Effects of gender and fatigue on strength and activity of gluteus medius muscle during a controlled cutting maneuver in preadolescent athletes

The present study aimed to investigate the effects of gender on hip muscle strength and activity during a controlled cutting maneuver in preadolescent athletes. Fifty-six football and handball preadolescent players participated (35 females and 21 males). Normalized mean activity of the gluteus medius (GM) muscle was measured using surface electromyography during cutting maneuvers in pre-activation and eccentric phases. The stance duration and the strength of hip abductors and external rotators were recorded with a force plate and a handheld dynamometer, respectively. Descriptive statistics and mixed model analysis were used to assess statistical difference (α = 0.05). The results showed that boys activate the GM muscle significantly more than girls during the pre-activation phase (P = 0.022). Boys also demonstrated greater normalized strength of hip external rotation than girls (P = 0.038), but not for hip abduction or duration of stance (P > 0.05). When adjusted for abduction strength, however, boys had significantly shorter stance duration than girls (P = 0.006). It seems that sex-dependent differences are present in preadolescent athletes as observed in the strength of hip external rotator muscles and neuromuscular activity of the GM muscle during a cutting maneuver. Future studies are needed to investigate whether these changes influence risk of lower limb/ACL injury during sport activities.

Altered medial versus lateral hamstring muscle activity during hop testing in female athletes 1-6 years after anterior cruciate ligament reconstruction

PURPOSE

The purpose of this study was to assess activation patterns of medial (MH) versus lateral (LH) hamstrings in female athletes who had undergone ACL reconstruction (ACLR) using a hamstrings-graft during single-limb functional testing.

METHODS

Eighteen athletes (1-6 years since ACLR) and 18 healthy controls were recruited from the Icelandic women's top divisions in football, handball, and basketball. Activation of the MH and LH was monitored bilaterally using surface electromyography. Peak activation of the normalized signal was identified for two phases of the single-limb crossover (SLC) hop test and performance (distance jumped) registered. Self-reported knee symptoms and function were evaluated with the Knee injury and Osteoarthritis Outcome Score (KOOS). A repeated measures general linear model was used for main statistical data analyses, comparing variables of interests between limbs (within-subjects factor) and between groups.

RESULTS

ACLR athletes had worse KOOS-symptoms scores (p < 0.05) than controls, while hop distance was equal. Overall, MH and LH muscle activation levels differed between the two phases of the SLC hop test (p < 0.05). Moreover, inter-limb differences in MH and LH activity were identified between groups (p < 0.05), mainly explained by greater LH than MH activation in the uninjured limb of ACLR athletes.

CONCLUSION

One to 6 years after ACLR, female athletes performed on par with uninjured controls, but demonstrated inter-limb differences in muscle activation patterns of the hamstrings that were not evident in controls. This may be an important factor to consider during postsurgical rehabilitation in order to lower the risk of a second injury.

LEVEL OF EVIDENCE

III.

Effect of 12-week resistance exercise program on body composition, muscle strength, physical function, and glucose metabolism in healthy, insulin-resistant, and diabetic elderly Icelanders

BACKGROUND

Insulin is a stimulator of skeletal muscle protein anabolism and insulin resistance might therefore negatively affect muscle protein metabolism. We investigated muscle mass and physical function before and after a resistance exercise program in participants with prediabetes or type 2 diabetes mellitus (T2DM) in comparison to healthy controls.

METHODS

This was a secondary analysis of a randomized controlled intervention designed to investigate resistance training among older adults. Glucose metabolism status was not a selection criteria for the trial, and group designation was done retrospectively. Participants (N = 237, 73.7 ± 5.7 y, 58.2% women) participated in a 12-week resistance exercise program (3 times/week; three sets, six to eight repetitions at 75%-80% of the one-repetition maximum), designed to increase strength and muscle mass of major muscle groups. Body composition, muscular strength, timed up and go test, 6-minute walk for distance, and blood chemical variables were measured at baseline and endpoint.

RESULTS

Participants completing the study (n = 213) experienced significant changes in muscle strength or muscle function, which did not differ significantly between healthy (n = 198), prediabetic (n = 20), and T2DM participants (n = 17). Changes in serum glucose during the intervention differed by group: only glucose improved significantly in the prediabetic group, glucose and triacylglycerol improved significantly in the healthy group, whereas no serum parameter improved significantly in the T2DM group.

CONCLUSIONS

A 12-week resistance exercise program improves muscle strength and muscle function to a similar extent in healthy, prediabetic, and T2DM elderly people. However, according to our data, T2DM participants do not experience favorable changes in fasting glucose or HbA(1C).

Physical function predicts improvement in quality of life in elderly Icelanders after 12 weeks of resistance exercise

BACKGROUND

Little is known about the effects of resistance training on health related quality of life (HRQL) in the elderly.

AIM

The main purpose of the study was to investigate the effects of resistance training on strength, body composition, functional capacity and HRQL in independent living elderly people. We hypothesised that resistance training would improve lean mass, muscle strength, physical function and HRQL.

METHODS

Subjects (N = 237, 73.7±5.7 yrs, 58.2% female) participated in a 12-week resistance exercise program (3 times/week; 3 sets, 6-8 repetitions at 75-80% of the 1-repetition maximum) designed to increase strength and muscle mass of major muscle groups. Body composition, quadriceps- and grip strength, timed up and go test (TUG), six minute walk for distance (6MW) and HRQL were measured at baseline and endpoint.

RESULTS

Two hundred-and-four participants completed the study. Although the increase in lean mass was small (+0.8 kg, P<0.01), quadriceps strength (+53.5 N), grip strength (+3.0 lb), TUG (-0.6 sec), 6MW (+33.6 m) and HRQL (+1.2 t-score) improved significantly (all P<0.01). Changes in 6MW predicted improvement in HRQL after 12 weeks.

CONCLUSIONS

Our study shows that a 12-week resistance exercise program significantly improves lean mass, muscle strength, physical function and HRQL in elderly individuals, and that improvements in physical function predict improvements in HRQL. Our study indicates that resistance training should be promoted for the elderly as it has the potential to improve physical performance, thereby prolonging healthy, independent aging.