Government guidelines suggest that we should all take part in approximately two and a half hours each week of moderate-intensity aerobic exercise. Older adults are particularly important as their overall health may decline as they get older. Therefore, exercising is important especially for older adults to improve heart and muscle health and functioning in carrying out tasks of daily living. The overall effects of aging on the body can make people less likely to withstand challenges to the body - this is termed 'resilience'. Although aerobic exercise is not super easy and requires continuity, it is not extremely difficult to get used to. However, we still do not know if some types of aerobic exercise are better for you than others at improving resilience. Therefore, this study will look at cycling vs walking to see if one is better at improving resilience in older adults who are 60-80 years old. You will be trained on either a treadmill or cycle ergometer and these exercise sessions will be done over 5 weeks, 3 days a week. Each session will last 40 minutes, start with warm-up and end with cool-down sessions. Assessments will include heart, lung, muscle, and memory and thinking measurements, all of which will be taken before and after the intervention period. This work will help us to better understand how we can improve exercise prescriptions for older adults to sustain their health and functioning in their daily life.

Physiological resilience refers to the capacity to retain or regain physical function in the presence of diseases or age-related impairments. Poor resilience may increase vulnerability to stress, which could lead to negative functional and clinical consequences like a prolonged course of illness/hospitalization, reduced physical activity, an elevated risk of frailty, and even mortality. Physiological resilience is particularly crucial because it declines, and the likelihood of many stresses rises with age. Therefore, it is important to promote older populations' physiological resilience reserves and resources (increase their readiness levels against potential future stressors that are more likely to be seen when an individual gets older). Since risk of having stressors increases with advanced age, there is a relationship between aging and reduced readiness to stressors (low physiological resilience).

The scientific data establishing the beneficial effects of exercise is undeniable, and the advantages of exercise considerably outweigh the hazards in most adults. Although the existing evidence supports that exercise interventions are a potent tool to foster resilience in older adults, there is still a need of future studies regarding this information. Aerobic exercise (AE), one of the most recommended exercise types by the literature, has also been stated as a beneficial tool to promote physiological resilience at all stages of life through increased growth factor expression and neuroplasticity, which lower the destructive effects of chronic stress. Also, aerobic fitness has been shown to be one of the best predictors of resilience. Government guidelines recommend performing moderate-intensity AE 150 minutes per week. However, the literature does not elaborate on the details of AE interventions on physiological resilience and there is a lack of information on which AE modality is better for this purpose. Although the literature supports the idea of AE being a beneficial tool to improve health and physical fitness goals as well as resilience, it can clearly be seen that there is a need for future research regarding both the comparison of AE modalities in older adults and the effects of AE intervention to promote physiological resilience. Thus, this study will be the first to compare the effects of moderate intensity time-matched AE modalities (cycle ergometer versus treadmill training versus control group) on the parameters associated with physiological resilience (muscle mass/strength, cognition, dexterity, functional ability, cardiorespiratory fitness, and neuromuscular function) in older adults. The intervention period will last 5 weeks, 3 days a week, with 40-minute sessions. The research question will be 'Which AE modality is better in improving determinants of physiological resilience?'. This work will allow us to understand the relationship between AE and physiological resilience in a more detailed way and to prescribe better exercise prescriptions in the future.

Inclusion Criteria:

• Participant is willing and able to give informed consent for participation in the study
• Participants who are able to perform exercises safely and freely
• Participants who are 60-80 years old

Exclusion Criteria:

• Cardiopulmonary diseases except for well-controlled hypertension and asthma
• Severe cognitive impairment
• Joint disorders avoiding exercise participation
• A recent heart attack, unstable angina, or severe heart failure
• Having taken part in a research study in the last 3 months involving invasive procedures or an inconvenience allowance
• Participants who are currently engaging in more than 150 min of moderate-intensity exercise per week or 75 min of vigorous-intensity exercise per week (WHO physical activity recommendations)