Suspension Training Improves the Muscle Quality of Older Adults

doi:10.21203/rs.3.rs-3299126/v1

Purpose

The aim of this study was to assess the effect of suspension training (ST) on muscle quality (MQ) in older adults.

Methods

Twenty-two physically independent elderly men and women were recruited and assigned to ST or control groups (CON). The MQ of the upper limbs (UL) and lower limbs (LL) was established by a ratio between maximum dynamic strength and lean body mass (LBM), assessed through the 1RM test and dual-energy X-ray absorptiometry, respectively, before and after a 12-week intervention period. The significance level was set at P ≤ 0.05.

Results

The ST was able to promote increases in the strength of the UL and LL (P < 0.0001). However, only LBM_UL increased after 12 weeks of ST (P = 0.031) compared to CON. ST increased MQ for both QM_UL (P = 0.011) and MQ_LL (P < 0.0001), while the CON group did not show any significant changes (P > 0.05).

Conclusion

these results indicate that ST can improve the MQ of older adults.

TRX training

older adults

lean body mass

muscle strength

Muscle quality (MQ) is the level of strength produced relative to the amount of muscle mass [1, 2]. It has been demonstrated that decreases in MQ are associated with reduced functional performance, which can affect daily living activities performance and increase the risk of falls in older adults [3–6]. Therefore, strategies capable of attenuating declines in MQ associated with aging are imperative.

Resistance training (RT), traditionally performed using machines and free weights, is highly recommended to maintain or improve MQ in older adults [7–9]. Alternatively, suspension training (ST) is a RT method that has become increasingly popular and frequently applied in older adults [10]. The application of ST involves suspending body segments using straps to create an unstable environment, enabling the performance of multiplanar and multijoint exercises to be performed using body weight as resistance. Notably, the ST method stands out for being considered low-cost, requiring minimal space for its implementation, and allowing for a wide variety of exercises that can be prescribed according to the individual's needs [11–13]. Due to its similarities to traditional RT and the possibility of applying progressive overload, it is reasonable to suggest that ST can also improve MQ.

Therefore, the aim of this study was to investigate the effects of ST on the MQ of older adults. We hypothesize that ST will lead to improvements in MQ.

Experimental Design

This study involves a secondary data analysis, including previously published data from Soligon et al. [13] and unpublished collected data. Initially, baseline values (Pre) were established by measuring the lean body mass (LBM) of the upper limbs (UL) and lower limbs (LL) using dual-energy X-ray absorptiometry (DXA) and assessing muscle strength through the one-repetition maximum (1RM) test. These measurements were performed for MQ calculation. Afterward, participants were allocated to one of the following groups: a) ST group or b) control group (CON). The ST sessions were conducted twice a week for 12 weeks, while the individuals in the CON group were instructed not to engage in any form of intervention or change their daily habits. The same assessments were performed 72 hours after the last training session (Post).

Participants

Twenty-three healthy male and female older adults aged between 60 and 75 years were recruited for the study. From these, 12 were allocated to the ST group (5 men and 7 women, age: 62 ± 4 years; height: 1.65 ± 0.1 m; body mass: 80.1 ± 12.9 kg; BMI: 29.3 ± 4.5 kg/m2), and 11 participants were allocated to the CON group (6 men and 5 women, age: 64 ± 4 years; height: 1.63 ± 0.1 m; body mass: 79.9 ± 21.4 kg; BMI: 29.9 ± 6.9 kg/m2). As inclusion criteria, participants were required to be free of cardiac symptoms, diabetes, arrhythmias, hypertension, obesity, and any musculoskeletal conditions that would hinder their participation in the tests and training protocol. Moreover, participants should refrain from any regular physical exercise practice for at least 12 months before the experimental period. Participants were advised to maintain their dietary habits, and 40 g of whey protein (Max Titanium®) was provided immediately after each ST session to maximize responses in protein synthesis and reduce variability [14]. All procedures conducted were in accordance with the Helsinki Declaration, and the study was approved by the University Ethics Committee (No. 2877542).

Dual-energy X-ray absorptiometry (DXA)

LBM was assessed through whole-body scanning using DXA. Before the analysis, participants were instructed to abstain from consuming food or liquids, except water, for at least 4 hours before the assessment. After calibrating the equipment (Hologic, Inc., Waltham, MA, USA), participants were instructed to remove any metal accessories and wear a medical gown provided by the researchers. The participants were aligned with the central line of the scanning bed, with their feet, hands, and head arranged as recommended in the equipment’s manual. The scanning was performed in the "Whole Body" mode, and the obtained image was subsequently analyzed using Hologic APEX 3.2 software. The LBM of the UL (LBM_UL) was obtained by the sum of right and left UL LBM, while the LBM of the LL (LBM_LL) was obtained by the sum of right and left LL LBM.

Maximum dynamic strength

Muscle strength was measured using the one-repetition maximum (1RM) test. Following the recommendations described by Brown and Weir [15] biceps curl and leg extension exercises were used to determine the UL and LL 1RM, respectively. Initially, participants performed a general warm-up on a cycle ergometer at 20 km h^− 1 for 5 minutes, followed by a specific warm-up of two sets performed in the same 1RM test equipment. In the first set, eight repetitions were performed at approximately 50% of the estimated 1RM, followed by a set of three repetitions at approximately 70% of 1RM. A rest interval of 2 minutes was used between warm-up sets. Participants had up to five attempts to reach their 1RM load. A rest interval of 3 minutes was allowed between attempts, and the one that achieved the considered appropriate range of motion with the highest load was considered the final 1RM value.

Muscle quality (MQ)

MQ was calculated as the ratio between the 1RM and LBM values. This calculation was performed for both the UL and the LL, as proposed by Barbat-Artigas et al. [16] and Fragala et al. [17].

The formula used for this calculation was:

$$MQ (kg/kgLBM)=1RM\left(kg\right) / LBM\left(kgLBM\right)$$

.

Suspension training (ST)

The ST was performed using hanging straps (Prime Sport, São Paulo, Brazil) in the following exercises: 1) bi or unilateral squats (e.g., participants started the training program bilaterally and switched to unilateral squats to progress the load and maintain the range of maximal repetitions [i.e., 10 to 15 repetitions]), 2) hamstring curl, 3) low row, 4) chest press, 5) deltoid fly in "Y" position, and 6) bicep curls. The order of the exercises was repeated for all training sessions. Three sets of 10–15 repetitions to concentric muscle failure were performed with a rest interval of 1 minute between sets and exercises. The progression of the training load was controlled by using markings with a measuring tape on the floor. Higher inclinations relative to anatomical position increase overload, while lower inclinations reduce the overload. Therefore, higher inclinations were used in the following session when participants completed the third set performing more than 15 repetitions. Similarly, the inclinations were decreased whenever fewer than 10 repetitions were performed.

Statistical analysis

The data underwent visual inspection, followed by an assessment of normality using the Shapiro‒Wilk test. Once normality was confirmed, an independent samples t test was conducted to compare the Pre values between the groups. Afterward, a mixed-effects model analysis was applied for each dependent variable (LBM_UL, LBM_LL, 1RM_UL, 1RM_LL, MQ_UL, and MQ_LL), with group (ST and CON) and time (Pre and Post) as fixed factors and individuals as random factors. Tukey's post hoc test was employed for multiple comparisons in case of a significant F value. The significance level was established at P ≤ 0.05.

The absolute difference between Pre and Post values (∆ = Post - Pre) was calculated with a 95% confidence interval (CI) for all dependent variables. All analyses were performed using SAS 9.3 software (SAS Institute Inc., Cary, NC) and GraphPad Prism 8.0 software (GraphPad Software, San Diego, CA). The data are expressed as the mean ± standard deviation.

Participants

Twenty-two of the 23 recruited participants completed the study. One participant from the CON group did not undergo the LBM final assessment. Regarding baseline values, the t test did not indicate significant differences for any variable (P > 0.05).

Lean body mass and muscle strength

A significant group vs. time interaction was observed only for LBM_UL (F_{[1, 20]} = 4.72; P = 0.042), while no interaction was found for LBM_LL (F_{[1, 20]} = 0.27; P = 0.612). The post hoc analysis indicated a significant improvement in LBM_ULonly for the ST group from Pre to Post (P = 0.031). However, it revealed a time effect for LBM_LL(F_{[1, 20]} = 11.90; P = 0.003) from Pre to Post (P = 0.003). There were no significant changes in LBM_UL for the CON group from Pre to Post (P > 0.05), and the results are summarized in Table 1.

Table 1. Lean Body Mass (LBM) before (Pre) and after (Post) suspension training (ST) and control group (CON).

Variables	ST (n = 12)			CON (n = 10)
Variables	Pre	Post	∆ (CI)	Pre	Post	∆ (CI)
LBM_UL (kgLBM)	5.5 ± 1.3	5.8 ± 1.5*	0.3 (0.2 a 0.5)	5.8 ± 1.5	5.8 ± 1.5	0 (-0.5 a 0.3)
LBM_LL (kgLBM)	15.4 ± 3.2	15.7 ± 3#	0.3 (-0.02 a 0.5)	16.3 ± 4	16.6 ± 4.1#	0.3 (0.1 a 0.6)

CI: confidence interval. *Significant difference from Pre (group vs. time interaction; P = 0.031); ^#Significant difference from Pre (time effect; P = 0.002). Data were expressed as mean ± standard deviation.

Regarding muscle strength, the analysis revealed a group vs. time interaction for the 1RM_UL (F_{[1, 20]} = 34.97; P < 0.0001) and 1RM_LL (F_{[1, 20]}= 41.76; P < 0.0001). The post hoc analysis indicated a significant improvement in 1RM only for ST from Pre to Post (1RM_ULand 1RM_LL: P < 0.0001). There were no significant changes in CON from Pre to Post (1RM_ULand 1RM_LL: P > 0.05). The 1RM mean and SD were previously reported in Soligon et al. [13]; please refer to the original study for further details.

Muscle quality

The mixed-effects model analysis revealed a significant interaction group vs. time for the MQ_UL (F_{[1, 20]} = 5.37; P = 0.031) and MQ_LL (F_{[1, 20]} = 27.76; P < 0.0001). The post hoc analysis indicated a significant improvement in MQ for the ST group from Pre to Post (MQ_UL: P = 0.011; MQ_LL: P < 0.0001). There were no significant changes for the CON group from Pre to Post (MQ_UL and MQ_LL: P > 0.05). Table 2 and Figure 2 present group and individual responses, respectively.

Table 2. Muscle quality of upper and lower limbs before (Pre) and after (Post) suspension training (ST) and control group (CON).

Variables	ST (n = 12)			CON (n = 10)
Variables	Pre	Post	∆ (CI)	Pre	Post	∆ (CI)
MQ_UL(kg/kgLBM)	4.5 ± 0.6	4.9 ± 0.5*	0.3 (0.1 a 0.6)	4.3 ± 0.7	4.3 ± 0.6	0 (-0.2 a 0.4)
MQ_LL (kg/kgLBM)	3.2 ± 0.6	3.7 ± 0.6*	0.5 (0.3 a 0.6)	3.1 ± 0.5	3.2 ± 0.4	0.1 (-0.1 a 0.3)

CI: confidence interval. * Significant difference from Pre (group vs. time interaction; P < 0.05). Data were expressed as mean ± standard deviation.

The aim of this study was to examine the effect of ST on the MQ of older adults. Our findings confirmed the hypothesis that ST can improve MQ in both upper and lower limbs.

Traditional RT is suggested to be the optimal strategy to prevent declines or improve MQ [18, 19] due to its ability to promote muscle strength and LBM increases [7, 8]. However, traditional RT commonly requires machines and/or free weights for moderate- to high-load exercise. We demonstrated for the first time that MQ can also be improved using only one device (i.e., the suspension tape). These findings expand those from other studies that demonstrated that different RT methods can be used in a training program aiming to improve MQ. In this regard, improvements in MQ have already been shown by both RT-using machines [20, 21] and elastic bands [22, 23]. The ST-induced MQ improvements may be related to the sets performed until concentric muscle failure. In fact, it has been reported that exercising until concentric muscle failure (i.e., inability to complete another repetition with an appropriate form) produces similar gains in muscle strength and mass, regardless of other RT variables (e.g., repetition duration, type of contraction, or exercise) [24, 25] or methods [13, 26]. Conversely, not even the traditional RT performed with 14 repetitions at 40% of 1-RM - possibly leaving the sets far from concentric muscle failure - induced MQ improvements [27]. Thus, it seems reasonable to suggest that ST performed until concentric muscle failure stimulates the neuromuscular system sufficiently to maximize gains in strength and muscle mass and, consequently, MQ [28, 29].

Our findings provide some practical implications. Traditional RT programs commonly require high-cost equipment available only in specific spaces (e.g., clubs, gyms, and training centers). These aspects can limit or decrease adherence to the training program, especially for those with lower functional performance levels (e.g., older adults). In this regard, ST presents an alternative that requires little space and allows complete training sessions to be performed at home or elderly care centers using a single device (i.e., suspension tape) [11, 12]. Although elastic bands can also be inexpensive and easy to apply, the possibilities for varying the exercises are limited compared with ST, which enables a wide variety of exercises to be performed for all muscle groups. Additionally, overload progression in elastic band training depends on different types of tapes, unlike ST, in which only one adjustment in body positioning is enough to promote greater overload [13, 22, 23].

In conclusion, ST performed until concentric muscle failure is a training method capable of promoting improvement in the MQ of elderly individuals.

STATEMENTS AND DECLARATIONS

The authors have no competing interests to declare that are relevant to the content of this article.

ACKNOWLEDGMENT

The authors sincerely thank all the individuals who generously participated in this study. Additionally, we thank the Supley Laboratory of Food and Nutritional Supplements (Max Titanium, São Paulo, Brazil) for their generous donation of whey protein.

This work was supported by the São Paulo Research Foundation (FAPESP) under grant (#2017/05331-6 to VA) and the National Council for Scientific and Technological Development (CNPq) under grant (#311387/2021-7 to CL and #115792/2023-6 to RAMJ).

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No competing interests reported.

Suspension Training Improves the Muscle Quality of Older Adults

Status:

Version 1

Abstract

Figures

INTRODUCTION

METHODS

Experimental Design

Participants

Dual-energy X-ray absorptiometry (DXA)

Maximum dynamic strength

Muscle quality (MQ)

Suspension training (ST)

Statistical analysis

RESULTS

Participants

Lean body mass and muscle strength

Muscle quality

DISCUSSION

Declarations

References

Additional Declarations

Status:

Version 1