Tone

What is tone? How is tone different from spasticity? Is it normal to have tone, or should it (continue to) be a therapeutic goal to “reduce tone”? While many take the terms and concepts of tone and spasticity to be the same, this is clearly not the case. Staying away from the comfortable couch of textbook definitions, we know that spasticity is a sign of an impaired nervous system, while tone can be beneficial – or inhibitory – in both normal and abnormal nervous systems. Think about spasticity as an abnormal braking system, being over-protective of muscle lengthening at speed, even when that speed is part of the intended motor program. Tone can be warranted and helpful as a background state of neuromuscular readiness appropriate for the task ahead. Recall that driving in a heavily-trafficked and icy roadway when you are late will both produce and warrant more readiness, more tone, in your arms to a desirable and often excessive/fatiguing level even in normal nervous system. In an impaired nervous system, tone can be unwarranted, unpredictable, excessive, and uncontrollable…causing an ankle to turn in or a hand to crush a paper cup – neither being a desired effect. Tone can interrupt a motor program, much like spasticity can – yet in much different ways. While spasticity inhibits the speed of the motor program (how quickly the muscle can relax and elongate in a ballistic movement being just one example; tone can cause a resting posture or position that could even be unsafe biomechanically (in the form of an inverted ankle or flexed wrist and hand complex). Tone can raise in times of stress (after conflict), when a task is perceived to be either difficult (accuracy or resistance), dangerous (balance threat), confusing (distractions, complex instructions or sequence).  While a brief primer, and not intended to be wholly comprehensive, I do hope this helps both foster communication and clarity.