Biomedical subjects

P Balikian

Publications and source records attributed to P Balikian.

4 recordsLinked to original sources

PubMed2003

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.

Adult↗

PubMed2000

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.

Adult↗

PubMed1998

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.

Journal Article↗

PubMed1992

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.

Aluminum↗