Body shape outlines and contours are important features that represent beauty and health. Individuals are increasingly considering body-sculpting procedures, exercise training, or surgical procedures [1-3]. Body contour is defined as the balance between the muscle outline and overlying subcutaneous fat (SF) thickness. Thick muscle mass provides a good outline, which is exhibited more obviously with thin overlying fat. This leads to the concepts of muscle training and fat burning. As for muscle training, active exercise is important for hyperplasia and hypertrophy of the myocytes [4]. However, the efficiency of active training is relatively low in the public because of the sequential recruitment property in voluntary contraction [5]; therefore, the training results build up slowly. With supra-maximal contraction (SMC) induced by high-intensity focused electromagnetic waves (HIFEM), the quantity of muscle being induced to contract maximal, which leads to more effective muscle growth [6,7]. Simultaneously, there is a corresponding decrease in the fat layer [7], which can be explained by catecholamine-induced lipolysis [8]. For Asian subjects training using HIFEM, it was found that the outcome is less effective than that for Caucasian subjects, and this study helped to evaluate a new protocol with longer treatment sessions each time.

The study comprised 13 participants (mean age, 37.4-year-old; body mass index [BMI], 22.5 kg/m²), of whom 9 were female and 4 were male.

The inclusion criteria for the study were BMI less than 27.5 kg/m², average abdominal fat thickness within 3 cm, average rectus abdominis (RA) thickness within 2 cm, and age 25–55 years. The exclusion criteria were previous abdominal surgery or other aesthetic procedures in the abdominal area, use of medication that affects fat and muscle composition, and contraindications stated by the device manufacturer. Participants were advised to maintain their daily activities. Basic biometric data were collected before the treatment.

Each participant received a total of six sessions of treatment. Treatment was repeated using the HIFEM device (Emsculpt; BTL industries, Inc., Boston, MA, USA) one to two times a week with at least a 2-day interval, and each session lasted for 60 minutes. The study and consent forms were provided and designed according to the guidelines of the Declaration of Helsinki [9]. The device provides electromagnetic pulses of 1.8 Tesla for each applicator, and the magnetic field focus can penetrate to a depth of 7 cm. The treatment targeted the area of the RA by placing the applicator at the level of the umbilicus. During the treatment, the participant was placed in a supine position, and the treatment was administered to the abdomen, targeting the RA. One or two applicators were used according to the size of the subject’s abdomen. During treatment, the intensity of the electromagnetic field was gradually increased to the highest tolerated level. All the participants were able to tolerate 100% intensity by the second treatment session. Abdominal muscle stimulation was closely monitored by the operator and fine adjustments were made to ensure equal stimulation of the muscle on both sides. A fixation belt was used to secure the applicator’s position.

The participants were evaluated at the first visit, last treatment visit, and 1 and 3 months after the last treatment.

The primary evaluation of the SF layer and RA thickness was performed using diagnostic M-mode ultrasound. A linear probe was used in this study. Six positions of the SF and RA were measured: the maximum thickness of the 2nd, 3rd, and 4th expansions (in the craniocaudal direction) of the RA on both sides, and their respective overlying SF (Fig. 1, 2). To avoid fat compression errors, the ultrasound probe was positioned to touch the surface of the skin without compression. To reduce operator error in the measurement, the average of the readings was calculated for statistical analysis (Table 1, 2).

Figure 1. Photo for change in subcutaneous fat (SF) and rectus abdominis (RA) thickness. (A) is the baseline measurement; (B) is 1 month post treatment; (C) is 3 months post treatment. A progressive decrease in SF thickness and increase in RA muscle thickness. 1D depicts the SF thickness and 2D, the RA thickness.

Figure 2. Photo for illustration of ultrasound measuring points. A total of six points from 2nd, 3rd, and 4th segments of rectus abdominis (RA) of both sides were measured and the averages of these six points readings for subcutaneous fat and RA thickness were calculated for a more reliable result.

Table 1 . Baseline subcutaneous fat (SF) thickness and changes in SF thickness on ultrasonography.

SF thickness	Mean decrease (cm)	p-value (two-tailed)
Baseline (before treatment)	1.56±0.59	-
Before vs. after treatment	0.31±0.11 (19.9%)	0.017
Before vs. 1-month follow-up	0.40±0.14 (25.6%)	0.014
Before vs. 3-month follow-up	0.53±0.10 (34.0%)	<0.001

Values are presented as mean±standard error of mean..

Table 2 . Baseline rectus abdominis (RA) thickness and changes of RA thickness by ultrasonography.

RA thickness	Mean increase(cm)	p-value (two-tailed)
Baseline (before treatment)	1.07±0.30	-
Before vs. after treatment	0.29±0.25	0.001
Before vs. 1-month follow-up	0.28±0.30	0.006
Before vs. 3-month follow-up	0.28±0.23	<0.001

Values are presented as mean±standard error of mean..

Standardized 2D and 3D digital photographs were taken to document the clinical progression. Participant satisfaction was assessed at the 1st and 3rd month follow-up visits using a standardized 5-point Likert Scale questionnaire graded as (1) strongly disagree, (2) disagree, (3) neutral, (4) agree, and (5) strongly agree (Table 3). The participant were advised and encouraged to report any adverse events during or after the treatment.

Table 3 . Participant satisfaction data according to the Likert scale.

Likert Scale	Number of participants (%)
(1) Strongly disagree	0
(2) Disagree	0
(3) Neutral	0
(4) Agree	12/13 (92.3)
(5) Strongly agree	1/13 (7.7)

The collected data were analyzed using IBM SPSS (version 27; IBM Corp., Armonk, NY, USA) using paired t-tests to determine clinical significance.

All participant completed the treatment and evaluation according to the protocols described in the Methods section. Ultrasound measurements showed an improvement in the SF and RA thickness after the treatment. Digital photographs showed aesthetic improvement in the abdominal region. Participant satisfaction was also reported to be high.

Ultrasound measurements

For fat, there were statistically significant reductions of the SF layer thickness at the last treatment visit, 1-month follow-up, and 3-month follow-up with a value of 0.31 cm (19.9%), 0.40 cm (25.6%), and 0.53 cm (34.0%), respectively (p=0.017, p=0.014, and p<0.001, respectively) when compared to the baseline before the treatment (1.56 cm). The results showed a clinically significant positive correlation between the decrease in the SF layer and HIFEM treatment. There were two cases with SF thickness increase after the whole set of treatment and at 1 month after the treatment, whereas there was one case with SF thickness increase 3 months after the treatment. A total of 11 cases showed a straight decrease in SF thickness.

Regarding muscle improvement, there was a statistically significant increment in RA thickness at the last treatment visit, 1-month follow-up, and 3-month follow-up with a value of 0.29 cm (27.8%), 0.28 cm (26.2%), and 0.28 cm (26.2%), respectively (p=0.001, p=0.006, and p<0.001, respectively) relative to the baseline period prior to the treatment (1.07 cm). The results demonstrated a clinically significant positive correlation between an increase in RA thickness and HIFEM treatment. The RA thickness of all participants increased after the entire treatment. There were two cases with a decrease in RA thickness after 1 month and one case after 3 months. Eleven participants showed a straight increase in RA thickness at 1 and 3 months of follow-up.

Digital photos and participant satisfaction and comfort

The photographs showed improvements in body shape, muscle outline, and waist circumference (Fig. 3, 4). The general satisfaction of the participants with the above improvements was high and correlated with the study results. The participants were satisfied with the results in terms of shape, muscle outline, and waist circumference. All cases (100%; 13 out of 13) marked a Likert scale response of 4 or above and 7.7% (1 out of 13) marked 5 (Table 3). No significant adverse effects or discomfort was reported by the participants.

Figure 3. Photo for progressive improvement of the body shape outline change at baseline (A), 1 month (B), and 3 months (C). It shows that the linea semilunaris and contour of the rectus abdominis segments are more and more obvious with time.

Figure 4. Photo for improvement of the body outline demonstrated by indicated by decrease in waist circumference and computed volume at 1 month (B, D) compared with the baseline (A, C).

Body contour is defined as the balance between muscle and fat thickness. For example, in the abdomen, the RA provides the contours of six packs (a combination of contours from the RA and tendinous intersection) and outlines of the vast line (linea semilunaris). However, regardless of how good the outline of the RA is, if the overlying fat is too thick to act as an apron to cover the underlying RA, the muscle contour is not well-defined, and the body does not appear not well shaped. To achieve a good body contour, we recommend training to enhance the muscle mass and reducing the amount of overlying SF.

Traditionally, to train the muscles, we need to perform active exercises, including weight and endurance training. However, recruitment of active muscle fibres in the general population is not sufficiently efficient [10,11]. Therefore, the training curve is long and steep. With passive biophysical induction of the muscle to a status of SMC, the efficiency is significantly increased [6,11]. HIFEM can biophysically induce motor neuron potentials, which cause muscle contractions [12]. A number of studies have shown that muscles can be effectively trained by HIFEM. A pilot study by Duncan et al. [6] showed that HIFEM increased 20.56% of muscle mass density and size increased by 12.15% in Yorkshire pigs. Kinney et al. [7] also used MRI to demonstrate an increase in muscle thickness from 0.111 cm to 0.127 cm (14.4%) at 2 months (p<0.001). Furthermore, four subjects with a 6-month follow-up period showed a continued effect with an increase in muscle thickness of 20.5%. These findings matched the result of this study where we found mean increases in RA thicknesses of 0.29 cm (27.8%), 0.28 cm (26.2%), and 0.28 cm (26.2%) at the last visit, 1-month follow-up, and 3-month follow-up, respectively (p=0.001, p=0.006, and p<0.001, respectively). Moreover, the increment in the muscle thickness was better than that in previous studies.

Although liposuction is a popular procedure for fat removal [13], it is traumatic and associated with several complications, morbidities, and mortality. Temperature-induced lipolysis, such as radiofrequency (RF) and cryolipolysis [3], was beyond the scope of this study. Metabolic fat reduction is another mechanism advocated for fat reduction. The main factor is the quality and quantity of the muscle, as the basal metabolic rate increases with increased muscle mass [14], and catecholamine-induced lipolysis can be achieved by muscle activities [8]. Apoptosis was also demonstrated by Weiss and Bernardy [15]. Muscle contraction and training-induced fat reduction have been demonstrated in several western clinical studies (Table 4). As the metabolism of fat and muscle may differ between Western and Asian countries, the authors found that it is slightly more difficult to reproduce the same effect as described in those papers [7,16]. Therefore, the authors conducted this study to lengthen the treatment duration from 30 to 60 minutes. In this way, our study reproduced similar results of fat reduction as in the Western studies, which showed 18.2% to 23.3% fat reduction. In comparison, this study showed even better results at 1- and 3-month follow-up, with a fat reduction of 25.6% and 34.0%, respectively (p=0.014 and <0.001, respectively). It was inferred that the momentum of the effect continued after treatment completion.

Table 4 . Outcomes of change of subcutaneous fat after the treatment compared with previous studies.

Study	Case number	Result	Protocol	Remark
This study	13	Decreased 0.31cm (19.9%), 0.40cm (25.6%) and 0.53cm (34.0%) after completion of treatment, at 1 and 3 month respectively (p=0.017, 0.014 and <0.001 respectively)	1–2 applicators	Asian people, Study performed in Hong Kong
			60 minutes of treatment
			6 treatments in total	Ultrasound assessment
			2–5 days of interval
Katz et al. [16]	33	Decreased 0.447 cm (19.0%) and 0.578 cm (23.3%) at 1 and 3 months after completion of treatment (p<0.01 and <0.01% respectively)	1 applicator	Study performed in New York, Pennsylvania
			30 minutes of treatment
			4 treatments in total	Study performed in New York, PennsylvaniaUltrasound assessment
			Minimum 2 days interval
Kinney and Lozanova [7]	22	Decreased 0.43 cm (18.2%) and 0.30 cm (11.8%) at 2 months and 6 months, respectively (p<0.001 and p not stated respectively)	1 applicator	Study performed in California, multiple centres
			30 minutes of treatment
			4 treatments in total	MRI assessment
			2–5 days interval

All three studies used Emsculpt (BTL Industries, Boston, MA, USA) as the treatment device..

The above data analyses imply that the new protocol is suitable for the Asian population and is more effective than previous protocols. As an increasing number of adipocytes and muscle metabolisms are understood in contemporary science, different mechanisms that work together will probably have synergistic effects. These studies included combined RF and cryolipolysis [17]. As for sculpturing both the muscle and SF, synchronized RF and HIFEM have also been demonstrated to be successful [18]. It was demonstrated in some preliminary data that using combined RF and HIFEM treatment, three sessions of 30-minute treatments on the abdomen can reduce 30.8% of SF and increase 26.1% muscle thickness as detected on MRI at 3 months by Jacob et al. [19], compared to 34.0% and 26.2%, respectively, in this study with a protocol of six sessions of 60-minute HIFEM treatment alone. The results showed that the improvements in both SF and muscles were similar, but the number and length of treatments were lower. If we adjust the protocol to more sessions and increased length of treatment, for example, combined treatment of RF and HIFEM for six sessions with 60-minute treatment each time or with shorter intervals between treatments, then the result may be even better.

In conclusion, based on the study results, the author concluded that HIFEM treatment effectively reduced SF thickness and built up RA, which is essential for body shape sculpting in Asian people and is well tolerated. Moreover, the effect was sustained for 3 months after the treatment. These results are consistent with other contemporary HIFEM research results. Combined therapy may have a synergistic effect, and further studies should be conducted to confirm this hypothesis.

The author has nothing to disclose.