Effect of High-Intensity Laser Acupuncture on Muscle Performance, Pain, and Quality of Life in Patients with Chronic Nonspecific Low Back Pain: A Randomized Placebo-Controlled Trial

Abstract

Objective

To examine the effectiveness of high-intensity laser acupuncture (HILA) combined with physical therapy exercises on trunk muscular performance, pain, and quality of life (QoL) in individuals with chronic nonspecific low back pain (CNSLBP).

Methods

A randomized, prospective, double-blind, controlled study was conducted at the outpatient clinic of the Faculty of Physical Therapy, Cairo University. Sixty patients aged 20–40 years with CNSLBP were randomly allocated to each group. The HILA group received HILA treatment and physical therapy exercises, whereas the sham group received a placebo laser and the same physical therapy exercises. The therapy was administered for four weeks, three times a week. Trunk muscular performance, pain, and QoL were evaluated before and after the intervention and at the 1-month follow-up using isokinetic dynamometry, the visual analog scale, and the World Health Organization QoL (WHOQOL-BREF), respectively.

Results

The differences between the baseline and post-intervention assessments were statistically significant for all variables in both groups, favoring the HILA group (all P < 0.05). A slight decrease was observed from post-intervention to follow-up in both groups, but the HILA group remained superior (P < 0.05), with follow-up Cohen’s d effect sizes of 0.849 (peak torque for trunk extensors), 0.636 (peak torque for trunk flexors), 0.875 (average power for trunk extensors), 0.888 (average power for trunk flexors), 1.729 (pain), and 0.586 (WHOQOL-BREF).

Conclusion

HILA therapy, combined with physical exercise therapy, may provide greater improvement in trunk muscular performance, pain, and QoL for patients with CNSLBP in the short term compared to physical exercise therapy alone. These findings suggest that HILA treatment may be a valid and safe adjunctive therapeutic option for patients with CNSLBP. Further research is necessary to assess the long-term effects and optimize treatment protocols.

Introduction

Chronic nonspecific low back pain (CNSLBP) is a multifactorial musculoskeletal disorder that affects approximately 84.8% of individuals during their lifetime. It is described in cases where pain lasts for more than three months and there is no clear cause.¹ Non-specific LBP has been associated with compromised musculature within the lumbar region, decreased muscular power, smaller trunk mass, and changes in trunk-area neuromuscular control.² Motion disorder and pain are related, as pain could lead to problems in the control of neuromuscular and avoiding behavior,³ which can lead to functional issues and even psychological problems, resulting in a decrease in quality of life (QoL).¹

The American College of Physicians (ACP) advises patients and medical professionals to consider alternative therapies to medications for chronic low back pain (LBP) first, which include exercise, multimodal rehabilitation, and acupuncture.⁴ It has been shown that acupuncture is useful in managing many disorders by activation of specific acupoints, and the World Health Organization has recognized the possible advantages of acupuncture in more than 40 conditions. Although conventional acupuncture has therapeutic benefits, it is not widely used because of its invasiveness, patients’ phobia toward needles, and issues such as needle breakage and infections. A promising noninvasive approach that could overcome these limitations is the multidisciplinary application of phototherapy in acupuncture treatment.⁵

Laser acupuncture (LA) makes use of laser light to activate the acupoints, hence inducing neuromuscular modulation and pain reduction through photobiomodulation (PBM) processes whereby increased adenosine triphosphate (ATP) formation takes place, as well as nociceptive modulation. There are several types of lasers used in LA, depending on their distinctive characteristics and therapeutic uses.³ A Class IV high-intensity (high-power) (>500 mW) laser is a safe rehabilitation treatment, particularly for persistent skeletal disorders and spinal pain. Since the goal area in LBP is in deep tissues, it would be more suitable to have a laser with wavelengths of 780–950 nm. High-intensity lasers facilitate functional improvement and pain relief, reduce inflammation,⁶ and increase muscle strength.⁷ According to Oliveira et al,⁸ PBM pre-training can enhance muscle function and reduce signs of inflammatory reactions and fatigue, regardless of the dose and wavelength utilized.

Although acupuncture therapy has demonstrated beneficial effects in patients with LBP,^9,10 and high-intensity laser therapy has also shown positive outcomes in reducing pain and improving function,^11–13 most previous studies have investigated these interventions separately, focused mainly on pain-related outcomes, or applied high-intensity laser therapy regionally rather than through specific acupuncture points. In addition, a preliminary conference presentation evaluated a 4-week high-power laser acupuncture intervention in patients with CNSLBP, with emphasis mainly on pain and lumbar range of motion.¹⁴ However, evidence regarding the effects of high-intensity laser acupuncture (HILA) on objective trunk muscular performance and QoL remains limited. Therefore, the present study aimed to address this gap by investigating the effects of HILA on trunk muscular performance, pain, and QoL in patients with CNSLBP, with both post-treatment and 1-month follow-up assessments of these outcomes.

Materials and Methods

Study Design

A double-blinded prospective randomized controlled study was conducted at the outpatient orthopedic physical therapy clinic affiliated with Cairo University from October 2024 to March 2025. Ethical approval to conduct this research study was obtained from the Research Ethics Committee of the Faculty of Physical Therapy at Cairo University (Number: P.T.REC/012/005224), followed by prospective recording on ClinicalTrials.gov (ID: NCT06612918). All study procedures were performed in accordance with the CONSORT regulations, which provide a comprehensive structure for study design, data collection, and reporting of results. Before being enrolled, the participants received comprehensive details about the goal of the research, the treatment procedures, expected advantages, and potential hazards, and they provided written consent for participation. All data collected from any participant was considered confidential and dealt with in such a manner.

Study Participants

Participants were included if they had CNSLBP (duration of 3 months or more) with no identifiable underlying causes determined by medical information and clinical examination.¹⁵ The referral was given by an orthopedist who was not part of this study. Participants (both males and females) aged between 20 and 40 years;¹⁶ a body mass index (BMI) from 18.5 to 24.9 kg/m² and a score for pain of no less than 30 mm on the Visual Analog Scale (VAS).¹⁷ Participants were not allowed to participate if they had a spine fracture or surgery in the last six months; received corticosteroid, anticonvulsant, or anti-inflammatory drugs; had an inserted pacemaker; had chronic cardiovascular disease; had photosensitivity disorder or injury or damage to the target area; were diagnosed with cancer, had cancer care in the last year, or had cancer in remission; had a neurological or infectious disease; had a systemic disease (rheumatologic disorders, lupus erythematosus, or type I/II diabetes); had thyroid disease; had spinal stenosis; had psychiatric or mental disorders; were pregnant; were obese; or had recent medical treatment for LBP (within the past three months) to minimize possible carry-over effects on the study outcomes. During the trial, the participants were asked to avoid any additional LBP treatment unless medically necessary. Any concurrent treatment would have been recorded, and the participant would have been withdrawn from the study; however, no such cases occurred.

Sample Size

The sample size was estimated using G*Power (version 3.1.9.4). The estimated effect size (Cohen’s f) was 0.201, based on a partial eta squared (ηp²) of 0.039 obtained from a pilot investigation of peak torque of trunk extensors, using F-tests—ANOVA (repeated measures, within-between interaction) at a significance level (α) of 0.05, a power of 90%, a correlation among repeated measures of 0.5, and a nonsphericity correction of 1. The total sample size was estimated to be 54 participants. The study will include 60 individuals, 30 in each group, with an expected dropout rate of 10%.

Randomization

Randomized blocks were carried out through a computer-based method at http://www.randomization.com/ to reduce bias and group disparities. Eligible participants were randomly assigned in a 1:1 ratio (30 participants in each group) to the HILA group (who underwent HILA and physical therapy exercises) or the sham group (who received placebo laser and the same physical therapy exercises) (Figure 1). Randomization was performed in blocks of four and executed by a separate researcher who was not engaged in recruiting individuals or collecting information or therapy. The allocation was concealed by sequentially numbering the randomization codes and placing them in sealed, opaque envelopes. The clinical investigator opened the envelope and initiated treatment based on group allocation. Data were collected pretreatment, four weeks post-treatment, and after a month of follow-up appointments by a blinded investigator.

Figure 1.

Flowchart based on CONSORT guidelines.

Abbreviation: HILA, High-intensity laser acupunctur.

Intervention

High-Intensity Laser Acupuncture

Laser application in individuals belonging to the HILA group was performed using a high-intensity laser from Zimmer Medizin Systeme (serial numbers 15200013306 and 4682), manufactured in Germany. It was operated with a probe of diameter 5 mm, having a spot area of 0.2 cm² (extendable to 3.1 cm² with the help of a small spacer) with a wavelength of approximately 810–980 nm. The treatment settings included a frequency of 5 Hz, a 50% duty cycle,¹⁴ and an intensity of 5 W. The energy delivery was 60 joules/point¹⁸ for 13s.

The environmental temperature was maintained at 20°C throughout the experiment. Before commencing the sessions, standard safety measures were followed, and the participant and therapist wore the appropriate eye protection. The participants were informed of the possible temporary exacerbation of symptoms post-therapy. The patient was positioned prone with cushions under his head and ankles, making the treatment area visible. Skin was prepared with an alcohol wipe and laser exposure perpendicular to 15 points bilaterally at BL20, BL23, BL24, BL25, and BL40 and GB30, and unilaterally at GV3, GV4, and GV5^17,19 (Figure 2). These acupoint locations were determined according to the World Health Organization guidelines,²⁰ and the treatment sequence was performed in the following order: unilateral GV3, GV4, and GV5; and then bilateral BL20, BL23, BL24, BL25, BL40, and GB30 by an experienced physiotherapist (>10 years of experience), not blinded to the group allocation, with a 195-second total irradiation duration per session.

Figure 2.

Acupoints targeted during laser acupuncture treatment.

Individuals in the sham group were also treated by the same physiotherapist with the same apparatus on the same identified acupuncture points for each individual. This scenario was similar to the active treatment case,²¹ except that the laser power was set to zero to prevent any therapeutic energy from being administered. To maintain the blinding procedure, both groups wore goggles, and the therapist contacts and duration of the sessions were made identical in the two groups. To reduce the possibility of communication between the two groups, the individuals met on different days, three times a week for four weeks.

Physical Therapy Exercises

The two groups underwent the same physical therapy exercises under the supervision of another physiotherapist, unaware of group distribution and laser therapy treatment. The exercise sessions included stretches for the back, hamstrings, and calves;²² for 30s, repeated four times for each.²³ Back stretching consisted of spinal flexion (knee-to-chest).²² Hamstring flexibility was assessed using supine straight-leg hamstring stretching, whereas calf stretching was performed using wall calf stretches with the knee extended and flexed to target the gastrocnemius and soleus muscles, respectively.²³ Additionally, stabilizing, back, and abdomen-strengthening exercises were included. Stabilizing exercises were included to activate and strengthen the deep lumbar muscles. The exercises included abdominal hollowing/draw-in in the crook-lying position, bridging, quadruped arm-leg raising, and side support exercises. Back and abdominal strengthening exercises were performed to activate the lumbar extensors and abdominal flexors. The exercises included prone trunk extension, partial curl-ups, pelvic tilts, and related dynamic trunk-strengthening exercises. Each exercise was performed for 10 repetitions with a 10-second hold, and exercise progression was adjusted gradually according to each participant’s tolerance.²⁴ All exercises were conducted three times a week for four weeks.

Outcome Measures

Trunk muscular performance (peak torque and average power) was tested using an isokinetic dynamometer (Biodex Medical Systems, Shirley, NY, USA). The machine was calibrated prior to testing.²⁵ The participants received instructions on how to execute the test, were then placed in a dual-position back extension/flexion machine, aligned correctly with respect to the anterior superior iliac spines, and secured in place to minimize any movement. Trunk motion was restricted to 50°, and warming up was performed at a submaximal level;²⁶ then maximal effort was performed during trunk extension and flexion at a rate of 60 ° per second.²⁵

Pain severity was measured using the VAS, a reliable and valid method for assessing pain levels.²⁷ QoL was evaluated using the World Health Organization QoL (WHOQOL-BREF) in the Arabic language, which is a valid and reliable instrument for measuring QoL with four distinctive dimensions: physical, psychological, social relationships, and environmental.²⁸

Adverse Event Monitoring

This study documented adverse events (AEs) through participant reporting, clinical examination, and medical records. Participants were informed that they might experience some adverse effects, such as pain, heat, inflammation, and redness, and any occurrence of such conditions should be reported to the researcher. Details about the nature of the adverse effect, time of occurrence, severity, and duration were documented using standard reporting sheets, and continuous observation was performed by the primary investigator. AEs were evaluated both before and after each session, and participants with notable or continuous AEs were temporarily excluded until their evaluation was complete.

Statistical Analysis

The SPSS statistical package version 25 (IBM Analytics, Armonk, New York, USA) was used. For categorical data, frequencies and percentages (N) were used for presentation, with the chi-square (χ²) test to compare the two groups. The Shapiro–Wilk test was used to check the normal distribution of continuous data and presented as mean ± standard deviation (SD). Levene’s test was used for testing the homogeneity of data. An independent t-test was employed to determine the differences among groups at baseline. A mixed repeated-measures ANOVA was performed to test the significance of the effect of treatment (a between-subjects factor) and time (a within-subjects factor) on a continuous dependent variable, with the post hoc Bonferroni test to adjust for several comparisons. The mean difference between the two groups was calculated using a 95% confidence interval (CI). Effect sizes were estimated using partial eta squared (ηp²) for mixed repeated-measures ANOVA and Cohen’s d for between-group comparisons. Statistical significance was set at p < 0.05.

Results

As shown in Table 1, the two groups were not statistically significantly different in terms of age, sex, body weight, height, BMI, duration of LBP, marital status, employment, peak torque (extensors/flexors), average power (extensors/flexors), pain, and WHOQOL-BREF (physical and psychological domains) (P > 0.05).

Table 1.

Features of Both Study Groups Prior to the Intervention

Variables	HILA Group (n=30)	Sham Group (n=30)	Test of Significance	p-value
Age (Years)	31.55±5.56	30.25±4.96	t = 0.956	0.343
Gender, N (%)			χ2 = 0.268	0.605
Male	13(43.3%)	15(50.0%)
Female	17(56.7%)	15(50.0%)
Weight (Kg)	61.99±5.92	59.24±6.75	t = 1.673	0.100
Height (cm)	164.86±4.45	165.61±4.07	t = −0.681	0.499
BMI (Kg/m2)	22.83±2.27	21.63±2.60	t = 1.914	0.061
Duration of LBP (months)	11.03±3.78	10.83±3.87	t = 0.202	0.840
Marital status, N (%)			t = 0.067	0.795
Single	16(53.3%)	17(56.7%)
Married	14(46.7%)	13(43.3%)
Employment, N (%)			t = 0.131	0.718
Employed	26(86.7%)	25(83.3%)
Unemployed	4(13.3%)	5(16.7%)
Peak Torque (N.m)
Extensors Flexors	116.05±9.09 101.69±6.68	117.26±10.14 102.13±9.52	t = −0.485 t = −0.206	0.629 0.838
Average Power (Watts)
Extensors	63.54±4.33	63.98±5.21	t = −0.356	0.723
Flexors	51.31±3.45	52.16±4.91	t = −0.776	0.441
Pain (mm)	68.73±10.87	68.13±7.36	t = 0.250	0.803
WHOQOL-BREF (Score)
Physical Domains	52.93±6.56	53.07±6.06	t = −0.082	0.935
Psychological Domains	56.70±5.90	56.57±5.28	t = 0.092	0.927

Notes: Data was presented as mean ± SD for continuous data, while N (%) for categorical data; t, independent t-test; χ², chi-square test.

Abbreviations: HILA, High-intensity laser acupuncture; BMI, body mass index; WHOQOL-BREF, World Health Organization quality of life.

For peak torque, a significant main effect of time and group for trunk extensors (F (2,116) = 166.364, ηp² = 0.741, p < 0.001; F (1,58) = 5.793, ηp² = 0.091, p = 0.019) and flexors (F (2,116) = 163.626, ηp² = 0.738, p < 0.001; F (1,58) = 4.232, ηp² = 0.068, p = 0.044) was observed (Table 2). Additionally, a significant interaction between group and time was noted for the trunk extensors (F (2,116) = 13.105, ηp² = 0.184, p < 0.001) and flexors (F (2,116) = 13.872, ηp² = 0.193, p < 0.001). In both groups, a statistically significant increase was observed from pre-intervention to post-intervention in both the HILA and sham groups for trunk extensors (MD = 23.68 N·m, 95% CI = 19.39, 27.97 and MD = 13.62 N·m, 95% CI = 9.33, 17.91, respectively) as well as flexors (MD = 17.76 N·m, 95% CI = 13.41, 22.10 and MD = 9.68 N·m, 95% CI = 8.50, 10.86) (P < 0.001 for all), with greater improvement in the HILA group (effect size Cohen’s d = 0.862, p = 0.001 for trunk extensors and effect size Cohen’s d = 0.844, p = 0.002 for flexors). At follow-up, there was also a statistically significant increase in trunk extensors (MD = 20.91 N·m, 95% CI = 16.07, 25.74 and MD = 11.31 N·m, 95% CI = 6.48, 16.15) and flexors (MD = 12.29 N·m, 95% CI = 8.02, 16.55; MD = 6.98 N·m, 95% CI = 5.29 to 8. 68) in the HILA and sham groups, respectively, compared to pre-intervention in the HILA and sham groups, respectively, with larger effects in the HILA group for trunk extensors (effect size Cohen’s d = 0.849, p = 0.002) and flexors (effect size Cohen’s d = 0.636, p = 0.017). However, a statistically significant decrease from post-intervention to follow-up was observed in both groups for the trunk (P = 0.001 and P = 0.006) and flexors (both P < 0.001).

Table 2.

Peak Torque and Average Power of Trunk Extensors and Flexors Pre- and Post-Intervention and Follow-Up in the Two Groups

Variables	Pre-Intervention	Post-Intervention	Follow-Up	p-valuea	Pairwise Time Comparison	MD (95% CI)	Post-Hoc p-value	Time X Group Interaction
								F	ηp2	p-value
Peak Torque of Trunk Extensors (N.m)
HILA Group (n=30)	116.05 ±9.09	139.73 ±10.20	136.96±10.14	<0.001	Pre vs Post	23.68 (19.39,27.97)	<0.001	13.105	0.184	<0.001
					Pre vs Follow-up	20.91 (16.07,25.74)	<0.001
					Post vs Follow-up	−2.77 (−4.52,−1.02)	0.001
Sham Group (n=30)	117.26 ±10.14	130.88 ±10.33	128.57 ±9.60	<0.001	Pre vs Post	13.62 (9.33,17.91)	<0.001
					Pre vs Follow-up	11.31 (6.48,16.15)	<0.001
					Post vs Follow-up	−2.31 (−4.05,−0.56)	0.006
MD (95% CI)	−1.21 (−6.18, 3.77)	8.85 (3.54,14.16)	8.39 (3.28,13.49)
P-valuec	0.629	0.001	0.002
Peak Torque of Trunk Flexors (N.m)
HILA Group (n=30)	101.69 ±6.68	119.45 ±8.75	113.98±7.69	<0.001	Pre vs Post	17.76 (13.41,22.10)	<0.001	13.872	0.193	<0.001
					Pre vs Follow-up	12.29 (8.02,16.55)	<0.001
					Post vs Follow-up	−5.47 (−7.46,−3.48)	<0.001
Sham Group (n=30)	102.13 ±9.52	111.81 ±9.36	109.11±7.63	<0.001	Pre vs Post	9.68 (8.50,10.86)	<0.001
					Pre vs Follow-up	6.98 (5.29,8.68)	<0.001
					Post vs Follow-up	−2.70 (−3.99,−1.41)	<0.001
MD (95% CI)	−0.44 (−4.68, 3.81)	7.64 (2.95,12.32)	4.87 (0.91, 8.83)
P-valuec	0.838	0.002	0.017
Average Power of Trunk Extensors (Watts)
HILA Group (n=30)	63.54 ±4.33	75.95 ±4.38	73.06 ±4.74	<0.001	Pre vs Post	12.41 (10.14,14.69)	<0.001	23.364	0.287	<0.001
					Pre vs Follow-up	9.52 (7.01, + 12.03)	<0.001
					Post vs Follow-up	−2.89 (−3.69,−2.09)	<0.001
Sham Group (n=30)	63.98 ±5.21	70.45 ±3.93	68.81 ±4.97	<0.001	Pre vs Post	6.47 (5.24,7.72)	<0.001
					Pre vs Follow-up	4.83 (3.74,5.92)	<0.001
					Post vs Follow-up	−1.64 (−2.82,−0.47)	0.004
MD (95% CI)	−0.44 (−2.91, 2.03)	5.50 (3.34,7.65)	4.25 (1.74,6.76)
P-valuec	0.723	<0.001	0.001
Average Power of Trunk Flexors (Watts)
HILA Group (n=30)	51.31 ±3.45	59.80 ±4.73	58.08 ±4.67	<0.001	Pre vs Post	8.49 (6.49,10.50)	<0.001	29.698	0.339	<0.001
					Pre vs Follow-up	6.77 (5.10,8.44)	<0.001
					Post vs Follow-up	−1.72 (−2.71,−0.74)	<0.001
Sham Group (n=30)	52.16 ±4.91	56.30 ±4.49	54.11 ±4.26	<0.001	Pre vs Post	4.14 (3.42,4.85)	<0.001
					Pre vs Follow-up	1.95 (1.11,2.79)	<0.001
					Post vs Follow-up	−2.19 (−2.66,−1.72)	<0.001
MD (95% CI)	−0.85 (−3.04,1.34)	3.51 (1.12,5.89)	3.97 (1.66,6.28)
P-valuec	0.441	0.005	0.001

Abbreviations: HILA, High-intensity laser acupuncture; F, Mixed repeated measures ANOVA; MD, Mean difference; CI, Confidence interval; P-value^a, Within-group comparison; P-value^c, Between-group comparison; ηp², Partial eta squared.

As for average power, significant main effects of time and group were revealed for both trunk extensors (F(2,116) = 231.817, ηp² = 0.800, p < 0.001, and F(1,58) = 8.445, ηp² = 0.127, p = 0.005) and flexors (F(2,116) = 175.708, ηp² = 0.752, p < 0.001, and F(1,58) = 4.207, ηp² = 0.068, p = 0.045). A significant interaction effect between time and group was also found for the trunk extensors (F(2,116) = 23.364, ηp² = 0.287, p < 0.001) and flexors (F(2,116) = 29.698, ηp² = 0.339, p < 0.001) (Table 2).

Both groups had significant increases from pre- to post-intervention in the average power of trunk extensors (MD = 12.41 Watts, 95% CI = 10.14, 14.69 for the HILA group and MD = 6.47 Watts, 95% CI = 5.24, 7.72 for the sham group) and flexors (MD = 8.49 Watts, 95% CI = 6.49, 10.50 for the HILA group and MD = 4.14 Watts, 95% CI = 3.42, 4.85 for the sham group) (p < 0.001), with a greater improvement in the HILA group for trunk extensors (effect size Cohen’s d = 1.322, p < 0.001) and flexors (effect size Cohen’s d = 0.759, p = 0.005). At the follow-up assessment, both the HILA and sham groups showed significant improvements in trunk extensors (MD = 9.52 Watts, 95% CI = 7.01, 12.03 and MD = 4.83 Watts, 95% CI = 3.74, 5.92, respectively) and flexors (MD = 6.77 Watts, 95% CI = 5.10, 8.44 and MD = 1.95 Watts, 95% CI = 1.11, 2.79, respectively) compared to pre-intervention (p < 0.001), with the HILA group still higher for trunk extensors (effect size Cohen’s d = 0.875, p = 0.001) and flexors (effect size Cohen’s d = 0.888, p = 0.001). However, there was a decrease in the power of the trunk extensors and flexors in the HILA (both p < 0.001) and sham groups (p = 0.004 and p < 0.001, respectively) from post-intervention to follow-up.

For pain, there were significant effects of time and group on pain (F(2,116) = 200.514, ηp² = 0.776, p < 0.001 and F(1,58) = 37.465, ηp² = 0.392, p < 0.001) and the interaction of time and group (F(2,116) = 26.515, ηp² = 0.314, p < 0.001). A significant reduction in pain from pre- to post-intervention for the HILA group (MD) = −31.03 mm, 95% CI = −36.81, −25.26) and the sham group (MD = −14.8 mm, 95% CI = −18.74, −10.8) (p < 0.001), with greater pain reduction in the HILA group (effect size Cohen’s d = −2.174, p < 0.001). Also, there was a statistically significant decrease in pain scores at follow-up compared to pre-intervention in both the HILA (MD = −26.73 mm, 95% CI = 33.05, −20.41, p < 0.001) and sham groups (MD = −12.00 mm, 95% CI = −16.41, −7.59, p < 0.001), but pain was still statistically significantly lower in the HILA group (effect size Cohen’s d = −1.729, p < 0.001). However, during follow-up, a significant increase in pain compared to post-intervention levels was observed in both groups (p < 0.001 and p = 0.030) (Figure 3 and Supplementary Table S1).

Figure 3.

Comparison of Mean Pain Between Groups Before, After Intervention, and Follow-up. Error bars represent 95% confidence intervals (95% CI).

Notes: ns, Not Statistically Significant at P > 0.05; *, Statistically Significant at P < 0.05.

Statistically significant time and group differences for the WHOQOL-BREF physical and psychological scores were obtained as F(2,116) = 62.533, ηp² = 0.519, p < 0.001 and F(1,58) = 4.139, ηp² = 0.067, p = 0.046; F(2,116) = 200.309, ηp² = 0.775, p < 0.001 and F(1,58) = 12.191, ηp² = 0.174, p = 0.001, respectively. In addition, a statistically significant interaction between time and group was established for physical (F (2,116) = 5.488, ηp² = 0.086, p = 0.005) and psychological (F(2, 116) = 32.208, ηp ² = 0.357, p < 0.001) scores. Both WHOQOL-BREF physical and psychological scores increased significantly from pre- to post-intervention in the HILA group (MD = 12.17, 95% CI: 8.39, 15.95 and MD = 13.27, 95% CI: 10.98, 15.56, respectively) and the sham group (MD = 6.83, 95% CI: 2.92, 10.75 and MD = 5.76, 95% CI: 3.87, 7.66, respectively) (all P < 0.001); however, the HILA group had significantly greater improvements in both the physical (effect size Cohen’s d = 0.677, P = 0.011) and psychological (effect size Cohen’s d = 1.301, P < 0.001) domains. In addition, there was a statistically significant increase in physical and psychological scores during follow-up compared to pre-intervention in the HILA group (MD = 9.90, 95% CI: 5.97, 13.83 and MD = 10.63, 95% CI = 8.41, 12.85, respectively) (p < 0.001 for both scores) and the sham group (MD = 5.00, 95% CI = 1.03, 8.97 and MD = 4.36, 95% CI = 2.47, 6.26) (p = 0.010 and p < 0.001, respectively), with the HILA group showing greater improvement in both WHOQOL-BREF physical and psychological scores (effect size Cohen’s d = 0.586, p = 0.027 and effect size Cohen’s d = 1.140, p < 0.001, respectively). In contrast, a significant reduction from post-intervention to follow-up occurred in the HILA (p < 0.001) and sham (p < 0.001) groups for both scores (Table 3).

Table 3.

WHOQOL-BREF Scores for Physical and Psychological Domains Between Two Groups Prior to Intervention, Following Intervention, and at Follow-Up

Variables	Pre-Intervention	Post-Intervention	Follow-Up	p-valuea	Pairwise Time Comparison	MD (95% CI)	p-valueb	Time X Group Interaction
								F	ηp2	p-value
Physical Domains
HILA Group (n=30)	52.93 ±6.56	65.10 ±9.06	62.83 ±9.40	<0.001	Pre vs Post	12.17 (8.39,15.95)	<0.001	5.488	0.086	0.005
					Pre vs Follow-up	9.90 (5.97,13.83)	<0.001
					Post vs Follow-up	−2.27(−2.90,−1.63)	<0.001
Sham Group (n=30)	53.07 ±6.06	59.90 ±5.99	58.07 ±6.59	0.003	Pre vs Post	6.83(2.92,10.75)	<0.001
					Pre vs Follow-up	5.00 (1.03, 8.97)	0.010
					Post vs Follow-up	−1.83 (−2.68,−0.99)	<0.001
MD (95% CI)	−0.13 (−3.40, 3.13)	5.20(1.23, 9.17)	4.77 (0.57,8.96)
P-valuec	0.935	0.011	0.027
Psychological Domains
HILA Group (n=30)	56.70 ±5.90	69.97 ±6.46	67.33 ±6.05	<0.001	Pre vs Post	13.27(10.98,15.56)	<0.001	32.208	0.357	<0.001
					Pre vs Follow-up	10.63(8.41,12.85)	<0.001
					Post vs Follow-up	−2.64(−3.94,−1.32)	<0.001
Sham Group (n=30)	56.57 ±5.28	62.33 ±5.22	60.93 ±5.14	<0.001	Pre vs Post	5.76 (3.87,7.66)	<0.001
					Pre vs Follow-up	4.36 (2.47,6.26)	<0.001
					Post vs Follow-up	−1.40(−2.03,−0.77)	<0.001
MD (95% CI)	0.13 (−2.76, 3.03)	7.63 (4.60,10.67)	6.40 (3.50,9.30)
P-valuec	0.927	<0.001	<0.001

Abbreviations: HILA, High-intensity laser acupuncture; F, Mixed repeated measures ANOVA; MD, Mean difference; CI, Confidence interval; P-value^a, Within-group comparison; P-value^b, Post hoc Bonferroni-adjusted for pairwise comparison; P-value^c, Between-group comparison; ηp², Partial eta squared.

Adverse Events

As far as AEs are concerned, there were no AEs noted during the study, and none of the participants had to stop receiving treatment due to any complications arising from the treatment itself. While undergoing treatment, six patients under the HILA regime reported mild warmth and flushing in the area where laser therapy was being provided. This was anticipated and did not hinder treatment but spontaneously resolved without requiring any intervention.

Discussion

The results obtained from this study indicated significant between-group differences at post-treatment and at the one-month follow-up period for all parameters (p < 0.05). Clinically, these findings indicate that HILA may be a useful adjunct to physical therapy exercises in CNSLBP rehabilitation, as it enhances trunk muscular performance, reduces pain, and improves QoL.

The improvement in trunk muscular performance in terms of extensor muscle peak torque and average power may result from improved ATP synthesis due to increased mitochondrial activity through laser therapy. PBM can deliver ergogenic effects by increasing microcirculation, enhancing antioxidant system function, and reducing lactic acid synthesis. A higher level of nitric oxide improves vasodilation and oxygenation of tissues and neuromuscular stimulation; this effect, in turn, might be responsible for muscle improvement.²⁹ The current study used a high-power laser that penetrated deeper into the tissue with beneficial anti-inflammatory, anti-edematous, and analgesic effects.⁶ All of these mechanisms can improve trunk muscle performance, consistent with the findings of a recent randomized controlled trial.³⁰

Previous studies support its potential effects on muscle strength and performance-related outcomes in musculoskeletal conditions. High-intensity lasers have been reported to improve isokinetic muscle strength in patients with subacromial impingement syndrome, ⁷ hand grip strength in lateral epicondylitis,³¹ knee muscles in knee osteoarthritis,³² and patellofemoral pain syndrome.³³ These findings support its possible role in enhancing muscle performance.

Although PBM protocols vary in terms of dosage and wavelength, pre-exercise PBM has been shown to improve muscular performance.⁸ Machado et al³⁴ also reported that light-emitting diode PBM moderately attenuated delayed-onset muscle soreness, although it did not significantly affect the recovery markers or running performance. In contrast, Ekici and Ordahan,³⁵ found no differences in knee muscular strength between high-intensity laser plus exercise and sham laser plus exercise in patients with knee osteoarthritis. This discrepancy may be due to variations in the treatment conditions, laser protocols, and the use of a regional laser rather than the laser applied to acupuncture points.

The current findings may also be explained by the effect of acupuncture stimulation. Acupuncture could positively affect muscle strength, as it enhances neuronal stimulation, post-activation potentiation of motor units, and muscle performance in general,³⁶ which was proven earlier.^37,38 Furthermore, LA provides a noninvasive method of acupoint stimulation and may contribute to motor function improvement beyond analgesia. A recent systematic review and meta-analysis reported that LA may improve pain intensity, physical function, joint stiffness, and range of motion in musculoskeletal disorders, with treatment effects influenced by laser parameters, particularly the wavelength and combined laser approaches.³ In addition, Hassanein et al³⁹ found that LA improved hip flexor and knee extensor muscle strength in spastic cerebral palsy, which supports a potential neuromuscular effect of LA on muscle performance.

The positive changes noted in trunk flexor performance, although the HILA predominantly targeted the extensors, can be attributed to the widespread neuromuscular impact of LA therapy. The findings show that the therapeutic effects of LA therapy on motor function are not associated with the analgesic effect alone; rather, these positive results could be directly related to the effects of the therapy on muscle performance, such as ATP generation and neuromuscular excitation.³ However, it is difficult to clearly interpret the clinical significance because the minimal clinically important difference (MCID) threshold for trunk muscle performance in CNSLBP remains undefined.

Changes in pain were found to be statistically and clinically significant, as they exceeded the minimum clinically important change (MCIC) for VAS in LBP (20 mm)²⁷ in favor of the HILA group. This finding is consistent with recent research³⁰ and a previously published conference paper on high-power LA in CNSLBP, which reported significantly greater pain improvement after a 4-week intervention in the active treatment group compared with the sham group. ¹⁴ High-intensity lasers treat pain both centrally and peripherally. It increases endorphin levels, inhibits the secretion of substance P and inflammation, and elevates the pain threshold.⁶ Enhancement of pain and functioning in LBP and musculoskeletal problems with high-intensity lasers has been described in systematic reviews and meta-analyses, respectively,^13,40 and in multiple studies of chronic LBP^1,11,12,41 and other cases.^{7,31–33,42–45}

Furthermore, stimulation of specific acupoints might help block pain due to gate control and stimulate endorphin production.⁴⁶ This effect has been confirmed in various studies.^5,9,10,38 Furthermore, LA was reported to influence pain perception and modulation in the central nervous system, making it possible to have clinical applications in dealing with chronic musculoskeletal pain and difficulty in movement due to pain³ and in relieving other clinical conditions.^5,21

However, regarding chronic LBP, no major difference was noted between LA and placebo treatment, although both groups recorded improvements,¹⁷ possibly due to shorter involvement periods. Similarly, Ekici and Ordahan,³⁵ found no significant differences in pain reduction between high-intensity laser plus exercise and sham laser plus exercise in knee osteoarthritis. These inconsistent findings may be explained by differences in the treatment conditions, laser parameters, treatment duration, and application technique.

The results of the study demonstrated improvements in QoL for participants receiving HILA (p < 0.05) compared to the sham group. High-intensity laser treatment can reduce pain and improve the capacity to perform activities.⁴³ It has been proven to be efficient in increasing physical activity, sleep behavior, well-being, and QoL.⁴⁷ Additionally, Choi et al⁴¹ reported that it could function as an effective, noninvasive approach for enhancing functionality in chronic pain. These findings are consistent with those of previous studies.^{1,7,31,43–45}. However, the absence of the MCID for the WHOQOL-BREF in CNSLBP makes clinical interpretation difficult.

Overall, the present results suggest that HILA may be a promising adjunct to the clinical management of CNSLBP, as it improves trunk muscular performance, pain, and QoL. These benefits may be due to the combined effects of PBM, the deeper penetration of high-intensity lasers into the tissue, and acupoint activation. Therefore, HILA may be considered a useful adjunct to exercise-based rehabilitation programs.

Physical therapy exercises improved all indicators of treatment outcomes. The ACP further recommends the use of exercise for chronic LBP.⁴ Lumbar stabilization and strengthening exercises help strengthen trunk muscles and reduce pain and disability associated with persistent LBP,²⁴ while core stabilization exercises positively affect muscle activation, pain, and health-related QoL.⁴⁸

Limitations and Recommendations

The present study had some drawbacks. First, the treatment was administered over a relatively short period. Second, the small age range in the current study may restrict its generalizability to patients with CNSLBP. Third, no further muscle testing was performed, such as electromyography. Future studies should consider a longer-term analysis and a wider age range. Researchers also need to investigate different HILA dosages.

Conclusion

A combination of HILA therapy and physical exercise therapy might produce more gains in trunk muscle performance, pain, and QoL in patients compared than physical exercise therapy alone within a relatively shorter period. The findings of this study suggest that HILA can be considered an adjunct therapy alongside physical therapy exercises in patients with CNSLBP. However, additional long-term studies are required.

Funding Statement

This research was funded by Princess Nourah bint Abdulrahman University Researchers Supporting Project number (PNURSP2026R168), Princess Nourah bint Abdulrahman University, Riyadh, Saudi Arabia. Additionally, this research was funded by Deanship of Graduate Studies and Scientific Research at Najran University for funding this work under the Female Scholars Funding Program grant code (NU/FSP/MRC/14/4347-2).

Data Sharing Statement

Data supporting this study are available from the corresponding author upon request.

Ethics Approval and Consent to Participate

The research procedure was authorized by the Committee for Research Ethics of the Faculty of Physical Therapy at the University of Cairo (Number: P.T.REC/012/005224) and was performed in accordance with the ethical criteria of the 1975 Declaration of Helsinki.

Disclosure

The authors declare no conflicts of interest.