Olga M. Rutherford

Hip bone mineral density is improved by high-impact aerobic exercise in postmenopausal women and men over 50 years

Fifteen men and women (six men) between the ages of 50 and 73 years were recruited to begin keep-fit classes. They were matched for sex, age, menopausal status and mass to 15 non-exercising controls. The keepfit classes were two to three times a week and included high-impact exercise, including step and jumping exercises specifically to load the proximal femur and spine. Proximal femur, lumbar spine and total body bone mineral density (BMD) were measured at 0 and 12 months. Urinary pyridinoline (Pyr) and deoxypyridinoline (dPyr) crosslinks were measured every 6 months to assess bone resorption. Quadriceps isometric strength was measured every 6 months. BMD increased non-significantly at the femoral neck [1.57 (0.8%] and Wards triangle [1.97 (1.4%], and significantly at the greater trochanter 2.21 (0.9)% (P=0.02) in the exercise group. Femoral neck BMD decreased by −1.9(0.8)% (P=0.049) in the control group, which was significantly different from the change in the exercise group (P=0.009). BMD did not change at the Wards triangle or trochanter in the controls. Lumbar spine BMD did not change in either group. Total body BMD did not change in the exercise group, but decreased by −0.79 (0.3)% (P=0.02) in the controls. Follwing 6 months of the exercise classes, Pyr and dPyr crosslinks were significantly reduced [−19.0 (7.2)%;P=0.0019 and −20.0 (7.7)%;P=0.021 respectively]. There was no significant change in crosslinks after 1 year, and no change at any time in the controls. Quadriceps strength changed by 5.4 (3.7)% in the exercise group and by −6.9 (2.5)% (P=0.01) in the control group after 12 months, being significant between groups (P=0.008). This study suggests that high-impact, aerobic exercise in postmenopausal women and men over 50 years old is feasible and effective at maintaining muscle strength and increasing proximal femur BMD but not spine or total body BMD.

Do oarsmen have asymmetries in the strength of their back and leg muscles

The aim of this study was to establish whether asymmetry of the strength of the leg and trunk musculature is more prominent in rowers than in controls. Nineteen oarsmen and 20 male controls matched for age, height and body mass performed a series of isokinetic and isometric strength tests on an isokinetic dynamometer. These strength tests focused on the trunk and leg muscles. Comparisons of strength were made between and within groups for right and left symmetry patterns, hamstring :quadriceps ratios, and trunk flexor and extensor ratios. The results revealed no left and right asymmetries in either the knee extensor or flexor strength parameters (including both isometric and isokinetic measures). Knee extensor strength was significantly greater in the rowing population, but knee flexor strength was similar between the two groups. No difference was seen between the groups for the hamstring:quadriceps strength ratio. In the rowing population, stroke side had no influence on leg strength. No differences were observed in the isometric strength of the trunk flexors and extensors between groups, although EMG activity was significantly higher in the rowing population. Patterns of asymmetry of muscle activity were observed between the left and right erector spinae muscles during extension, which was significantly related to rowing side ( P < 0.01). These observations could be related to the high incidence of low back pain in oarsmen.

The human force:velocity relationship; activity in the knee flexor and extensor muscles before and after eccentric practice.

Abstract The human voluntary force:velocity relationship frequently fails to demonstrate the expected high eccentric forces. Possible explanations include unique activation strategies which might be affected by neural learning mechanisms. We investigated the effect of practicing eccentric contractions on (1) the force: velocity relationship of the human knee extensor muscles and (2) the extent of agonist and antagonist muscle activity. Eight healthy adults [seven women, group mean age 31 (SEM 5) years ± ] practised twice a week for 4 weeks using their non-dominant legs. Each session comprised three isokinetic concentric and eccentric maximal voluntary contractions (MVC) at randomised angular velocities of 100, 200 and 300° · s−1. Before and after, the force:velocity relationship was determined bilaterally (angular velocities 0–300° · s−1). There were no significant differences in the forces generated or relative electromyogram (EMG) activity after practice, although there was a trend for dynamic forces to increase. Beforehand, the bilateral eccentric MVC forces were lower than isometric (P < 0.0025); afterwards they were broadly similar. The agonist EMG was similar during isometric and eccentric contractions, but lower during concentric (P < 0.03). Antagonist EMG activity showed considerable individual variation, was similar during all contraction types and tended to be greater during dynamic contractions. These data indicate that neither central learning mechanisms nor total muscle activation strategies underlie the human failure to produce the expected high eccentric voluntary forces in humans.

Rate and Risk of Anterior Cruciate Ligament Injury Among Sportswomen in Slovenia

CONTEXT Anterior cruciate ligament (ACL)-injury rate is greater among female athletes than among male athletes. OBJECTIVE To investigate the rate and risk of ACL injury among Slovenian sportswomen playing professional basketball, team handball, or volleyball. DESIGN Prospective cohort study. SETTING The Slovenian National Organizations of basketball, team handball, and volleyball. PATIENTS OR OTHER PARTICIPANTS During the 2003-2004 season, we prospectively followed 585 Slovenian sportswomen registered in the Slovenian National Organizations of basketball, team handball, and volleyball. MAIN OUTCOME MEASURE(S) We asked sportswomen and coaches to document the occurrence of every significant traumatic knee injury requiring medical attention. Injury rate and injury risk were calculated for sportswomen in each sport group. To calculate injury rate, we estimated the average exposure of each sportswoman during the research period. RESULTS During the 2003-2004 season, 585 Slovenian sportswomen sustained 12 ACL injuries. The ACL-injury risk was different in athletes participating in the various sports, with basketball players having the greatest ACL-injury risk and volleyball players having the lowest ACL-injury risk (P  =  .04). The risk of ACL injury among Slovenian sportswomen was 2.1 per 100 athletes (95% confidence interval  =  0.9, 3.2), whereas the rate of ACL injury was 0.037 per 1000 exposure hours (95% confidence interval  =  0.016, 0.06). CONCLUSIONS Overall differences in injury risk were found among sports, but no differences were noted among divisions within sports. No differences for injury rate were observed between or within sports. The rate and risk of ACL injury among Slovenian sportswomen are high, with basketball players having the greatest ACL-injury risk.

Do knee injuries have long-term consequences for isometric and dynamic muscle strength?

Abstract. To ascertain whether decrements in knee extensor muscle strength persist years after a traumatic ligamentous or meniscal knee injury, with reference to (1) the type of muscle activity, (2) the dominance of injury, and (3) the time since injury, 36 subjects with previous unilateral knee injuries were assessed. Peak voluntary quadriceps muscle strength was measured using the KinCom 500H dynamometer during isometric, concentric (30°·s–1 and 120°·s–1) and eccentric contractions (30·s–1), and the findings for each type of contraction were compared. Significant differences in quadriceps muscle strength were seen between (1) the injured and uninjured limbs during maximal voluntary isometric (P=0.0003), concentric (P<0.0001) and eccentric (P<0.0001) contractions, and (2) the isometric and concentric decrements (P=0.004), and the isometric and eccentric decrements (P=0.012) within the same injured limb. The decrements in eccentric strength were significantly greater if they affected the dominant rather than the non-dominant limb (P=0.0186). No relationship was seen between the time since injury and the degree of isometric or dynamic decrement. Deficits in quadriceps muscle strength remained for a long time after traumatic knee injury, with exercise levels rarely returning to the previously uninjured state. The degree of decrement in muscle strength was dependent upon the type of muscle activity, with concentric and eccentric activity showing greater decrements than those seen with isometric activity. Deficits in the type of activity varied widely in the same individual, and eccentric decrements were significantly worse following dominant knee injuries. Possible explanations for these findings and the implications for rehabilitation following knee injury are discussed.

Correlates of knee anterior laxity in sportswomen

The purpose of this study was to evaluate whether any of the following factors are related to knee anterior laxity in healthy sportswomen: anthropometric characteristics, lower limb alignment characteristics, hormone-related factors and sport history. Six hundred and sixteen sportswomen were tested in the pre-season. The data have been analysed using linear regression for possible association of knee anterior laxity with other variables. Univariate linear regression indicated a positive association of knee anterior laxity with knee extension and navicular drop and a negative association with body height. Multivariate linear regression analysis showed statistically significant associations between knee anterior laxity and the combination of passive knee extension and the chosen sport (R(2)=0.089; p<0.05). The combination of passive knee extension and sport type was found to be related to the amount of knee anterior laxity, although the association was weak with this combination of factors able to explain only about 9% of the variability in laxity. Knowing which factors influence the amount of knee anterior laxity will help us to better interpret the results of knee anterior laxity testing and help us to understand the possible role of knee anterior laxity as a risk factor for knee injury.

The Long-term Effects of Unilateral Lower Limb Musculoskeletal Injury on Bone Mineral Density and Isometric Quadriceps Strength

Summary Musculoskeletal injuries of the lower limb are commonplace and can lead to long-standing deficits in bone mineral density (BMD) and muscle strength. This may predispose subjects to re-injury and lower their threshold for functional ability. This study aims to investigate the relationship between BMD and peak isometric quadriceps strength and considers whether subsequent strength training is of benefit. Ten subjects (two female) with previous lower limb musculoskeletal injuries were assessed. The BMD in the knee region was measured bilaterally using dual energy X-ray absorptometry (DEXA, model DPX-L). The peak isometric quadriceps strength was assessed using the KinCom 500H isokinetic dynamometer. The injured limb was compared to the uninjured limb (I/UI%). Significant differences were seen between the injured and uninjured limb for BMD in the femur (p = 0.039), tibia (p = 0.014) and in the combined site (p = 0.017); and peak isometric quadriceps strength (p > 0.001). No relationship was found between the decrements in muscle strength and BMD. A further pilot study (n = 6) was conducted to assess the impact of a 12-week home exercise training programme on the BMD and isometric quadriceps strength deficits. These results were encouraging with increases in the quadriceps strength and/or BMD and a statistically significant increase in the load lifted in training.