Fitness goals in the military are endurance, strength, flexibility and agility. General conditioning to maintain basic levels of all four most frequently includes stretching, running and various calisthenics. Physical fitness tests to judge the efficacy of training include a timed run, push-ups and sit-ups. These are designed to measure endurance, core strength and upper body strength. Troops often run each day and do strength exercises on alternating days as part of their calisthenics regimen.
Combat conditioning is more diverse and includes interval runs, long-distance runs, rucksack marches, obstacle courses, weight training, swimming and strenuous combat drills. Frequency is matched to intensity -- when an exercise is particularly intense, greater recovery time is allowed before stressing the same physical systems. Overall intensity is gradually increased to improve general conditioning over training cycles designed to "peak," in much the same way athletes push toward training peaks. Then a less intense cycle is implemented to allow the body to rest and recover.
The military is fond of acronyms, and the acronym that includes "frequency" is FITT -- which stands for frequency, intensity, time and type. Frequency refers to how often a particular exercise is performed. Intensity refers to how closely the troop approaches muscular or aerobic failure while exercising. Time is how long the person exercises. Type is the specific exercise itself. Increasing intensity or time generally corresponds to decreasing frequency, again, because greater time is required to allow muscular and metabolic recovery.
Frequency of exercises, workouts and regimens are often calibrated to particular events. A unit that is approaching a semi-annual fitness test will attempt to "peak" just as the test is administered. Some troops train to participate in military competitions, like the annual Best Ranger competition, and will undergo an increasingly strenuous combat conditioning regimen that peaks on the competition dates. Some troops will prepare for difficult selection, assessment and training courses, like Basic Underwater Demolition Training or the Special Forces Assessment and Selection, and will determine the frequency of training based on peaking when they arrive.