Welcome to module three, dedicated to aspects of fitness and performance. This module will exam training adaptations associated with both endurance and strength training. Nutritional considerations for both endurance and strength activities. The causes of muscle fatigue and soreness, and conclude by discussing the various performance enhancing drugs. In today's video and the next, I will discuss the training guidelines put forth by the American College of Sports Medicine. Designed principally for adults, whose goal is to improve their cardiovascular fitness as well as muscular strength and endurance. I will also address the underlying mechanisms responsible for these training adaptations. Today's video will focus on cardiovascular or endurance training. Please be aware that the guidelines put forth today are meant for the general population who wish to improve their cardiovascular fitness. These guidelines are not designed for elite endurance athletes, whose training regimen is more involved and intense. I will conclude this video by examining the consequence of a prolonged period of inactivity or detraining. First, I want to remind you of the overload principle that was explained in our very first video. As stated, if you habitually overload a system, it will respond and adapt. Basically, when you engage in physical activity, the stress imposed by a single bout of exercise elicits and immediate or an acute response by the body. However, if you exercise three to five times a week for several months, the body will make long-term or chronic adaptations to the repeated stress of regular exercise. The four major variables to be considered in optimizing adaptations to any training program include the exercise training frequency, intensity, duration and mode of activity. Ideally, the frequency of exercise sessions should be three to five days per week of moderate to vigorous exercise. If you can only exercise three times a week, try to avoid being a weekend warrior who only exercises Friday, Saturday, Sunday. It would be best to have alternating days in between workouts. Also, if you can only exercise three days a week as opposed to five, it will be better to exercise at a more vigorous intensity if tolerated. The exercise intensity is a key factor in eliciting optimal training adaptations. While the majority of people do not know, nor have access to equipment to measure their VO2 max, intensity training guidelines are typically based on a percentage of one's maximum heart rate. Heart rate monitors are readily available for this purpose. It is recommended that the exercise intensity range from 50 to 85% of your heart rate reserve. Your heart rate reserve can easily be determined by subtracting your resting heart rate from your maximal heart rate. In the example provided here, an individual with a maximum heart rate of 210 beats per minute and a resting heart rate of 70 beats per minute will have a heart rate reserve of 140 beats per minute. This is the range your heart rate can fluctuate above resting levels. In my example, if someone wished to have a training target heart rate zone between 60 and 75% of their heart rate reserve, that would translate into a range of 154 to 175 beats per minute. For individuals just starting an exercise program or have been inactive for a period of time, it is best to start at the lower suggested heart rate ranges. As you become more fit, you can increase your target heart rate to higher ranges. Here is a typical heart rate chart you may have seen posted at your local health club or gym. In this example, a training sensitive zone between 70 and 90% of age predicted maximum heart rate is highlighted. While maximum heart rate does decline with age, it varies greatly among individuals. Thus, it is best to accurately determine exactly what yours is. The duration of the exercise session also has a range that is dependent upon both the exercise intensity, as well as your current fitness level. A minimum of 20 minutes per session is recommended. Again, as you become more fit, you can increase the duration accordingly. The final variable is the type or mode of activity. The exercise session should involve large muscle groups that can be maintained continuously over time. Thus, during the course of training, both training intensity and duration can be progressively increased over time as you become more fit. Care should be taken to incorporate programmed recovery days, as well as to alter hard training weeks with those of lesser intensity to avoid injury and overtraining. The term muscle plasticity refers to the capacity for adaptive change. It is characterized by altered gene expression following a repeated stimulus such as occurs with endurance training. It applies to all types of muscle proteins, including structural, contractile and regulatory protein. In this example, a single bout of exercise activates a number of primary signals that when chronically activated over weeks will initiate the formation of new mitochondrial proteins. Thereby, increasing their size and number in the trained muscles. As discussed in previous videos, this increase in mitochondrial oxidative capacity associated with endurance training will result in a greater ability to utilize fats for fuel. Thereby, sparing carbohydrate stores. Finally, as discussed in the cardiovascular system videos, endurance training will also lead to an increase in maximal oxygen consumption. All components of the fifth equation both maximal cardiac output and maximal arteriovenous oxygen difference respond, and adapt via the overload principle to the training stimulus. Now, let's look at what happens when training is stopped. This may occur due to illness, injury or lack of motivation. This relates to the principle of reversibility also discussed in our very first video. As a reminder, this principle states that whereas overloading will result in training adaptations, inactivity or detraining will result in a return to baseline. Once the chronic stimulus of regular training has been removed, any adaptations made during training will eventually return to baseline or pre-training levels. Shown here is a classic example of the reversibility principle. Previously, sedentary individuals were endurance trained for eight weeks. The standard markers for endurance training adaptations were measured. This include markers of mitochondrial oxidative capacity in the vastus lateralis muscle and maximal oxygen uptake. As can be seen as per the overload principle, eight weeks of endurance training resulted in increases in all of these variables. However, when these same individuals stopped all training for a period of six weeks, notice mitochondrial oxidative capacity rapidly returned to pre-training values while maximum oxygen uptake had a more gradual decline. Thus, once the stimulus of regular exercise training has been removed, you will eventually lose any previous training adaptations. Just as rapidly as mitochondrial numbers can increase in previously untrained individuals who initiate an exercise training program, detraining will result in a rapid decline to pre-training values. For this reason, some elite athletes resort to various techniques such as electrical stimulation of muscles to prevent this decline when they are unable to train due to illness or injury. When looking at the timeline for the detraining responses, not all variables decline at the same rate. While mitochondria oxydated capacity decreases at a rapid rate, the decreases in the maximal stroke volume is slower to develop. Both contribute to the decline in maximal oxygen consumption associated with the prolong period of inactivity. In summary, adherence to the proper training frequency, intensity and duration are essential to optimize training adaptations. Muscle plasticity and altered gene expression following an exercise stimulus are the hallmark of training adaptations. When the stimulus is removed as in detraining, adaptations revert back to baseline with varying timelines.