Exercise with weight vest plus chicken protein supplementation delayed muscle and bone loss in older female adults

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Abstract

INTRODUCTION

Age-related structural and physiological changes affect various body systems, including the musculoskeletal, cardiovascular, respiratory, and autonomic systems [1]. The decline in muscle strength and mass associated with aging substantially contribute to challenges in mobility and balance, thereby increasing the risk of falls and fractures in the older adults [2]. These musculoskeletal changes negatively affect the quality of life and physical abilities, and limits independence [1-3].

Sarcopenia, a condition defined by the gradual reduction in muscle mass, strength, and overall performance in older adults, affects a substantial proportion of the population [4]. Recently, the treatment and management of sarcopenia has garnered considerable attention because of the aging population in many developed countries, which limits health services [5]. Factors contributing to sarcopenia include decreased protein synthesis, hormonal imbalances, inflammation, mitochondrial dysfunction, and oxidative stress [1,3,6,7]. Maintaining muscle mass and strength is essential to prevent frailty, and regular exercise and adequate protein intake are recommended for this purpose [8,9].

Protein and vitamin supplementation can enhance muscle mass, strength, gait speed, physical activity, and bone metabolism in patients with sarcopenia [10-12]. Resistance and endurance exercises are recommended to preserve muscle and bone health [13]. Combining protein supplementation and resistance exercise for sarcopenia intervention produced the best outcomes, compared with that of other interventions [14]. A recent meta-analysis indicated that protein supplementation along with resistance exercise provided greater benefits to muscle health in older adults than those with exercise or diet alone [8,15,16]. Lean body mass increased more in the exercise combined with protein groups than the control groups, this difference was quantified by a standard mean difference of 0.58 (95% CI: 0.32–0.84; p < 0.0001) [16].

Multicomponent exercises, including resistance, strengthening, and aerobic training, are recommended for frail individuals to improve muscle and bone mass, physical function, and prevent falls17. The use of weighted vests in fitness training enhances muscle contraction, lower body strength, balance, and mobility in older adults [18,19]. Weighted vest training involves wearing a vest containing additional weight to increase resistance to bodyweight exercises or cardiovascular activities [20]. Vests loaded with 5% and 10% of an individual’s body weight significantly increase mechanical stress on active muscles [21,22]. A 12-week use of a weighted vest (progressively increasing up to 15% of the individual’s body weight) during multimodal exercises substantially reduced serum osteocalcin levels and improved ankle plantar flexor strength in postmenopausal women [23]. Srisaphonphusitti et al. revealed an 8-week combination of whole-body vibration and weighted vest exercise (5% of body weight in the first two weeks and a 10% body weight increase from weeks 3 to 8) and found improved muscle strength, muscle thickness, total muscle mass, and physical performance in older adults [19]. We postulated that the use of a weighted vest could potentially preserve muscle mass and bone health through the application of muscular forces or direct mechanical stimulation of mechanoreceptor cells.

Aging reduces protein absorption, impairing the musculoskeletal system and physical activity due to changes in stomach acid production and enzymatic activity [13,24]. Protein supplementation counteracts these effects and enhances the musculoskeletal health and physical performance [8,11]. Thai native chickens, such as the Pradu Hang Dam, are known for their unique flavor and soft, yet firm, texture. KKUONE, a commercial broiler and native Thai crossbreed, contains 25% Thai native genetics. To enhance meat quality and reduce production costs, KKU-ONE meat has lower purine levels than that of commercial chicken meat, thereby meeting modern consumer demand [25]. KKU-ONE is low in fat [26], and high in protein25, antioxidant dipeptides [27], and muscle fibre [28], making it a potential functional food. A previous study showed that KKU-ONE-fed rats had improved blood marker levels compared with that of those fed commercial broilers after 5 weeks [25]. Therefore, combining this protein with resistance exercises using a weighted vest may help prevent loss of muscle and bone mass in older women.

Incorporating resistance training into the exercise routines of older adults can lead to increased muscle mass and improved bone density [29,30]; however, noticeable improvements in bone mass typically require at least six months to one year of consistent effort [31,32]. This study incorporated weight-bearing exercises using a weight vest to achieve bone mass improvement over a shorter period when combined with protein supplementation. Therefore, we to investigate whether combining these two interventions would produce additional benefits for older adults.

METHODS

Study design

Randomization was accomplished using a computer-generated random number of sequences, and allocation concealment was maintained using sealed envelopes prepared by an independent statistician. To ensure balance across communities, participants were stratified based on their geographical location during the randomization process. The randomization process was executed by an independent research coordinator who was not involved in the recruitment or assessment of participants, thereby minimizing the risk of selection bias. After the 8-week training program, 52 participants completed the intervention: control (CON, n = 17), weighted vest (WV, n = 19), and weighted vest plus protein supplementation (WVP, n = 16). Body composition; muscle strength (handgrip strength); dual-energy X-ray absorptiometry (DEXA) scan for muscle, body fat, and bone mass; physical performance tests; and blood tests were assessed before and after the intervention. All the participants were asked to maintain a normal diet throughout the study period. (Figure 1). This study was approved by the Human Research Ethics Committee of Khon Kaen University, Thailand (Study ID: HE651353). Informed consent for participation in the study was obtained prior to the procedure.

Figure 1.

CONSORT diagram.

Experimental protocols

Participants in all groups received the same advice and completed the same exercise throughout the 8 weeks; however, the WV group completed the exercise while wearing a weighted vest filled with sand equivalent to 5% (first 2 weeks) and then 10% (last 6 weeks) of their body mass [19], whereas the WVP group completed the exercise while wearing a weighted vest and consuming protein supplements (Chick-Tab Dietary Supplement Product; 3 g of protein per day).

Exercise program

Participants in all groups were asked to complete the exercise protocol three times per week for 8 weeks (Table 1). The exercise started with a 5-min warm-up, followed by brisk walking, eight sets of strengthening exercises (30 s on 30 s off), and finishing with a 5-min cooldown. Before each training session, the researchers monitored the participants’ BP and resting heart rate.

Table 1.

Exercise program

Protein supplementation

The participants in the WVP group consumed Thai native chicken breast meat (KKU-ONE) in the form of six tablets daily for eight weeks; two tablets taken with meals [24] (KKU-selected Chic-Tab protein supplementation, Khon Kaen University, Thailand). The supplement consisted of 552 mg of chicken powder, 0.25 mg of vitamin B6, 7.5 mg of ascorbic acid, and 9.36 mg of zinc amino acid chelate (20% concentration) per tablet25.

RESULTS

There were no significant differences in the clinical characteristics or physiological variables of the participants between the groups at baseline (Table 2). All the participants completed at least 90% of their exercise training sessions. Throughout the study, no negative consequences of training, such as back or leg pain, were observed in any participant.

Table 2.

Clinical characteristics and physiological variables of participants in the three groups at baseline.

Bone mineral contents and body composition

There were no substantial changes in body mass within or between groups during the 8-week intervention period (Table 2). Significant interaction effects in bone mineral content were observed over time: rib BMC (p = 0.014) and T-spine BMC (p < 0.001) (Table 3). Body composition (Table 4) revealed significant group-by-time interaction effects for several variables over time, including trunk lean mass (p = 0.05), total body lean mass (p = 0.007), leg fat mass (p < 0.001), total body fat mass (p < 0.001), and body fat percentage (p < 0.001). Moreover, a significant interaction effect for T-score was observed between the groups (WVCON, p = 0.004; WVP-CON, p = 0.01) (Figure 2).

Table 3.

Changes in the bone mineral content of participants in the three groups.

Table 4.

Changes in body composition parameters of the participants in the three groups.

Figure 2.

Dual-Energy X-ray Absorptiometry (DEXA) analysis of changes in T-scores.

Data were mean ± SEM. Control (CON, n=17), weighted vest (WV, n=19), and weighted vest supplemented with protein (WVP, n=16) groups. ^a indicates a significant difference between the CON and WVP groups. ^b indicates a significant difference between the CON and WV groups.

The within-group results showed that the variables significantly changed in the CON group (arm BMC: −5.0 g, p = 0.016; leg BMC: 8.8 g, p = 0.009; total body BMC: −11.9 g, p = 0.011; trunk lean mass: −0.4 kg, p = 0.033; and total body lean mass: −0.7 kg, p = 0.003) and significantly changed in WV group (ribs BMC −11 g, p = 0.01; T-spine BMC −3.9 g, p = 0.012; trunk lean mass: −0.3 kg, p = 0.028; leg lean mass: −0.2 kg, p = 0.044; total body lean mass: −0.8 kg, p = 0.002; leg fat mass: 0.3 kg, p = 0.002; total body fat mass: 0.6 kg, p = 0.001; and body fat percentage: 1.3%, p < 0.001) (Table 3 and 4).

T-spine BMC showed a significant change of 8.4 g (p = 0.001) in the WVP group, indicating a significant difference between the CON and WV groups (p = 0.001 and p <0.001, respectively) (Table 3). Additionally, only the WVP participants increased their total body lean mass over the period of the study (0.2 ± 1.0 kg, p < 0.001), while the CON and WV participants both lost their total body lean mass (−0.7 ± 0.9 kg and −0.8 ± 0.9 kg, respectively). Leg fat mass, total body fat mass, and body fat percentage significantly decreased in the WVP group (−0.3 kg; p =0.003; −0.6 kg, p < 0.001; and −0.6%, p = 0.028 respectively) (Table 4).

Blood sugar and lipid profiles

The fasting blood glucose reduction in the WVP participants was significantly higher than that of the WV or CON participants (−21.1 mg/dL and −20.5 mg/dL, p = 0.004 and p = 0.007, respectively). Participants in the two weighted vest groups showed significantly reduced triglyceride concentrations compared with that at the baseline (−32.9 ± 45.0 mg/dL and −31.2 ± 40.7 mg/dL, p = 0.008, p = 0.010 for the WV and WVP groups, respectively). Additionally, only the WVP participants showed improved HDL−C levels post− training (4.9 ± 6.2 mg/dL, p = 0.007). Significant interaction effects were observed over time for fasting blood glucose (p = 0.002) and triglyceride levels (p = 0.037) (Table 5), indicating the effectiveness of exercise with a weighted vest, and a combination of a weighted vest and protein supplementation on blood sugar and triglycerides.

Table 5.

Changes in blood sugar and lipids profile of the participants in the three groups.

Handgrip strength and physical performance

Consistent with the increased lean muscle mass in the WVP participants, only this group demonstrated a significant increase in handgrip strength (2.2 ± 2.5 kg, p = 0.004), resulting in a statistically significant difference between the WVP and CON groups (−2.4 kg, p = 0.024) (Table 6). All groups showed similar improvements in the functional movement tests, with the WV group showing improvements greater than those in the CON or WVP groups (−6.3 s in 5TSTS, p = 0.001, p = 0.002; and 73.1 m in 6 MWT, p < 0.001, p = 0.001, respectively). Moreover, significant interaction effects were observed over time for the 5TSTS (p < 0.001), 6MWT (p = 0.001), and handgrip strength (p = 0.019) (Table 6), indicating the effectiveness of wearing a weighted vest with or without protein supplementation during exercise for improving physical performance.

Table 6.

Changes in handgrip strength and physical performance of the participants in the three groups

DISCUSSION

Given the increasing aging population globally, degenerative diseases, such as sarcopenia and osteoporosis, have become important health problems, and new or practical exercise interventions are urgently needed. This study addresses the critical gap in identifying effective, shortterm interventions that target both muscle and bone health, which are the keys to maintaining functional independence in older adults. The findings revealed that the WVP group had enhanced bone mineral content, lean muscle mass, handgrip strength, and walking endurance compared with those in the CON and WV groups. This study highlights the importance of exercising with extra weight (weight vest) and protein intake in reducing the risk of muscle and bone loss in older females.

This study also revealed that engaging in moderate-to-heavy exercise three times a week for an 8-week period had detrimental effects on bone mineral content (T-spine BMC) in both the CON and WV groups. Notably, the WVP group had more effective improvements in T-spine BMC. Our findings contrast with those of previous studies that demonstrated the beneficial effects of training while wearing weighted vests on bone turnover [23] in older adults. This may be due to the intensity and duration of the exercise training, which could have induced excessive mechanical stress and metabolic demand in the muscles and bone joints, potentially leading to higher energy consumption [34]. The increased physiological stress caused by the weighted vest may have caused the decreased bone mass observed in the present study. Nevertheless, it is difficult to establish the ideal frequency and intensity of bone loading necessary to maintain bone density. In contrast, the present study revealed that combined weighted vest exercises and protein supplementation resulted in a significant increase BMC in the T-spine (8.4 g). The added protein may enhance bone metabolism through the augmentation of calcium absorption and retention, in conjunction with increased secretion of growth factors, such as IGF-1, which may also confer benefits to bone health35,36. Moreover, the significant interaction effects on the T-score suggest that protein supplementation enhances the positive effects of weighted vest training on the T-score. Muscle activation and increased protein availability increase the ability of bone cells to lay down more bone tissue. However, further research is required to elucidate the metabolic costs of using weighted vests. Additional investigations are necessary to firmly establish the influence of protein consumption on bone mineral density and BMC. Caloric balance should be maintained when weighted vest exercises are performed in older adults.

This study also found that the WV group experienced a decrease in lean mass, but an increase in body fat. We postulated that the weight vest exercise intensity may not be sufficient to stimulate protein synthesis and fat oxidation in older females. We also hypothesized that weight vest exercise could lead to microtrauma, limit muscle protein synthesis, cause muscle damage [37], and may be associated with insufficient protein intake. Specifically, the weighted vest group likely expended more calories than that consumed because of the increased workload by 25% compared to that in the previous study [19], leading to muscle and bone mass loss over eight weeks. Additionally, stress from intense exercise can lead to increased cortisol levels, a hormone that catabolizes muscle tissue and promotes fat storage [38]. Nutritional interventions, including protein, creatine, and essential amino acids, can enhance the anabolic response of skeletal muscles to resistance exercise in older individuals [39]. These results suggest that traditional exercise (CON) and weighted vest exercise (WV), may be insufficient to prevent muscle deterioration and reduce bone density.

Protein supplementation likely provided the necessary amino acids to counteract muscle degradation during and after exercise, particularly in older adults who often consume suboptimal levels of protein (1.0–1.2 g/kg/day) in their diet [14,24]. Previous meta-analyses conducted in older adults reported no additional beneficial effects of resistance training combined with protein supplementation in improving muscle mass, strength, or physical performance in elderly adults [15,40]. This study provides initial evidence that consuming a low-dose protein supplement derived from Thai native chicken breast meat (all participants maintained their normal diet) combined with weight-bearing exercises can improve body composition and increase lean mass at 0.2 kg in older adults. This observation in the WVP group may be explained by the enhanced muscle protein synthesis [15,41,42] and increased secretion of growth factors to increase muscle mass [35,36]. Higher levels of amino acids and anserine in the KKU-ONE breast meat have potential advantages for muscle synthesis and protection against oxidative stress during physical activity [25,43]. Moreover, the decrease in total body fat observed in the WVP group of -0.6 kg may be due to the synergist effects of weighted vest training combined with protein intake. The protein derived from native Thai chicken breast meat is beneficial for fat-promoting effects in humans, and associated with peroxisome activated receptor (PPAR) [26] and adipocyte-type fatty acid-binding protein (A-FAB) gene expression in humans [44].

The effects of low-dose protein supplementation and weight vest workouts in older adults are limited. Although low-dose protein supplements were used in this study, benefits were observed for bone and muscle mass. The reason for these improvements may be the regular low-protein diet of older adults. Previous studies revealed that the dietary habits of elderly individuals residing in Northeastern Thailand typically involve the intake of significant amounts of carbohydrates and sugars from foods, including white rice [45,46]. This study indicated that combining weighted vest exercises with protein supplementation could enhance muscle protein synthesis and promote greater gains in muscle mass and strength. Although the preliminary results are promising, further investigation is necessary to assess the duration or determine the optimal KKU-ONE protein dosage.

Notably, blood glucose levels were significantly reduced after exercise training in the WVP group compared with those in the other exercise groups. This may be because native Thai crossbred chicken breast meat has a positive effect on insulin sensitivity, which can help regulate blood glucose levels [47], enhance metabolic rate, improve insulin sensitivity and secretion, and increase muscle glucose uptake [48] and fat oxidation [44]. This is consistent with previous studies indicating that protein supplementation can improve lipid metabolism [48,49], as evidenced by the significant reductions in fasting blood sugar (-16.4 mg/dL) and triglyceride levels (-31.2 mg/dL) observed in the WVP group. These findings support a previous report that Thai native crossbred chicken breast meat can reduce fat and triglyceride content in rats after five weeks of intervention [25]. Therefore, we postulated that the combination of weight vest exercise and protein supplementation could synergistically improve blood sugar, triglyceride, and HDL-C levels [48,50-52].

In the present study, similar physical performance improvements (e.g., improved 6MWT, TUG, and 5TSTS scores) were observed in the WV and WVP groups. This aligns with previous research, which found that using a weight ves, equivalent to 5–10% of an individual’s body weight during exercise improved sit-to-stand and aerobic endurance in community-dwelling older adults [19,21,22]. We hypothesized that adding loads during exercise (WV and WVP groups) may enhance mechanical stress on the working muscle and increase the recruitment of type II fibers, leading to hypertrophy and strength gains [34]. However, further investigations are required to confirm this mechanism. Overall, these results suggest that incorporating physical activity using a weighted vest and protein supplementation is beneficial for enhancing bone health, lean mass, body fat mass, handgrip strength, and certain aspects of physical performance.

This study had several limitations. First, the participants in all three groups were asked to maintain their regular eating routines throughout the study and the researchers were unable to entirely regulate or gather comprehensive information on each participant’s daily dietary and nutritional consumption, which could have affected the measured outcome variables. Second, lower-body muscle strength tests were not included in this study. Instead, we measured upper-body strength (handgrip strength), which was not directly correlated with the exercise training provided (mostly walking and lower-body exercises). However, further research is required to validate and expand upon these results.

In conclusion, this study provides valuable insights into the effects of different interventions on body composition, bone health, blood lipid and glucose markers, and physical performance in older female adults. These findings suggest that healthcare professionals should consider combining weighted vest exercises and protein supplementation in older adults, especially in those at risk of developing musculoskeletal conditions. The findings are important for healthy aging, because strength, mobility, and bone health are essential for independence and quality of life.

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