Objective: To examine the relationship between bed hardness and muscle activity during sleep.

Design: All subjects sleep on mattresses of varying hardness. Mattress hardness is determined by the Australian Spinal Research Foundation rating protocol on a one to five scale. The beds used are designated as soft, medium and firm. Each subject will sleep three nights on each of the three beds. Following an acclimatisation period, electromyographic readings will be taken throughout sleep.

Setting: A sleep laboratory developed by the authors at Macquarie University.

Subjects: Young healthy subjects, age 18 to 45 will be used in this study.

Main Outcome Measures: Electrical activity will be measured by a Medelec Sapphire Premiere EMG computerised system. Total electrical activity will be compared between subjects. Additionally, an index of  rest-fullness be reported on showing the frequency of movement occurring during sleep.

Grant Value: $15,000
Chief Investigator: Dr Henry Pollard – Macquarie University
Status: Complete

Researcher updates:

Final project summary September 1996
Summary of aims

  • To establish a methodology for the assessment of motor activity of neck and back muscles during sleep on beds of various hardness levels.
  • To examine the relationship between bed hardness and muscle activity during rest on beds of different hardness.
  • To identify key factors for clinicians to better advise patients on their bedding

Findings / Outcomes

The initial pilot data collection indicated a high likelihood that significant differences in motor activity could be elicited and measured.

Three mattresses were employed; rated I (very soft), 3 (medium hardness), and 5(very hard). Real time surface EMG traces derived from cervical, upper and lower thoracic, and lumbar paravertebral muscles showed clearly visible differences between mattress types.

Integrating the function of the rectified traces gave area under the curve calculations for level of action potentials generated in each of the muscle groups on the three different mattresses. Statistically significant differences were found at the p < 0.05 level between the mattresses rated I and 5, and between the mattresses rated 3 and 5.

This study shows clearly that motor activity in sleeping subjects is significantly greater on harder mattresses. This relates directly to the level of work performed by these muscle groups, and may also be related to fatiguability.

Implications may be –

  • Patients with muscle tension disorders such as tension headache or spasticity may be better suited to soft mattresses.
  • Osteoporosis sufferers may benefit from higher levels of muscle tension during sleep as a strategy to maintain electrical stimulus to muscles and physical tension on ligaments and bones, potentially helping to prevent progressive bone loss during sleep
  • Those patients undergoing certain motor strength rehabilitation programs may be best advised to sleep on harder mattresses.

 

Researcher update – January 1996
Pilot findings

  1. Significant levels of muscle activity do exist in sleep. Iu this contextthe word significant is qual For different individuals the level of significance will vary.
  2. Beds of different hardness cause different levels of motor activity in the same Importantly, initial findings do show a relationship between mattress hardness and motor activity. The implications of this finding will be discussed below.
  3. Beds of different hardness probably have significantly different effects on different in different subjects. Sec below
  4. The rate of tossing and turning may be related to mattress hardness. By this is meant that our findings show initial evidence of the different mattress hardnesses having an effect on the degree of tossing and turning when all other factors are controlled. This represents, probably, the first evidence of one bed type being genuinely more ‘restful’ than another.

Implications of findings
 A number of important implications can already be drawn from the findings. Some of these implications have promotional and commercial potential.                                                                                    •

  1. For a number of people the choice of bed type may be an important health consideration.
  2. The hardness of a bed may be a vital factor in the rehabilitation of patients or the management of certain health problems. Arthritis and osteoporosis are two very commonly occurring conditions for which careful selection of mattress hardness may be an important.
  3. Mattress hardness considerations may be important in terms of preventative health care strategies. Additionally, mattress choice in child bedding may take on a new significance never before realised.
  4. Individuals with special needs, such as those who suffer chronic fatigue syndrome, or for others who may have a greater need than the average for a more restful sleep may also benefit from judicious advice on bedding factors.
  5. Specialist markets , such as nursing home and hospital settings should also be interested in the findings.

Conclusion
Some very encouraging and surprising results have already come to light in this project.

The frustrations normally associated with new areas of research have once again been encountered and now surmounted.

Very useful data has already arisen and begins to show sign of consistency so that statistically significant quantities are being defined.

It is arguable that very important findings have arisen which may bring new importance to bedding choice decisions for a great many people.