How does your body respond to intense exercise? When you begin to exercise, your body is put under stress, needing more energy as your activity level rises. The demands on your muscles grow, and in response, your body triggers a range of physiological and metabolic changes. These shifts are crucial to deliver the necessary energy to your muscles in action. However, they can also lead to temporary side effects like harm to your muscle tissue and impacts on your immune system. Let’s delve into some of the key changes that occur and the repercussions of these.
Increased heart rate
Let’s start with one of the most immediate and noticeable changes: your heart rate. Your heart feels like a drum, pounding faster and faster, actively responding to your body’s demand for oxygen. This amazing feat is all down to the unique nature of your cardiovascular system and its dynamic response to exercise. The moment you kick-start any physical activity, your heart begins to pump more blood, essentially to fuel your exercising muscles with oxygen and nutrients. Every beat signifies the ejection of a higher volume of blood, and as a result, your heart rate skyrockets. Simply put, your heart is working overtime to ensure you have the energy to keep going, showcasing the impressive adaptability of the cardiovascular system when faced with increased physical demands.
Imagine you’re hitting the gym for a resistance workout. To perform those movements, your muscle fibers crave a swift energy source. That’s where ATP molecules come into play. When ATP breaks down, it releases the energy needed to fuel muscle contraction. But here’s the catch; muscles only store enough ATP for a few seconds of all-out effort. So, ATP has to be continually replenished during repetitive or intense muscle movements. The main actors in this ATP recharging process? Enter creatine phosphate (CP) and muscle glycogen.
You might feel invincible during those first ten to twelve seconds of maximum-intensity action thanks to CP. However, CP, like ATP, is also limited and quickly used up. Combine these limited stores of ATP and CP, and it becomes clear; that you’ve only got enough power for twelve to eighteen seconds of exercise. This is where the anaerobic energy system, or glycolysis, saves the day, ensuring a seamless flow of ATP and CP.
Let’s take a moment to appreciate muscle glycogen. The unsung hero of this energy generation process, it gets broken down in the anaerobic energy system to generate ATP. While you might not realize, that your muscle glycogen is significantly consumed during a workout. A simple sequence of ten bicep curls results in a 12 percent decrease in muscle glycogen. Add two more sets, and you’re looking at a 35 percent drop. Make it six in total, and you’ve used up 40 percent of your muscle glycogen. Now, that’s quite a feat!
Increased breathing rate
When you exercise, your respiratory system kicks into high gear to meet the body’s increased demand for oxygen. Your lung capacity expands as you take in more air per minute, and consequently, the frequency of your breaths escalates. Your breathing muscles, the diaphragm, and intercostals, also work harder to facilitate this increased airflow. This isn’t just about drawing in more oxygen though; it’s equally crucial for the removal of carbon dioxide – a byproduct of metabolism – that your body builds up during a training session. The elevated breathing rate helps to clear this waste product more swiftly from your system, keeping your body’s internal environment optimally balanced.
When you engage in weight-bearing activities, your body undergoes significant hormonal shifts. Anabolic hormones – testosterone, growth hormone, and IGF-1 for instance – experience a temporary spike, though they’re not considered key players in the exercise process. Simultaneously, your body releases more of the catabolic hormones epinephrine and norepinephrine. These two hormones drive the usage of muscle glycogen and fat as energy sources. Nonetheless, the real MVPs of the hormonal changes during exercise are insulin and cortisol. Their opposing activities greatly influence the extent of muscle damage and glycogen exhaustion during your workout. Without any nutritional aid, as you exercise, you’ll see a drop in your insulin levels as cortisol levels start to escalate.
Raised body temperature
When you engage in physical activity, your muscles demand more energy, and your body responds by increasing metabolic processes. Part of this response involves raising the body temperature. It’s similar to revving up a car engine, with heat being a by-product of burning fuel. Interestingly enough, your body, like an intelligent machine, has a cooling system to manage and regulate this increase in temperature – your sweat glands. They step up their function, releasing sweat, a liquid that evaporates on your skin, thereby cooling your body and maintaining a healthy, stable internal temperature. This ensures you don’t overheat while you get your moves on.
As your muscles work harder during exercise, their demand for energy and nutrients skyrockets, causing a surge in blood flow by up to 500 percent. With this supercharged circulation, your body can deliver fuel and oxygen at a quicker rate, while also efficiently eliminating metabolic by-products, like lactic acid and carbon dioxide.
Effect on the Protein Pool
When you engage in long-term physical exercise, your muscles end up losing protein. This is primarily due to an elevated need for branched-chain amino acids (BCAAs) as an energy source. When your muscles break down, they produce BCAAs. These BCAAs act as the building blocks for creating glutamine, which significantly diminishes your muscle’s glutamine reserve in the process. In your muscles, glutamine is the most prevalent amino acid and it’s crucial for fueling your immune system. However, during periods of intense and prolonged exercise, your glutamine reserves can be nearly emptied, which could potentially put your immune system at risk.
When you engage in physical activity, your mean arterial blood pressure (the average pressure in your arteries during one cardiac cycle) tends to increase. This situation mainly arises due to a spike in your systolic blood pressure (pressure when your heart pushes blood out), while your diastolic blood pressure (pressure when your heart is resting between beats) usually maintains near-rest values.
As your exercise intensity escalates, systolic blood pressure tends to increase in a straight line, peaking anywhere from 200 to 240 millimeters of mercury for those with normal blood pressure. When we talk about mean arterial pressure, we’re effectively referring to the product of your cardiac output and total peripheral resistance. Thus, the noted rise in mean arterial pressure during exercise occurs because of an elevated cardiac output overriding a simultaneous decrease in total peripheral resistance.
This augmentation in mean arterial pressure is not only a natural response but also a beneficial one. It results from the arterial baroreflex adjusting to a higher pressure level. Without such an adjustment, intense physical activity could cause severe arterial hypotension (low blood pressure). Nevertheless, individuals with high blood pressure can hit higher systolic blood pressure levels for equivalent work rates and might even see an increase in diastolic blood pressure, resulting in generally higher mean arterial pressure due to a lesser drop in total peripheral resistance.
In the initial couple of hours following your workout, your blood pressure might drop even below pre-exercise resting levels, a phenomenon known as post-exercise hypotension. The exact mechanisms triggering this response remain unclear. Nevertheless, these short-term variations in blood pressure post-exercise could play a significant part in the ability of physical activity to help regulate blood pressure in individuals with hypertension.
Resistance workouts can lead to a significant physiological impact – muscle damage. It’s tracked by exercise physiologists using specific biochemical signs. Components like 3-methylhistidine, creatine phosphokinase (CPK), and lactate dehydrogenase (LDH) are often used as these markers. For instance, the exclusive presence of 3-methyl-histidine in muscle contractile protein implies that there is muscle fiber damage when it is found in urine. Similarly, CPK and LDH, generally confined within the muscle fiber, are spotted in the blood when the muscle fiber membranes suffer damage.
The underlying reasons for muscle damage linked to exercise are varied and broadly divided into physical, hormonal, and biochemical categories. Initial damage is typically a result of physical strain on the muscle cell. Actions such as eccentric exercise, where muscle fibers extend while contracting, can cause considerable strain on the fibers, resulting in an overstretch and rupture of the contractile proteins, and consequently inflammation. However, some of this damage can be favorable, as it triggers the reformation of muscle cell fibers, leading eventually to improved strength and mass. William Kraemer, from the University of Connecticut, used the term ‘muscle tissue disruption’ to refer to such damage, emphasizing that the muscle tissue, despite the damage, can recover within a day and maintain its adaptive response to training.
Cortisol, a hormone, is the second causative factor for muscle damage, stimulating muscle protein breakage. The third origin of muscle damage is free radicals creation, which are highly reactive molecules that can impair muscle protein. These radicals can originate either in the mitochondria, capillaries, or certain cells related to the immune system. Regardless of their source, free radicals can devastate cell membranes and indirectly inactivate primary enzymes necessary for the immune system’s functionality.
Acute Inflammatory Response
Consider the acute inflammatory response as your body’s initial defense against tissue damage – whether it be from strenuous exercise, a mishap resulting in a sprained ankle, or a simple cut. In the event of an injury, specific cells, aptly named neutrophils, rush to the problem area to eliminate tissue debris. This undertaking leads to inflammation and swelling, which subsequently induces further harm to the muscle cell membranes. Interestingly, this acute inflammatory response doesn’t just stop on a dime after your workout – it’s a principal reason why you may not feel that familiar muscle soreness until a day or so later.
Ever wondered how exercise affects your immune system? Well, just like how our body reacts to a virus or injury, it similarly responds when we engage in resistance exercise. This response manifests as an elevated level of white blood cells, natural killer (NK) cells, and T cells – all pivotal in combating infections. Yet, things change when we push ourselves with prolonged and intense workout sessions. The immune system actually enters a sort of “low power mode”, with T cells and NK cells seeing a notable decrease. This downshift in our immune defense is directly proportional to the intensity and duration of the exercise. What’s more, this suppressed state can last for up to seventy-two hours after your workout, potentially making you more susceptible to infections.
It’s no secret that water plays an indispensable role in our body’s function. As the main component of blood, it’s absolutely crucial for maintaining blood volume, regulating body temperature, and relieving the heart’s strain. Never is this truer than during your exercise routine. We can’t stress enough – fluid replacement tops the nutrition list for endurance athletes. Why, you ask? Simply put, dehydration is their number one physiological nemesis while engaging in intense physical activities. Consider this: just a 2 percent body water reduction – equivalent to a mere 3.6 pounds for an athlete weighing 180 pounds – could compromise performance. And it’s not just in endurance sports. Even in football, basketball, and soccer, you’d frequently come across athletes losing more than 2 percent of their body weight in fluids.
Although resistance exercise might not result in such dramatic fluid losses as aerobic exercise, understand that dehydration can still creep in. According to Old Dominion University research, even a 1.5 percent body weight reduction due to dehydration can have an adverse effect on your strength performance. We all now grasp the significance of hydration and replenishment of carbohydrates during training. However, as we’ll explore in the next section, a typical sports drink – combining water with carbohydrates – is not enough to satisfy the complex nutrient needs of your hard-working muscles.
The table below summarizes the many physiological and metabolic changes that take place within the muscle and related systems during intense exercise.
|MUSCLE GLYCOGEN LEVELS
|ACUTE INFLAMMATORY RESPONSE
|BLOOD FLOW RO MUSCLES
In conclusion, the changes your body undergoes when you exercise extend far beyond what we can see or feel. From cardiovascular responses to metabolic shifts, these alterations have significant long-term effects on your overall health. So, the more you understand and appreciate these changes, the more you can optimize your workouts to meet your specific health goals.