Muscle fiber characteristics and performance correlates of male Olympic-style weightlifters

Biopsies fro the vastus lateralis muscle of male weightlifters (WL; n=6; X +/- SE, age=27.0 +/- 2.1 years), and non-weight-trained men (CON; n=7; age=27.0 +/- 2.0 years) were compared for fiber types, myosin heavy chain (MHC) and titin content, and fiber type-specific capillary density. Differences (p<0.05) were observed for percent fiber types IIC (WL=0.4 +/- 0.2, CON=2.4 +/- 0.8); IIA (WL=50.5 +/- 3.2, CON=26.9 +/- 3.7); and IIB (WL=1.7 +/- 1.4, CON=21.0 +/- 5.3), as well as percent MHC IIa (WL=65.3 +/- 2.4, CON=52.1 +/- 4.2) and percent MHC IIB (WL=0.9 +/- 0.9; CON=18.2 +/- 6.1). All WL exhibited only the titin-1 isoform. Capillary density (caps.mm(-2)) for all fiber types combined was greater for the CON subjects (WL=192.7 +/- 17.3; CON=262.9 +/- 26.3), due primarily to a greater capillary density in the IIA fibers. Weightlifting performances and vertical jump power were correlated with type II fiber characteristics. These results suggest that successful weightlifting performance is not dependent on IIB fibers, and that weightlifters exhibit large percentages of type IIA muscle fibers and MHC IIa isoform content.     

The impact of different warm-up protocols on vertical jump performance in male collegiate athletes

The purpose of this study was to compare the impact of different types of warm-up on countermovement vertical jump (VJ) performance. Sixty-four male Division I collegiate football players completed a pretest for VJ height. The participants were then randomly assigned to a warm-up only condition, a warm-up plus static stretching condition, a warm-up plus dynamic stretching condition, or a warm-up plus dynamic flexibility condition. VJ performance was tested immediately after the completion of the warm-up. The results showed that there was a significant difference (P < .05) in VJ performance between the warm-up groups. Posttest jump performance improved in all groups; however, the mean for the static stretching group was significantly lower than the means for the other 3 groups. The static stretching negated the benefits gained from a general warm-up when performed immediately before a VJ test.     

A new mathematical model for the homeostatic effects of sleep loss on neurobehavioral performance

The two-process model of sleep regulation makes accurate predictions of sleep timing and duration for a variety of experimental sleep deprivation and nap sleep scenarios. Upon extending its application to waking neurobehavioral performance, however, the model fails to predict the effects of chronic sleep restriction. Here we show that the two-process model belongs to a broader class of models formulated in terms of coupled non-homogeneous first-order ordinary differential equations, which have a dynamic repertoire capturing waking neurobehavioral functions across a wide range of wake/sleep schedules. We examine a specific case of this new model class, and demonstrate the existence of a bifurcation: for daily amounts of wakefulness less than a critical threshold, neurobehavioral performance is predicted to converge to an asymptotically stable state of equilibrium; whereas for daily wakefulness extended beyond the critical threshold, neurobehavioral performance is predicted to diverge from an unstable state of equilibrium. Comparison of model simulations to laboratory observations of lapses of attention on a psychomotor vigilance test (PVT), in experiments on the effects of chronic sleep restriction and acute total sleep deprivation, suggests that this bifurcation is an essential feature of performance impairment due to sleep loss. We present three new predictions that may be experimentally verified to validate the model. These predictions, if confirmed, challenge conventional notions about the effects of sleep and sleep loss on neurobehavioral performance. The new model class implicates a biological system analogous to two connected compartments containing interacting compounds with time-varying concentrations as being a key mechanism for the regulation of psychomotor vigilance as a function of sleep loss. We suggest that the adenosinergic neuromodulator/receptor system may provide the underlying neurobiology.     

Effects of self-selected mass loss on performance and mood in collegiate wrestlers

Wrestlers abruptly lose body mass before competition; however, the effects of "weight cutting" are poorly understood because of conflicting evidence. This study aimed to determine the effects of self-selected mass loss on precompetition mood, grip strength, and lower body power in collegiate wrestlers. Sixteen male collegiate wrestlers (age = 20 ± 2 years, height = 177.5 ± 7.2 cm) were weighed 10 days before (D-10) a competitive meet. Euhydrated subjects were administered the Brunel Mood Scale (BRUMS), tested on grip strength, and given a 30-second Wingate Anaerobic Power test to determine lower body power. Additional weigh-ins were conducted 6 (D-6) and 2 (D-2) days before competition. Subjects repeated the testing battery the day of competition (D-0). During the study, wrestlers self-selected the method and timing of mass loss. Wrestlers lost 0.0-8.1% of their body mass using exercise, caloric restriction, or fluid deprivation. Most mass loss occurred between D-2 and D-0 (mean ± SD, D-10 = 81.7 ± 18.2 kg, D-6 = 81.2 ± 17.8 kg, D-2 = 81.1 ± 18.5 kg, D-0 = 79.0 ± 19.2 kg). Wrestlers losing ≥ 4% body mass became significantly more confused (D-10 = 0 ± 0, D-0 = 3 ± 3); subjects losing less mass showed no difference in confusion. No significant differences existed across time for remaining BRUMS variables, grip strength, and Wingate variables. These results suggest that wrestlers self-select large, rapid mass loss that impairs aspects of psychological functioning without affecting grip strength or lower-body power.     

The effects of double-shifts (15.5 hours) on sleep, fatigue and health

The aim of the present study was to investigate how "double-shifts" (15.5 hours) affects sleep, fatigue and self-rated health. The study was carried out on male construction workers of which 80% were long-distance commuters. The schedule involved two work periods and each work period involved two double shifts in a row. The subjects filled in a sleep/wake diary at 8 times across a year and a questionnaire at 3 times. They also wore an actigraph during one shift cycle. The results showed that sleepiness, and to a certain extent, mental fatigue increased during double shifts and accumulated across days. The short rest time (8.5 hours) between days caused insufficient sleep and approximately 5.5 hours of sleep was obtained between double shifts. Questionnaire data showed that complaints of insufficient sleep, exhaustion on awakening and pain symptoms increased across the year. It was concluded that a shift system involving double shifts has a negative effect on fatigue, recovery and health-related well-being.     

The effects of blood loss on the performance of physical exercise

Seven male subjects were studied before and up to 53 days after the loss of 11 of blood. The resting hematocrit fell from 44.0 to 38.7% and returned to control level after 3 weeks. Maximal oxygen uptake decreased from 4.00 1/min to 3.54 1/min and returned to the initial level within 2 weeks. Submaximal oxygen uptake, pulmonary ventilation, maximal heart rate and blood lactate were not found to change significantly. Submaximal heart rate was increased from 125 beats . min-1 to about 135 beats . min-1 and remained elevated for 3 weeks, whereas blood lactate was increased only in the first week. Maximal work time decreased from 5.1 min to 3.8 min and remained low for the first 2 weeks, but rose thereafter above the starting level. Comparison with a control study suggested that there is some training effect, which, when allowed for, indicates that maximal work time returns to starting values at the same time as does the maximal oxygen uptake. It is concluded that the drop in Hct, maximal oxygen uptake and work capacity, found after the loss of 11 of blood, are related to each other both in magnitude and duration.     

The effects of sleep deprivation and time of day on cognitive performance

The extent to which the diurnal fluctuations of different cognitive processes could be affected by sleep loss may be explored to predict performance decrements observed in the real world. Twenty healthy male subjects voluntarily took part in 8 test sessions at 06:00, 10:00, 14:00, and 18:00 h, following either a night with or without sleep in random order. Measurements included oral temperature, simple reaction time, sign cancelation, Go/NoGo, and the Purdue pegboard test. The results indicate that simple reaction time and motor coordination had morning–afternoon variations closely following the rhythms of temperature and vigilance. Inhibitory attention (Go/NoGo) presented no morning–afternoon variations. Sleep deprivation may affect the profiles of cognitive performance depending on the processes solicited. Sustained and inhibitory attention are particularly affected in the morning (after 24 and 28 waking hours), while a complex task (visuo-motor coordination) would be affected after 32 waking hours only.     

The effects of training volume and competition on the salivary cortisol concentrations of Olympic weightlifters

This study examined the effects of training volume and competition on the salivary cortisol (Sal-C) concentrations of Olympic weightlifters. Male (n = 5) and female (n = 4) Olympic weightlifters provided saliva samples across a 5-week experimental = period. The first aim was to assess the weekly effects of high (≥ 200 sets) and low (≤ 100 sets) training volume on Sal-C. The second aim was to compare Sal-C concentrations and 1 repetition maximum (1RM) performance during 2 simulated and 2 actual competitions. Performance was assessed using the snatch, clean and jerk, and the Olympic total lift. Data from each competition setting were pooled before analysis. There were no significant weekly changes in Sal-C levels (p > 0.05). The actual competitions produced higher (128-130%) Sal-C concentrations (p < 0.001) and superior 1RM lifts (1.9-2.6%) for the clean and jerk, and the Olympic total, than the simulated competitions (p < 0.05). Individual Sal-C concentrations before the simulated competitions were positively correlated to all of the 1RM lifts (r = 0.48-0.49, p < 0.05). In conclusion, actual competitions produced greater Sal-C responses than simulated competitions, and this appeared to benefit the 1RM performance of Olympic weightlifters. Individuals with higher Sal-C concentrations also tended to exhibit superior 1RM lifts during the simulated competitions. Given these findings, greater emphasis should be placed upon the monitoring of C to establish normative values, training standards and to assist with performance prediction.     

Efficacy of potentiation of performance through overweight implement throws on male and female collegiate and elite weight throwers

The purpose of this investigation was to determine the acute effects of 2 different overweight implements on weight throw performance. Seventeen collegiate and elite weight throwers were recruited to participate. A within-subject design was used to compare the difference between mean and peak distance after warm-up with a regulation weight (STAND), 1.37-kg overweight (OVRWGHT1), and 2.27-kg overweight implement (OVRWGHT2). Repeated-measures analysis of variance revealed a main effect for Treatment (p = 0.006) and a significant interaction effect for Treatment by Time (p = 0.041). The means for the OVRWGHT1 treatment (16.08 ± 2.5 m) and OVRWGHT2 (16.08 ± 2.7 m) were not different; however, the mean for STAND was significantly lower than that for the other treatments (15.58 ± 2.5, p < 0.02). Changes in performance between OVRWGHT treatments and STAND were found to correlate to one-repetition maximum (1RM) Power Clean (improvement for OVRWGHT 1, r = 0.536, p = 0.016; improvement for OVRWGHT2, r = 0.548, p = 0.014). The results suggest that in collegiate and elite athletes overweight implement warm-up may improve performance and that stronger athletes may be better suited to take advantage of this effect.     

The acute effects of different stretching exercises on jump performance

The purpose of this study was to demonstrate the short-term effects of different stretching exercises during the warm-up period on the lower limbs. A controlled, crossover clinical study involving 49 volunteers (14 women and 35 men; mean age: 20.4 years) enrolled in a "physical and sporting activities monitor" program. The explosive force was assessed using the Bosco test. The protocol was as follows: The test involved a (pre) jump test, general warm-up, intervention and (post) jump test. Each volunteer was subjected to each of the 5 interventions (no stretching [NS] and stretching: static passive stretching [P]; proprioceptive neuromuscular facilitation [PNF] techniques; static active stretching in passive tension [PT]; static active stretching in active tension [AT]) in a random order. The jump test was used to assess the squat jump, countermovement jump (CMJ), elasticity index (EI), and drop jump. An intragroup statistical analysis was performed before and after each intervention to compare the differences between the different stretching exercises. An intergroup analysis was also performed. Significant differences (p < 0.05) were found between all variables for the interventions "P," "PNF," and "TA" in the intragroup analysis, with each value being higher in the postjump test. Only the "P" intervention showed a significant difference (p = 0.046) for "EI," with the postvalue being lower. Likewise, significant differences (p < 0.05) were observed for the "CMJ" measurements during the intergroup analysis, especially between "NS" and the interventions "P," "PNF," "AT," and "PT," with each value, particularly that for "AT," being higher after stretching. The results of this study suggest that static active stretching in AT can be recommended during the warm-up for explosive force disciplines.     

The acute potentiating effects of back squats on athlete performance

Crewther, BT, Kilduff, LP, Cook, CJ, Middleton, MK, Bunce, PJ, and Yang, G-Z. The acute potentiating effects of back squats on athlete performance. J Strength Cond Res 25(12): 3319-3325, 2011-This study examined the acute potentiating effects of back squats on athlete performance with a specific focus on movement specificity and the individual timing of potentiation. Nine subelite male rugby players performed 3 protocols on separate occasions using a randomized, crossover, and counterbalanced design. Each protocol consisted of performance testing before a single set of 3 repetition maximum (3RM) back squats, followed by retesting at ～15 seconds, 4, 8, 12, and 16 minutes. The 3 tests were countermovement jumps (CMJs), sprint performance (5 and 10 m), and 3-m horizontal sled pushes with a 100-kg load. Relationships between the individual changes in salivary testosterone and cortisol concentrations and performance were also examined. The 3RM squats significantly (p < 0.001) improved CMJ height at 4 (3.9 ± 1.9%), 8 (3.5 ± 1.5%), and 12 (3.0 ± 1.4%) minutes compared with baseline values, but no temporal changes in sprinting and sled times were identified. On an individual level, the peak relative changes in CMJ height (6.4 ± 2.1%, p < 0.001) were greater than the 3-m sled (1.4 ± 0.6%), 5-m (2.6 ± 1.0%), and 10-m sprint tests (1.8 ± 1.0%). In conclusion, a single set of 3RM squats was found effective in acutely enhancing CMJ height in the study population, especially when the recovery period was individualized for each athlete. The study results also suggest that the potentiating effects of squats may exhibit some degree of movement specificity, being greater for those exercises with similar movement patterns. The current findings have practical implications for prescribing warm-up exercises, individualizing training programs, and for interpreting postactivation potentiation research.     

Effects of acute and chronic sleep loss on immune modulation of rats

Sleep deprivation is now recognized as an increasingly common condition inherent to modern society, and one that in many ways, is detrimental to certain physiological systems, namely, immune function. Although sleep is now viewed by a significant body of researchers as being essential for the proper working of a host of defense systems, the consequences of a lack of sleep on immune function remains to be fully comprehended. The aim of the current study was to investigate how paradoxical sleep deprivation (PSD) for 24 and 96 h and sleep restriction (SR) for 21 days by the modified multiple-platform method, and their respective 24-h recovery periods, affect immune activation in rats. To this end, we assessed circulating white blood cell counts, lymphocyte count within immune organs, as well as Ig and complement production. The data revealed that PSD for 96 h increased complement C3 and corticosterone concentration in relation to the control group. In contrast, the spleen weight, total leukocytes, and lymphocytes decreased during SR for 21 days when compared with the control group, although production of a certain class of immunoglobulin, the IgM, did increase. After recovery sleep, lymphocyte count in axillary lymph nodes grew when rats had rebound sleep after PSD for 24 h, neutrophils increased after PSD 96 h and lymphocytes numbers were higher after SR 21 days. Such alterations during sleep deprivation suggest only minor alterations of nonspecific immune parameters during acute PSD, and a significant impairment in cellular response during chronic SR.     

The effects of training history, player position, and body composition on exercise performance in collegiate football players

Performance data for 261 NCAA Division 1A collegiate football players were analyzed to determine if player position, body weight, body fat, and training time were correlated with changes in performance in the following events: power clean (PC), bench press (BP), squat (SQ), vertical jump (VJ), 40-yd dash (40yd), and 20-yd shuttle (20yd). Individual positions were combined into the following groups: (A) wide receivers, defensive backs, and running backs, (B) linebackers, kickers, tight ends, quarterbacks, and specialists, and (C) linemen. Increases in body weight were positively correlated with increases in BP and PC performance for all groups. Increases in body fat were negatively correlated with performance in the PC and VJ for all groups. For group C, increases in body fat were also negatively correlated with performance in the 40yd and 20yd. Group and training time exhibited no linear relationship with performance in any of the tested events. No linear relationships were observed between the independent variables and performance in the SQ. When individual training data were analyzed longitudinally, a nonlinear increase in performance in the PC, BP, and SQ was observed as training time increased, with the greatest rate of change occurring between the first and second semesters of training.     

Kinematical analysis of the snatch in elite male junior weightlifters of different weight categories

The purpose of this study was to analyze the differences in the technical pattern of the snatch in elite junior weightlifters of different weight categories. The sample was a group of 33 men weightlifters from different weight categories. The comparative study included 2 groups, taking into account weight categories. Group A included 17 weightlifters from the lightest categories, 56 and 62 kg; group B included 16 weightlifters from the heaviest categories, 85 and 105 kg. Three-dimensional photogrammetry technique was utilized. Regarding group differences, we can conclude that lifters belonging to heavier categories are more efficient, as they manage to have longer barbell propulsion trajectories, which allows them to exert actions on the barbell for a longer period, especially in the initial lifting phase. They attain greater barbell vertical velocity (p = 0.029), a longer vertical bar trajectory normalized on first pull (p = 0.011), and a greater, although limited, bar height loss on the catch (p = 0.008). Besides, intergroup differences evidence that heavier category lifters observe a different temporal organization of the movement based on a longer first pull (p = 0.000), a shorter transition (p = 0.030), and a longer turnover (p = 0.049). No significant differences were found in the analyzed angular parameters during the first and second pull. We believe the intergroup differences found not to be determining enough to consider a technical model adapted to the characteristics of each body weight category. This confirms that a successful lift is multifactor based and individual dependent. Given its transcendence, this evidence should be taken into account in the technical training of young lifters.