If you're like most weekend warriors, your body is an accident waiting to happen. That's because the average guy is hamstrung with weaknesses that can lead to serious injuries. Multiply that risk by 10 if you play sports. Trouble is, your body is a lot like a woman: It doesn't always provide direct feedback. That's why I've created the MF Diagnostic Test®. It's a series of self-tests designed to evaluate the most common problem areas for guys. In just 10 minutes, you'll find out how performance-ready your body really is.

And in case you're disappointed, I've included all the tools you need to fix it yourself. That'll keep you playing at the top of your game, injury-free, all year long--whether you need a tuneup or a total-body overhaul.

HOW TO IMPROVE: CORE STABILITY
Your core muscles, the ones that support your abdomen, spine, hips, and pelvis, are critical in almost every sport. That's because they provide spinal stability, which allows you to generate more power--a combination of strength and speed--for quick changes of direction and faster body rotation, the key ingredients for long drives in golf and home-run swings in baseball and softball.

The Problem
The limiting factor for core strength is usually the transverse abdominis, a deep abdominal muscle. The typical reason: abdominal training built around crunches, whose limited range of motion--you lift only your head and shoulders off the floor--doesn't force you to activate the transverse abdominis.

Self-Test
Slow Sit-up
Lie on your back on the floor with your knees bent 90 degrees and your feet flat. Hold your arms straight at your sides with your palms down and keep them parallel with the floor through-out the entire move.
1. Your feet must remain flat on the floor during the entire move.
2. Slowly raise your upper body by rounding your spine. Take a full five seconds to sit all the way up.
3. Pause for one second, then take five seconds to lower your body back to the floor.

You pass if:
+ You can complete 10 full reps without the use of momentum. (No cheating.)
You fail if:
- You're not able to do at least 10 reps. The problem is that your abs are essentially "locking up" after the first 30 degrees of the range of motion--the highest point you lift your body during a crunch.

The Fix
You need to train with exercises that work your transverse abdominis, two days a week at the beginning of your workout. That prioritizes the muscle and allows you to work it harder because it's fresh. Follow the directions here for the "Plank" and "Slow Sit-up," performing the moves in that order.

HOW TO IMPROVE: SHOULDER STABILITY
The stability of your shoulders is critical in preventing repetitive-stress injuries that occur in sports--for instance, when you're throwing a baseball or hitting a forehand in tennis. A weak network of muscles that stabilize your shoulders can lead to joint, rotator-cuff, and nerve damage.

The Problem
Poor shoulder stability can be caused by a lack of development of the muscles around the shoulder, or an overdevelopment of muscles that oppose them. So guys who lift weights regularly are as much at risk as guys who don't work out at all.

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Self-Test
Posture
Your posture is a good indicator of shoulder stability. Stand sideways in front of a mirror in a relaxed state--the way you are when no one is watching you. Then look at your shoulder position.

You pass if:
+ Your shoulders line up directly beneath your ears.
You fail if:
- Your shoulders are pulled forward to the point where it looks like you're trying to hide your chest.
- Your hands hang in front of your thighs--so it looks like you're approaching a urinal--instead of next to them.

The Fix
Step 1: Concentrate on exercises that force you to retract, or squeeze, your shoulder blades together--for instance, seated rows, bent-over rows, and rear lateral raises. (For the seated and bent-over rows, use a wide grip with your elbows out, so your upper arms stay perpendicular to your body.) Do two sets of these exercises for every set of chest (dips and bench presses) and lat (pull-ups and pull-downs) exercises you perform.

Step 2: Stretch your internal rotators, the muscles you work when you do bench presses and lats. See "Dowel Over" here for an ideal stretch.

Step 3: Work your external rotators with this move, called the "Scarecrow." Do two sets of 10-12 repetitions, 2-3 times a week.

HOW TO IMPROVE: FLEXIBILITY
Good flexibility is crucial in any sport that forces you into an outstretched position. It provides an increased mechanical advantage and a greater range of motion.

The Problem
Most guys have tight hip flexors--the muscles that allow you to lift your upper leg--and a lack of shoulder flexibility. Both lead to injuries and poor performance.

Self-Test
Overhead Squat
1. Hold an unloaded barbell (a broomstick works just as well) with a twice-shoulder-width overhand grip. Press the bar over your head so your arms are fully extended (locked) above your head and pinch your shoulder blades together. The bar should be directly over your head. Set your feet shoulder-width apart, knees slightly bent, back straight, and eyes focused straight ahead. Keep your back naturally arched throughout the entire lift.
2. Without allowing the bar to move forward, slowly lower your body as far as you can, keeping your torso as upright as possible. Pause momentarily, then repeat 1-2 times.

You pass if:
+ Your heels stay flat on the floor.
+ Your butt nearly touches your heel at your lowest point.
+ The barbell stays directly over your head.
You fail if:
- Your heels come off the floor at any time, indicating poor hip-flexor flexibility.
- The bar moves forward as you descend, revealing poor shoulder flexibility.
- Both your heels rise and the bar moves forward--a combination of both poor hip-flexor and shoulder-girdle flexibility.

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The Fix
Stretch. Use the "Three-Point Stretch" here if you have tight hip flexors, and the "Dowel Over" here if you have tight shoulders. (You may need to do both based on your test results.)

HOW TO IMPROVE: MUSCULAR BALANCE
Muscular balance is extremely important in running sports--for instance, basketball and soccer--in order to reduce knee strain, improve mobility, and prevent muscle pulls. It doesn't mean that all muscles are equally strong, but that they're as strong as they're supposed to be relative to other muscles.

The Problem
When one muscle or muscle group is relatively weaker than another, it can be overpowered by the stronger muscle--causing pulls and tears. In fact, research shows that strength imbalances between the quads and hamstrings are the most important factor in recurring hamstring injuries.

Self-Test
Single-Leg Squat and Reach
How to do it: Set a dumbbell at arm's reach on the floor in front of you. Bend one leg 90 degrees and hold it behind you. Simultaneously squat down and reach forward for the object with both hands. At your lowest point, your thighs should be at or below parallel. Pause and stand up.

You pass if:
+ You touched the dumbbell without allowing your heels to rise or your leg or hip to pinch inward.
You fail if:
- You couldn't keep your heels down. That's a sign of weak hamstrings and tight hip flexors (see "Flexibility").
- You kept your heels down but your knee pinched inward. If your same-side also rotated in, it's likely that you have tight hip adductors--the inner-thigh muscles that pull your leg sideways toward your body. If your hip didn't rotate in, you have a weak vastus medialis, the quadriceps muscle on the inside of your thigh.

The Fix
Weak hamstrings: Do four sets of hamstring and hip-dominant exercises--regular deadlifts and Romanian deadlifts--for every one set of a quadriceps-dominant exercise--such as front squats or lunges.
Tight hip adductors: Use the "butterfly" to stretch your groin. Sit on the floor and place the soles of your feet together and close to your body. Place your elbows on the insides of your lower legs. Then press down with your elbows for 15 seconds. Rest for 30 seconds and repeat two times.
Weak vastus medialis: Do 2-3 sets of 6-8 reps twice a week of Bulgarian split squats (found here) with your front-foot toe turned slightly out. Rest 60-90 seconds between