Daniel Juárez Santos-García

Efficacy of Two Different Stretch Training Programs (passive vs. Proprioceptive Neuromuscular Facilitation) on Shoulder and Hip Range of Motion in Older People

Abstract González-Ravé, JM, Sánchez-Gómez, A, and Santos-García, DJ. Efficacy of 2 different stretch training programs (passive vs. proprioceptive neuromuscular facilitation) on shoulder and hip range of motion in older people. J Strength Cond Res 26(4): 1045–1051, 2012—The aim of this study was to determine the influence of 2 methods of stretch training (passive and proprioceptive neuromuscular facilitation [PNF]) on range of motion (ROM) in older people between the age of 60 and 70 years over a period of 13 weeks. Fifty-four participants (39 women and 15 men) were divided into 3 groups: passive (n = 17; 66.5 ± 6.5 years), PNF (n = 17; age, 64.7 ± 4.0 years old), and control (n = 17; age, 66.4 ± 4.5 years). The subjects trained 2 times per week on nonconsecutive days for 13 weeks. Each training session included 2 flexibility exercises focused on the shoulder and hip joints. The PNF group performed 6 seconds of passive stretching, 3 seconds of muscular contractions, and 2 seconds of relaxation. The passive group performed 10 seconds of stretching and 5 seconds of relaxation. This sequence was repeated 3 times by each group. The control group did not perform any stretching. In the PNF group, there was an increase in hip ROM (p < 0.001) between pretest and posttest in the passive group and an improvement (p < 0.001) was observed between pretest and posttest, whereas in the control group, there was a significant decrease (p < 0.01) in hip ROM between pretest and posttest. In shoulder ROM, there was an increase (p < 0.001) between pretest and posttest in the passive group and an improvement (p < 0.001) was observed between pretest and posttest in the PNF group. There were no changes in shoulder ROM between pretest and posttest in the control group. The analysis of variance showed significant differences in hip and shoulder ROM between passive and control groups and PNF and control groups, but no significant differences were found between passive and PNF. The main finding was that the ability of physically active older people to increase ROM in response to stretching techniques is similar for both passive and PNF techniques.

Interrelationships between different loads in resisted sprints, half-squat 1 RM and kinematic variables in trained athletes

Abstract Resisted sprint running is a common training method for improving sprint-specific strength. It is well-known that an athletes time to complete a sled-towing sprint increases linearly with increasing sled load. However, to our knowledge, the relationship between the maximum load in sled-towing sprint and the sprint time is unknown, The main purpose of this research was to analyze the relationship between the maximum load in sled-towing sprint, half-squat maximal dynamic strength and the velocity in the acceleration phase in 20-m sprint. A second aim was to compare sprint performance when athletes ran under different conditions: un-resisted and towing sleds. Twenty-one participants (17.86±2.27 years; 1.77±0.06 m and 69.24±7.20 kg) completed a one repetition maximum test (1 RM) from a half-squat position (159.68±22.61 kg) and a series of sled-towing sprints with loads of 0, 5, 10, 15, 20, 25, 30% body mass (Bm) and the maximum resisted sprint load. No significant correlation (P<0.05) was found between half-squat 1 RM and the sprint time in different loaded conditions. Conversely, significant correlations (P<0.05) were found between maximum load in resisted sprint and sprint time (20-m sprint time, r=−0.71; 5% Bm, r=−0.73; 10% Bm, r=−0.53; 15% Bm, r=−0.55; 20% Bm, r=−0.65; 25% Bm, r=−0.44; 30% Bm, r=−0.63; MaxLoad, r= 0.93). The sprinting velocity significantly decreased by 4–22% with all load increases. Stride length (SL) also decreased (17%) significantly across all resisted conditions. In addition, there were significant differences in stride frequency (SF) with loads over 15% Bm. It could be concluded thatthe knowledge of the individual maximal load in resisted sprint and the effects on the sprinting kinematic with different loads, could be interesting to determinate the optimal load to improve the acceleration phase at sprint running.

Effects of High-intensity Warm-ups on Running Performance

The objective of this study was to determine the effects of high-intensity warm-ups (WUs) on performance, physiological, neuromuscular and biomechanical parameters. Three randomized cross-over 105%vVO2max time limit trials (TLimT) were performed by 11 well-trained runners following three different WU protocols. These included two experimental high-intensity variants and one control WU variant: (i) 9x20-sec level strides (105%vVO2max; 1% gradient) with 60 s of recovery (level); (ii) 6x6-sec uphill strides (105%vVO2max; 5% gradient), with the same recovery (uphill) and (iii) 7 min at 60%vVO2max as control condition (control). The uphill and level WUs resulted in a greater performance during TLimT (160.0±6.62 s and 152.64±10.88 s, respectively) compared to control WUs (144.82±6.60 s). All WU conditions reduced the energy cost (EC) of running, respiratory exchange ratio, and step frequency (SF) after the experimental and control phases of WU, while blood lactate (BLC) increased in uphill and level WUs and decreased in control WUs. Changes in kinematic variables were found without differences between WU conditions during TLimT. BLC rose at conclusion of TLimT without differences between WU conditions. Both high-intensity WUs show a longer TLimT. EC is deteriorated after the high-intensity WU exercise due to a change of substrate utilization, increase of BLC and SF. A long transient phase (18 min) is necessary to avoid impairing the performance.