is why a recent ForceDecks update added the yielding and unloading sub-phases – as defined by Harry et al. (2020) and Krzyszkowski et al. (2022) – and metrics specific to these eccentric sub-phases. This refinement acknowledges that unloading is characterized by reduced vertical ground reaction force, while yielding captures the subsequent rise in force application prior to deceleration.

The eccentric yielding phase coincides with increases in force and power, and the onset of electromyographic (EMG) activity during the CMJ.

The yielding phase marks the beginning of eccentric power development and follows the onset of EMG activity in hip and ankle musculature.

The yielding phase marks the beginning of eccentric power development (Harry et al., 2020) and follows the onset of EMG activity in lower-limb musculature (Sahrom et al., 2020). Research has shown that this phase responds distinctly to both rehabilitation (Taberner et al., 2020) and periods of deconditioning (Cohen et al., 2021).

Importantly, ForceDecks has historically included the yielding phase as part of the braking phase, providing insights unavailable through other commercial systems. With the new update, metrics for the yielding and unloading sub-phases are now accessible without affecting historical results.

Distinguishing these phases has practical benefits:

  • Performance Practitioners: Examining unloading and yielding phases may be useful in characterizing movement strategy.
  • Clinicians: Separating these phases may better quantify asymmetries that could be critical in return-to-play and rehabilitation contexts.

As research and applied practice evolves, so too must the tools we use to interpret performance and rehabilitation. These refinements to ForceDecks improve clarity and increase the assessment precision, better informing practitioners’ decision-making.

These refinements to ForceDecks improve clarity and enhance assessment precision, better informing practitioners’ decision-making.

Summary of ForceDecks software CMJ phases and sub-phase definitions:

PhaseSub-PhaseExplanation
EccentricUnloadingFrom start of movement to minimum force
Yielding [New]From minimum force to beginning of deceleration (point of eccentric peak velocity [EPV])
BrakingFrom minimum force to moment of zero velocity (end of eccentric phase)
DecelerationFrom EPV to moment of zero velocity (end of eccentric phase)
ConcentricPhase 1The first 50% of the concentric (upward) phase of the CMJ
Phase 2The second 50% of the concentric (upward) phase of the CMJ
Flight–From takeoff to landing, the time the athlete spends in the air
Landing–From landing to the end of the rep

If you would like to learn more about how the latest ForceDecks updates enhance CMJ phase analysis and support more precise performance and rehabilitation decisions, get in touch with our team. 

Contact Us

References

  1. Cormie, P., McBride, J. M., & McCaulley, G. O. (2009). Power-time, force-time, and velocity-time curve analysis of the countermovement jump: Impact of training. Journal of Strength and Conditioning Research, 23(1), 177–186. https://doi.org/10.1519/jsc.0b013e3181889324
  2. Cormie, P., McCaulley, G. O., & McBride, J. M. (2007). Power versus strength-power jump squat training: Influence on the load-power relationship. Medicine and Science in Sports and Exercise, 39(6), 996–1003. https://doi.org/10.1097/mss.0b013e3180408e0c
  3. Jakobsen, M. D., Sundstrup, E., Randers, M. B., Andersen, L. L., Petersen, J., Bandholm, T., & Aagaard, P. (2012). The effect of strength training, recreational soccer and running exercise on stretch–shortening cycle muscle performance during countermovement jumping. Human Movement Science, 31(4), 970–986. https://doi.org/10.1016/j.humov.2011.10.001
  4. Gathercole, R. J., Stellingwerff, T., & Sporer, B. C. (2015). Effect of acute fatigue and training adaptation on countermovement jump performance in elite snowboard cross athletes. The Journal of Strength & Conditioning Research, 29(1), 37–46. https://doi.org/10.1519/JSC.0000000000000622
  5. Gathercole, R., Sporer, B., Stellingwerff, T., & Sleivert, G. (2013). Alternative countermovement-jump analysis to quantify acute neuromuscular fatigue. International Journal of Sports Physiology and Performance, 10(1), 84–92. https://doi.org/10.1123/ijspp.2013-0413
  6. Harry, J. R., Barker, L. A., & Paquette, M. R. (2020). A joint power approach to define countermovement jump phases using force platforms. Medicine and Science in Sports and Exercise, 52(4), 993–1000. https://doi.org/10.1249/MSS.0000000000002197
  7. Krzyszkowski, J., Chowning, L. D., & Harry, J. R. (2022). Phase-specific predictors of countermovement jump performance that distinguish good from poor jumpers. The Journal of Strength & Conditioning Research, 36(5), 1257–1263.  https://doi.org/10.1519/jsc.0000000000003645
  8. Sahrom, S. B., Wilkie, J. C., Nosaka, K., & Blazevich, A. J. (2020). The use of yank-time signal as an alternative to identify kinematic events and define phases in human countermovement jumping. Royal Society Open Science, 7(8), 192093. https://doi.org/10.1098/rsos.192093
  9. Taberner, M., van Dyk, N., Allen, T., Jain, N., Richter, C., Drust, B., Betancur, E., & Cohen, D. D. (2020). Physical preparation and return to performance of an elite female football player following ACL reconstruction: A journey to the FIFA Women’s World Cup. BMJ Open Sport & Exercise Medicine, 6(1). https://doi.org/10.1136/bmjsem-2020-000843
  10. Cohen, D. D., Restrepo, A., Richter, C., Harry, J. R., Franchi, M. V., Restrepo, C., Poletto, R., & Taberner, M. (2021). Detraining of specific neuromuscular qualities in elite footballers during COVID-19 quarantine. Science and Medicine in Football, 5(sup1), 26–31. https://doi.org/10.1080/24733938.2020.1834123