Sense of effort is distorted in people with chronic low back pain

BACKGROUND

Proprioceptive deficits in people with low back pain (LBP) have traditionally been attributed to altered paraspinal muscle spindle afference and its central processing. Studies conducted in the upper limb demonstrated that sense of effort is also an important source of kinaesthetic information.

OBJECTIVES

To better understand proprioceptive deficits in people with chronic LBP (cLBP), this study aimed to test whether sense of effort is affected in people with cLBP.

DESIGN

Cross-sectional study.

METHOD

Fourteen participants with cLBP and fourteen healthy participants performed a 120 s force matching task with their trunk extensor muscles at a low intensity.

RESULTS

When visual feedback of the generated force was provided, both groups performed the task accurately. Removal of visual feedback resulted in an increase in error for both groups (p < 0.0001), but the increase in error was significantly larger for the cLBP group (p = 0.023). This larger error could be attributed to undershooting of the target force (p = 0.020). The control group did not consistently undershoot or overshoot the target force (p = 0.93). Furthermore, the amount of undershooting for the cLBP group increased as the task progressed (p = 0.016), which was not observed for the control group (p = 0.80).

CONCLUSIONS

The results of this study revealed that sense of effort is affected in cLBP. People with cLBP overestimated the trunk extension force they generated, and the error increased as the trial progressed. With visual feedback however, people with cLBP were able to compensate and perform the task as accurately as people without cLBP.

Can asthma treatment in sports be doping? The effect of the rapid onset, long-acting inhaled beta2-agonist formoterol upon endurance performance in healthy well-trained athletes

Inhaled beta2-agonists have been subject to restrictions in relationship to sports due to fear of possible improvement in endurance performance. According to the international doping regulations only inhaled salbutamol, terbutaline and salmeterol are allowed for use in sports. Formoterol is a recently introduced rapid onset-long-acting inhaled beta2-agonist. The main aim of the present randomized, double-blind placebo-controlled study was to investigate possible improvement in endurance performance of inhaled formoterol in 24 healthy well-trained competitive male athletes, 21-29 years old. Lung function (flow-volume loops) was measured before, 15 min after each inhaled study drug and before and repeatedly after exercise. On day 1, maximum oxygen uptake (VO2max), peak ventilation (VEpeak) and running time till exhaustion were measured and used to determine the exercise load on days 2 and 3. On days 2 and 3 the subjects inhaled the study drugs, rested for 1 h, then exercised, and VO2max, VEpeak and running time until exhaustion were determined. Inhaled formoterol did not improve any parameter of endurance performance. On the other hand a statistically significant, although not clinically significant (0.05 ml(-1) min kg(-1)), change was found in estimated difference of VO2max between formoterol and placebo in favour of placebo. Lung function increased significantly after inhaled formoterol, and after exercise also for placebo, but without differences between the beta2-agonist and placebo after exercise. In conclusion, inhaled formoterol did not improve endurance performance compared to placebo.