Does Physical Activity Prevent Low Back Pain?
What do we know about physical activity and low back pain? Is it a risk factor? Or a preventive aid? The authors of this study from The Netherlands suggest that too little or too much activity might be a risk factor for low back pain.
Some studies have already shown that high physical loads (e.g., twisting, bending, lifting, extreme sports) are linked with episodes of low back pain. Others point out the effect of being too sedentary (inactive) as a possible risk factor. So that leaves us with the question: how much activity is the right amount to promote a healthy back?
One reason we don't have a quick and easy answer to this question is the wide range of variables to consider. For example, a person's occupation, participation in leisure activities, lifting and carrying activities, and exposure to physical load are all potential factors in the development of low back pain.
More than 10 years ago, a group of researchers suggested that maybe the relationship between physical activity and low back pain looks like a U-shape. At one end (the upper left side of the U), total inactivity and high risk of low back pain go together. In the middle (the bottom of the U-shape), low to moderate intensity of activity is paired with low risk of back pain. And at the far end (the upper right side of the U-shape) reflects how maximum activity results in a high risk of back pain.
The authors of this study decided to test out this theory. They sent a survey to 8000 adults in Denmark asking about health, levels of physical activity, presence of low back pain, and number of visits to the doctor (or other health care provider) for back pain. The questionnaire also assessed work and health for the year just before the survey. Patient characteristics such as age, gender, occupation, education level, and perception of health were also recorded.
Not all studies use the same criteria to define activity level. The researchers involved with this study took the time to divide up activity into three groups: light, moderate intensity, and vigorous. Each category was based on age and metabolic equivalent (MET). Two age groups were used: 18 to 55 years old and over 55.
Metabolic equivalent values are a standard way to measure intensity of an activity. One MET is defined as the amount of energy used while sitting quietly. For this study, activity intensity was labeled as light, moderate, and vigorous. Light intensity for the younger age group was any activity performed between two and four METs. Moderate intensity was a MET value of four up to 6.5. Anything with a MET value greater than 6.5 was considered a vigorous activity. Metabolic equivalent measures used for the older age group were divided into light (less than three METs), moderate (three to five METs), and vigorous (more than five METs).
Activities ranged from leisure, and sports to occupational, travel, and domestic- or school-related activities. Using these guidelines, it was possible to look at all kinds of physical activities like gardening, bicycling, walking, and doing odd jobs. Specific sports such as golf, weight-lifting, speed skating, tennis, and football were also included.
Low activity levels (being sedentary) were defined as less than 30 minutes of moderate activity each day for at least five days each week. High levels of physical activity were calculated using number of hours engaged in the activity and intensity. Total physical activity patterns were analyzed by including all daily activities of all kinds. Type and range of different physical activities and their relationship to chronic low back pain were also analyzed.
The results showed that the relationship between physical activity and chronic low back pain is indeed U-shaped. Two-thirds of the people surveyed listed enough activities to meet the Dutch health recommendations for healthy living (30 minutes or more of moderate activity every day for five out of seven days). About 11 per cent of the group was inactive/sedentary. And they did have statistically more back pain than those in the moderate activity range.
Likewise, the remaining 30 per cent in the high physical activity level also experienced greater amounts of chronic low back pain. This U-shaped relationship seemed to hold true more for women than for men. The reason(s) for this remain unknown.
Type of activity also made a difference. Anyone involved in sports activities had a lower risk of developing low back pain. The authors suggest that back loading forces are different for sports activities and this dynamic may account for the reduced risk of chronic low back pain.
Beyond this, it was difficult to say if daily routine activity was more or less likely to be linked with low back pain compared with leisure time activities or other specific physical activities. The reason for this is because most people engage in a wide range of different activities everyday. Data analysis really had to be all or nothing -- all activities grouped together rather than measuring level and intensity for each activity type for each person each day.
But even so, the data was enough to show that it's not a matter of just: are you active or not? Activity level is on a continuum from low to high. Different activity levels have different risks of chronic low back pain. Low or high activity has the highest risk just as the U-shaped model predicted.
Hans Heneweer, et al. Physical Activity and Low Back Pain: A U-Shaped Relation? In PAIN. May 2009. Vol. 143. No. 1-2. Pp. 21-25.