Milivoj Dopsaj

Aerobic exercise training as a potential source of natural antibodies protective against human immunodeficiency virus‐1

Despite the effectiveness of HAART in controlling HIV‐1 replication, the emergence of drug‐resistant viruses in infected patients and the severe side effects caused by the currently used drug regimens and the lack of an effective vaccine necessitate the continued search for new therapeutic strategies for prevention and therapy of HIV disease. Previously we reported that natural autoantibodies, recognizing peptide FTDNAKTI (peptide NTM1) derived from the C2 domain of HIV‐1 gp120, contribute to the control of HIV disease. Here we demonstrated that sera from well‐trained athletic (HIV‐negative) subjects showed high reactivity with peptide NTM1. This result confirms that aerobic exercise training stimulates production of natural autoantibodies, which recognize peptide NTM1. Bioinformatics analysis indicates that these natural autoantibodies could slow down disease progression by blocking the superantigenic site on HIV‐1 gp120. The results suggest that aerobic exercise training may be a promising non‐toxic and inexpensive adjunctive anti‐HIV therapy.

BODY COMPOSITION AND MUSCLE STRENGTH PREDICTORS OF JUMPING PERFORMANCE: DIFFERENCES BETWEEN ELITE FEMALE VOLLEYBALL COMPETITORS AND NONTRAINED INDIVIDUALS

Abstract Ćopić, N, Dopsaj, M, Ivanović, J, Nešić, G, and Jarić, S. Body composition and muscle strength predictors of jumping performance: Differences between elite female volleyball competitors and nontrained individuals. J Strength Cond Res 28(10): 2709–2716, 2014—Studies of the role of various anthropometric, physiological, and biomechanical variables in performance of rapid movements have generally revealed inconsistent findings. Within this study, we tested the hypotheses that (a) both body composition and leg extensor strength variables would reveal significant relationship with jumping performance, whereas (b) the same relationships would be stronger in physically active nonathletes than in the elite athletes proficient in vertical jumping. Top-level female volleyball players (VP; N = 35) and physically active female nonathletes (PA; N = 21) were tested on maximum vertical jumps performed with and without arm swing, as well as on body composition (percent fat and muscle) and leg press strength (maximum force and the rate of force development). The results revealed significant relationships between the jumping performance and body composition variables that appeared to be higher in PA (r = 0.65–0.76; all p < 0.01) than in VP (r = 0.37–0.42; all p ⩽ 0.05). The relationships between the jumping performance and the leg strength variables were mainly significant (r = 0.23–0.68) and similar in 2 groups. We conclude that not only the leg extensor strength but also the body composition variables could be valid predictors of jumping performance and, possibly, other rapid movements. Moreover, the body composition variables that have been mainly neglected in the literature could be particularly strong predictors of performance of jumping in nonathletes, as compared with relatively homogeneous populations of elite athletes.

Acute responses of biomechanical parameters to different sizes of hand paddles in front-crawl stroke

Abstract This study investigated the acute effects of different sizes of paddles on the force-time curve during tethered swimming and swimming velocity in front-crawl stroke. Fourteen male swimmers (20.0 ± 3.7 years; 100-m best time: 53.70 ± 0.87 s) performed two 10-s maximal efforts in tethered swimming to obtain peak force, average force, impulse, rate of force development, stroke duration and time to peak force. Swimming velocity, stroke rate and stroke length were obtained from two 25-m maximal swims. Both tests were repeated in five conditions: free swimming, wearing small (280 cm 2 ), medium (352 cm 2 ), large (462 cm 2 ) and extra-large (552 cm 2 ) hand paddles. Compared to free swimming, paddles provided significant increases of peak force (medium: 11.5%, large: 16.7%, extra-large: 21.7%), impulse (medium: 15.2%, large: 22.4%, extra-large: 30.9%), average force (medium: 5.1%, large: 7.5%), rate of force development (extra-large: 11.3%), stroke duration (medium: 9.3%, large: 11.8%, extra-large: 18.5%), time to peak force (medium: 11.1%, large: 15.9%, extra-large: 22.1%), swimming velocity (medium: 2.2%, large: 3.2%, extra-large: 3.7%) and stroke length (medium: 9.0%, large: 9.0%, extra-large: 14.8%), while stroke rate decreased (medium: –6.2%, large: –5.5%, extra-large: –9.5%). It is concluded that medium, large and extra-large paddles influence the force-time curve and change swimming velocity, suggesting these sizes may be useful for force development in water.

Factor structure differences of indicators for evaluating isometric leg extensors explosive force in female volleyball athletes and different trained female population

Background Adequate leg extensors preparation is highly important especially in volleyball which involve several jumping techniques. Values of developed force in the function of time generated during the isometric (static) muscle contraction, with its own F-t curve characteristics are the fundamental data on contractile ability. Objective Factor structure differences of indicators for evaluating isometric leg extensors explosive force (RFDLEGEXTISO) regarding different trained female population will be examined in this research. Setting and participants Sample included 50 examinees: top level female volleyball players (Elite N=20), unspecific trained female athletes (Nonspec N=18) and untrained female (Control N=12). Methods In order to assess characteristics of the F-t isometric leg extensors force, tensiometric probe and standardized ‘seating leg extension’ test were used. The measurement range was defined by 11 variables regarding the contractile characteristics of the leg extensors isometric muscle force at the level of 100, 50, 30, 50–100% of maximal force (FmaxLEGEXTISO): rate of force development (RFD) analysed from the aspect of absolute and relative (allometric) values – the indicators of basic (RFDBASICLEGEXTISO, RFDallomLEGEXTISO), specific (RFD50%LEGEXTISO, RFDallomLEGEXTISO50%), special (RFD30%LEGEXTISO, RFDallomLEGEXTISO30%), at 50–100% (RFD50–100%LEGEXTISO) level of RFD, Synergy Index as a criterion of relation between RFDLEGEXTISO and FmaxLEGEXTISO at the basic level of 100% – IndexSNGBASIC, specific level of 50% – IndexSNGSPEC and special level of 30% – IndexSNGSPECIJ. Results Factor analysis set apart two factors in all the observed groups, which have explained 96.491% in Elite, 95.502% in Nonspec, 96.512% in Control of valid variance. The differences in structure and in number of parameters for separated factors were established especially between tested trained and untrained population. They can be explained with differences in muscle tissue and maximal nervous activation of muscles during the specific training, that is, adaptation to specific training. Conclusions The obtained results can possibly be used as an indicator of potential of leg explosiveness and jumping performances in volleyball players selection.

Water polo shots notational analysis according to player positions

The objective of this study was to examine the offense positions a shot is taken in the field and the ending points of the shots taken from a spot of equal number of defense and offense players (6-6). Matches were recorded (14 match) by a camera and recordings were analyzed by marking and collecting data with notation match analysis method. Repeated measures of ANOVA was used for the statistical analysis. Significant differences were found in 4 of the 6 positions (p3, p4, p5, p6) in shot efficiency (p<0.05). No significant difference was found in shot efficiencies of the five areas (p>0.05). The highest shot efficiency was in P6 (65.35%) and at the overhead (52.52%) in goal. Significant differences were found in 4 of the 6 positions (p1, p3, p5, p6) in goal efficiency (p<0.05). P6 had the highest (27.64%) goal efficiency. P3 was the position with the highest number of shots (140) constituting 30.4% of the total shots (461). 42 (28.2%) of the 149 goal-bound shots depending on the positions were taken from P6. In conclusion, the results of this study show the importance of center players (P6); the number of shot scores from P3 is higher than the other positions. Most players preferred down corners.

Differences in the Efficiency Between the Grab and Track Starts for Both Genders in Greek Young Swimmers

Differences in the Efficiency Between the Grab and Track Starts for Both Genders in Greek Young Swimmers The aim of this study was to determine the differences in the kinematic parameters between the grab and track starts and the differences in these two starts between genders. A total of 27 swimmers at the competitive level participated in the study, 13 boys (mean ± SD: age 15.8 ± 0.8 years, body mass 67.7 ± 7.7 kg and body height 178.6 ± 5.7 cm) and 14 girls (mean ± SD: age 16 ± 0.8 years, body mass 59.2 ± 6.6 kg and body height 166.2 ± 6.7 cm). Each swimmer performed three attempts for both start techniques. The best attempt of the grab start and the track start was taken for further analysis. The following kinematic parameters were analysed: flight distance, flight time, flight velocity, entry angle and reaction time. The males had greater numeric values for the results in all kinematic parameters for the grab start compared with the track start, except for flight velocity and entry angle (flight time 0.42 vs. 0.41 s, flight distance 3.21 vs. 3.14 m, flight velocity 7.76 vs. 7.83 m/s, entry angle 44.22 vs. 43.85 degrees and reaction time 0.86 vs. 0.81 s). The females also had greater numeric values for the results in all kinematic parameters for the grab start compared with the track start, except for flight time (flight time 0.38 vs. 0.38 s, flight distance 2.82 vs. 2.73 m, flight velocity 7.47 vs. 7.31 m/s, entry angle 45.18 vs. 44.79 degrees and reaction time 0.88 vs. 0.82 s). These results indicate that the males had significantly better results for flight time and flight distance compared with the females for the grab start (flight time 0.42 vs. 0.38 s, flight distance 3.21 vs. 2.82 m). In the case of the track start, the males had significantly better results for flight distance (3.14 vs. 2.73 m). Exploring the characteristics of the two starts did not lead to any significant kinematic differences. Therefore, a conclusion that demonstrates the superiority of one of the techniques cannot be reached. The coach, together with each swimmer individually, should devote some time to decide after some tests what type of start is better for the body type and general qualifications of the swimmer.

Physical Activity and Natural Anti-VIP Antibodies: Potential Role in Breast and Prostate Cancer Therapy

Background There is convincing evidence from numerous clinical and epidemiological studies that physical activity can reduce the risk for breast and prostate cancer. The biological mechanisms underlying this phenomenon remain elusive. Herein we suggest a role for naturally produced antibodies reactive with the vasoactive intestinal peptide (VIP) in the suppression of breast and prostate cancer, which we believe could offer a possible molecular mechanism underlying control of these cancers by physical exercise. Methodology and Results We found that sera from individuals having breast and prostate cancers have decreased titers of VIP natural antibodies as demonstrated by a lower reactivity against peptide NTM1, having similar informational and structural properties as VIP. In contrast, sera collected from elite athletes, exhibited titers of natural NTM1-reactive antibodies that are significantly increased, suggesting that physical activity boosts production of these antibodies. Significance Presented results suggest that physical exercise stimulates production of natural anti-VIP antibodies and likely results in suppression of VIP. This, in turn, may play a protective role against breast and prostate cancers. Physical exercise should be further investigated as a potential tool in the treatment of these diseases.

Oxidative stress status in elite female volleyball athletes with depleted iron stores

Background Oxidative stress has been defined as a disturbance in the equilibrium status of pro-oxidant and antioxidant systems in favour of pro-oxidation. The elevated metabolic rate associated with exercise leads to increased mitochondrial oxygen consumption in tissues, free radical generation, metabolite oxidation and antioxidant depletion. Objective The aim of the present work was to examine the association of iron depletion and acute phase response with oxidative stress in female athletes. Setting and participants Based on serum ferritin values (cut-off 22 μg/L), 54 elite female volleyball athletes were divided into two groups: with iron depletion and with normal iron stores. Samples were taken from athletes who were members of the top two senior women volleyball teams in Serbia during the 2007/2008 competition season. Interventions The following parameters were measured: ferritin, C-reactive protein, interleukin-6, oxidative stress parameters (reactive oxygen metabolites – ROMs and lipid hydroperoxides – LOOH) and antioxidative defence parameters (biological antioxidative potential – BAP and superoxide-dismutase). Results A general linear model indicated significant differences between athletes (Wilkss λ=0.698, F=5.092, p=0.002) in reactive oxygen metabolites (278±57 vs 333±56; p=0.001) which were significantly higher in athletes with iron depletion and biological antioxidative potential (2547±257 vs 2366±297; p=0.026) which was significantly lower in this group. Besides iron depletion, multivariate analysis of covariance revealed C-reactive protein (p<0.047) to be significant covariate with 18.2% proportion of variability for superoxide-dismutase activity. Iron depletion accounted for the largest proportion of variability for all oxidative stress parameters (30.2%). Conclusions Oxidative stress that occurs during exercise is related to acute phase response and iron depletion plays a significant role in processes that lead to free radical generation in professional athletes. Athletes with ferritin values below 22 μg/L had a decreased antioxidatve defence and were more susceptible to oxidative stress compared to those with adequate iron status.

Early detection of iron deficiency in elite athletes: could microcytic anemia factor (Maf) be useful?

The aim of this study was to establish the sensitivity and specificity of the microcytic anemia factor (Maf®), which is generated by the Coulter LH 750 analyzer in the evaluation of iron depletion and iron‐deficient erythropoiesis in athletes.

Match performance in young female basketball players: relationship with laboratory and field tests

Abstract The aim of this study was to examine the quantitative relationship between the results of laboratory and field tests assessing functional, metabolic and motor abilities and the match performances of young female basketball players. The research included the U16 female basketball players of the top three basketball clubs of the Serbian first under-16 league (N=30), (14.98 ± 0.68 yrs). The complex model method we applied included: laboratory and field testing and match performance analysis. The relations between the criterion and the system of predictors were determined by applying the multiple regression analysis, which defined the model of multiple relations and prediction. The research results have shown that the predictor variables are statistically significant, describing the criterion with 84.4% probability, meaning that there is a high multidimensional correlation between the results of laboratory and field tests and the match performance index. The practical application of this study implies a system of controlling the efficacy of the training process in the preparation stage, the selection and the creation of the model characteristics of functional, metabolic and motor abilities of young basketball players.