The base of support (BOS) refers to the area beneath an object or person that includes every point of contact that the object or person makes with the supporting surface. These points of contact may be body parts e.g. feet , legs, arms or hands, or they may include things like crutches or the chair a person is sitting in.
Physical support can alter postural tone:
- A larger base of support e.g. lying down, allows greater muscle relaxation and therefore decreases muscle tone
- A smaller base of support e.g. standing up, encourages more activity in muscles and therefore increases muscle tone
By manipulating a patient’s base of support it is possible to alter the patterns of muscle tone.
A larger base of support provides stability where the normal muscle activity is lacking after stroke.
Positions can influence muscle tone:
- Sitting – flexion
- Prone lying (face down) – flexion
- Standing – extension
- Supine lying (face up) – extension
Being in any position for too long will affect tone. Muscles need to be well positioned, regularly stretched and where possible be actively used in normal tasks for tone management to be effective. This will change as the patient starts to recover from their stroke and should be regularly reviewed, plans updated and communicated to staff, patient and carers.
Video notes
0:07 Watch how Allan stands in this clip.
Look at the tone and position of his limbs when he is standing.
How symmetrical does he look?
2:04 As you see Allan stand this time, what is different about his right arm?
His symmetry? His balance?
2:49 After Allan is sitting down, how does he look?
Compare the spastic patterns in his right arm from the first stand up to the second stand.
Video transcript
Sit to stand from a chair – How method can affect tone
M. Ok Allan. I’d just like to see how you stand up from the chair. Just show me how you normally do it.
A. OK.
M. Ok very good and have a sit down again.
So the last time you stood up you managed to get on your feet very well but I was aware that you used the left side of your body predominately. So you were mostly stood on your left leg. You were pushing up with your left hand and what we saw was quite a lot of tension appearing in the right side of your body. Now the chair was quite low so we have put in an additional cushion just to raise you up a little bit. But I am going to suggest a slightly different technique OK. That will hopefully mean that the muscle tone in your right side is slightly better controlled when you stand up and we see more balance between the two sides of your body. So we have raised the height of the seat a little bit. I want you to bring your feet back just as far as you can both sides and we will have them equally positioned. That’s great. That’s OK, maybe a little bit wider apart if you can. Perfect, OK. Now in this position we have got a nice straight spine. What I’d like you to do is just bend forward from the waist and take your hands down towards the floor between your knees. As you come forward you should feel the weight coming on to your feet. If you can stand up from there. Good, nice and slow. Nice and slow, well done. OK well done. Now in that position. Just let your arms relax. We have got a lot less increased tone going on in your right arm than we did when you were predominantly using you left side. So we can use this technique if you like to get you standing more on your right leg than just and no more.
A. It’s more balanced.
M. You look more balanced.
A. Yeah.
M. You definitely do. It is the opposite situation for sitting down. All you need to do is hold on to your wrist gently OK. Soften your knees and then take your hands down towards the floor. Keep bending, keep bending, keep bending and then drop your bottom on to the chair. Come back and you can see then you sit down with a nice relaxed right arm. It’s also a nice stretch for your ankle. It relates to what we were talking about on the bed.
Page last reviewed: 04 May 2020
