Whilst exercise while young positively affects peak bone mass, exercise during adulthood can maintain bone mass and can potentially prevent women from osteoporosis.

In particular, impact exercise that induces high strains at high rates in the bone has been found to promote bone strength.

Research published in November’s BMC Musculoskeletal Disorders, studied how bone changes over time during a 12 month course of exercise.

The aim was to evaluate the association between exercise intensity at 3, 6 and 12 month intervals and changes  in the Bone Mineral Density (BMD) of the femur (thigh bone), during high-impact exercise in premenopausal women.

• The subjects were 35 healthy women (age 35-40 years, average BMI of 25.5). Before the study began they were not participating in impact-type exercises or long-distance running more than three times a week.
• Accelerometers, (portable, cheap, light-weight machines, worn on the waist) were used to continuously measure daily physical activity.
• The subjects were supervised during a 60-minute training workout, consisting of a warm-up period, high-impact training and a cool-down period. The progressive high-impact period included versatile movements, such as step aerobic patterns, stamping, jumping, and running, three times a week for 12 months.
• The programs were modified bimonthly to become progressively more demanding by including higher jumps and drops.
• The participants were also given a home program (10 min daily), which consisted of patterns of exercise similar to those in the supervised sessions.
• The BMD of the femur, and the trochanters (the projections from the femur where the hip and thigh muscles attach), were measured using x-ray absorptiometry and activity data was correlated with changes in bone density.

The researchers from Finland found that the average daily number of high impacts during six months of training was significantly associated with 12-month positive BMD changes at the femoral neck and trochanter area.

These results agreed with many previous studies, in which only five to six months of high-impact exercise were needed to increase BMD in the femoral neck and trochanter and the greatest changes were seen on this time period, than during 12 or 18month interventions.

Lead author Riikka Ahola, suggests these results provide new information for designing optimal and feasible training programs that can prevent bone loss in premenopausal women

Because bone cells adapt to regular loading, one important feature that the researchers recommend is for an exercise program to be progressive. ‘A progressive exercise program sustains overload and the bone adaptation process. ‘

‘Loads should be increased with time to produce a sufficient stimulus. An exercise program that maintains the same loading for many years would stimulate bone formation only during the first months of training.’

Now a study from Victoria University, Australia has set out to examine the effects of creatine supplementation on the recovery of muscle proteins and force after eccentrically induced muscle damage.

Eccentric contractions are used to decelerate a body part or object, such as when you lower an object gently rather than just letting it drop. Damage caused by eccentric exercise is known to lead to a reduction in muscle force, increased muscle soreness and impaired muscle function.

During the study 14 untrained male subjects consumed either creatine and carbohydrate (Cr-CHO) or only carbohydrate (CHO) for five days before a resistance exercise session. The Cr-CHO group consumed a daily supplement of creatine (0.3 g per kg of body weight) and glucose (1.2 g per kg of body weight); The CHO group took glucose only.

The workout consisted of three exercises: 1) leg press; 2) leg extension and 3) leg curl. For each exercise their concentric 1-RM (repetition maximum) was determined. This is the maximum weight that a single repetition could be performed of a muscle shortening exercise, such as a curl. The resistance exercise session involved 4 sets of 10 eccentric only repetitions at 120% of their maximum concentric 1-RM, lowering the weight by themselves through the entire range of motion over 4 seconds.

Every day for 14 days whilst recovering from the exercises the Cr-CHO group took 0.1 g per kg of body weight of creatine and 0.4 g per kg of body weight of glucose, again the CHO group took glucose only.

The study found isokinetic strength, (where the muscle contracts and shortens at a constant speed), was 10% greater during recovery in the Cr-CHO group compared to the placebo group of CHO alone.

During isometric knee extension (where the muscle length stays the same even though it contracts), it was also found that the creatine supplemented groups had significantly greater strength (21%) during recovery from exercise induced muscle damage.

The paper’s author Matthew Cooke concluded that there is a significant improvement in the rate of recovery of knee extensor muscle function after creatine supplementation following injury. Blood creatine kinase (CK) activity was significantly lower by an average of 84% after 48hrs recovery in the creatine supplement group and peaked at 96hrs. Levels had returned to baseline by 7 days in both groups.

Blood CK levels can be raised from damage of the muscle tissue as a result of intense training, but also due to a number of other factors:

• Age – levels decline slightly with age
• Gender – at rest CK levels are lower in females than males.
• Race – black men usually have higher values than Caucasians.
• Climate – standard exercise in cold weather induces higher blood CK levels than the same exercise in warm weather.
• Muscle mass and physical activity – at rest CK levels in athletes are higher than in sedentary subjects, this may be due to persistent training which keeps the CK levels elevated.

However, if trained and untrained subjects do the same exercise the CK levels will still be lower in athletes than the untrained. This study published in the Journal of International Society Sports Nutrition did involve untrained subjects which may have resulted in the very high CK levels initially following the exercise.

The major finding of this study was the significantly higher muscle strength after creatine supplementation during recovery from a muscle damaging exercise session; this may be due in part to a faster muscle growth during the recovery period. The study did not report if the subjects gained weight before or after the exercise session as is often reported with taking creatine supplements.

It is not known how creatine may act to increase recovery although it may be that the reduced leakage of creatine kinase from the muscle is an indication of less initial damage to the muscle.  There appears to be a large number of studies supporting the use of creatine supplements whether to increase muscle mass or aiding recovery to allow further training. Maybe now scientists need to discover just how creatine supplements work so they can advise athletes on the ideal duration and concentration to use to aid recovery, optimise weight gain and avoid side effects.