Exercise is Medicine

Abstract

Moving aerobically means moving using oxygen. Our muscles move by using oxygen as their fuel. In various studies, after 30 minutes of aerobic physical exercise, the concentration of free fatty acids in the blood significantly increases. This indicates that, from the 30-minute mark, fats start to mobilize from adipose tissue. Aerobic exercise and endurance training are highly effective in improving physical performance. Anaerobic is a state in which our body moves without oxygen intake. This state can occur, but only for a short period, ranging up to 14 seconds, after which mitochondria must resume working with oxygen as fuel. Despite short-term aerobic exercise training in IR patients, it has a positive effect as a trigger for needs frequency, intensity, time, and type. Frequency is how many days you do exercise in a week. Intensity is how hard exercise is done based on heart rate calculations. Time is how many hours you do exercise in a week. Type exercise could be aerobic, anaerobic, or muscle strengthening.

1. Introduction

All activities carried out by humans are movements that represent cooperation from head to toe integrated from the abilities and coordination of the brain, cardio, pulmonary, muscles, ligaments, and even all organs that support life [1, 2, 3] from organ-level metabolism to cell-level. All these activities are carried out comprehensively and cannot be compartmentalized. Weakness on one side will become weakness and even cause pain throughout the body [4, 5]. An injury to the elbow is not just a matter of the elbow but of the entire arm, trunk, and even the whole body [6, 7].

In this dynamic system that remains integrated in one order, it will be more harmonious when arranged carefully, studied, researched, and performed, so that it can be agreed that exercise is also a prescription for fitness and even healing, and thus it can be said that exercise is medicine [8, 9, 10].

Aerobic means using oxygen. Moving aerobically means moving using oxygen. Our muscles move by using oxygen as their fuel. This movement requires a supply of oxygen pumped and circulated through the bloodstream. The lungs must meet the demand for oxygen as fuel, and we will breathe as quickly as possible to meet that oxygen debt. Our hearts beat rapidly to meet this oxygen demand and deliver it to the cells [11].

The subjective and objective experiences of aerobic exercise can vary from person to person. Subjectively, it can be felt differently by each individual or perhaps felt the same but with different levels or thresholds. Objectively, the workload of aerobic exercise can be measured in simple ways, such as measuring our pulse. More advanced measurements can be obtained from the results of a cardiopulmonary exercise test (CPET) [12].

Anaerobic is a state in which our body moves without oxygen intake. This state can occur, but only for a short period, ranging up to 14 seconds, after which mitochondria must resume working with oxygen as fuel. Do we often engage in anaerobic movements? Yes, of course. In our daily lives, we rarely perform movements in an anaerobic state, but during exercise, anaerobic movements can occur. An example is sprinting 100 meters in sports. Anaerobic movements can be performed at high speeds with high explosive power but in a short time. In everyday life, anaerobic movements can occur when we have to hurry, for example, when urgently trying to reach a destination, such as when chasing someone [11, 13].

How do we know the benefits and drawbacks of exercising? In what conditions can we exercise or engage in sports? To what extent should we do it? The body undergoes various activities from a holistic level, starting from cells to organ levels. The main organs involved are the heart, lungs, and muscles. When engaging in activities, the entire body collaborates to ensure that the goals are achieved [14].

Physical fitness describes a person’s ability to sustain daily activities with full energy, awareness, and without excessive fatigue [11]. Physical fitness is evaluated based on the following five components [13]:

1. Cardiorespiratory endurance: the ability of the circulatory and respiratory systems to supply oxygen and nutrients during physical activity.

2. Body composition: the proportion of muscle, fat, and bone.

3. Muscle strength: the maximum force generated by muscles or muscle groups at a specific speed.

4. Muscle endurance: the ability of muscles to perform activities without causing excessive fatigue.

5. Flexibility: the range of joint motion for achieving movements [11, 12].

These components are related to the body’s abilities that need to be trained, such as agility, coordination, balance, power, reaction time, and speed.

2. Energy metabolism for physical exercise

Physical activity begins with the contraction of skeletal muscles, involving complex interactions between neural and local regulations [14]. This complex interaction is also strongly influenced by hormones, as hormones play a role in muscle development. Testosterone hormone gives characteristic differences between males and females, as it increases male muscle mass by more than 50% compared to females [15].

The body increases the demand for supplies when physical activity occurs through the mechanisms of delivering oxygen and nutrients as fuel to produce energy. The energy source needed to initiate active processes in moving skeletal muscles, and forming physical activities, is known as adenosine triphosphate (ATP). A small amount of ATP is formed in muscle fibers when contraction begins. Only during this brief period is ATP used for muscle contraction and converted into adenosine diphosphate (ADP). Another compound, phosphocreatine (PCr), transfers energy from high-energy phosphate bonds to ADP, replenishing the muscle’s ATP supply (Figure 1) [14, 15].

Figure 1.

Cell respiration and ATP production [16].

Energy reserves in muscles can only last for about 15 seconds for heavy physical exercises such as sprinting or weightlifting. After 15 seconds, muscle fibers must form additional ATP from stored energy in nutrition. Some nutrition molecules are stored in muscles, but many must be transferred from the liver and adipose tissues, and then transported through the circulatory system into the muscles [14]. The main sources of energy formation are carbohydrates and fats. If cells have enough oxygen storage for oxidative phosphorylation, glucose and fatty acids can be metabolized to produce and supply ATP. Over time, the energy production obtained from glucose and fatty acids through aerobic pathways decreases, and glucose metabolism automatically switches to anaerobic pathways [14].

The most effective ATP production occurs through the aerobic pathway, such as the glycolysis-citric acid cycle, compared to the anaerobic pathway. This is due to the difference in the amount of ATP produced, namely 32 ATP from the aerobic pathway and 2 ATP from the anaerobic pathway [16]. The aerobic pathway involves cellular respiration, which breaks down energy-rich molecules to produce ATP using oxygen (O2) and generates carbon dioxide (CO₂) in the process. Broadly speaking, aerobic metabolism consists of three main stages: glycolysis, the citric acid cycle, and oxidative phosphorylation. Glycolysis, occurring in the cell’s cytosol, converts primary energy sources such as glucose and other molecules into pyruvate, producing 2 ATP. The produced pyruvate is transported to the mitochondria matrix to enter the citric acid cycle, resulting in the next stage with the production of NADH (reduced nicotinamide adenine dinucleotide-NAD) and FADH2 (reduced flavin adenine dinucleotide-FAD), and contributing to an additional 2 ATP. Oxidative phosphorylation, taking place in the inner mitochondrial membrane, can generate 28 ATP through the electron transport system and chemiosmosis [16].

The anaerobic pathway is characterized by low oxygen levels. When cells lack oxygen for oxidative phosphorylation, the end product of glycolysis, pyruvate, is converted into lactate instead of acetyl-CoA, which would enter the citric acid cycle [14]. Anaerobic metabolism has advantages in terms of early time and speed, as it can metabolize and produce ATP 2.5 times faster than aerobic metabolism. However, this advantage comes with two disadvantages: (a) anaerobic metabolism only produces 2 ATP for every glucose used, while in the aerobic or oxidative process, each processed glucose will yield 30–32 ATP. (b) Anaerobic metabolism contributes to the occurrence of metabolic acidosis by producing H+ (Figure 2) [14].

Figure 2.

Energy metabolism [15].

The body has three glucose storage sites: in blood plasma, intracellular muscle, and the liver in the form of glycogen, as well as newly produced glucose by the liver through gluconeogenesis. The glycogen reserves in muscle and liver are sufficient to provide 2000 kcal, equivalent to running approximately 32.187 kilometers in a normal person. This amount of energy is generally enough for regular physical exercise, but insufficient for activities like marathon running, where energy is sourced from stored fats [14].

In various studies, after 30 minutes of aerobic physical exercise, the concentration of free fatty acids in the blood significantly increases. This indicates that from the 30-minute mark, fats start to mobilize from adipose tissue. However, the breakdown of fatty acids is slower compared to glucose metabolism through glycolysis. Therefore, the energy formation mechanism in muscles involves a combination of fatty acids and glucose. During low-intensity physical exercise, the largest energy source for ATP production comes from fats, given that more than 30 minutes have passed. In contrast, during moderate- to high-intensity physical exercise, the primary source of energy comes from carbohydrates [14].

Aerobic exercise and endurance training are highly effective in improving physical performance. Aerobic exercise increases fat and glycogen stores in muscle fibers, allowing for a large reserve of energy in the muscles that can be quickly mobilized. Endurance training transforms fast-twitch glycolytic muscle fibers into fast-twitch oxidative-glycolytic fibers [14].

3. Cardiovascular response to physical exercise

At rest, the heart pumps about 5–5.8 L/minute of blood. During heavy activity or physical exercise, cardiac output can drastically increase. In individuals with a sedentary lifestyle, cardiac output during intense activity can reach 20 L/minute. However, trained individuals can experience a 6- to 8-fold increase, reaching 40 L/minute. Oxygen delivery is a crucial factor in determining physical exercise capacity, as seen in scientific studies on exercise metabolism. Those who engage in gradual, sustained, and continuous physical exercise can handle more strenuous workouts than untrained individuals. Heart rate (HR) calculation becomes a crucial variable related to the measurement formula for physical exercise capacity [16].

During physical exercise, the oxygen and nutrient requirements in muscles increase. At rest, skeletal muscles receive about a quarter of the cardiac output, plus 1.2 L/minute. During heavy activity or intense physical exercise, an estimated 88% of the cardiac output is directed to the active muscles. The combination of increased cardiac output and vasodilation in the target muscles allows blood flow to reach 22 L/minute. Vasodilation in active muscles is followed by vasoconstriction in other tissues due to sympathetic signals, but as the muscles become more active, changes occur in the microenvironment of muscle tissue, such as a decrease in tissue O2 concentration and an increase in temperature, CO₂, and interstitial fluid acidity. These factors act as paracrines, causing local vasodilation that can replace sympathetic signals for vasoconstriction [15].

3.1 Ventilatory response to physical exercise

When physical exercise begins and muscles start moving, mechanoreceptors and proprioceptors in the muscles and joints send information about body movement to the motor cortex of the brain. This pathway is excited, and signals travel to the respiratory control center in the medulla oblongata. In response to the movement of physical exercise, the existing signals increase ventilation to maintain oxygen supply as a consequence of increased oxygen utilization [14, 17, 18].

Muscle contractions continue and sensory information provides feedback to the respiratory control that the active body is sufficiently supplied with oxygen and nutrients. Involved sensory receptors include central chemoreceptors, carotid and aortic chemoreceptors, joint proprioceptors, as well as receptors in the muscles, to monitor PO2, PCO2, and pH [18].

Hyperventilation occurring during activity increases proportionally with the intensity of the activity performed. This hyperventilation helps to maintain arterial PO2 and PCO2 close to normal levels. This compensation is crucial and operates effectively, so when monitoring arterial PO2, PCO2, and pH during activity, even heading toward high levels, these parameters do not show significant changes [18].

The K+ ion factor also affects signals. Even during light-intensity activities, extracellular K+ increases with repeated action potentials in muscle fibers, allowing K+ ions to exit the cells. The movement of K+ ions is well captured by carotid chemoreceptors to increase ventilation and balance with the metabolic needs during activity [18].

3.2 Physical activity intensity

The intensity of exercise and physical activity depends significantly on individual factors such as fitness status, age, health status, genetics, psychological factors, social aspects, and exercise habits. Exercise that is too heavy or too light will not contribute to improving an individual’s fitness, meaning it will not enhance the ability to consume oxygen per unit time (VO2max). A study suggests that to achieve 95–100% VO2max, an individual needs to engage in regular physical exercise with high intensity. An alternative to the commonly used assessment of VO2max to evaluate an individual’s physical activity intensity is heart rate. This is supported by research by Schantz et al. [19] which indicates a close relationship between heart rate and estimating an individual’s oxygen consumption. Heart rate and percentage of oxygen consumption capacity are also equivalent in determining the level of an individual’s physical activity intensity (Table 1).

Intensity	%HRR atau %VO2R	%HRmaks	% VO2maks
Very low	< 20	< 50	< 37
Low	20–39	50–63	37–45
Moderate	40–59	64–76	46–64
High	60–84	77–93	64–91
Very high	≥ 85	≥ 94	≥ 91
Maximum	100	100

Table 1.

Physical activity estimation method [19].

The commonly used formula to calculate the maximum heart rate is 220 minus age, but this formula may yield values that are either lower or higher than the actual ones. Consequently, several other formulas, which have undergone specific regression in various studies, are available [11]. In cases where individuals have disabilities involving thoracolumbar spinal nerve paralysis and engage in physical activities primarily using their arms, such as propelling a wheelchair, a lower constant of 200 minus age is employed [20].

Various studies concur on a linear relationship or a direct proportion between heart rate and oxygen consumption capacity in assessing an individual’s fitness. These studies were conducted across different levels of physical activity intensity. The correlation remains valid at high intensities; however, at extremely low levels of physical activity intensity, the heart rate may exaggerate an individual’s fitness value [21].

4. Concept of maximum oxygen uptake capacity

Fitness measurement is established using the measurement of oxygen consumption per unit time (VO2max). The most common formula is expressed in (L.kg⁻¹.min⁻¹). VO2max is the product of maximum cardiac output (CO) or maximal cardiac output (L.blood.min⁻¹) and the difference in oxygen levels between the arterial and venous blood (mLO².L.blood⁻¹). Oxygen consumption is an agreed-upon measure of cellular respiration, expressed in liters of oxygen consumed every minute. The greater the VO2max value, the greater an individual’s ability to engage in activities. Up to a certain point, an individual has the ability to continue physical exercise or stop the physical exercise due to fatigue or other factors such as breathlessness, headache, dizziness, or pain. Factors limiting aerobic physical exercise include:

1. The cardiovascular system’s ability to supply oxygen and nutrients to tissues,

2. The respiratory system’s ability to supply oxygen to the blood, and

3. The muscle’s ability to acquire and use oxygen and nutrients efficiently.

Cellular oxygenation occurs within the mitochondria, so the use of oxygen in producing ATP is greatly influenced by the number of mitochondria in the cell. According to physiological studies, muscle metabolism is proven to supply only up to submaximal exercise; in other words, it cannot meet maximal physical exercise activities. Additional energy from outside the muscle and the ability to oxygenate cells are required if someone aims to achieve physical exercise beyond submaximal levels. Increasing the number of mitochondria in muscle cells can be achieved through measured, gradual, continuous, and purposeful exercise that can be accounted for. The transportation of oxygen to each cell in the body heavily depends on the hemoglobin levels in the blood. The normal average hemoglobin level in blood is 15 g/dL for adult males and 14 g/dL for adult females. In addition to hemoglobin levels, it is essential to know the value of oxygen saturation or SaO2. Oxygen saturation indicates the amount of hemoglobin bound to oxygen for transport throughout the body. The normal value of oxygen saturation in average arteries is above 97% [16].

5. Application of cardiorespiratory testing in physical activities

The Duke Activity Status Index is a form commonly used to assess the level of physical activity in terms of metabolic equivalents (METs). A value of 1 MET represents the oxygen consumption of an adult at rest, which is 3.5 L.kg⁻¹.min⁻¹ for a person weighing 70 kg in a sitting position. Every active individual should achieve at least a value of 4 METs. An example of daily activities equivalent to this is climbing 12–13 stairs [16].

The use of cardiopulmonary exercise testing (CPET) is non-invasive and low-risk yet remains accurate for assessing heart, lung, and metabolic functions. During this test, the CPET device is utilized throughout the examination while engaging in physical activities. With increasing workload and time, the output of ventilation gas (VE), oxygen consumption (VO2), and carbon dioxide production per minute will increase. Additionally, there will be an observed increase in the accumulation of lactic acid in the muscles [18].

The CPET device can measure the achievement of maximum oxygen consumption per unit time (L/kgBW/min), also known as VO2max. VO2max is the product of maximum cardiac output and the difference in oxygen levels between the arterial and venous blood. VO2max is considered a criterion for measuring physical fitness as it is closely related to the functional capacity of the heart, lungs, and muscles. Some literature also indicates a direct correlation between achieving VO2max and achieving maximum heart rate (HRmax) [11].

The anaerobic threshold (AT) can be considered an estimate of the onset of anaerobic metabolism induced by lactic acidosis levels. This occurs due to an imbalance between the required oxygen supply and the oxygen available in the muscles during activity. While this measurement is rarely invasive, it can be detected on the CPET monitor when the individual exhales an increased amount of CO₂ as compensation for the rise in lactic acidosis levels. The point at which the oxygen consumption curve inverts with the production of VCO2 and VE is the point where lactic acid levels rapidly increase. This point is captured by CPET as the VO2max value for that individual. VO2max also correlates with gender, age, body weight, and the intensity of a specific activity [22].

CPET: research conducted by the author using CPET equipment in 2015 showed that the highest VO2max value in a group of post injured soldiers (PIS) propelling wheelchairs was 38 L/min/kgBW, while for normal soldier (NS) engaged in running, it was 64 L/min/kgBW. In other words, the VO2max value in the group of PIS propelling wheelchairs only reached 45% compared to soldiers running [20]. By investigating the equivalence of VO2max between running and wheelchair-propelling activities for soldiers post-injury who cannot or eventually cannot run again, an equivalence value can be sought to assess physical ability.

6. Effects of immobilization and inactive musculoskeletal system

The state of immobilization or a sedentary lifestyle will lead to a loss of strength, commonly known as a decrease in muscle strength, which ultimately reduces the strength and tolerance of physical endurance for daily activities. During total bed rest for a duration of 1 week, muscle strength and endurance tolerance will decrease by 10–15% from the initial strength. Even in healthy individuals undergoing bed rest for more than 5 weeks, losses can persist, reaching up to 35–50%. Research involving dynamic leg press during the immobilization period showed that extensor and flexor strength of the knee could be maintained, but the strength of the plantar flexors of the ankle and dorsiflexors of the ankle could not be sustained. Therefore, the best exercises are functional walking or mobilization. In conclusion, muscle atrophy resulting from disuse is more evident in the legs than in the arms. Studies on individuals with total bed rest indicate a strength decrease of 20–40% in the legs, while a decrease of only +5% occurs in the arms. The decrease in myofibril strength per unit volume of muscle fibers appears to be reduced [12].

The loss of strength and muscle mass will continue to decline until the individual finds it difficult to rise from an immobilized state. Exercises can be done gradually, continuously, and sustainably, with quantifiable and justifiable progress. To reverse the effects of immobilization syndrome after 45 days, functional mobilization exercises and electrical stimulation therapy assistance for around 45 days can be employed to maintain the ability to return to basic mobility [12].

Immobilization syndrome has also been proven to decrease muscle endurance due to a decrease in the concentration of ATP and muscle glycogen reserves. Decreases in muscle protein synthesis, oxidative enzyme function, acceleration into the anaerobic cycle, and the accumulation of lactic acid are a set of factors leading to the onset of fatigue. Changes in the shape and size of motor end-plates and dysfunction of acetylcholine receptors further impair the function of skeletal muscle endurance. The reduced oxygen demand of muscles during immobilization significantly affects the number and size of mitochondria.

After 42 days of immobilization, there is a 16% reduction in VO2max, a decrease in cardiac output by up to 30%, a 40% reduction in oxygen transport flow, and a 28% reduction in mitochondrial volume [12].

6.1 High intensity interval training (HIIT)

Since the 1950s, Olympic athletes have been introduced to HIIT as one of the exercises to enhance their performance. The first introduced interval training was sprint interval training, where athletes perform exercises reaching 100% of their maximal heart rate (HR), followed by a gradual descent. This cycle is repeated several times. According to a survey conducted by the American College of Sports Medicine in 2014, HIIT has become popular among the general public. This exercise takes 30 minutes, including both aerobic and resistance training phases with vigorous intensity [20, 23, 24].

Research using mice aims to prove whether high-intensity interval training (HIIT) and/or moderate-intensity continuous training (MICT) can contribute to or even enhance cardioprotection. In the mechanism of increasing Klotho protein and reducing TRPC6 (which, when increased, causes stress and leads to dysfunction and heart diseases), some studies show that the cardioprotective factor in patients with myocardial ischemia-reperfusion (IR) is highly influenced by the intensity of exercise rather than the duration of exercise [20, 23, 24, 25, 26].

HIIT is an exercise with a repetitive pattern at high intensity, reaching 85–90% peak VO2. HIIT starts with a 5-minute warm-up achieving 40–50% of the maximum heart rate (low intensity). Entering the core of the HIIT exercise for 6 × 2 minutes (with high intensity at 85–90% of the maximum heart rate) is interspersed with 5 × 2 minutes (with low intensity at 50–60% of the maximum heart rate), known as the active recovery period. It concludes with a 5-minute cooling down period with an intensity of 40–50% of the maximum heart rate. On the other hand, MICT begins with a 5-minute warm-up at 40–50% of the maximum heart rate and concludes with a 5-minute cooling down period at a low intensity. The core exercise reaches 70% of the maximum heart rate. MICT exercises should be performed for a minimum of 30 minutes [27, 28, 29].

This study successfully noted that after all experimental animals performed exercises for five consecutive days, there was a reduction in the size of the infarct area compared to mice without physical exercise. Moreover, it turns out that HIIT exercises have a more positive effect compared to MICT. Thus, it can be concluded that, despite short-term aerobic exercise training in IR patients, it has a positive effect as a trigger for cardioprotection [30, 31, 32].

6.2 The relationship between exercise and immune system

Research on the connection between physical performance and the immune system has significantly evolved since the 1900s and continues to progress [33]. The current focus remains on three aspects:

1. Reducing fat, especially visceral fat.

2. Increasing the production of the immune system’s building blocks. Lowering the risk of diseases such as diabetes, heart disease, and stroke by up to 80% [34].

3. Releasing anti-inflammatory or anti-cytokine substances resulting from the contraction of skeletal muscles [35].

6.3 Measured exercise

To determine the intensity of the exercise we engage in, we need to calculate our age, measure our pulse, and refer to a table estimating physical activity. For example:

Age: 50 years, then use the formula: 200–50 (age) = 170 (Maximum heart rate).

(A)

Check your pulse while exercising, count for 1 minute. Suppose it’s 150 beats/minute.

(B)

Calculate the intensity: (achieved pulse (B) 150) / (maximum pulse (A) 170) = 88% intensity.

Check the Table 2.

Intensity	% Maximum heart rate
Very light	< 57
Light	57 – <64
Moderate	64 – <76
Hard	76 – <96
Very hard	≥ 96

Table 2.

Estimation table of daily activity.

After referring to the table above, it turns out that it falls into the heavy intensity category [33, 36].

Frequency: The recommended frequency for physical activity is 5 days a week.

This is an ideal frequency. To ensure that your exercise provides optimal immune system benefits, it is recommended to exercise at least three times a week, with an optimal frequency of five times a week, allowing the body to experience rest for energy restoration [33, 36].

Time: the recommended daily exercise duration is a minimum of 30 minutes to 60 minutes. Based on the breakdown of fat after moderate-intensity exercise for 30 minutes, exercising for 4 hours a week reduces the risk of diabetes, stroke, and heart attacks by 80% [33, 34, 36].

Type: various types of exercises can be chosen.

1. Aerobic: exercises that consistently use oxygen in every movement, characterized by not getting too breathless. Examples include walking, jogging, dancing, cycling, swimming, and golf.

2. Anaerobic: high speed, short-duration exercises, such as sprinting 100 m or chasing a ball in soccer with high speed for a short time, repeated.

3. Muscle strengthening: using weights or body weight as resistance [33, 36].

After understanding FITT (frequency, intensity, time, and type), you can combine them. If you find it challenging to maintain heavy intensity for 5 days a week, especially at a very high level, you can combine FITT elements according to your capability. See Table 3, for example.

Monday	Tuesday	Wednesday	Thursday	Friday	Saturday	Sunday
Light intensity + muscle strengthening	Moderate intensity	Rest day	Moderate intensity	Light intensity + muscle strengthening	Heavy intensity	Rest day
Brisk walk + weight lifting for 60 minutes	Light jogging for 60 minutes		Light jogging for 60 minutes	Light dancing + weight lifting for 45 minutes	Running/cycling/swimming/golf

Table 3.

Types of exercises.

7. Conclusion

1. Moderate to heavy-intensity exercise with the right FITT will enhance immunity to improve health status, physical fitness, and quality of life.

2. Very low or very high-intensity exercises with very long durations can be detrimental to health status, physical fitness, and quality of life [34, 36].

3. Always consider your overall health condition, age, monitor your heart rate during exercise, time, and the type of exercise you engage in.

4. This exercise prescription is unique to each individual. Consult with a doctor if you have any underlying health conditions.

Here is an example of a study to establish a home program with important limitations that are easily understood by the community.

How likely is it for a post-leg injury patient to exercise with a wheelchair? Can wheelchair exercise be turned into a home program? These questions often arise in the minds of physiotherapists when encountering individuals with leg injuries who still require assistive devices for ambulation. The following facts from a wheelchair sports exercise test conducted on normal soldiers (NS) and injured and post-injured soldier (PIS) will be presented. This can help physiotherapists make decisions and establish criteria that can be implemented for injured patients still in need of ambulatory aids, using a wheelchair as a means of exercise to maintain the fitness of patients or individuals with disabilities [37].

Serving in the military comes with the risk of injuries, and data from the Rehabilitation Center (Pusrehab) from 2009 to December 2018 recorded 6640 post-injured soldiers. This accounts for approximately 1.66% of all active soldiers to date [37]. About 75% of them suffered injuries from the lumbar region downward. This significantly affects the physical condition of soldiers returning to duty, especially in combat or sports, depending on their functional abilities. To fulfill the country’s obligation to protect its citizens, especially injured and post injured military personnel (PIS), the Rehabilitation Center of the Ministry of Defense of the Republic of Indonesia (PUSREHAB) was established to provide comprehensive medical rehabilitation services [38].

In the second semester of 2021, PUSREHAB conducted medical rehabilitation for 75 male PIS, with an average injury duration of 4 years. A total of 50 of them have undergone evaluation using a wheelchair exercise test. At the same time, 104 male NS also underwent the wheelchair exercise test. All evaluations were approved by Pusrehab and Pusdikkes KodiklatAD. A total of 154 active, healthy male soldiers who had undergone a prior Medical Check-Up (MCU) stating no acute infectious diseases or uncontrolled illnesses were selected. Subjects with balanced arm capabilities for wheelchair exercise were chosen for this test, using a sports wheelchair (Figures 3 and 4) [38].

Figure 3.

Distance traveled using wheelchair.

Figure 4.

Exercise intensity using wheelchair.

Looking at the results of Table 4 to assess the general characteristics, no significant differences were found between PIS and NS. When the data are grouped per 10 years of age, there are significant differences for the age group of 19 to 29 years in terms of age, body weight, and BMI. The PIS age for this group is senior compared to NS. The BMI reaches 28 (obesity category 1) [38]. This almost homogeneous data will simplify data analysis.

Variable	Age	Normal soldier; n = 104	Post injured soldier; n = 50	Sig.
Age (years)		32 (19–49)	31 (23–51)	0.404
	19–29	22 (19–29)	26 ± 2	0.000*
	30–39	33 (31–38)	35 ± 3	0.072
	40–49	44 ± 3	44. ± 4	0.721
Weight (kg)		69.7 ± 8.2	72.18 ± 10.55	0.241
	19–29	64.1 ± 8	69.8 ± 10.7	0.016*
	30–39	75.1 ± 5.8	75.1 ± 11.2	0.994
	40–49	72.1 ± 4.9	72.4 ± 8	0.884
Height (cm)		170 (163–183)	169.6 ± 4.0	0.866
	19–29	169.1 ± 4.1	170 ± 3.9	0.432
	30–39	170.7 ± 4.6	169.7 ± 4.7	0.302
	40–49	168.5 ± 3.9	168.4 ± 3	0.922
Body mass index (BMI) (Kg/m^2)		24.22 ± 2.5	24.67 ± 5.0	0.393
	19–29	22.3 ± 2.2	24.2 ± 3.8	0.044*
	30–39	26.3 (20–29)	25.8 ± 1.7	0.893
	40–49	25.6 (21–27)	25.5 ± 2.5	0.847
Blood pressure (systole) (mmHg)		120 (90–146)	123.86 ± 13.5	0.455
	19–29	120 ± 12	121 ± 10	0.989
	30–39	120 (98–130)	123 ± 13	0.275
	40–49	125 ± 12	133 ± 19	0.151
Blood pressure (diastole) (mmHg)		80 (58–100)	78.92 ± 7.4	0.617
	19–29	73 (58–100)	77 ± 7	0.088
	30–39	81 ± 8	80 ± 7	0.791
	40–49	80 (67–91)	82 ± 9	0.937
Hemoglobin (g/dL)		15.0 ± 1.3	14.9 ± 1.1	0.550
	19–29	14.8 ± 1.2	15 ± 1	0.644
	30–39	15.3 ± 1.3	14.9 ± 1.3	0.324
	40–49	15 ± 1.4	14.7 ± 1.1	0.536
Blood sugar (g/dL)		95.8 ± 15.9	92.5 (74 ± 391)	0.914
	19–29	95 ± 18	88 (77–121)	0.488
	30–39	95 ± 15	96 (70–126)	0465
	40–49	98 ± 15	101 (89–391)	0.395

Table 4.

Subject characteristic.

From the conducted tests, differences were found in the results of this fitness evaluation. As seen in Table 4, there are significant differences in the distance covered in the wheelchair exercise test between PIS and NS. In general, there is a mean difference of 117 meters, with NS covering a greater distance than PIS. When classified into age groups, the differences in distance are: for 19–29 years, 182 meters; for 30–39 years, 55 meters; and for the age group of 40–49 years, 118 meters. The results show that, in all age groups, NS covers a greater distance than PIS. It is clear that as age increases, the covered distance decreases. This happens in both groups. The difference in covered distance between NS and PIS indicates different fitness results for these two groups. NS appears to be superior to PIS.

Qi and colleagues state that the functional speed wheelchair distance is 720–936 meters per 12 minutes [39]. When compared with the achievements in this evaluation for the age groups of 19–29, 30–39, and 40–49 years (1555, 1400, 1330 m), it can be said that they have entered the exercise range.

An interesting aspect is the intensity of the exercise achieved during the data collection. All subjects performed this test with moderate intensity in the age group under 40. However, those above 40 years, entered vigorous intensity, but none of the subjects reached maximal intensity. Observations of the intensity of wheelchair exercise performed by soldiers under 40 can still be considered safe since it is within the moderate range. For those above 40, it is also considered safe but should be done with caution because it reaches an average intensity of 83% (heavy intensity). Therefore, recording the pulse during the activity can be used as one of the benchmarks for a home program exercise independently [39].

From the two data sets above, it can be seen that as a person ages, more effort is needed to perform activities, as shown by the increased intensity of activities, although the covered distance will decrease. In other words, a person’s fitness will decline with age. This aligns with the aging journal, which states a decrease in VO2peak by 3–6% per decade starting at the age of 30–40 years [40].

In conclusion, the fitness outcomes for post-injured soldiers (PIS) continue to lag behind those of Normal Soldiers (NS), underscoring the necessity for comprehensive medical rehabilitation programs for every post-injured soldier. The distance covered and pulse rate attained during wheelchair exercise serve as reliable indicators for assessing the safety of patients engaging in such activities. Moreover, the pulse rates achieved during these exercises fall within the moderate category, indicating that they remain safe for individuals recovering from injuries. These findings emphasize the importance of tailored rehabilitation efforts and ongoing monitoring to ensure the well-being and progress of post-injury patients, particularly those utilizing wheelchairs as part of their exercise regimen.