The bones that make up the framework within your body are comprised of living tissue.  Bones react to resistances placed on them by growing and strengthening much the same way that muscles do.  This is because bones are made of dynamic living tissue  with  cells called osteoblasts and osteoclasts that build up and tear down bone, respectively.   As we age the amount of osteoblasts within bone tissue decrease which could potentially cause osteoporosis.  Weight training helps to lessen the risk of osteoporosis by ameliorating the resorption of osteoblasts.   In other words, exercise that involves lifting weights helps to slow or prevent bone loss.  
     Weight-bearing exercise can also improve muscle and bone strength which helps to reduce the risk of falls and the fractures that typically occur as a result.  Exercises performed in the standing position (e.g., shoulder presses, bicep curls, overhead tricep extensions) are ideal in developing good overall muscle and bone strength.   The more the load placed on your bones, the more the effect of bone stimulation and growth.  
     Excellent weight-bearing exercises include running, jump roping, stair climbing, dancing, basketball, volleyball, tennis, skiing, skating, soccer, hiking, gymnastics, and of course weight training.   These types of exercises tend to have the most effect on maintaining or increasing bone mineral density because they involve jumping or hopping.   Short bouts of vigorous weight-bearing exercises tend to be more effective for bone strengthening than long-duration sessions.  For example, a short sprint is better at stimulating bone growth than a long jog.  Satisfactory weight-bearing exercises include walking and using the elliptical machine.  Non-impact exercises such as swimming, biking, yoga, and tai chi have very little effect in terms of bone stimulation and therefore are least beneficial for bone growth. 

BOTTOM LINE:   To maintain or increase bone strength, perform short bouts (i.e., 5  to 10 minutes) of weight-bearing exercise (e.g., jump roping, sprints) most days of the week.  If you are older, perform walking most days of the week.  Even the small gains in bone strength from walking can lessen the risk of fracture.       

     Many people who exercise may still incur injuries or lack stamina even though they are active.  For instance, a runner may pull his or her iliotibial band (ITB) when running because of weakened core muscles or a weight lifter may lack the endurance to run up a series of steps without feeling quite winded.  Avid bicyclists may lose bone density due to a lack of impact and resistance on the bone tissue.  How can those who perform certain exercises (e.g., running, swimming, biking, weight lifting, etc.) reduce their risk of injury while increasing their overall performance?   The solution is to perform well-rounded exercise programs which encompass resistance training, cardiovascular training as well as flexibility.  
     A comprehensive training program is necessary to enable your body to adapt and withstand multiple stimuli in order for it to perform at its peak level.  Thus, runners should perform weight training exercises (i.e., overhead dumbbell presses, squats, lunges, leg extensions, etc.) to strengthen upper body and core muscles and to reduce injury risk.  Weight lifters should run, bike and/or swim to increase their endurance and cardiorespiratory capacity.  Cyclists should perform weightlifting exercises to maintain bone mass.  All active people should perform stretching exercises to increase joint, muscle and tendon flexibility.  Yoga can benefit any active person.  No one particular exercise should predominate your regime.  Instead, complimentary exercises are necessary in order to ensure moderation and balance.          
     
      

    Those cast-iron or steel balls which look like small cannonballs with a thick metal looped handle on top can be useful for working on joint flexibility as well as functional-type movements (e.g., deadlifts).  One of the key benefits of working with kettlebells is the possibility to work the entire body for a powerful and efficient workout.  Other benefits include increasing strength (including core strength), power, endurance, flexibility, mobility and cardiovascular capacity.  You can achieve a strenuous workout in less than thirty minutes.  
     Standard kettlebell exercises should incorporate four basic movements:  the press, the pull, the squat, and the deadlift.  Examples include shoulder press, bent-over row, sumo squat, and Romanian deadlift.  Swinging the kettlebell (e.g., single- or double-arm swings) is another example of a pulling movement that makes the kettlebell uniquely beneficial for training purposes.  The end result is the incorporation of more muscle groups, including your core muscles (i.e., abs, lower back, glutes, and hamstrings), being worked.  Studies have shown that using kettlebells can improve coordination and balance in addition to increased muscle strength and endurance.  By swinging one or two kettlebells, you will be able to target your hips, back, glutes, shoulders, and legs.  An additional benefit is increasing grip strength.
     If you minimize the rest periods between sets, you can also get a cardiovascular workout with kettlebells.  Be sure to start out with lighter weights in order to get a feel for the movements and an understanding of how to properly control the weights.  The risk of injury (i.e., torn muscle, tendon, ligament) increases greatly if the kettlebells are too heavy, are swung incorrectly (i.e., away from the sagittal plane) or are swung too strenuously.  Focus on using good form by improving your technique.  Sloppiness is a recipe for injury.  
     The benefits of kettlebell training include:

• Efficient, quick workout incorporating many fitness components (i.e., strength, endurance, power, flexibility, cardiovascular)
• Requires minimal space
• Relatively inexpensive
• Excellent way to condition your body for sports due to functional movements
• Ideal tool for gaining core strength

     The drawbacks of kettlebell training include:

• Limited weight capacity
• Fixed weights

Bottom line:  Kettlebells can be useful for anybody but should be utilized as a complement to your workout program rather than your exclusive workout program.  Kettlebells should be thought of as a tool in conjunction with dumbbells, barbells, machines, and cables as another means to enable yourself to gain strength, balance, coordination, endurance, and good cardiovascular conditioning.  

    The human body tends to lose about 1 to 2 percent muscle mass after age 50 as a result of the normal aging process.  This means that most people lose muscle and gain fat as they get older.  Along with less muscle comes all of the assorted health maladies that go along with it such as loss of strength, increased frailty, and the development of chronic diseases (e.g., obesity, diabetes, hypertension, etc.).   But this dire situation is not inevitable!  The solution:  you guessed it...get off the couch and spend time exercising.  
    The old saying of "use it or lose it" is quite applicable here.  Resistance training is the answer when it comes to maintaining (if not gaining) muscle mass and strength.  A recent study published in Journal of Strength and Conditioning Research (2011, volume 25[1], 1-9) has indicated that age-related sarcopenia (muscle loss) is not inevitable as long as resistance training occurs.  The resistance training promotes the release of insulin-like growth factor 1 (IGF-1), a hormone associated with muscle growth.  If you have been sedentary for a while, the recommendation is to begin a gradual training program of weight lifting.  You will discover dramatic improvements in muscle mass and strength gain.   In addition, you'll feel more energized, be able to sleep much better at night, and have a more upbeat attitude!
    Consider increasing your protein intake (e.g., whey and casein protein post-exercise) to accommodate the increased muscle mass.   But don't go overboard on increasing your protein intake as too much may affect kidney function and cause kidney stone formation.  Good sources of protein include chicken, fish, milk, eggs, yogurt, beans, and  peanuts.   
    The Institute of Medicine (IOM) has recently recommended that adults over age 50 should get 1200 mg and 800 IUs of calcium and vitamin D, respectively.  These nutrients help maintain bone density and muscle health.  Vitamin D has been found to have antioxidant properties and may reduce the risk of cancer, heart disease, autoimmune diseases, and diabetes.

    Correct posture is absolutely essential when executing resistance exercises such as overhead presses, bench presses, squats, etc.  Improper form when lifting will undoubtedly detract from an efficient workout that maximally targets the intended muscles.  The key to safely and effectively engage your muscles is to assume stability in your body when lifting.  In order to do this, you need to practice and adhere to the following fundamentals of posture no matter your body position in space (e.g., standing, sitting, supine):

• Eyes focused on a reference point in front of your head
• Shoulder blades squeezed
• Chest out
• Abs tucked in
• Lower back arched so that your butt is to the rear (anterior pelvic tilt) 

      Note:  Most clients have trouble assuming the anterior pelvic tilt posture but it is absolutely essential in order to effectively target muscles such as the hamstrings or gluteals when performing an exercise like the deadlift.  To practice, try lying in a supine position (i.e., face up) on a floor and arch and flatten your lower back repetitively for up to 25 reps for 3 sets daily.  Be sure to feel your lumbar contact and lift off the floor as you flatten and arch your lower back.  Next, practice performing the same maneuver of arching and flattening your lower back while standing sideways to a mirror.  Be sure to observe the action while looking at your profile to ensure it is done properly.  

• Knees slightly bent (applies primarily to standing posture)
• Feet at least shoulder width apart   
  
• Bench press:  feet should be pressing into the floor at all times!

    In addition, be sure to always inhale when performing a pulling action and exhale when executing a pushing action.  For example, when performing a bench press, inhale as the weight is lowered to the chest and exhale as you press the weight upward.  Another example, when executing a squat, inhale as you bend your knees and exhale when straightening your knees as you press upward.  
    By following the aforementioned recommendations you will find you will be much more successful in achieving your fitness goals.  Remember to always work smarter, not harder!