Effects of Different Levels of Weightlifting Training on Bone Mineral Density in a Group of Adolescents.

The aim of the current study was to evaluate the effects of different levels of weightlifting training on bone mineral density (BMD) at different body sites (whole body (WB), lumbar spine (LS), femoral neck (FN), upper limbs (UL) and lower limbs (LL)) in a group of adolescents. Three groups of pubertal boys aged 13-15 years were recruited, including a control group (which included 13 untrained adolescents), a moderately trained group (which included 13 non-elite weightlifters, with four sessions of 2 hours per week) and a highly trained group (which included 13 elite weightlifters, with eight sessions of 2 hours per week). The three groups were paired for age and maturation index (using Tanner stages). Body composition, bone mineral content (BMC) and BMD were evaluated by dual-energy X ray absorptiometry (DXA). Physical performance variables (including weightlifting specific exercises, counter movement jump and squat jump) were measured using validated methods. Results showed that the values of BMD and physical performance variables were greater in the group of elite weightlifters compared to the group of non-elite weightlifters and the control group. In addition, the values of BMD and physical performance variables were higher in the group of the non-elite weightlifters compared to those of the control group. After adjusting for lean mass and squat jump, lumbar spine BMD, FN BMD, UL BMD and LL BMD remained significantly higher in the elite weightlifters' group compared to the two other groups. In conclusion, the current study suggests that elite adolescent weightlifters have greater bone health parameters compared to moderately-trained adolescent weightlifters and untrained adolescents.

Weightlifting Is Better Than Plyometric Training to Improve Strength, Counter Movement Jump, and Change of Direction Skills in Tunisian Elite Male Junior Table Tennis Players.

ABSTRACT: Kaabi, S, Mabrouk, RH, and Passelergue, P. Weightlifting is better than plyometric training to improve strength, counter movement jump, and change of direction skills in Tunisian elite male junior table tennis players. J Strength Cond Res 36(10): 2912-2919, 2022-This study aimed to compare the effect of integrating weightlifting (WL) resistance training or plyometric training for 8 weeks on physical performance among elite male junior table tennis players. Forty-five players were randomly divided into 3 groups. A WL resistance training group ( n = 15), plyometric (P) group ( n = 15), and a control (C) group ( n = 15). Weightlifting group and P group were trained for 8 weeks (2 sessions per week with 3 different exercises each time) in addition to the usual practice of table tennis during the preparatory phase, whereas the C group continued classical table tennis training sessions. Subjects were tested for 5-m sprint time, change of direction (CD) test on a 20-m "T" shape course, jumping tests such as standing long jump, squat jump (SJ) and countermovement jump, hang grip, and 1 repetition maximum strength tests as the bench press and back squat before (T0) and after (T1) the training program. There was no statistical difference between the 3 groups before the beginning of the training program. After the 8-week training program, only P and WL groups significantly improved their performances for all the tests. Combining all the tests, the WL group had larger improvement (12.6 vs. 8.2%) and effect sizes (1.88 vs. 1.22) than the P group. Thus, WL training seems more efficient than P training to improve neuromuscular performance of table tennis players, especially for a sport-specific table tennis change-of-direction test such as the 20-m CD test.

Salivary hormonal responses and performance changes during 15 weeks of mixed aerobic and weight training in elite junior wrestlers.

To prepare efficiently for competition, wrestlers usually train physically for a period of approximately 12-20 weeks. Numerous physical qualities must be developed during this period of preparation: aerobic fitness, maximal strength, muscular endurance, power, and speed. However, numerous studies have concluded that it is difficult to concurrently develop strength and aerobic fitness for several reasons, in particular antagonistic endocrine variations. The study involved 15 elite junior wrestlers who trained at a sports training school for 15 weeks. To investigate the effects of long-term training and to assess the relationships between hormonal concentrations (salivary testosterone [T] and cortisol [C]) and performance changes during simultaneous strength and aerobic fitness training, 6 saliva samples and 3 physical tests and 2 measures of body composition were made during the training period. Wrestlers had a significant increase (+1.5 kg) in body weight without changes in percentage body fat. Apart from the 20-m maximal shuttle speed, all performances increased significantly during the 15 weeks of training: maximum mechanical power output (Pmax: +12.8%), mean power during 30 seconds (Pmean: +10.8%), bench press (+5.7%), squat (+23.1%), power clean (+6.1%), time to 3,000- and 30-m sprints (-3.6, -1.3% respectively). During the period that the C increased, there was no significant variation for the T. The T/C ratio followed a variation pattern contrary to that of the C. We found strong correlations between salivary T, C, and T/C and the variation in explosive strength. Our results suggest that data about subjects' salivary C, T, and T/C may be employed to optimize the training process for sports people who need to develop strength and aerobic fitness simultaneously.

Repeated-sprint ability and aerobic fitness.

The purpose of this study was to reinvestigate the relationship between aerobic fitness and fatigue indices of repeated-sprint ability (RSA), with special attention to methodological normalization. Soldiers were divided into low (n = 10) and high (n = 9) fitness groups according to a preset maximal aerobic speed (MAS) of 17 km·h(-1) (∼60 ml O2·kg(-1)·min) measured with the University of Montreal Track Test (UMTT). Subjects' assessment included the RSA test (3 sets of 5 40-m sprints with 1-minute rest between sprints and 1.5 minutes between sets), a 40-m sprint (criterion test used in the computation of fatigue indices for the RSA test), strength and power measurement of the lower limbs, and the 20-m shuttle run test (20-m SRT) and the UMTT, which are measures of maximal aerobic power. The highest correlation with the RSA fatigue indices was obtained with the 20-m SRT (r = 0.90, p = 0.0001, n = 19), a test with 180° direction changes and accelerations and decelerations. The lower correlation (r = 0.66, p < 0.01, n = 19) with the UMTT (continuous forward running) suggests that some aerobic tests better disclose the importance of aerobic fitness for RSA and that aerobic power is not the sole determinant of RSA. However, neither strength nor vertical jumping power was correlated to the RSA fatigue indices. Subjects with greater MAS were able to maintain almost constant level of speed throughout series of repeated sprints and achieved better recovery between series. A MAS of at least 17 km·h(-1) favors constant and high speed level during repeated sprints. From a practical point of view, a high aerobic fitness is a precious asset in counteracting fatigue in sports with numerous sprint repetitions.

Comparison of heart rate deflection and ventilatory threshold during a field cross-country roller-skiing test.

This study was to assess whether the point of deflection from linearity of heart rate (HRd) could be an accurate predictor of ventilatory threshold (VT2) during a specific cross-country roller-skiing (RS) test. Ten well-trained cross-country skiers performed a maximal and incremental RS test in the field and a standardized maximal and incremental treadmill running (TR) test in the laboratory. Values of oxygen uptake (VO2) and heart rate (HR) were continuously recorded during all exercises by a portable breath-by-breath gas exchange measurement system and a wireless Polar monitoring system, respectively. The VT2 and HRd points were individually determined by visual analysis during RS. Maximal VO2 (VO2 max) and HR were higher (p < 0.05) during TR (67.1 +/- 7.3 ml x min(-1) x kg(-1) and 196.0 +/- 14.1 bpm, respectively) compared with RS (64.2 +/- 7.3 ml x min(-1) x kg(-1) and 191.5 +/- 13.1 bpm, respectively). However, a high correlation (r = 0.94, p < 0.01) between TR and VO2 max was observed. Paired t-tests showed no significant differences in HR (183.6 +/- 15.1 vs. 185.2 +/- 13.9 bpm) and VO2 (55.5 +/- 7.1 vs. 55.8 +/- 6.1 ml x min(-1) x kg(-1)) at intensities corresponding to HRd and VT2 during the RS test, respectively; Pearson product-moment correlation coefficients demonstrated significant relationships for HR at the HRd and VT2 points (r = 0.99, p < 0.001) as well as for VO2 (r = 0.95, p < 0.001). Our results indicate that the specific incremental RS test is effective in eliciting HRd in the field for all skiers and is an accurate predictor of VT2. These findings give very interesting practical applications to cross-country coaches and skiers to evaluate and control specific aerobic training loads.

No influence of hypoxia on coordination between respiratory and locomotor rhythms during rowing at moderate intensity.

Besides neuro-mechanical constraints, chemical or metabolic stimuli have also been proposed to interfere with the coordination between respiratory and locomotor rhythms. In the light of the conflicting data observed in the literature, this study aimed to assess whether acute hypoxia modifies the degree of coordination between respiratory and locomotor rhythms during rowing exercises in order to investigate competitive interactions between neuro-mechanical (movement) and chemical (hypoxia) respiratory drives. Nine male healthy subjects performed one submaximal 6-min rowing exercise on a rowing ergometer in both normoxia (altitude: 304 m) and acute hypoxia (altitude: 2877 m). The exercise intensity was about 40 % and 35 % (for normoxia and hypoxia conditions, respectively) of the individual maximal power output measured during an incremental rowing test to volitional exhaustion carried out in normoxia. Metabolic rate and minute ventilation were continuously collected throughout exercise. Locomotor movement and breathing rhythms were continuously recorded and synchronized cycle-by-cycle. The degree of coordination was expressed as a percentage of breaths starting during the same phase of the locomotor cycle. For a same and a constant metabolic rate, acute hypoxia did not influence significantly the degree of coordination (mean ± SEM, normoxia: 20.0 ± 6.2 %, hypoxia: 21.3 ± 11.1 %, p > 0.05) while ventilation and breathing frequency were significantly greater in hypoxia. Our results may suggest that during rowing exercise at a moderate metabolic load, neuro-mechanical locomotion-linked respiratory stimuli appear "stronger "than peripheral chemoreceptors- linked respiratory stimuli induced by hypoxia, in the context of our study. Key pointsChanges in breathing frequency and ventilation induced by altitude have no effect on the degree of coordination between locomotor and breathing rhythms during moderate rowing exercise.During moderate rowing exercise in hypoxia, the neuro-mechanical drives still dominate over chemoreceptive stimuli.These above statements have to be taken carefully because it might be quite different during activities where the coupling between locomotor and breathing rhythms is less constrained (e.g., running, cycling).

Utility of the Conconi's heart rate deflection to monitor the intensity of aerobic training.

The Conconi's heart-rate deflection point (HRd) in the heart rate (HR)/speed curve is often used to set aerobic training loads. Training could either be set in percentage running speed or HR at HRd. In order to establish the limits and usefulness of various aerobic-training modalities for intermediate athletic level (physical-education students), acute responses were analyzed while running for a typical 40-minute training session. Speed, HR, lactate, and cortisol were thus recorded during training at 90 and 100% of running speed (RS: n = 14) and HR (HR: n = 16) at HRd (90% running speed [RS90], 100% running speed [RS100], 90% HR [HR90], and 100% HR [HR100]). During constant HR training, RS decreases while HR drifts upward during constant RS training. Half of the subjects can not finish the 40-minute RS100 session. For HR90, RS90, HR100, and RS100, average intensities are 67, 69, 74.9, and 77% maximal aerobic speed (multistage test), respectively. This study indicates that (1) training at HR100 and RS100 is more appropriate to improve high-intensity metabolic capacities (increased cortisol and lactate) while RS100 is too difficult to be maintained for 40 minutes for subjects at that level at least, (2) training at HR90, however, is better to improve endurance and capacity to do a large amount of work considering cortisol and lactate homeostasis, and (3) training at a constant HR using a HR monitor is a good method to control the intensity of the training with subjects not used to pacing themselves with the split-time approach.

Electrical stimulation superimposed onto voluntary muscular contraction.

Electrical stimulation (ES) reverses the order of recruitment of motor units (MU) observed with voluntary muscular contraction (VOL) since under ES, large MU are recruited before small MU. The superimposition of ES onto VOL (superimposed technique: application of an electrical stimulus during a voluntary muscle action) can theoretically activate more motor units than VOL performed alone, which can engender an increase of the contraction force. Two superimposed techniques can be used: (i) the twitch interpolation technique (ITT), which consists of interjecting an electrical stimulus onto the muscle nerve; and (ii) the percutaneous superimposed electrical stimulation technique (PST), where the stimulation is applied to the muscle belly. These two superimposed techniques can be used to evaluate the ability to fully activate a muscle. They can thus be employed to distinguish the central or peripheral nature of fatigue after exhausting exercise. In general, whatever the technique employed, the superimposition of ES onto volitional exercise does not recruit more MU than VOL, except with eccentric actions. Nevertheless, the neuromuscular response associated with the use of the superimposed technique (ITT and PST) depends on the parameter of the superimposed current. The sex and the training level of the subjects can also modify the physiological impact of the superimposed technique. Although the motor control differs drastically between training with ES and VOL, the integration of the superimposed technique in training programmes with healthy subjects does not reveal significant benefits compared with programmes performed only with voluntary exercises. Nevertheless, in a therapeutic context, training programmes using ES superimposition compensate volume and muscle strength deficit with more efficiency than programmes using VOL or ES separately.