One of the factors that determine performance in sports is the physical work capacity. To improve physical work
capacity required training programs that meet the aerobic-anaerobic metabolic elements that proportion depends on
the metabolic pathways of energy systems. Means to determine the metabolic pathways of energy systems is the
intensity of exercise in accordance with the predominant energy system (ATP-PC, ATP-PC-LA, LA-O2). The intensity of
exercise that most effectively improves the physical work capacity is still unknown. To measure the physical work
capacity is used indicator of the anaerobic threshold. The purpose of this study was to prove the effects of various kinds
of exercise intensity on the anaerobic threshold. This experimental study using the design of randomized control group
pretest-posttest design on 100 respondent students boarding school al-Mukmin Ngruki, Solo, which is divided into four
groups, namely the intensity of the intensive group (ATP-PC), extensive intensity group (ATP-PC-LA), moderateintensity
group (LA-O2) and the control group. From the results of paired t-test found that the three types of exercise
intensity can increase anaerobic threshold significantly (p <0.01). Increased anaerobic threshold is marked by a shift
value of lactate 4 mmol/L to a heavier workload, which means an increase in physical work capacity. Anacova test
results, showed a highly significant difference between the intensity of the intensive group with extensive intensity group
(p < 0.01), there are significant differences between groups of intensity intensive with moderate intensity group (p
0.05). Exercise
load achieved by an extensive group of the most effective intensity increase anaerobic threshold, then follow the
moderate intensity exercise group. Intensity exercise group intensive increase anaerobic threshold, but less effective
