Effects of velocity loss during resistance training on athletic performance, strength gains and muscle adaptations.

We compared the effects of two resistance training (RT) programs only differing in the repetition velocity loss allowed in each set: 20% (VL20) vs 40% (VL40) on muscle structural and functional adaptations. Twenty-two young males were randomly assigned to a VL20 (n = 12) or VL40 (n = 10) group. Subjects followed an 8-week velocity-based RT program using the squat exercise while monitoring repetition velocity. Pre- and post-training assessments included: magnetic resonance imaging, vastus lateralis biopsies for muscle cross-sectional area (CSA) and fiber type analyses, one-repetition maximum strength and full load-velocity squat profile, countermovement jump (CMJ), and 20-m sprint running. VL20 resulted in similar squat strength gains than VL40 and greater improvements in CMJ (9.5% vs 3.5%, P < 0.05), despite VL20 performing 40% fewer repetitions. Although both groups increased mean fiber CSA and whole quadriceps muscle volume, VL40 training elicited a greater hypertrophy of vastus lateralis and intermedius than VL20. Training resulted in a reduction of myosin heavy chain IIX percentage in VL40, whereas it was preserved in VL20. In conclusion, the progressive accumulation of muscle fatigue as indicated by a more pronounced repetition velocity loss appears as an important variable in the configuration of the resistance exercise stimulus as it influences functional and structural neuromuscular adaptations.

A reliable unipedal stance test for the assessment of balance using a force platform.

BACKGROUND: The aim was to develop a unipedal stance test for the assessment of balance using a force platform. METHODS: A single-leg balance test was conducted in 23 students (mean ± SD) age: 23 ± 3 years) in a standard position limiting the movement of the arms and non-supporting leg. Six attempts, with both the jumping (JL) and the contralateral leg (CL), were performed under 3 conditions: 1) eyes opened; 2) eyes closed; 3) eyes opened and executing a precision task. The same protocol was repeated two-week apart. RESULTS: The mean and the best result of the six attempts performed each day were taken as representative of balance. The speed of the centre of pressure (CP-Speed) showed excellent reliability for the "best result" analysis in all tests (ICCs 0.87-0.97), except in the test with the eyes closed performed on the CL (ICC<0.4). The CP-Speed had better reliability with the "best result" than with the "mean result" analysis (P<0.05), whilst no significant differences were observed between the JL and the CL (P=0.71 and P=0.96 for mean and best results analysis, respectively). A lower dispersion in the Bland and Altman graph was observed with the eyes opened than closed, and the dynamic test. CONCLUSION: The single-leg stance balance test proposed is a reliable method to assess balance, especially when performed in a static position, with the eyes opened and using the best result of six attempts as reference, independently of the stance leg.

Effects of training frequency on physical fitness in male prepubertal tennis players.

AIM: Aim of the present study was to test if training frequency determines physical fitness and fat mass accumulation in prepubertal male tennis players (TP). METHODS: Body composition scans (DXA), jump performance (SJ and CMJ) and 30 m running speed tests were conducted in 24 TP (10.6 years) and 17 physically active boys. Tennis players were divided into two groups (TP5: playing 5 d/week, n.=14; TP2: playing 2 d/week, n.=10). RESULTS: Compared to TP5 and TP2, controls had more total body fat (+23-28%) and fat mass in the trunk (+42-43%) and legs (+13-19%), respectively (P<0.05). The relative VO2max was higher in TP2 (12%) and TP5 (15%) than in controls (P<0.001). A positive correlation was observed between weekly trainng hours and VO2max (r=0.42, P<0.05, N.=24). Compared to controls, TP5 and TP2 jumped higher in SJ and CMJ (P<0.05) and ran faster in the 30 m test (P<0.05). Similar VO2max, jumping heights and running speed times were observed between TP5 and TP2. After adjustment for the percentage of body fat and age, TPs reached higher VO2max values than controls, while differences in SJ, CMJ and 30 m did not reach statistical significance. CONCLUSION: Playing tennis 2 d/week at prepubertal ages was associated to enhanced aerobic power and reduced total and regional adiposity (trunk and legs) compared to non-active boys. Playing 5 d/week only has a small additional effect. TPs had also higher jumping and sprinting performance than the controls, although these differences were accounted for by the increased fat mass of the control boys.

The upper extremity of the professional tennis player: muscle volumes, fiber-type distribution and muscle strength.

The effects of professional tennis participation on dominant and non-dominant upper extremity muscle volumes, and on fiber types of triceps brachii (lateral head) and vastus lateralis muscles were assessed in 15 professional tennis players. Magnetic resonance imaging (MRI, n=8) examination and dual-energy x-ray absorptiometry (DXA, n=7) were used to assess muscle volumes and lean body mass. Muscle fiber-type distribution assessed by biopsy sampling was similar in both triceps brachii (2/3 were type 2 and 1/3 type 1 fibers). The VL was composed of 1/3 of type 2 and 2/3 of type 1 fibers. The dominant had 12-15% higher lean mass (DXA/MRI) than the non-dominant (P<0.05). Type 1, 2a and 2x muscle fibers of the dominant were hypertrophied compared with the non-dominant by 20%, 22% and 34% (all P<0.01), respectively. The deltoid, triceps brachii, arm flexors and forearm superficial flexor muscles of the dominant were hypertrophied (MRI) compared with the non-dominant by 11-15%. These muscles represented a similar fraction of the whole muscle volume in both upper extremities. Dominant muscle volume was correlated with 1RM on the one-arm cable triceps pushdown exercise (r=0.84, P<0.05). Peak power during vertical jump correlated with VL muscle fibers's cross-sectional area (r=0.82-0.95, P<0.05).

Bone mass in prepubertal tennis players.

To assess if exercise before puberty affects bone mineral content (BMC) and bone mineral density (BMD) we determined BMC and BMD in the dominant arm (DA) and non-dominant arm (NDA), lumbar spine and femoral neck in 25 tennis players (TP), 21 soccer players (SP) and 22 physically active controls (CG). All of them were under 12 years of age and prepubertal. In TP the DA was heavier than the NDA (7.5+/-0.8%), due to a greater lean mass (10.2+/-1.2%) and BMC (16.3+/-2.2%). The increased BMC is due to a greater DA bone area (11.1+/-1.9%) and BMD (4.1+/-0.7%). BMC inter-arm asymmetry was 50-75% of that previously observed in professional TP. Inter-arm asymmetry in lean mass, BMC, BMD and bone area was significantly higher in TP than in SP and CG. Lumbar spine BMC and BMD were similar across groups. TP and CG had similar femoral neck BMDs, whilst SP had higher femoral neck BMD than TP. In conclusion, tennis participation before puberty is associated with increased lean mass and bone mass, due to an enhanced bone size and areal BMD in the playing arm.

Inter-arm asymmetry in bone mineral content and bone area in postmenopausal recreational tennis players.

OBJECTIVE: To determine whether long-term recreational tennis participation is associated with increased bone and muscle mass in the dominant compared to the non-dominant arm, in postmenopausal tennis players. METHODS: Dual-energy X-ray whole body scans were performed in 10 postmenopausal tennis players (mean +/- S.D.; 59.7 +/- 4.8 years) and 12 postmenopausal non-active women (62.8 +/- 7.2 years) matched for age and height. Tennis players started in this sport at 31.4 +/- 8.8 years, and had been playing for 26.8 +/- 6.8 years, at least 3 h per week. In addition, shoulder isokinetic muscular strength was also evaluated. RESULTS: Tennis participation resulted in a lower whole mass and fat mass in both arms (P < 0.05). Dominant arm muscle mass and shoulder joint isokinetic strength were essentially similar in both groups, however, the tennis players showed 8% greater bone mineral content and 7% greater osseous area in the dominant than in the non-dominant arm (P < 0.05). No inter-arm differences were found in bone mineral density. A relationship was observed between the length of tennis participation and the degree of inter-arm asymmetry in bone mineral content (r = 0.81, P < 0.01) and bone area (r = 0.78, P < 0.01). However, the BMD of the arms was essentially similar in both groups. No differences were observed in femoral and lumbar bone mass and density between groups. CONCLUSIONS: Long-term tennis participation is associated with increased bone mass, but not BMD, in the dominant arm of postmenopausal tennis players. The magnitude of the inter-arm asymmetry of postmenopausal tennis players is proportional to the length of tennis participation.

Bone mass, bone mineral density and muscle mass in professional golfers.

The aim of this study was to determine the effects of long-term professional golf participation on whole-body and regional bone mass and density. Dual-energy X-ray absorptiometry was performed on 15 male professional golfers and 18 sedentary individuals, matched for sex, race, age (29+/-1 and 25+/-1 years, respectively), body mass (79+/-2 and 74+/-2 kg), height (1.78+/-0.01 and 1.77+/-0.02 m) and percent body fat (20+/-2 and 21+/-2%; mean +/- sx). We found that long-term professional golf participation is not associated with significant increments in regional or whole-body bone mass or density. Neither the lumbar spine nor the femoral neck showed any noticeable enhancement of bone mass in professional golfers compared with controls from the same population. The only effect of professional golf participation on regional body composition was a 9% increase in muscle mass in the dominant arm (P < 0.05).

¿Aporta alguna ventaja ingerir proteínas después del ejercicio intenso? / Is there any advantage from protein ingestion after intense exercise?

Múltiples estudios han demostrado que las necesidades dietéticas de aminoácidos están aumentadas en los deportistas. En los practicantes de resistencia se produce oxidación de aminoácidos durante el esfuerzo, aunque su contribución relativa al gasto energético total es pequeña, puede llegar a representar más de un 10-15 per cent del gasto energético cuando la reserva muscular y hepática de glucógeno están agotadas. En el caso de los practicantes de disciplinas en las que la fuerza y la potencia muscular son cruciales, las necesidades de proteínas están aumentadas para poder satisfacer la demanda de aminoácidos que genera el proceso de hipertrofia muscular, que depende de la síntesis de proteínas. La ingestión de alimentos en las horas siguientes a la finalización de un esfuerzo permite acelerar la recuperación por dos mecanismos principales. Primero facilitan sustratos para el proceso de recuperación (hidratos de carbono y aminoácidos). Segundo, contribuyen a transformar más rápidamente el ambiente hormonal catabólico, propio del final del esfuerzo intenso, en un ambiente hormonal con un perfil más anabólico, acelerando la recuperación muscular de glucógeno y la incorporación neta de aminoácidos en las fibras musculares. La ingestión de proteínas (en forma completa o como hidrolizados peptídicos) conjuntamente con hidratos de carbono parece, de momento, la combinación ideal para acelerar la recuperación. Los suplementos que combinan aminoácidos e hidratos de carbono permiten reponer más rápidamente las pérdidas de aminoácidos que se producen durante el ejercicio aeróbico prolongado y facilitan el proceso de hipertrofia muscular después de las sesiones de entrenamiento de fuerza (AU)

El entrenamiento para la mejora de la capacidad de salto / Training to improve the jumping capacity

La capacidad de salto es un factor importante para el rendimiento en una gran cantidad de actividades deportivas. Se sabe que los niveles de mejora de la capacidad de salto tras el entrenamiento dependen en gran medida de los niveles iniciales de fuerza del sujeto, pero lo que no está del todo claro es qué sistema es más eficaz en el entrenamiento de la mejora de la capacidad de salto, si los métodos más tradicionales, como el entrenamiento con cargas (o sobrecargas) o el entrenamiento pliométrico, o bien quizá los métodos más modernos basados en la combinación de ambos. El objetivo de este trabajo ha sido profundizar en el conocimiento actual acerca de los procedimientos más eficaces para mejorar mediante el entrenamiento la capacidad de salto, analizando los diferentes estudios que se han llevado a cabo sobre el tema y aportando las conclusiones más novedosas a las que se ha llegado en la literatura, así como las aplicaciones prácticas que podemos extraer de ellos. Otras técnicas que se han propuesto para mejorar la capacidad de salto vertical, basadas en la utilización de electroestimulación o vibración corporal, no serán abordadas en esta revisión (AU)