Physical Therapy Korea

Since the 1990s, exercises based on Pilates concepts have become popular in various fields, including rehabilitation settings for general orthopedic, geriatric, chronic pain, and neurologic populations. Early rehabilitation Pilates exercises began mainly as mat exercises, but with the development of Pilates techniques in rehabilitation, various types of equipment have been developed to achieve functional movements more efficiently and safely [1]. Regardless of the use of equipment, to achieve correct posture while maintaining abdominal pressure, the Pilates exercise program consists of a specific Pilates breathing method for chest enlargement, core muscle contraction exercise, and flexibility exercise [2,3]. The Pilates core exercise program is focused on strengthening the core muscles of the abdominals, pelvic floor, and multifidus, while maintaining the ideal alignment position of the spine and developing a simultaneous contraction mechanism with the muscles surrounding the spine, which provides a stiffening mechanism to the vertebral joints. Therefore, increasing the endurance of the abdomen and pelvic peripheral muscles through the movement of the limbs while maintaining the neutrality of the spinal column ameliorates the coordination of the trunk and limbs to help improve balance [4-7].

In a study by HwangBo [8], mat Pilates was applied to scoliosis patients with a Cobb’s angle of 20° or less for 12 weeks, and 4° decreased. Measurements using a 3D imaging analyzer showed a significant decrease in pelvic tilt, spinal scoliosis, and front, back, left, and right tilt of the trunk. In a study by Seo and Hong [9], mat Pilates was applied to scoliosis patients for 10 weeks, and Cobb’s angle decreased by 5°. Mat Pilates uses weight and gravity to perform exercises for posture correction, spinal muscle stretching, and muscle strengthening. However, for a more effective exercise, most Pilates practitioners use reformers.

The reformer is one of the most commonly used Pilates instruments, which can provide adequate resistance and assistance in various positions depending on the user’s condition and can be effectively used in rehabilitation Pilates. In particular, the size of the resistance is adjusted during exercise through various springs attached to the part of the reformer, providing various difficulties for exercise at the level of the user. Moon and Chung [10] reported that the application of the reformer exercise program to modern dance majors improved body composition, physical strength, lower extremity muscle strength, and balance ability. Furthermore, Kang and Park [11] reported that as a result of 8 weeks of performing Pilates by dance-majoring college students, the muscle mass of the extremities and the total muscle mass were significantly increased. In addition, performing regular reformer exercises for 8 weeks was reported to improve the sense of balance of the feet by reducing changes in the left, right, front, and back foot pressure and caused significant positive changes in the alignment of the frontal plane through stabilization of the lower back area and improvement of pelvic alignment by strengthening the abdominal and back muscles [10-12].

Many studies have reported the positive effect of Pilates exercises that emphasizes strength, stretching, and chest expansion with breathing techniques in postural correction through achieving spinal stabilization [9,12]. However, despite its frequent use in clinical practice in rehabilitation settings, clinical research on the link between Pilates and the enhancement of physical function in the field of physical therapy remains insufficient [1]. To date, no studies have compared the effects of equipment and mat exercises [7,12]. Therefore, this study aimed to investigate the effect of Pilates reformer equipment and Pilates mat exercise on the alignment of standing posture in the frontal plane when the exercises were applied for 8 weeks.

1. Subjects

Thirty adult female subjects between the ages of 20 and 50 years were randomly assigned to a Pilates reformer exercise group (REG) or a mat exercise group (MEG). The exclusion criteria were as follows: 1) those who had attended more than 10 Pilates exercise sessions; 2) those who were unable to perform the exercise program of this study normally due to diseases, such as osteoarthritis, fractures, cancer, and stroke; and 3) men who were fewer in number and were difficult to generalize. This study was approved by the Yonsei University Mirae Institutional Review Board (IRB no. 1041849-202207-BM-130-02). All participants provided written informed consent prior to their participation in the training. This study was conducted after both the Pilates instructor who was a skilled practitioner with 10 years of experience and the subject had gained adequate knowledge about this experiment.

2. Data Collection

Prior to the intervention, all subjects were assessed for body composition, including body alignment. Body alignment in the standing posture was assessed before and after the 8-week intervention using Exbody^® 9100 MOMI musculoskeletal analysis equipment (Exbody Inc., Seoul, Korea). According to the manufacturer’s manual, 12 markers were placed at reference points on the anterior and posterior surfaces of the body. On the anterior surface, markers were attached bilaterally to the tragus, acromion, anterior superior iliac spine (ASIS), center of the patella, and center of the ankle joint. Markers were attached bilaterally to the inferior angle of the scapula on the posterior surface. The subjects maintained a static standing posture for 10 seconds each in the front and back standing positions in the Exbody^® 9100 MOMI musculoskeletal analysis. As dependent variables, the difference in vertical height between the left and right sides in the frontal plane was calculated using Exbody posture analyzer software (Figure 1) [7].

Figure 1. Standing posture alignment using the Exbody^® 9100 MOMI musculoskeletal analysis (Exbody Inc.) in fontal plane. (A) Anterior surface, (B) posterior surface.

3. Intervention

The subjects in both the reformer and MEGs participated in the Pilates core exercise program for 60 minutes per session, three times a week, for a total of 8 weeks. The exercise program for each group consisted of 10 movements. The Pilates exercise intervention performed in this study referred to the Stott Pilates method performed in previous studies and consisted of 10 minutes of warm-up, 40 minutes of main exercise, and 10 minutes of cool-down exercise. A 30 seconds rest was provided between the sets. For this study, 20 Pilates exercises (10 pairs of movements) were selected using the Stott Pilates method (Figure 2). The two exercises in the same pair achieve the same motor goal by promoting the same target muscle by performing the same type of muscle contraction (Table 1). One was selected to be performed using a reformer, and the other was selected as suitable as a mat exercise without a reformer. Therefore, the intervention in each group consisted of 10 Pilates exercises.

Table 1 . Pilates exercises and targeted muscle contractions.

Reformer	Mat	Targeted muscle contraction
		Co-contraction	Concentric	Eccentric
Hundred	Hundred	Transvers abdominis, pelvic floor	Abdominals, hip flexor/adductor, back extensor
Short spine	Rolling like a ball	Transvers abdominis, pelvic floor	Abdominals, hip flexor/adductor	Abdominals, hip flexor/adductor
Leg circle	Single leg circle	Transvers abdominis, pelvic floor	Abdominals, hip flexor/extensor/adductor/abductor
Foot work	Side kick	Transvers abdominis, pelvic floor, back extensor	Hip flexor/extensor
Short box-round back	Full roll up	Transvers abdominis, pelvic floor	Abdominals, hip flexor/adductor	Abdominals, hip flexor
Short box-straight back
Short box-twist reach	Saw	Transvers abdominis, pelvic floor	Abdominals (especially oblique), hip flexor
Pull strap	Double leg kick	Transvers abdominis, pelvic floor	Back extensor, hip extensor	Back extensor, hip extensor
Back stroke	Double leg stretch	Transvers abdominis, pelvic floor	Abdominals, hip flexor/adductor	Back extensor
	Single leg stretch
Teaser	Teaser	Transvers abdominis, pelvic floor	Abdominals, hip flexor/adductor	Abdominals, hip flexor/adductor

Figure 2. (A) Pilates reformer exercises: (A-1) hundred, (A-2) short spine, (A-3) leg circle, (A-4) foot work, (A-5) short box-round back, (A-6) short box-straight back, (A-7) short box-twist reach, (A-8) pull strap, (A-9) back stroke, and (A-10) teaser. (B) Pilates mat exercises: (B-1) hundred, (B-2) rolling like a ball, (B-3) single leg circle, (B-4) side kick, (B-5) full roll up, (B-6) saw, (B-7) double leg kick, (B-8) double leg stretch, (B-9) single leg stretch, and (B-10) teaser.

The 10 Pilates reformer exercises were: (A-1) hundred, (A-2) short spine, (A-3) leg circle, (A-4) footwork, (A-5) short box-round back, (A-6) short box-straight back, (A-7) short box-twist reach, (A-8) pull strap, (A-9) backstroke, and (A-10) easier programs (Figure 2A). Pilates mat exercises consisted of 10 movements: (B-1) hundred, (B-2) rolling like a ball, (B-3) single leg circle, (B-4) side kick, (B-5) full roll up, (B-6) saw, (B-7) double leg kick, (B-8) double leg stretch, (B-9) single leg stretch, and (B-10) teaser programs (Figure 2B).

4. Statistical Analysis

The collected data were analyzed using PASW Statistics ver. 18.0 (IBM Co., Armonk, NY, USA), and the measured values of all items were calculated as the mean and standard deviation. An independent t-test was used for the homogeneity test, and a two-way mixed ANOVA test with between-group (REG, MEG) and within-group (pre-test, post-test) was used to determine the group × time interaction effect (p < 0.05). When a significant interaction effect between the group and time was found, the simple effect by the group was analyzed by independent t-test and the simple effect by time was analyzed by paired t-test. When no interaction effect was found, the main effect was analyzed (p < 0.05).

1. Pre-intervention Comparisons Between Groups (N = 30)

Table 2 shows that the average values of age, height, and weight were not significantly different between groups. Furthermore, independent t-tests revealed that left and right height differences in the frontal plane of the markers on the tragus, acromion, inferior angle of the scapula, ASIS, center of the patella, and center of the ankle joint in the standing posture were also not significantly different between groups (Table 3). All subjects completed the program, with a session attendance rate of 100%.

Table 2 . General characteristics of the subjects (N = 30).

Variable	Reformer group	Mat group	p-value
Sex (female)	15	15
Age (y)	32.80 ± 6.45	31.20 ± 5.02	0.412
Height (cm)	161.67 ± 4.45	162.67 ± 4.59	0.832
Weight (kg)	55.67 ± 6.09	54.13 ± 7.24	0.616

Values are presented as number only, or mean ± standard deviation. Independent t-test..

Table 3 . Pre-intervention between group comparisons (N = 30).

Variablea	Reformer group	Mat group	p-value
Tragus (mm)	11.80 ± 3.03	9.47 ± 3.89	0.692
Acromion (mm)	14.87 ± 8.41	14.60 ± 10.93	0.164
Inferior angle of scapula (mm)	15.80 ± 7.17	13.60 ± 6.90	0.623
ASIS (mm)	13.07 ± 7.58	11.33 ± 7.35	0.712
Center of patella (mm)	8.40 ± 5.88	8.73 ± 5.68	0.751
Ankle joint (mm)	7.20 ± 4.23	8.27 ± 3.63	0.665

Values are presented as mean ± standard deviation. Independent t-test. ASIS, anterior superior iliac spine. aDifference of right and left height..

2. Comparison Before and After Intra/Inter-group Intervention

The height difference is defined as the “Vertical height difference between the markers attached to the left and right side of the landmarks.” The results of ANOVA showed a significant time × group interaction on the height difference (p < 0.05) only in the tragus (Table 4). The simple effect by time was analyzed using a paired t-test for each group. In both the REG and MEG, the difference in the right and left height of the tragus significantly decreased after the intervention (p < 0.001). However, the height of the tragus did not differ between the groups after the intervention (p = 0.480).

Table 4 . Comparison of anterior and posterior standing postural alignment pre- and post-test values after intervention (N = 30).

Variablea	Reformer group			Mat group		Effect	p-value
	Pre-test	Post-test		Pre-test	Post-test
Tragus (mm)	11.80 ± 3.03	3.00 ± 3.14		9.47 ± 3.89	3.80 ± 2.98	Time	< 0.001***
						Time×Group	0.024*
						Group	0.451
Acromion (mm)	14.87 ± 8.42	5.93 ± 4.40		14.60 ± 10.93	7.00 ± 6.39	Time	< 0.001***
						Time×Group	0.714
						Group	0.861
Inferior angle of scapula (mm)	15.80 ± 7.17	6.60 ± 2.59		13.60 ± 6.90	8.20 ± 4.57	Time	< 0.001***
						Time×Group	0.082
						Group	0.866
ASIS (mm)	13.07 ± 7.58	2.40 ± 2.38		11.33 ± 7.35	5.00 ± 4.28	Time	< 0.001***
						Time×Group	0.187
						Group	0.759
Center of patella (mm)	8.40 ± 5.88	4.80 ± 2.60		8.73 ± 5.68	3.80 ± 2.60	Time	< 0.001***
						Time×Group	0.532
						Group	0.792
Ankle joint (mm)	7.20 ± 4.23	2.67 ± 2.32		8.27 ± 3.63	3.27 ± 2.71	Time	< 0.001***
						Time×Group	0.792
						Group	0.325

Values are presented as mean ± standard deviation. Two-way mixed ANOVA test. ASIS, anterior superior iliac spine. aDifference of right and left height. *p < 0.05, ***p < 0.001..

Except for the tragus, no significant time × group interaction was noted on the height difference (p < 0.05), along with significant main effects by time (p < 0.05) and not by group (p > 0.05) (Table 4). The height difference of both shoulders, scapulae, pelvis, knees, and ankles decreased (p < 0.001) after the Pilates exercises.

The general purpose of this study was to determine whether the patients’ standing alignment in the frontal plane showed a difference before and after the intervention when the Pilates reformer core exercise and mat core exercise program were applied in clinical practice. Specifically, this study aimed to determine the most effective exercise. The Stott Pilates exercise method was applied to the Pilates reformer and mat exercises.

Contrary to the Pilates experts’ general expectations that exercise using reformers will be more effective than mat exercise [12], height differences in the subject’s standing posture in the frontal plane were not significantly different between the groups after the 8-week intervention. The contents of the exercise programs for reformer and mat exercises applied in this study were designed to facilitate the same target muscle contraction. Furthermore, because the participants in this study were beginners in Pilates, the exercise program in both groups mainly included relatively low levels of core exercise on a stable surface. If the effects of mat and reformer exercises were compared with higher-level Pilates users, the advantage of the reformer, which can modify the level of task difficulty by changing the resistance and stability of the supporting surface, could have been more prominent.

Previous studies have reported the positive effects of Pilates on postural alignment in both healthy and unhealthy people. According to de Souza and Vieira [13], the main user group of Pilates exercise is middle-aged women; one-quarter of them perform Pilates to reduce pain and disability, and three-quarters to improve posture and flexibility. McMillan et al. [14] reported that dynamic posture control was improved in a healthy dancer group by performing a combination of reformer and mat Pilates exercises. Furthermore, Pilates was effective in improving abdominal and lumbopelvic stability and muscular activity [15], and it increased endurance of the upper extremity and abdominal muscles and flexibility of the hamstring in healthy people [16].

Seo and Hong [9] observed a significant reduction in Cobb’s angle using X-ray imaging techniques to verify the effectiveness after 10 weeks of Pilates exercise in patients with scoliosis, and the effect of body alignment was confirmed by obtaining a significant decrease in Cobb’s angle [8]. Pilates exercise has been reported to be effective not only in posture correction but also in relieving back pain [17].

Kloubec [15] observed that when Pilates exercises were applied for 12 weeks, participants became significantly taller, which was determined to be due to structural changes in the spine. Since the Pilates exercises performed in this study were based on the spinal stabilization theory, it is believed that, as in previous studies, Pilates interventions had a positive effect on postural alignment by ensuring that the mechanical changes, and abdominal pressures of the muscles, tendons, and ligaments around the vertebral joint were properly controlled [18-20].

In a literature survey with nine studies of Level III evidence, Di Lorenzo [21] suggested that Pilates exercises are reasonable as a part of rehabilitation. He also explained the mechanism of Pilates-induced benefit from the motor control perspective that performing Pilates motivates the body’s mobility and stability through the brain to make it move functionally so that it activates certain muscles in order and contributes to the regulation of movement through the speed, quality, and accuracy of muscle contraction [21].

We suggest that the benefits of Pilates reformer exercise must be studied further with symptomatic people as well as healthy subjects in various aspects of anatomical and functional aspects of participants such as pain, alignment, height, posture, muscle strength, flexibility, muscle activity, flexibility, balance, gait, and other body functions. Further studies with higher-level Pilates users would reveal the advantages of the reformer by providing more advanced exercise efficiently.

When adult women performed Pilates reformer or mat exercises to strengthen the core muscles for 8 weeks, both groups showed a positive effect on standing posture alignment after the intervention. The process of stabilizing the spine through muscle contraction is thought to influence the alignment of the spine, leading to correct postural alignment. However, no significant differences were found between the groups after the intervention. It was found that the composition of the exercise program is important because if the target muscles are well set, and the exercise program is properly composed, the same effect can be achieved only with mat exercise without using the reformer equipment at the beginner stage.

None.

None to declare.

No potential conflict of interest relevant to this article was reported.

Conceptualization: GS, DK, HJ. Data curation: GS, DK, HJ. Formal analysis: GS, DK, HJ. Investigation: GS, DK, HJ. Methodology: GS, DK, HJ. Project administration: GS, DK, HJ. Resources: GS, DK, HJ. Software: GS, DK. Supervision: GS, DK, HJ. Validation: GS, DK, HJ. Visualization: GS, DK, HJ. Writing - original draft: GS. Writing - review & editing: GS, HJ.