Introduction: The efficiency of the cardiovascular system to recover following an exercise bout is measured by oxygen (VO2) recovery kinetics. In older adults with a chronic disease, a higher aerobic capacity (VO2peak) and faster VO2 recovery kinetics are associated with higher muscle strength and physical capacity. Yet, this relationship in healthy older adults remains unclear. The aim of this cross-sectional study was to determine whether a higher VO2peak and faster VO2 recovery kinetics are associated with higher muscle strength and physical performance in healthy community-dwelling older adults. Methods: Thirty-five healthy older adults (female 25/male 10, mean age 73 ± 6 years) performed a graded exercise test on a cycle ergometer. VO2peak and VO2 recovery kinetics were assessed through gas exchange analysis. Muscle strength was determined by maximal leg (one-repetition maximum on leg press; 1RM) and grip strength, and physical performance was determined by the physical performance test (PPT) which assessed gait speed, stair ascent and descent, and timed up-and-go. Results: Higher VO2peak was associated with stronger leg (r = 0.59, p < 0.001) and grip strength (r = 0.39, p < 0.03), but no relationship to PPT (p > 0.05). There was also no relationship between VO2 recovery kinetics and leg and grip strength or PPT (p > 0.05). Conclusion: In healthy community-dwelling older adults, VO2peak, but not VO2 recovery kinetics, is associated with muscle strength. This suggests that muscle strength may be an important factor related to aerobic capacity that could assist in identifying older adults who should be prioritized for resistance training.

Average life expectancy has increased dramatically over the last 100 years due to advances in medical care and treatment [1, 2]. However, ageing is associated with a decline in muscle mass, strength, and power [3, 4], increasing the risk of chronic diseases such as sarcopenia and cardiovascular disease [1, 5‒7]. These conditions result in a reduced capacity to perform activities of daily living (ADLs) [8, 9], poorer quality of life (QOL), and an increased burden on individuals and the public health system [10].

Peak aerobic capacity (VO2peak) is the highest level of oxygen consumption (VO2) attained during a graded exercise test (GXT) [11]. A higher aerobic capacity is generally accepted as important for health and longevity in the general population [12‒14] and is associated with higher muscle strength and physical performance [15‒17]. This includes higher maximal leg strength (1RM leg press) and greater mobility (faster timed up-and-go (TUG)), across older adult populations and clinical populations (e.g., chronic heart failure (CHF)) [15‒17]. However, achieving a true VO2peak may be challenging for older adults and clinical populations as it requires a high level of participant motivation [18, 19]. Therefore, exploring alternative measures obtained during a GXT that are not reliant on a true peak being achieved could be of clinical value. This is particularly true if they are associated with other clinically meaningful measures, such as muscle strength and physical performance, which are significant indicators of ADL capacity.

Previous literature has reported that the recovery kinetics following the cessation of a GXT, such as changes in VO2 or ventilatory exchange, can be a similar, or better, predictor of muscle strength than VO2peak in older adults with CHF and those with poor aerobic capacity  [15, 16, 20]. However, whether this is true for healthy older adults is not clear as data are limited [15, 16, 20]. The aim of this study was to test the hypothesis that a higher VO2peak and faster VO2 recovery kinetics are associated with higher muscle strength and physical performance in healthy community-dwelling older adults.

Participants

This study was conducted as part of a larger clinical trial, the Wellderly Study; the study protocol was previously published [21]. The trial is a multicentre clinical trial conducted at the Institute for Health and Sport (IHES), Victoria University, Melbourne, VIC, Australia, and the Australian Institute for Musculoskeletal Science (AIMSS) in Western Health, St Albans, VIC, Australia. Older adults aged 60 years or over were recruited. Female participants needed to be at least 12 months post-menopause. Exclusion criterion included any fractures within the previous 3 months; commencing a new osteoporotic treatment within the previous <3 months or having begun taking antiresorptive medications within the previous <3 months; having diabetes mellitus or taking hyperglycaemic medications; any haematological, myelodysplastic, or myeloproliferative disorder; any bone malignancy; taking warfarin or vitamin K supplementation or restriction; having a BMI ≥40 kg/m2; and engaging in resistance exercise regime for more than two sessions per week. This study was approved by the Melbourne Health Human Research Ethics Committee (reference number: 2017/08) and is registered with the Australian New Zealand Clinical Trials Registry (trial number: ACTRN12618001756213). The trial was conducted in accordance with the Helsinki Declaration, and reporting of the study adhered to the CONSORT (Consolidates Standards of Reporting Trials) guidelines [22, 23].

Assessments

Sign and Symptoms GXT with Gas Analyser

Aerobic capacity was determined during a GXT on a cycle ergometer. Initial intensity was set at 10–30 watts (W) and increased by 10–30 W per minute according to participant ability. Oxygen consumption was measured using gas analysis, breath-by-breath data, and then averaged every 15-s interval, with routine calibration of gas concentration and flow before each test. During and following the test, expiratory gases were analysed using MedGraphics (BreezeEx, version 3.02, Medical Graphics Corporation). Test was stopped based on participant’s self-reported fatigue and perceived exertion (RPE = 17), clinical signs or symptoms, or the inability to maintain the required revolutions per minute of 60. Oxygen consumption during recovery (VO2 recovery kinetics) was also recorded. VO2 recovery kinetics were then calculated as percentage of VO2peak at 1 and 2 min of recovery (%VO2 1 and 2 min recovery).

Muscle Strength and Physical Performance Assessments

Lower limb muscle strength was assessed using a one-repetition maximum (1RM) test on a cable-loaded leg press machine; the protocol has been previously described [21]. Participants underwent the protocol twice, with one session serving as familiarization prior to assessment. Grip strength was assessed using a hand dynamometer (TTM Advanced, HMG Direct, Australia) with a standard protocol. Three trials were completed with the highest value of the dominant hand being recorded.

Physical performance test (PPT) was adapted from Levinger et al. [24] and included four functional mobility tasks including (i) gait velocity; (ii) stair time to ascend 10 stairs; (iii) time to descend 10 stairs; and (iv) TUG test. Tests were scored in time (seconds). Gait velocity was determined using a 4-metre instrumented walkway using GAITRite (CIR Systems, Inc.), which also includes 1 m of acceleration and deceleration phase. Participants underwent three trials, with the fastest time being the reported value [21]. The TUG test is a simple performance-based assessment that requires minimal equipment, including a standard armchair (46 cm), a 3 m walkway with a floor mark, and a stopwatch (time, s). It is performed as time (s) taken to rise from a seated position, walk 3 m at a normal pace, turn, walk back to the chair, and then sit. Stair descent was calculated as the time to safely descend 10 stairs. Rest time between ascent and descent was 45 s. Four attempts were permitted, and the best time was recorded for each task. The final overall PPT score was the calculated sum of the fastest times recorded for each test.

Statistical Analysis

The relationship between VO2peak and VO2 recovery kinetics with measures of muscle strength and physical performance (1RM leg press, grip strength, PPT) was analysed using SPSS statistics (Version 28.0.1.0 [142]). Based on the Shapiro-Wilk test, all data were normally distributed (p > 0.05). Partial correlations were used to determine the association between VO2 (VO2peak, or %VO2 1 min or %VO2 2 min) and muscle strength and PPTs (1RM leg press, grip strength, and PPT). Correlations were adjusted for BMI and age, as these were independently associated with VO2peak as determined by bivariate correlation. Participant characteristics were determined using an independent sample t test. Significance was set at 95% (p ≤ 0.05) for conducting statistical analysis. Data are reported as mean ± standard deviation.

Thirty-five older adults (25 females and 10 males, mean age 73 ± 6 years) participated in the study. Participant characteristics are described in Table 1.

Table 1.

Descriptive characteristics

Whole cohort, N = 35
characteristicmean±SD
Age, years 73±6 
% female 71 
Body mass index (BMI), kg/m2 28.28±3.6 
VO2peak, mL/kg/min 20.03±4.3 
%VO2 1 min 54.51±12.7 
%VO2 2 min 39.52±8.8 
PPT, s 22.16±4.1 
1RM leg press, kg 109.47±65.5 
Grip strength, kg 30.63±9 
Whole cohort, N = 35
characteristicmean±SD
Age, years 73±6 
% female 71 
Body mass index (BMI), kg/m2 28.28±3.6 
VO2peak, mL/kg/min 20.03±4.3 
%VO2 1 min 54.51±12.7 
%VO2 2 min 39.52±8.8 
PPT, s 22.16±4.1 
1RM leg press, kg 109.47±65.5 
Grip strength, kg 30.63±9 

1RM, one-repetition maximum; TUG, timed up-and-go; PPT, physical performance test; %VO2 1 min, percentage from VO2peak at 1 min of aerobic recovery; %VO2 2 min, percentage from VO2peak at 2 min of aerobic recovery; VO2peak, peak oxygen consumption.

Relationship between VO2peak and VO2 Recovery Kinetics with Muscle Strength and Physical Performance

A higher VO2peak was associated with a higher leg (r = 0.59, p < 0.001) (Fig. 1a) and grip strength (r = 0.39, p < 0.027) (Fig. 1b). There was no association between VO2peak and PPT scores (or any components of the PPT) (p > 0.05). There was also no association between VO2 recovery kinetics and any measures of muscle strength (Fig. 1c, d) or the PPT test or its components (p > 0.05).

Fig. 1.

The relationship between VO2peak (mL/kg/min) with leg press strength (a) and grip strength (b) and the percentage of VO2 following 1-min recovery, from peak, leg press strength (c), and grip strength (d).

Fig. 1.

The relationship between VO2peak (mL/kg/min) with leg press strength (a) and grip strength (b) and the percentage of VO2 following 1-min recovery, from peak, leg press strength (c), and grip strength (d).

Close modal

We report that in community-dwelling healthy older adults, a higher VO2peak is associated with higher muscle strength but not physical performance. VO2 recovery kinetics do not appear to be associated with muscle strength or physical performance.

Previous research has reported that faster recovery kinetics following the cessation of a GXT are related to better muscle strength and physical performance in patients with CHF and those with a low aerobic capacity [15‒17]. However, there is limited data on the relationship between VO2peak or VO2 recovery kinetics and muscle strength or physical performance in community-dwelling healthy older adults. In the current study, we report that a higher VO2peak was associated with higher leg and grip strength. This has implications for exercise prescription and clinical practice as it suggests that VO2peak has broader clinical utility than mortality and disease risk [20, 25, 26] as it may also provide important information regarding muscular strength status in healthy older adults.

Based on our findings, a relationship exists between VO2peak and muscle strength. Whereby, in older adults, increases in VO2peak may positively affect muscle strength outcomes and vice versa. This suggests that by implementing resistance training into exercise interventions for healthy older adults, practitioners may subsequently improve their patients’ aerobic capacity and risk of cardiovascular disease. This supports previous findings in CHF patients, who reported significant increases in VO2peak following 8 weeks of peripheral muscle exercise [27].

While VO2peak was correlated with muscle strength, the same association was not identified with VO2 recovery kinetics. VO2 recovery kinetics were not related to muscle strength and physical performance in our participants. This result is in contrast to findings in clinical populations, such as CHF, which have reported associations between measurements of recovery kinetics, such as VO2 consumption and ventilatory exchange, and muscle strength and physical performance, such as 1RM leg press and gait speed [15‒17]. The lack of correlation in the current study may be due to healthy older adults having a higher VO2peak compared to clinical populations such as patients with CHF (e.g., 20.03 ± 4.3 ml/kg/min vs. 12.9 ± 0.7 mL/kg/min, respectively) [15, 16, 20]. This difference in aerobic capacity may expose both populations to varying relative intensities under the same workload, consequently influencing associations between VO2peak, VO2 recovery kinetics, muscle strength, and physical performance between both populations. This has been indicated in previous research where individuals with CHF utilised a higher proportion of their VO2peak, peak ventilation, and peak heart rate during performance of self-paced ADLs, such as bathing, folding towels, compared to their healthy counterparts [28]. Thus, it is appropriate to anticipate a similar phenomenon likely exists within muscle strength and physical performance assessments.

There are some potential limitations to this study. The cohort is probably only representative of older adults that are community dwelling and the sample size is relatively small, particularly for male participants. However, we consider these findings hypothesis generating. Larger cohort studies, also across different ethnic groups, should be performed in the future to confirm the current study findings. There are also many different protocols that have been used to explore VO2 recovery kinetics across the available limited literature. This may potentially explain the discrepancies between the findings. A strength of the current study is that we have included both active and recovery measures of VO2 to explore its relationship with muscle function. A standardized approach to define and explore VO2 recovery kinetics is required; this will enable a better comparison between study findings.

In conclusion, muscle strength may be an important factor related to aerobic capacity that could assist in identifying older adults who should be prioritized for resistance training. VO2 recovery kinetics appear to provide no additional insight into muscle strength and physical performance in healthy older adults.

This study and its protocols and data collection tools were approved by the Melbourne Health (MH) Human Research Ethics Committee (HREC/17/MH/335; local project number: 2017/208). The study was also approved, mirror approval, by Victoria University Human Research Committee. Written informed consent was obtained from all participants prior to their participation in this study.

The authors have none to declare.

This study was partly funded by the Tom Penrose Community Service Award from Exercise and Sport Science Australia and a seed grant from AIMSS. The salary of CS is supported by A/Prof Joshua Lewis’s National Heart Foundation of Australia Future Leader Fellowship (ID: 102817). The grants awarded to this trial did not have any role in or contribution to the design of the study and the collection, analysis, or interpretation of the data; the grants awarded to this trial will not contribute to the writing of any associated manuscripts.

Rhiannon Healy drafted the manuscript and was involved in the analysis and interpretation of the results. Cassandra Smith, Itamar Levinger and Mary Weoessner were involved in data collection, statistical analysis and interpretation and concept design of the work. Rhiannon Healy, Cassandra Smith, Mary Woessner and Itamar Levinger all contributed substantially to the critical revision, intellectual content and approved the final version of the manuscript.

Additional Information

Rhiannon D. Healy and Cassandra Smith shared first-authorship.

Data will be available upon request. All data requests will require an ethics approval to share individual data. Further enquiries can be directed to the corresponding author.

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