Resumen de Effects of elastic-based exercise interventions on oxidative stress, bone health, body composition, neuromuscular strength and physical function in older women: training intensity and modality as key exercise programming parameters
Background The aging of the global population is recognized by the World Health Organization (WHO) as a major issue due to the disabilities and comorbidities related to this process, with women being the gender most affected. Due to the physiological and psychological age-associated declines, physical activity and exercise are proven strategies for reducing the impact of aging. However, it is still unknown what kind of training program could be the most effective in reversing deleterious age-related changes in older women. Regarding this, the type of training intensity and exercise modality are two key training parameters in exercise programming, and, therefore, different adaptations could be induced in older adults through the modification of these parameters. Furthermore, the type of training device is a significant factor and can act as a barrier or facilitator in older adults' participation in physical activities and exercise programs. Therefore, this dissertation's primary goals are to compare the effects of a 32-week elastic resistance training program at high and moderate intensity and 20-week elastic-based multi-component, power strength and traditional high-intensity resistance training programs on oxidative stress, bone health, body composition muscle strength and physical function in older women.
Methods This dissertation is composed of two projects/studies involving two cohorts of female volunteers (first project: 93 subjects aged 60–88 years [69.93± 6.27]; second project: 136 subjects aged 60–82 years [67.97± 4.77]). In the first project, the subjects were randomly assigned to a 32-week progressive elastic-based resistance training program at high (HI; n = 39) or moderate intensity (M; n = 31) or a self-management control group (C; n = 23). In the second project, the participants were randomly assigned to a 20-week multi-component (MT; n = 34), power strength (P; n = 34) or traditional high-intensity resistance training (T; n = 34) elastic-based interventions or to a self-management control group (C; n = 34).
In the first project, the exercise groups engaged in progressive elastic-based resistance training twice a week with three to four sets of six (HI) or 15 (M) repetitions including six overall body exercises at a rate of perceived exertion (RPE) of 6–7 in the first four weeks and 8–9 in the remaining weeks on the OMNI-Resistance Exercise Scale (RES). Members of the control group were instructed to continue their everyday lives. In the second project, the P and T groups performed the same progressive elastic-based resistance training in terms of exercises (six whole-body exercises) and sets (three to four sets per exercise) twice a week, but the P group displaced the load in the concentric phase as fast as possible, while in the T group the speed of execution was 2s for the concentric phase and 2s for the eccentric phase. The P group performed 12 submaximal repetitions in each set in the first two weeks to consolidate the technique and 10 during the rest of the program with a perceived exertion of 3–4 (very low) on the OMNI-RES scale in the first repetition, which is equivalent to 40%–60% 1RM (low-load or low intensity), never exceeding the value 6 at the end of the 10 repetitions. The T group performed six submaximal repetitions, equivalent to 85% of the 1RM per exercise, at OMNI-RES scale values of 6–7 in the first four weeks and 8–9 in the remaining 16 weeks. The multi-component training was composed of balance, strength, aerobic, flexibility, and coordination exercises in the same session and was also performed twice a week.
Oxidative stress, bone health, body composition, neuromuscular strength, and physical function were assessed in both studies. Oxidative stress status was assessed in deoxyribonucleic acid (DNA) (urinary 8-oxo-2-deoxyguanosine [8-oxo-dG] in both projects), lipids (F2-isoprostanes[8-iso-P] in both projects; malonaldehyde [MDA] in the first project), and proteins (protein carbonyls in the first project) products together with antioxidant enzymes (superoxide dismutase [SOD] and glutathione peroxidase [GPx] in both projects; catalase [CAT] in the second project) and thiol redox state (reduced glutathione [GSH], oxidized glutathione [GSSG], and the GSSG/GSH ratio in both projects; total glutathione and the GSH/GSSG ratio in the second project). Bone health was integrated by measures of areal bone mineral density (aBMD) and the T-score of the lumbar spine (L1–L4 segments, L2–L4 segments, and L1, L2, L3, and L4 individual vertebrae, in both projects) and proximal femur (femoral neck, trochanter, intertrochanter, Ward's triangle, and total hip in both projects) assessed by dual-energy X-ray absorptiometry (DXA). Additionally bone health was also composed by fracture risk (the 10-year probability of a major osteoporotic fracture and the 10-year probability of a hip fracture), bone turnover markers (BTMs) of bone formation (procollagen type I N propeptide [P1NP] in both projects, a bone-specific isoform of alkaline phosphatase [bALP] in the first project, and osteocalcin [OC] in the second project) and bone resorption (a β-isomerized form of C-terminal telopeptide of type I collagen [β-CTx] in both projects), and their relationship (bALP/ β-CTx ratio in the first project). Body composition (total body mass, total fat mass, total fat-free mass, and total body fat percentage) was measured in both projects by DXA, while in the second project the cardiovascular risk was assessed through anthropometric measures (waist circumference [WC], hip circumference [HC], the waist-to-hip ratio [WHR], and the waist-to-height ratio [WHtR]). Moreover, the neuromuscular strength of upper limbs (elbow flexor and extensor muscles) and lower limbs (hip abductor and hip adductor along with knee flexor and extensor muscles) was assessed through isokinetic dynamometry at low (60°/s) and high (180°/s) velocities in both projects. Finally, physical performance was measured using various functional tests and batteries widely used in the literature, such as the 30 seconds chair stand (30sec-CS) and 30 seconds arm curl (30sec-AC) for muscle strength/endurance of the lower and upper limbs (used in both projects); time up and go (TUG) for dynamic balance/agility (used in both projects); the six-minute walking test (6MWT) for aerobic endurance (used in both projects); five sit-to-stand (5STS), stair-climbing, stair-climbing speed (SCS), and stair-climbing power (SCP) for muscle power of the lower limbs (used in the second project); and the functional reach test (FRT) for proactive balance (used in the second project).
Data were analyzed using the intention-to-treat (ITT) and per-protocol analysis (PPA) approaches in both projects. After applying Kolmogorov-Smirnov and Levene tests for checking data distribution and homogeneity, the non-normally distributed data were transformed using a natural logarithm (log10). A two-way analysis of variance (ANOVA) for repeated measures was used to examine time, group, and interactions effects, and Bonferroni corrections were then applied. A two-way analysis of covariance (ANCOVA) for repeated measures adjusting for baseline values and age was also applied. The Cohen's d effect size (ES) and delta percentage (Δ%) were also calculated. Data are reported as the means ± the standard deviations (SD) with 95% confidence intervals (CI). Statistical significance was set at p ≤ 0.05. The SPSS Version 25.0 commercial software was used for the statistical analysis.
Results Regarding oxidative stress, in the first project, after 16 weeks of training, the M group achieved significant decreases in 8-oxo-dG (-21.34%), 8-iso-P (-15.85%), and MDA (-19.12%), with moderate ES in all these, while the HI group showed significant increases in 8-oxo-dG (+60.49%; large ES) and 8-iso-P (+24.40%; moderate ES). No significant differences by time were found in protein carbonyls. Significant time × group interaction was found in MDA in the M and C groups. After the ANCOVA, differences in 8-oxo-dG were found in the HI vs M and HI vs C groups, and differences in MDA were found in the M vs C groups. In addition, the M group showed an increase in CAT levels (+5.40%; small ES) (p ≤ 0.05), while the HI group showed a significant decrease in the GPx (-8.95%; moderate ES) and GSH (-9.31%; moderate ES). In the second project, after 20 weeks both the MT and P groups improved their oxidative stress status by decreasing the 8-oxo-dG (MT: -48.56%, moderate ES; P: -65.79%, large ES) and 8-iso-P (MT: -30.49%, moderate ES; P: -26.98%, small ES). Additionally, the MT group significantly increased the values of the SOD enzyme (small ES). Significant differences in 8-oxo-dG were found between the P and C groups, and significant differences in SOD were found between both experimental groups and the C group. The P group also achieved positive changes in the thiol redox state (p ≤ 0.05) (an increase in total glutathione, GSH, and the GSSG/GSH ratio and a decrease in GSSG). After ANCOVA, the MT group showed a significant decrease in GSSG and the GSSG/GSH ratio. The ES of the thiol state changes ranged from small to large.
Regarding bone health, in the first project, after 32 weeks both the HI and M groups achieved a significant increase in total lumbar spine aBMD (M: +0.89%; HI: +1.12%) with trivial ES, but only the HI group showed a significant difference from the C group. In the proximal femur scores, both the HI and M groups increased (p ≤ 0.05) aBMD of femoral neck (M: +1.57%; HI: +1.39%), Ward’s triangle (M: +2.59%; HI: +2.47%), and total hip (M: +1.13%; HI: + 1.21%), while the HI group also improved significantly the trochanter aBMD (+ 1.38%). The ES were all trivial, and no significant differences between groups were found. Moreover, the risk of major osteoporotic or hip fracture was also reduced (p ≤ 0.05) in the HI and M groups. The changes in aBMD were accompanied by significant changes in bone formation and bone resorption biomarkers after 16 weeks, as was the case for P1NP (M: +11.24%; HI: +8.23%), bALP (HI: +4.68%), β-CTx (M: -6.65%; HI: -8.07%), and the bALP/β-CTx ratio (M: +13.71%; HI: +9.58%). These changes were also seen after 32 weeks for P1NP (M: +19.76%; HI: +23.89%), bALP (M: +8.07%; HI: +9.95%), β-CTx (M: -7.24%; HI: -9.80%), and the bALP/β-CTx ratio (M: +20.86%; HI: +19.56%). In all the parameters, the magnitude of the change was considered trivial or small. An ANCOVA revealed significant differences between the HI and C groups in bALP, β-CTx and the bALP/β-CTx ratio, and between exercise groups in bALP. In the second project, only the P group significantly improved the aBMD of the total lumbar spine (+1.28%, trivial ES), some parts of the proximal femur such as the intertrochanteric area (+1.38%, trivial ES), Ward's triangle (+4.66%, small ES), and total hip (+1.03%, trivial ES), with no differences between groups—except between the P and C groups—in intertrochanteric and total hip aBMD after ANCOVA. All the training groups significantly reduced fracture risk, and both the MT and P groups showed positive adaptations (p ≤ 0.05) in BTMs by increasing OC (MT: +16.37%, moderate ES; P: +24.82%, large ES) and reducing β-CTx (MT: -9.05%, small ES; P: -8.76%, small ES).
Regarding body composition, in the first project, the M group achieved significant decreases in total fat mass (-8.04%) and total body fat percentage (-2.90%) along with a significant increase in total fat-free mass (+2.98%), with small ES in all the parameters. The HI group showed a significant increase (trivial ES) in total fat-free mass (+2.10%) along with a significant decrease in the total body fat percentage (-2.21%), with small ES in both cases. No significant differences between groups were found. After ANCOVA, differences in total fat mass were found between the M and C groups, and differences in total fat-free mass and total body fat percentage were found between the training groups and the C group. In the second project, significant declines in all the training groups were found in WC (MT: -2.75%; P: -2.25%; T: -1.32%), HC (MT: -2.37%; P: -1.97%; T: -0.91%), WHtR (MT: -2.73%; P: -2.26%; T: -1.32%), total fat mass (MT: -4.24%; P: -2.75%; T: -2.44%), and total body fat percentage (MT: -4.53%; P: -3.69%; T: -2.44%), with ES ranging between trivial and small. In addition, the MT and T groups improved (p ≤ 0.05) the total fat-free mass (MT: +1.52%; T: +1.58%), with trivial ES. Significant differences between the training groups and the C group were found in WC, HC, WHtR, and total body fat percentage.
Regarding neuromuscular strength, in the first project, the HI and M groups significantly improved the strength of the hip abductor (M: +23.71%; HI: +53.28%), hip adductor (M: +15.89%; HI: +23.07%) muscles at 60°/s, while the HI group also increased their strength (p ≤ 0.05) at 180°/s (hip abductor: +49.78%; hip adductor: +15.52%). The ES ranged between trivial and large. No significant differences were found between the training groups, but there were differences with the C group. The HI and M groups achieved significant increases in knee flexor and extensor muscle strength at both low and high velocities (moderate and large ES), with no significant differences between the training groups. However, both the HI and M groups showed significant differences with the C group in all the knee parameters. The same results were obtained for the upper limbs, where both the HI and M groups showed significant improvements in elbow flexor and extensor muscle strength at both velocities (moderate and large ES). No significant differences were found between the training groups, but there were significant differences between both training groups and the C group in all the parameters. In the second project, after ANOVA or ANCOVA analysis all training modalities significantly improved the neuromuscular strength at the hip, knee, and elbow joints (small to large ES), except the P and MT groups in the knee flexion and elbow flexion at 60°/s, respectively. The P group achieved significant differences from the other exercise modalities in muscle strength at hip abduction and adduction and elbow extension and flexion at 180°/s. Additionally, the T group also showed significant differences from the MT and P groups in elbow extension at low velocities.
Regarding physical function, in the first project, both training groups improved significantly in all the parameters analyzed, with the HI group achieving large ES in 30-secCS (+75.93%), 30sec-AC (+79.08%), TUG (-18.80%), and 6MWT (+10.50%) tests, while the M group achieved large ES in all the tests, apart from moderate ES in 6MWT (+7.93%). No significant differences were found between the training groups, but both training groups showed significant differences from the C group in all the parameters. In the second project, all the training groups improved all the parameters of physical function analyzed, obtaining mainly moderate and large ES. After ANCOVA, significant differences in training modalities were found in the measure of the power of 5STS between the P group and the rest of the training strategies (moderate ES). Furthermore, significant differences were obtained between the three training modalities and the C group in all the variables.
Conclusions A progressive elastic resistance training program at a moderate rather than high intensity may be the best strategy for reducing oxidative stress in older women after 16 weeks, while multi-component training—particularly power strength training—is effective in improving oxidative stress and bone turnover rate in older women after 20 weeks of training. In addition, elastic-based resistance training programs at high and moderate intensity effectively improve bone health, body composition, neuromuscular strength, and physical function in older women after 32 weeks of training. Likewise, multi-component, power strength, and high-intensity resistance training are also effective elastic-based strategies for improving the same health parameters in older women after 20 weeks. In the short-term (16 weeks), high-intensity resistance training is the most effective strategy for increasing the bone formation rate in older women, while power strength training modality seems to be the most appropriate for producing muscle power adaptations. At the same time, multi-component training produces the most significant adaptations in body composition. Finally, all the elastic-based exercise interventions analyzed were well-tolerated and safe for older women, as demonstrated by the lack of serious adverse events, the low attrition rate, and the attendance and compliance rates reported in both projects.
