RESUMO
The American College of Sports Medicine recommends resistance training using at least 70% one repetition maximum to improve muscular strength and hypertrophy; however, these intensities may not be safe for all populations. A training technique that has been reported to elicit increases in strength and muscle size uses low intensity resistance training or low load training in combination with blood flow restriction (BFR) to the working muscle. Although the acute effects of BFR on muscle strength and size are well established, the effects of BFR on muscular power are not definitively known. Resistance trained males (n = 14) completed three experimental sessions in which lower body power output and vertical jump height were measured pre and post exercise protocol. The barbell back squat was performed with either low load and blood flow restriction, high load (90% 1 RM, HL), or control (CON). A significant mean difference between pre (M = 46.35 ± 5.61 cm) and post (M = 43.63 ± 4.59 cm) vertical jump heights following 15 repetitions at 20% 1 RM with BFR was observed (p = 0.034), but not with HL or a CON. A decrement in vertical jump height was experienced after an acute bout of BFR with low load resistance exercise. Low load resistance exercise with BFR or high intensity resistance exercise may not be beneficial as part of a warm-up to acutely enhance vertical jump or power output.
RESUMO
OBJECTIVE: The initiation of cardiopulmonary resuscitation (CPR) can be complicated by the use of protective equipment in contact sports, and the rate of success in resuscitating the patient depends on the time from incident to start of CPR. The aim of our study was to see if (1) previous training, (2) the presence of audiovisual feedback and (3) the presence of football shoulder pads (FSP) affected the quality of chest compressions. METHODS: Six basic life support certified athletic training students (BLS-ATS), six basic life support certified emergency medical service personnel (BLS-EMS) and six advanced cardiac life support certified emergency medical service personnel (ACLS-EMS) participated in a crossover manikin study. A quasi-experimental repeated measures design was used to measure the chest compression depth (cm), rate (cpm), depth accuracy (%) and rate accuracy (%) on four different conditions by using feedback and/or FSP. Real CPR Help manufactured by ZOLL (Chelmsford, Massachusetts, USA) was used for the audiovisual feedback. Three participants from each group performed 2 min of chest compressions at baseline first, followed by compressions with FSP, with feedback and with both FSP and feedback (FSP+feedback). The other three participants from each group performed compressions at baseline first, followed by compressions with FSP+feedback, feedback and FSP. RESULTS: CPR performance did not differ between the groups at baseline (median (IQR), BLS-ATS: 5.0 (4.4-6.1) cm, 114(96-131) cpm; BLS-EMS: 5.4 (4.1-6.4) cm, 112(99-131) cpm; ACLS-EMS: 6.4 (5.7-6.7) cm, 138(113-140) cpm; depth p=0.10, rate p=0.37). A statistically significant difference in the percentage of depth accuracy was found with feedback (median (IQR), 13.8 (0.9-49.2)% vs 69.6 (32.3-85.8)%; p=0.0002). The rate accuracy was changed from 17.1 (0-80.7)% without feedback to 59.2 (17.3-74.3)% with feedback (p=0.50). The use of feedback was effective for depth accuracy, especially in the BLS-ATS group, regardless of the presence of FSP (median (IQR), 22.0 (7.3-36.2)% vs 71.3 (35.4-86.5)%; p=0.0002). CONCLUSIONS: The use of audiovisual feedback positively affects the quality of the depth of CPR. Both feedback and FSP do not alter the rate measurements. Medically trained personnel are able to deliver the desired depth regardless of the presence of FSP even though shallower chest compressions depth can be seen in CPR with FSP. A feedback device must be introduced into the athletic training settings.
