Acute metformin administration increases mean power and the early Power phase during a Wingate test in healthy male subjects

The present study tested the hypothesis that acute metformin would increase peak power measured during a Wingate test. Fourteen men (24 ± 6 years; 75.8 ± 10.2 kg; 177 ± 7 cm) participated in four test sessions, conducted in a crossover, counterbalanced, double-blind model. The first and second sessions consisted of anthropometric measurements and one Wingate test per day to assess test-retest reliability. In the last two sessions, the Wingate tests were performed on metformin (500 mg capsule, 1 hour before) or placebo (cellulose capsule, 1 hour before) condition. No differences were found between the placebo and metformin for peak power (1056.8 ± 215.8 W vs. 1095.2 ± 199.3 W, respectively; p = 0.24). Mean power (630.9 ± 87.8 W vs. 613.1 ± 94.8 W, respectively; p=0.01) and total work (18928 ± 2633 kJ vs. 18393 ± 2845 kJ, respectively; p = 0.01) in the metformin condition were higher than the placebo. The power were greater in metformin when compared to the placebo in moments 3 (p = 0.01), 4 (p = 0.01), 5 (p = 0.04), 6 (p = 0.04), 7 (p = 0.02), 8 (p = 0.03) and 9 (p = 0.01) seconds. There were no differences between conditions for the peak lactate (p = 0.08) and the rating of perceived exertion (p = 0.84). Acute metformin administration increased the early power phase and the mean power of a Wingate test.

Stage length, spline function and lactate minimum swimming speed

AIM

Lactate minimum test (LMT) has become popular in running evaluation. This study analysed the influence of different stage lengths and determination methods on lactate minimum swimming speed (LMS) and its validity for maximal lactate steady-state speed (MLSS-S) assessment.

METHODS

Twelve male swimmers (19.7+/-1.6 years, 70.3+/-8.7 kg, 181.4+/-7.9 cm) randomly underwent 4-5 evaluations in a 2-week period. LMS was accessed by simple visualisation (SV) and spline function (SF) methods during 200 and 300 m stages LMT (LMT200 and LMT300, respectively), and MLSS-S was determined during constant speed 2000 m efforts.

RESULTS

Respectively, SV and SF provided LMS during LMT200 (1.31+/-0.12 m x s-1 and 1.32+/-0.10 m x sec-1) and LMT300 (1.28+/-0.11 m x sec-1 and 1.28+/-0.10 m x sec-1) which were not significantly different (p>0.05) from each other. However, LMS accessed during LMT200 were significantly greater (p<0.05) than MLSS-S (1.25+/-0.06 m x sec-1). In addition, significant relationships (r=0.79 to 0.98; p<0.05) were found between all studied speeds and lactate minimum values during LMT300 were not significantly different (p>0.05) from those found during LMT200 (5.4+/-2.2 and 5.5+/-2.2 mM vs 6.8+/-2.5 and 7.0+/-2.6 mM, respectively for SV and SF).

CONCLUSIONS

Our results suggest that LMS is not affected by different stage lengths and determination

METHODS

However, LMT300 results seems to provide a more accurate MLSS-S prediction, being adequate for swimmers evaluation.

Consumo máximo de oxigênio e limiar anaeróbio de jogadores de futebol: comparação entre as diferentes posições

O grau de desenvolvimento das capacidades físicas no futebol é fator determinante do nível desportivo do jogador. O objetivo do presente estudo foi comparar valores de limiar anaeróbio e consumo máximo de oxigênio entre jogadores profissionais de futebol de diferentes posições. Para tanto, 25 atletas (idade = 22,08 ± 8,28 anos, peso = 76,12 ± 9,8kg, altura = 179,8 ± 7,1cm e relação corporal = 12,21 ± 3,67% de gordura corporal) foram divididos em cinco grupos, como se segue: goleiros (GO), zagueiros (ZA), laterais (LA), meio-campistas (MC) e atacantes (AT). O VO2max foi determinado em esteira ergométrica através de análise direta e a velocidade de corrida correspondente ao limiar anaeróbio fixo de 4mM (V4mM), em teste de campo (2 x 1.000m a 90 e 95% da velocidade máxima para a distância) através de interpolação linear. A V4mM foi menor (p < 0,05) para o grupo GO em relação aos demais grupos. Além disso, os grupos LA e MC apresentaram valores de V4mM significantemente maiores em relação aos grupos ZA e AT. O grupo GO mostrou VO2max significantemente menor em relação a todos os outros grupos, sendo que estes últimos não apresentaram diferença entre si. Uma vez que os atletas de diferentes posições não realizavam treinamento diferenciado, os autores creditam as diferenças encontradas à especificidade da movimentação durante partidas e coletivos.

The effects of wet suits on physiological and biomechanical indices during swimming

The objectives of this study were to verify the effects of wet suits (WS) on the performance during 1500m swimming (V1500), on the velocity corresponding to the anaerobic threshold (VAT) and on the drag force (AD) as well as its coefficient (Cx). 19 swimmers randomly completed the following protocols on different days (with and without WS): 1) maximal performance of 1500m swimming; 2) VAT in field test, with fixed concentration of blood lactate (4 mM) and 3) determination of hydrodynamic indices (AD and Cx). The results demonstrated significant differences (p < 0.05) in the VAT (1.27 +/- 0.09; 1.21 +/- 0.06 m.s-1), and in the V1500 (1.21 +/- 0.08; 1.17 +/- 0.08 m.s-1), with and without WS, respectively. However the AD, and its Cx did not present significant differences (p>0.05) for the respective maximal speeds of swimming. In summary, we can conclude that WS allows swimmers to reach greater speeds in both, long- and short-course swims. This improvement can be related to the decrease of the AD, since with higher speeds (with WS) the subjects presented the same resistance, as they did when compared to speeds without a WS. Moreover, these data suggest that the methodology used in this study to determine the Cx is unable to detect the improvement caused by WS.

Bone mineral density and broadband ultrasound attenuation with estrogen treatment of postmenopausal women

The purpose of the current study was to determine the changes in lumbar spine, hip, and calcaneus bone mineral density (BMD), and in calcaneus broadband ultrasound attenuation (BUA) in early menopausal women and to assess the effects of estrogen replacement therapy (ERT) on bone mass at these sites over a 2-yr period. Fifty-three Caucasian women who were at least 6 mo postmenopausal were divided into two groups based on estrogen use. Twenty-one women, average age 53.0 +/- 0.6 yr and 2.9 +/- 0.3 yr since menopause, had been receiving estrogen in combination with progesterone for at least 6 mo prior to enrollment in the study. Thirty-two women, average age 52.7 +/- 0.8 yr and 2.8 +/- 0.3 yr since menopause, had never received ERT. During the 2-yr study, women not receiving ERT had significant decreases in BMD of the spine -2.3 +/- 0.6%, femoral neck -2.2 +/- 0.8%, and calcaneus -4.7 +/- 0.9%, and in BUA of the calcaneus -14.3 +/- 1.8%. ERT prevented the decreases in BMD at the spine +0.4 +/- 0.6% and calcaneus -2.3 +/- 1.1%, but did not prevent a significant decrease in bone mass at the femoral neck -1.9 +/- 0.8% and BUA at the calcaneus -17.8 +/- 3.2%. Neither group had significant decreases in total hip BMD. This study demonstrates again that ERT prevents the menopause-associated decreases in spine BMD. However, in this group of women, ERT did not prevent loss in femoral neck BMD or BUA. The results suggest that women being treated with estrogen for maintenance of BMD in early menopause need to be monitored to ensure efficacy of therapy, especially in the maintenance of femoral neck BMD.

Aluminum inhibits neurofilament protein degradation by multiple cytoskeleton-associated proteases

The environmental neurotoxin aluminum exerts several distinct biochemical effects on neurofilament proteins, including subunit aggregation, disruption of the normal segregation of phosphorylated subunits within axons leading to abnormal perikaryal accumulation, and inhibition of in vitro degradation by the calcium-dependent neutral protease, calpain. In the present study, we demonstrate that exposure of mouse CNS cytoskeletal preparations to aluminum chloride inhibits the degradation of neurofilament proteins by both calcium-dependent and -independent proteases that co-purify with cytoskeletons. Aluminum inhibited both calcium-dependent and calcium-independent proteolysis of the high and middle molecular weight neurofilament subunits, but inhibited only calcium-dependent, and not calcium-independent proteolysis of the low molecular weight neurofilament subunit. These findings demonstrate that aluminum interferes with multiple aspects of neurofilament protein metabolism.