Lumbopelvic movement control is crucial for movement stability during weight loading training, and also an important risk factor for the occurrence and recurrence of low back pain (LBP). Previous studies indicated that athletes with LBP had poorer lumbopelvic movement control, and the deficits in lumbopelvic control could be remained after LBP remission. However, there has been no study investigating the effect of LBP history (LBPH) on the performance of the loaded squatting task, and lumbopelvic movement control in people who practice regular weight training.

Therefore, the aims of this study are to examine the differences in lumbopelvic movement control, kinematics and muscle activation during the loaded squatting task in weight training practitioners with LBP, LBPH, and asymptomatic controls, to compare the cortical control mechanisms between 3 types of motor control training strategies, and to investigate the intervention effect of motor control training on restoring the lumbopelvic movement control and squatting performance.

Lumbopelvic movement control is crucial for movement stability during high weight loading training, and also an important risk factor for the occurrence and recurrence of low back pain (LBP). Previous studies indicated that athletes with LBP had poorer lumbopelvic movement control, and for those athletes who have recovered from LBP, some research data still showed that poor lumbopelvic control remained. However, there has been no study investigating the effect of LBP history (LBPH) on the performance of the loaded squatting task, and lumbopelvic movement control in people who practice regular weight training.

Therefore, the aims of this study are to examine the differences in lumbopelvic movement control, kinematics and muscle activation during the loaded squatting task in weight training practitioners with LBP, LBPH, and asymptomatic controls. In the next part of the study, investigators will further investigate the intervention effect of motor control training on restoring the lumbopelvic movement control and squatting performance. Methods: This is an exploratory, cross-sectional, and intervention study. First part: investigators plan to recruit 15 participants between 20-40 years old, practicing loaded squatting for 1 day a week for at least one year, and having LBPH; 15 matched participants with current LBP, and 15 controls for the study. All subjects will undergo a series of squatting task (4 X 10 repetitions) and the kinematics and muscle activation of the rectus abdominus, transverse abdominus/internal obliqus, eractor spinae, and gluteus maximus will be recorded and analyzed using Noraxon myoRESEARCH (Noraxon U.S.A., Inc., Scottsdale, AZ, USA). A set of lumbopelvic movement control tests will also be conducted. The kinematics, muscle activation, and movement control test scores will be compared between groups. The second part, investigators plan to recruit 45 weight training practitioners with LBPH, randomized into three groups (core muscle training, movement control training, combined imagery and movement control training), and compare the effect of 4-week training on squatting performance and lumbopelvic movement control. Statistical analysis: Comparisons of all continuous variables are performed using the analysis of variance (ANOVA), and the intervention effect will be assessed using the repeated measures ANOVA. Chi squared test is used to examine the group differences in lumbopelvic movement control testing. The significance level is set at 0.05.

Inclusion Criteria:

Frequency of weight loading squatting training:

1. At least 1 time/week, at least 1 year.

LBP group:

1. Present symptoms from T12 to the upper buttock
2. Numerical rating scale (NRS) score ≥ 3/10
3. Present episode of LBP lasting > 24 hours

LBPH group:

1. Previous symptoms from T12 to the upper buttock
2. Presently in symptom remission
3. At least 2 episodes of LBP in the past 1 year, each lasting > 24 hours, and following a period of at least 2~4 weeks pain-free, OR at least 1 episode of LBP, each lasting 2 months.

Asymptomatic controls:

1. Without any history of LBP that limited their function or required treatment from a health professional in the past 2 years.

Exclusion Criteria:

1. Inability to perform parallel-squat due to LBP
2. Pain and ROM limitation in lower extremities
3. LBP due to traumatic injury
4. Previous spine surgery
5. Spinal deformities: HIVD, spondylosis, scoliosis, spinal stenosis
6. Neurological sign, and radiating pain to lower extremities
7. Systematic disease: rheumatoid arthritis