It may be five o’clock somewhere, but according to some fitness experts, happy hour could be sabotaging your fitness goals.Of course we’re not talking about an occasional glass of red wine (hello, heart health and brain power), but routinely downing even one or two cocktails each night can hinder your physical performance.“Studies have shown the lingering effects of alcohol can result in decreased strength and power outputs, decreased ability to perform aerobic exercise and decreased motor skills,” says Jessica Matthews, exercise physiologist and certified personal trainer with the American Council on Exercise (ACE). Those effects can last up to 72 hours after girls’ night out, according to Matthews.MORE: The Best Way to Relieve Muscle SorenessHere are five ways that too much booze can be a fitness buzz-kill:Decreased muscle mass. Consuming alcohol reduces blood flow to the muscles, which in turn, causes weakness and deterioration. In fact, one study in rats found that continuous high-dose consumption of alcohol after 14 weeks resulted in the deterioration of lean muscle mass and skeletal muscle of the gastrocnemius (your calf muscle) by 22 percent and the psoas (muscle than runs from your spine to your hip and femur) by 20 percent. Not only that, the researchers also found that the heart weighed 10 percent less—meaning, too much heavy drinking for prolonged periods can adversely affect heart function, which can put people who have arrhythmias at a higher risk of mortality.Lowered physical performance. You know those faster times you’re trying to log during your morning run? Alcohol is not helping. In fact, it can decrease your motor skills the next day, including reaction time, balance, hand-eye coordination and endurance. Know what else that booze does? It acts as a diuretic and depletes your body of valuable fluids and electrolytes, which can also hamper your performance. So does this mean we should go on the wagon when we’re training for a marathon or other endurance race? That depends, says Matthews. “A general recommendation when gearing up for a big event is to limit alcohol during training and avoid it during the days right beforehand,” she says.MORE: Would You Run in Minimalist Shoes?Disrupted muscle repair during sleep. That nightcap may help you fall asleep, but it won’t help you feel more rested the next day. That’s because alcohol can actually disrupt your slumber during the middle of the night, causing you to wake up more often. This, in turn, robs our bodies of precious shut-eye needed to regenerate tissue and build muscle and bone. Less of this quality rest equals more muscle fatigue for the next day’s workout. “Deep sleep is really important for someone in training or preparing for an endurance event,” says Matthews. “It’s when our bodies repair themselves, and it helps prevent injuries.”Impaired nutrition for recovery. Not only are those martinis void of any nutrition, but they can also inhibit key nutrients from being absorbed by your body. That’s because alcohol decreases the secretion of digestive enzymes from the pancreas, which breaks food down into usable nutrients. It also adversely affects blood glucose levels and damages the cells lining of the stomach and intestines. As if that’s not bad enough, even if nutrients are digested and absorbed, alcohol can prevent them from being fully utilized by altering their transport, storage and excretion. As a result, overall energy and functioning are compromised—clearly something that is not welcomed in the midst of that 10-mile run or power yoga class.Expanded waistline. Those cocktails may go down all too easily, but the calories in them add up just as quickly. Take, for example, a standard 5-ounce glass of wine, which contains about 125 calories, or a 12-ounce beer, which has 150 calories a pop. Empty calories aside, those drinks could sabotage one of the very things you’re trying to eliminate with exercise: belly fat. “Alcohol will not help your body fat to muscle mass ratio,” says Matthews. “It actually increases fat composition.” And if you eat high-fat foods while drinking (munchies, anyone?), the fat from these foods also gets stored as fat. Talk about a double recipe for waistline woes.MORE: Strength-Training At Home—No Equipment RequiredThe bottom line? You don’t necessarily have to give up happy hour—just don’t go overboard on booze, especially if you need to be at peak performance levels the next day. “It is important that we look at what our alcohol consumption is like,” adds Matthews. “We may be consuming more calories than we think, and they are often unnecessary calories for our health and fitness goals.” Guess that means we should skip bar hopping after that next race.