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High intensity, rapid intent and increased tendon stiffness are three separate claims. None follows automatically from a movement looking fast or feeling demanding.
Define the property before promising to change it
Tendon stiffness describes the relationship between force and elongation. Young’s modulus describes material behaviour after accounting for dimensions, while cross-sectional area describes size. These are not interchangeable meanings of “strong tendons”. In a synthesis of 61 articles on healthy lower-limb tendons, loading was associated with larger changes in stiffness and modulus than in tendon size. The pooled estimates describe the studied tendons and interventions, not a measured effect of the drill criticised in the video. [1]
Intensity cannot be read from movement speed
A useful description of a protocol includes external resistance, force relative to the relevant maximum, joint position, loading duration and progression. For tendon adaptation, local strain is particularly relevant; the same external weight need not create the same strain in two people. A short, light movement may be fast without imposing the loading assumed by the label “high intensity”. Equally, without measuring it, one should not claim to know exactly how little force it produces. [1, 2]
Four questions behind a tendon-training claim
How much force, relative to which maximum?
What deformation reaches the tendon?
Fast force rise or sustained effort?
Was tendon adaptation measured?
Explosive intent is not a visible jerk
RFD concerns the rise of force over time. It can be trained against an immovable resistance, where the intent is rapid despite the absence of visible motion. Early and later portions of the force-time curve also have partly different determinants. The video is right to separate speed of movement from rate of force production, but the usefulness of a particular time window cannot be dismissed universally. Its relevance depends on the task, the athlete and the reliability of measurement. [2, 3]
Use a claim checklist, not an internet verdict
To demonstrate tendon stiffening, a study would need appropriate before-and-after tendon measurements, a defined intervention and a defensible comparison. To establish comparative safety, it would need more than a plausible mechanical explanation. The supplied material does not provide such a trial of this exact drill. Its potential benefits and risks therefore remain uncertain. The reasonable training principle is to select a controllable stimulus with a clear goal and progression, rather than treat a catchy protocol name as evidence of adaptation. [1, 2]
What this does not tell us
This article analyses claims, not the unseen execution of an exercise. It neither proves that the demonstrated drill is ineffective nor quantifies its injury risk. Lower-limb tendon findings cannot be converted directly into a validated wrist or elbow protocol.
Source materials
Tendons & isometrics: visual evidencePDF in English · 9 pagesTraining RFD: evidence reportPDF in English · 14 pagesReferences
Based on the supplied English video transcript and the sources below.
- Lazarczuk SL, et al. (2022). Mechanical, Material and Morphological Adaptations of Healthy Lower Limb Tendons to Mechanical Loading: A Systematic Review and Meta-Analysis. Sports Medicine. 52:2405–2429.
- Oranchuk DJ, Storey AG, Nelson AR, Cronin JB. (2019). Isometric training and long-term adaptations: Effects of muscle length, intensity, and intent: A systematic review. Scandinavian Journal of Medicine & Science in Sports. 29:484–503.
- Maffiuletti NA, Aagaard P, Blazevich AJ, Folland J, Tillin N, Duchateau J. (2016). Rate of force development: physiological and methodological considerations. European Journal of Applied Physiology. 116:1091–1116.
