Prehabilitation is an attractive care strategy for the older population as it aims to increase functional capacity during the preoperative period in anticipation of the upcoming stress of surgery and the metabolic cost of recovery. It begins in the preoperative period and is part of an integrated enhanced recovery after surgery (ERAS) program which include best intra- and postoperative practices to attenuate surgical stress, encourage patient autonomy, and preserve function. The importance of education and empowerment cannot be understated. Treatment of coexisting medical conditions includes glycemic control, anemia and malnutrition correction, and smoking and alcohol cessation [7].

Evaluation of physiological status and identification of age-related diseases, rather than chronological aging itself, should be the focus for preoperative assessment of the elderly population and for planning perioperative care. To optimize organ function in preparation for surgery, the functional reserve has to be assessed and the specific disease process within each organ system identified. Functional reserve is not only limited to the physical status but also includes nutritional, metabolic, and mental components. Therefore, the functional reserve represents a safety margin that may be needed to meet increased demands for cardiac output, carbon dioxide excretion, protein synthesis, immune responsiveness, etc. Since the functional reserve decreases with age, any organ system dysfunction places the elderly population at risk [13]. When analyzing components of mortality in the elderly population, the probability of death from cardiac, vascular, and pulmonary causes increases dramatically in the oldest fractions of the geriatric group, while malignancy and metabolic disorders play a lesser role [16]. There is strong evidence that older adults who are physically active, in good nutritional state, and with adequate mental function have higher levels of functional health and lower postoperative complications [17].

Limitations in aerobic capacity have repeatedly been shown to affect outcomes. Diminished peak oxygen uptake (VO2 _Peak) and oxygen uptake at anaerobic threshold (AT), as assessed by cardiopulmonary exercise testing (CPET ), have been identified to increase risks of postoperative mortality and morbidity after major surgery [18–20]. These factors may well influence access to surgery in this age group, a view that the elderly are unable to withstand the rigors of major surgery and contribute to the steep decline in survival rates after the age of 70 years seen in most cancers. Bowel cancer 5-year survival is 65% in 60–69-year-olds, while in the over 80-year-old age group, 5-year survival drops to 43% [21].

A structured exercise program is the central component of prehabilitation. The premise is that repeatedly exposing patients to the physiological stress of physical activity will improve reserve and allow them to tolerate surgery better. Participating in regular physical activity has been shown to decrease mortality and risks of developing chronic conditions such as diabetes mellitus , cardiovascular disease , chronic lung disease , Alzheimer’s disease , and most types of cancers. Studies in colorectal cancer survivors found that physical activity may decrease cancer recurrence and mortality [22]. The US Department of Health and Human Services guidelines recommend that older adults should perform at least 150 min per week of moderate-intensity or 75 min of vigorous-intensity physical activity to have substantial health benefits (Table 6.1). It is also recommended that aerobic activity should be spread throughout the week with sessions of at least 10 min and be accompanied with muscle strengthening exercises [23].

Exercise decreases inflammation, increases aerobic capacity, improves insulin sensitivity, increases the ratio of lean body mass to body fat, decreases sympathetic reactivity, improves mood, and decreases anxiety [13]. For optimal results, a presurgical exercise program should consist of both resistance and aerobic training and be supplemented by flexibility exercises. It has been shown that aerobic and resistance training in elderly patients increases muscle strength and endurance, favors weight loss, reduces incidence of falls, and increases range of motion in a number of joints. Of course, one type of exercise does not fit all, and personalization of the exercise intervention is necessary to achieve success without harm. In terms of defining the specific exercise requirements of an effective prehabilitation program, it must be pointed out that there is a difference between physical activity and exercise: physical activity can be defined as any body movement produced by skeletal muscle that results in a measurable energy expenditure. Exercise encompasses regular physical activity that is incorporated into a planned and structured program for the specific goal of improving fitness, that is, enhancing aerobic and anaerobic capacities, strength, and balance. In the case of prehabilitation, a structured program that specifies exercise intensity, frequency, and modality is the goal [24]. The aerobic exercise prescription is based on the American College of Sports Medicine (ACSM) Guidelines for Exercise Testing and Prescription [25]. Training intensities are based on percentage of heart rate reserve (HRR) calculated with the Karvonen formula (target heart rate = [(heart rate_max – heart rate_rest) × %intensity] + HR_rest). Individuals who are classified as having low initial fitness will show improvements in functional capacity with training intensities that produces heart rates above their resting rate. It is recommended for them to start exercising at an intensity of 55% of heart rate reserve (HRR), which, in a 75-year-old adult with a resting heart rate of 55, would correspond to a target heart rate of 105 beats per minute. Another tool to assess exercise intensity is the Borg scale, or rating of perceived exertion (RPE) scale . It is a visual scale on which patients are asked to rate how intense they felt their effort from 6 (being no perceived effort) to 20 (being maximal exertion) [26]. Moderate intensity would be quantified as 12–14 on the RPE or 50–70% of HRR and vigorous intensity 15–17 or 70–85% of HRR.

Age-related declines in muscle strength are directly related to sarcopenia (loss of skeletal muscle mass). Since total muscle cross-sectional area decreases by 40% between the ages of 20 and 60 years, strength training should be implemented to prevent this decline. Thus, strength training should be implemented in elderly people because of its positive effects on their functionality, health, and quality of life [24]. If elderly people are properly supervised, shown how to use the equipment, and taught the appropriate techniques, then there is no reason why weight training should not be implemented given the huge potential benefit that certainly outweighs any minimal risk. In general, individuals who have been the least fit and the most sedentary show the most improvements when they initiate an exercise program. Since their physiologic reserve is limited, even small amounts of physical training can yield significant improvements.

Great care must be taken in designing an exercise program for seniors, as only 30% of individuals over the age of 65 years old regularly participate in physical activities [27]. The F.I.T.T. principle is the basis of a structured exercise program, and its acronym stands for the four important parameters to define when prescribing such a program [25]:

Another important element in the implementation of a personalized exercise program is to identify when and how exercise progression should occur to maximize functional status improvement over a short period of time. Exercise intensity should be increased to match the increase in fitness, for instance, when a patient doesn’t reach their target heart rate or RPE target when performing the prescribed exercises. For example, for aerobic training, walking speed or incline can be increased, and for resistance exercise, weight or number of sets and repetitions could be increased. As for balance exercises, they could initially be done with the help of a stable support with progression to no support [23]. See below (Table 6.2) an example of an exercise program.

Step counting devices (accelerometers and pedometers) offers an opportunity to monitor and encourage daily ambulatory activity, particularly in the elderly, although it is not clear what amount is required according to the public health guidelines. It is recommended that with a daily background of 5,000 steps/day (which can be too high for some older adults and special populations), 7,000 steps will include a target of achieving 30 min of moderate-to-vigorous physical activity .

The nutritional aspect of aging has lately received more attention in view of the strong relationship between malnutrition and poor postoperative outcome. In addition, there seems to be a better understanding of the synergy between physical activity and protein intake. Early studies into the role of protein turnover in age-related sarcopenia reported that muscle wasting in the elderly was due to a decline in basal rates of muscle protein synthesis, elevated rates of muscle protein breakdown, or a combination of the two processes resulting in a negative protein balance [29, 30]. The elderly are less able to utilize amino acids for muscle protein synthesis, and this can be explained by some sort of anabolic resistance of elderly muscle to a physiological dose of amino acids. Thus older muscles appear to be blunted in their capacity to mount a robust response to resistance exercise similar to the one achieved by a young person [31]. The superimposed stress of surgery and the elevated state of insulin resistance make the blunted anabolic sensitivity to low doses of amino acids even greater. A dietary plan that includes sufficient high-quality protein per meal will provide sufficient essential amino acids, particularly leucine, which is needed to elicit muscle protein synthetic response and accretion of muscle protein. The addition of resistance exercise to an intake of high dose of proteins favors muscle mass buildup and will improve strength and physical function [32].

Many elderly arrive to surgery poorly nourished. Malnutrition can be defined simply as “bad nutrition.” More specifically, it arises from inadequate intake and/or metabolic and inflammatory changes that alter nutrient requirements or absorption, which, ultimately, leads to wasting and diminished physical function [33]. Malnourished patients have been found to suffer increased morbidity, longer hospital stay and readmissions, prolonged surgical recovery, and poorer quality of life. Moreover, recent North American surgical consensus recommendations suggest moving beyond treating malnutrition to preventative preoperative nutrition therapy in all at-risk patients to potentially mitigate any malnutrition-induced complications throughout the perioperative period [34]. As a result, early identification of malnutrition risk, for the purpose of eliciting a comprehensive dietary consult, throughout the continuum of care surgical patients is increasingly recognized as a significant component of quality care [35]. A systematic approach to identify and treat patients at risk of malnutrition must be established.

Observational evidence suggests that patients with higher preoperative lean body mass (i.e., reserve) are better able to cope with surgical stress as determined by reduced complications and earlier discharge [36, 37]. The primary goal of perioperative nutritional care is thus to promote GI tolerance, enhance immunity, support normoglycemia, and provide sufficient protein to achieve anabolism and sufficient energy to maintain body weight. A combination of both individualized nutrition counseling and oral nutrient supplementation (ONS) has proven to be effective in building functional capacity in prehabilitation trials [38]. Prehabilitation nutritional care plans are therefore focused on meeting the aforementioned nutritional goals as well as supporting the exercise component of prehabilitation to build and maintain physiologic reserve prior to surgery. After a single bout of resistance exercise, both muscle protein synthesis (MPS) and muscle protein breakdown are simultaneously stimulated in healthy individuals [39]. In order to generate a positive net protein balance in favor of lean body mass accretion, exogenous amino acids must be administered to produce a state in which protein synthesis exceeds that of protein breakdown [40]. Indeed, exercise alone, in the absence of adequate nutrition, will not lead to muscle protein accretion [41] or maximal improvements in functional capacity [42]. Twenty to thirty grams of protein taken immediately after resistance exercise in liquid form is regarded as sufficient to maximally stimulate MPS in healthy individuals [32]. The optimal post-exercise diet to support lean body mass accretion in elderly patients is still not known. Finally, supplemental omega-3 fatty acids, particularly eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) , which are found naturally in fish oils, have been identified in several randomized controlled trials to reduce oxidative stress and inflammation [43]. Prehabilitation nutritional care should also focus on meeting established dietary requirements of these essential fatty acids. Attention to nutrition is an important component to prehabilitation primarily because it supports other aspects essential to the improvement of functional reserve (Fig. 6.2).

Recently a consensus was reached among a group of surgeons that preoperative exercise is beneficial in the management of cancer patients, and more work in this field should be supported [44]. As prehabilitation encompasses the whole perioperative period and impacts on short- and long-term recovery, constructs must be appropriate. The first assessment should include whether the prehabilitation intervention is feasible. Can a program of prehabilitation be implemented in the present hospital structure? Is there a support for this type of initiative? What are the barriers and the costs? Where should the program be administered? Compliance by participants to the program needs to be assessed together with their level of satisfaction. The second assessment would include performance measures testing the value of the physiological outcome and those measures based on self-reports by the patient. These tests would address whether the intervention (e.g., exercise, nutrition) impacts on aspects of functional capacity, a proxy measure of physical activity and strength.