Effects of Strength Training in Chronic Low Back Pain Patients

Although it is known that chronic low back pain (CLBP) have a multifactorial etiology, the investigations about it are mostly specific to each investigation area, making difficult to understand this complex condition. The purpose of the study was to investigate CLBP from a multidisciplinary approach, analyzing biomechanical, morphological and inflammatory parameters aiming to compare the influence of two strength training protocols, one of low intensity and low volume (LIT) and one of high intensity and high volume (HIT). In both experiments, pain intensity and level of functional disability were analyzed (by analogue scale of pain and Oswestry Index), Ground Reaction Forces (GRF - AMTI BP600900 - 2000 force plate), kinematics of lower limbs (Inertial Sensors by Noraxon) and electromyography of the rectus abdominis, external oblique, lumbar multifidus, medial gluteus, vastus lateralis and biceps femoris muscles (TelemyoDTS) during gait and sit-to-stand, inflammatory cytokines by Multiplex in blood samples and cross-sectional area (CSA) of the lumbar multifidus by ultrasound imaging.

The subjects with CLBP were randomly assigned to two groups: the high intensity resistance training (HIRT) group and the low intensity resistance training (LIRT) groups.

All of the participants were informed of the purposes and procedures involved in the study and signed an informed consent form before participation. The experimental protocol was approved by the Institutional Review Board.

The intervention for both groups consisted of 12 weeks of two weekly training sessions, with at least 48 hours of interval between sessions. The HIRT performed the squat, deadlift and lunge exercises, as these exercises induce high core muscles activity. HIRT started with two weeks of low intensity exercises emphasizing the activation of core muscles (pelvic elevation with feet on the floor, "superman", static supine bridge on bosu), and the technique of the selected resistance exercises (e.g. squat, deadlift, and lunges). Participants performed 3 sets of 10 repetitions per exercise. In the third and forth weeks, participants performed the exercises from the previous weeks and also static unipedal forward flexion on bosu and dynamic unipedal forward flexion and the main exercises with a load corresponding to (50% of the 1 RM load (Brzycki, 1993).This formula is applied in a test that the subject is encouraged to perform the maximal number of repetitions possible with a predetermined load. The chosen load must allow the subject to achieve a maximum of ten repetitions, which guarantee a good RM prediction. The weight lifted and repetitions performed are applied in the equation to calculate the 1 RM estimation.

From the 5th to the 12th week, participants performed only the selected resistance exercises (squat, deadlift and lundge) with progressive higher intensities (from 12RM to 8RM). A 3-min rest interval was allowed between sets and exercises.

The LIRT group performed very low intensity and volume exercises (i.e. 1 set per exercise). Exercises started with participants lying on a firm surface, with the back supported, knees bent and feet flat on the floor. Then, participants performed the following exercises: 1) inhaling and exhaling and then isometrically contract in gluteal and abdominal muscles for 20 seconds and relax; 2) raising the head, lifting the chin and shoulders toward the chest for 20 seconds and relax; 3) raising one knee towards the chest and raising the head and shoulders likewise in the second exercise for 20s, relaxing, and changing the leg.; 4) raising both knees towards the chest in the same time that raise the head and shoulder off the floor during 20 seconds and relax.

Eligibility Criteria:
Inclusion Criteria:

* Being ≥18 years old
* Present low back or lumbo-sacral pain and function restriction (i.e. \>15% in the Oswestry Questionnaire) for 12 weeks or longer
* Do not present any functional anatomical-abnormalities, neuromuscular joint diseases and acute symptoms of pain
* Recent participation in an exercise program (at least 12 weeks)
* Pregnancy or diseases that can directly impact systemic inflammation (i.e: cancer, diabetes, hypertension)

Exclusion Criteria:

• Minimum adherence to the training protocol, defined as performing at least 75% of the training sessions.