No confounding effect was observed from gender or age, and analyses were thus not adjusted. Recruitment started in June 2017 and continued throughout August the same year. Fig. 1 illustrates the flow of participants through the study. Out of 25 participants tested at baseline, 24 were included in the intention-to-treat analysis as one individual was excluded due to structural changes in the thoracic spine which had not been detected earlier and thus did not satisfy the eligibility criteria. 23 participants were tested at midtest and 21 at posttest. 20 were included in the per protocol analysis. The drop- out rate from baseline to 8 weeks was 4.2% and from baseline to 16 weeks it was 12.5%.
Baseline characteristics of the participants are presented in table 2. Mean age was 40 years (range: 22-65 years). Most participants were full- or part time employed, and none were fully or partially sick listed. All the participants had completed either high school or had a university degree. In addition to LBP, most of the participants reported other painful sites. 50% had neck pain, 33% shoulder pain, 29% hip pain, 8% upper back pain and 8% knee pain.
Intention to treat analysis
Changes in outcomes in the intention to treat analysis are presented in table 3. Mean difference in current LBP on the NPRS from baseline to 8 weeks was 1.3 (95% CI: 0.6-1.9), and from baseline to 16 weeks 1.4 (95% CI: 0.7-2.0). Mean difference in LBP the last two weeks on NPRS from baseline to 8 weeks was 2.6 (95% CI: 1.8-3.6) and from baseline to 16 weeks 3.4 (95% CI: 2.5-4.4). Mean difference in NPRS the last four weeks from baseline to 8 weeks was 2.5 (95% CI: 1.7-3.4), from baseline to 16 weeks it was 3.2 (95% CI: 2.4-4.1).
Mean difference from baseline to 8 weeks in ODI was 2.2 (95% CI: 0.7-3.7), and from baseline to 16 weeks it was 3.9 (95% CI: 2.3-5.5). Mean difference in PSEQ from baseline to 8 weeks was 5.5 (95% CI: 3.3-7.8), and from baseline to 16 weeks 7.7 (95% CI: 5.4-10.1). Moreover, there were improvements in 1RM strength throughout the training period (Table 3).
Per protocol analysis
20 of the participants completed ³70% of the training sessions and were included in the per protocol analysis. Only minor differences were observed between the main analysis and the per protocol analysis as presented in Table 4.
Only one participant reported a slight worsening of LBP and had an increase in LBP from 4 to 5 the last four weeks on NPRS.
Two participants experienced minor injuries during the intervention. One participant got a muscle strain in his hamstring at the myotendinous part of the biceps femoris in week 7. No acute symptoms were observed. A clinical examination was performed on the participant to exclude the possibility of a muscle rupture. No signs indicated any severe tear. The participant was not able to perform the deadlift and pendlay row without pain causing compensatory movements for the remaining intervention period. Hence, only squat and bench press were performed thereafter. Because of the injury the participant was only able to perform 1RM bench press at posttest. The other participant got an injury while performing the deadlift in week 9 and a clinical examination indicated a muscle strain in the quadratus lumborum. Because of acute pain and increased tension of the muscle and nearby muscles, the participant was not allowed to continue the training on that day. An examination of the participant´s back was performed during the following training session to ensure no severe injury had occurred. Through modification of the deadlift and the pendlay row the participant was able to perform all exercises. After 3 weeks with an adjusted program, the participant was able to resume the exercises on the desired level of 1RM.
One participant was not able to do the 1RM bench press midtest because of a painful shoulder, and one participant was not able to perform 1RM in the squat at posttest because of LBP.
Experiences with taking part in the training program
During the group interviews, participants shared their experiences with taking part in the training program, and their perspectives on outcomes and benefits. The main topics covered by the interviews were challenges regarding technique, the importance of supervision, and advantages of periodization.
Challenges regarding technique
Several of the participants described that learning the technical aspects of the exercises was difficult. Positioning the body segments was perceived as particularly demanding, as well as understanding the instructions. Most participants described the adaptation phase (i.e., first four weeks) as the most challenging part, and that their understanding and execution of exercises progressed throughout the program. Many of the participants said that they initially were skeptical of performing the exercises, especially with heavy load. This skepticism subsided after receiving thorough introduction and being positively surprised by the progression.
I dare to push myself when lifting […]. It is not dangerous! Before I was skeptical but now it feels good that I dare pushing myself - and nothing bad happens.
Most of the participants said that they found the deadlift exercise challenging. Performing the exercise with proper technique was perceived as difficult – maintaining balance, abdominal bracing and performing the Valsalva maneuver (30), i.e. a special breathing technique used in powerlifting. Many said that they felt a bit frustrated, especially during week 3 and 4, by all the technical details, but that this got better later in the program.
When I was performing deadlift, I often got feedback that my back and hips did not move in the correct order. [The instructor] showed me what I was doing wrong and I saw what he did wrong when demonstrating, but I did not get my body to do the same. I did not understand which muscles I should use to do it correctly... I cannot say that I consciously do anything different now from in the beginning, but now my hips and back move in the correct order. My body has understood it despite not understanding it myself.
Two of the participants felt that they were struggling when performing squat. They stated that barbell squat was one of the exercises they felt they did not master properly, especially with a heavy load. When performing heavy barbell squats, they experienced LBP but the level of pain did not exceed the pain they had before the program started.
I feel pain in my back when I am descending and then something happens mentally. I am afraid of descending and that I will not be able to fixate enough. I am not sure what happens but I find that really challenging.
Four participants reported that they found it difficult to maintain correct body position in bench press and some found it to be the most difficult exercise. In the initial phase, they found it difficult to lay supine on the bench because of stiffness in the lumbar spine.
I felt that I was struggling a lot to master the exercises. Especially in bench press to press the shoulder blades together. This is something I still have to work with. I perceived it as mentally challenging to understand what to do.
Some of the participants described that they initially felt that 4 weeks focusing on technique and using light weights was unnecessary, since they had previous experience with low intensity resistance training. However, as the program progressed they appreciated the value of the adaptation phase as it made them understand the lifting mechanics more and reduced the fear and avoidance towards certain movements. Several participants reported that after the adaptation phase they managed to perform the exercises more or less consistently in every repetition and to a greater extent detect nuances of the movements throughout the range of motion.
The importance of supervision
The participants emphasized the importance of supervision, describing this as a crucial element. Several reported that they would have considered to not participate if they had just been given a short introduction and a sheet with exercises.
I would have tried it, but I know now that I would never have been able to do it correct technically. I would never have lifted as heavy and I would probably have stopped after a short period.
Many participants mentioned that the small group size was positive and a prerequisite for receiving proper individualized supervision and feedback. Another aspect pointed out by the participants was that they would not have dared to use heavy weights or push themselves if they had to perform the training sessions without supervision and feedback. Knowing qualified personnel was present during training made the participants feel safer and more confident.
I would never challenge myself as much without knowing or getting feedback along the way that what you are doing is actually correct.
The advantages of periodization
All participants described positive experiences with the variation in volume and stimuli in the training program. The variation from week to week was perceived as motivating and preventing the training from becoming monotonous. Some participants said that particularly the higher repetition sets were very demanding, and that heavier weights for fewer repetitions, actually were easier on the body.
If we were only given series with 12 repetitions I wouldn’t have been able to walk the last couple of weeks. After the sessions with 12 repetitions, I am unbelievably tired. I can feel it when I am going home, my head feels heavy, and the only things you´re able to think is that you have to move the right foot and then the left foot. When we’re performing 8 and 4 repetitions our bodies don’t become nearly as exhausted as when we’re doing 12 repetitions.
Several participants said that they first thought that to perform the same exercises every training session would get boring. However, the variation in load and repetitions constituted a motivating factor. Many participants said that it gave a sense of achievement to experience that it was possible to perform the exercises with heavy load with few repetitions, as well as lower load with high repetitions.
I think it has been really good, because then you can set new goals as well as noticing that you are challenging yourself. You are moving the boundaries for each cycle. You realize that you are actually able to lift heavier weights without anything bad happening.
Perceived outcomes and benefits from the program
The participants described several benefits from taking part in the training program. They talked about different improvements regarding pain, daily functioning, energy level and sleep, as well as changes in their views on physical activity and training.
Changes in pain
Whereas some of the participants described minor or no changes, others said that their LBP had changed a great deal. Some described that their LBP had almost disappeared during the training program.
…I notice that before being part of the program I used to feel tension in my lower back when I was sitting a lot at work. I haven’t noticed this anymore and that probably means that it is gone or that it isn’t present to the same extent as before.
A few of the participants said that although their LBP did not change much during the program, they described being able to stand for a longer time with less pain. In addition, some described being able to handle the pain a lot better, noticing less fear and avoidance of movements. Some participants experienced increased symptoms during the first weeks with periodized strength training, but that this gradually declined and became better than before the program started. Others experienced that their symptoms were undulating during the program.
It has varied a little during the training period. One period I was almost completely pain free and was shocked how that was possible. But then it became a bit worse again. Still, since the day we started with the training I haven’t experienced pain coming from my lower back going down the backside of my thighs.
Improved daily functioning
Participants described that the improvement in strength made activities in everyday life easier than before. Regarding daily home chores usually inducing LBP, several reported that they managed to perform tasks with reduced or no pain. Tasks such as freshening up morning and night, vacuum cleaning, or cleaning the house, or carrying groceries and heavy objects were described as less challenging.
We had to buy a new washing machine. It had to be carried into our house and my husband said he had to call a friend for assistance. However, this time I insisted on carrying it together with him and I managed to carry it without any back pain. Surprisingly, it even felt easy.
Participants also reported that previous difficulties getting out of bed in the morning due to LBP had improved during the training program. In addition, some said that they now could be more active with their children.
I’m not sure if it’s the training but I notice that I have become a lot more active with the kids. I want to play with them and I actually have the capacity to do so. Previously, my kids had to walk on my back and give me a massage before I was able to play with them. This is something they don’t have to do anymore.
Two of the participants reported that in terms of general physical activity, it had not changed their view but that their view on lifting heavy objects had changed drastically. It was something they previously considered unwise, and they not were capable of doing because of fear.
My view on lifting heavy loads have changed. I used to believe that it was something that was not very smart to do and something I never could do. However, my view on physical activity in general has not changed. Lifting as heavy as we did with low back pain was something I never thought was possible.
Others expressed that they now dared to try other activities. Leisure time activities such as jogging - and especially downhill jogging – were described as less painful or pain free after going through the training program.
Improved energy and sleep
Whereas some of the participants described still feeling tired and with no change in energy level, others felt that their energy level had increased. Several said that the energy surplus made them seek out other activities in their leisure time. Others described that the intervention made them feel fatigued in the first 6 weeks of periodized training. They perceived it as temporary and felt more energized towards the second half of the program. Many were also surprised over how well the body handled the high load and that the body was able to recover between the training sessions.
I really want to train more and that is a feeling I have not felt in a really long time. Despite being tired, I have started to walk and run because of increased energy and I really enjoy it.
Half of the participants said they experienced improved quality of sleep throughout the study. Common for the participants that had experienced reduced quality of sleep was that the LBP had disturbed their sleep to such an extent that they had to get up during the night to do light physical activity. For many, this changed significantly during the training program with lower pain intensity and frequency, allowing them to sleep throughout the night.
I have had a lot of pain in my back during the night or I have woken up in the middle of the night and experienced pain in my back. I have had to get up and move around in order to be able to go to sleep again because of tension in the back. It is still present but a lot less prominent and not nearly as frequent. Now I can sleep through a whole night and I cannot remember the last time I did that before.
Continuing resistance training
When asked whether they would continue with the resistance training after the program, all participants replied that they wanted to maintain the training to some degree. Some said that training two times a week would be difficult to maintain due to a busy life, but that they would try to keep up the training whenever it was possible. Most participants said that they had to continue training since they already had invested a lot in completing the program. Some said that they felt committed to maintain the training because of the noticeable improvements in pain and functioning.
I really want to continue and maintain the improvements in pain and function when I have become so much better in such a short period. I have invested so much time in this that I do not want it to disappear.
Several of the participants reported that it would be challenging to continue the training by themselves. They said that this meant that they would not focus on lifting heavier, but increase the load at a slower pace and have more long-term goals. Some participants also mentioned that in addition to the resistance training they wanted to add some other exercise modalities to maintain their motivation.