Fascinating Facts about the Physical Affects of Caffeine in Coffee (source: Wikipedia):

Caffeine is a proven ergogenic aid in humans.[45] Caffeine improves athletic performance in aerobic (especially endurance sports) and anaerobic conditions.[45] Moderate doses of caffeine (around 5 mg/kg[45]) can improve sprint performance,[46] cycling and running time trial performance,[45] endurance (i.e., it delays the onset of muscle fatigue and central fatigue),[45][47][48] and cycling power output.[45] Caffeine increases basal metabolic rate in adults.[49][50][51] Caffeine ingestion prior to aerobic exercise increases fat oxidation, particularly in persons with low physical fitness.[52]

Caffeine improves muscular strength and power,[53] and may enhance muscular endurance.[54] Caffeine also enhances performance on anaerobic tests.[55] Caffeine consumption before constant load exercise is associated with reduced perceived exertion. While this effect is not present during exercise-to-exhaustion exercise, performance is significantly enhanced. This is congruent with caffeine reducing perceived exertion, because exercise-to-exhaustion should end at the same point of fatigue.[56] Caffeine also improves power output and reduces time to completion in aerobic time trials,[57] an effect positively (but not exclusively) associated with longer duration exercise.[58]