The Acute Effects of Ischemic Preconditioning on Short-Duration Cycling: A Randomized Crossover Study.

There is recent interest from coaches and athletes regarding IPC as an effective way to generate better competitive outcomes. Regarding cycling specifically, the impact of IPC remains unclear. This study aimed to assess the effectiveness of IPC treatment for improving athletic performance during short-duration cycling. After the exclusion and inclusion criteria, there were 11 volunteers for the 3-minute cycling TT and 13 volunteers for the 6-minute cycling TT. All volunteers were competitive athletes of aerobic sports. The IPC treatment consisted of three alternating cycles of 5 minutes of 100% occlusion followed by 5 minutes of reperfusion to each leg. The sham treatment consisted of three alternating cycles of 1 minute of 100% occlusion followed by 1 minute of reperfusion to each leg. The main finding was that IPC significantly improved (p<0.05) power output during 3-minute (4.22%) and 6-minute (2.29%) cycling TT relative to a sham. Additionally, about one-third of our participants required a tourniquet pressure higher than 220 mmHg to achieve 100% occlusion. These findings indicate ischemic preconditioning, administered bilaterally as three rounds of 5 minutes of total occlusion and ensuing reperfusion 20 minutes before a cycling TT, significantly enhanced average power output.

The Acute Effects of Ischemic Preconditioning on Power and Sprint Performance.

INTRODUCTION: Ischemic preconditioning (IPC) has been shown to induce positive effects on skeletal muscle resulting in enhanced physical performance. Data display that IPC positively impacts both aerobic and anaerobic performance. However, there is inconclusive data exemplifying IPC's effects on power and sprint performance. We hypothesized 15 minutes of bilateral lower limb IPC, applied 25-45 minutes prior to power and sprint activity, would enhance power and sprint performance. METHODS: Using a randomized crossover design, 14 NCAA Division II athletes received IPC (100 percent occlusion) and sham (50 mmHg) treatments followed by either a 0 minute or a 20 minute rest. A Delfi Personalized Tourniquet System (PTS) for blood flow restriction with an internal doppler radar was used to occlude blood flow to the lower extremities. Followed by IPC treatment, power and sprint performance was assessed using a vertical jump, reactive strength index (RSI), broad jump, flying 10m dash, and pro-agility. Each of the fourteen subjects in the experimental group received all four protocols. RESULTS: Using an ANOVA, no statistical significance was found between the type of treatment (i.e., sham 0 min, sham 20 min, IPC 0 min, IPC 20 min) and the performance tests: vertical jump (p=0.97), RSI (p=0.73), broad jump (p=0.98), flying 10m dash (p=0.99), and pro-agility (p=0.90). In addition, no statistical significance was found between the order of treatments and the performance tests (p=0.97). CONCLUSION: Despite previous research suggesting IPC enhances anaerobic and anaerobic performance, the current results indicate IPC doesn't significantly enhance power and sprint performance in highly trained athletes.

Physical performance is not improved with vitamin D repletion: a randomized trial.

BACKGROUND: Studies enrolling physically active participants have used various vitamin D dosing strategies which can result in diverse post supplementation vitamin D status due to individual body weight and initial vitamin D status. Emerging evidence suggests serum 25(OH)D levels of 100-120 nmol/L are optimal for peak performance, however, studies generally administer the same dose for all participants regardless of initial 25(OH)D status and body weight. This approach will not likely get all participants to the optimal 25(OH)D level proposed for optimal physical performance. Therefore, it's important to enroll vitamin D insufficient/deficient participants to observe the effects of vitamin D supplementation on physical performance. We assessed vitamin D repletion on markers of anaerobic performance in physically active adults by replenishing insufficient/deficient vitamin D to the target of 100-120 nmol/L suggested for optimal physical performance. METHODS: We conducted a double-blind randomized control trial in 42 physically active participants, 18-42 years of age in the winter months. Physically active participants with insufficient/deficient 25(OH)D status (<75 nmol/L) were supplemented with an individualized dosing strategy to achieve 25(OH)D of 120 nmol/L with eight weeks of supplementation using the following formula: Dose (IU)=40•[Target 25(OH)D3 - Initial 25(OH)D3]•Body Weight (kg). A modified Wingate test, 10m and 40m sprints, vertical jump, hand grip strength, pushups, and isokinetic knee flexion and extension were assessed before and after repletion of 25(OH)D. RESULTS: Thirty-nine out of 42 participants completed the study. Twenty-seven participants in the vitamin D group significantly increased 25(OH)D from 61 nmol/L to 123 nmol/L (P<0.001). 12 participants in the Placebo group had a significant decrease in 25(OH)D from 98 nmol/L to 83 nmol/L (P=0.02). Despite these changes in 25(OH)D status in each group, no significant changes in anaerobic performance markers were found. CONCLUSIONS: These findings indicate that vitamin D repletion to levels sufficient for optimal physical performance does not improve anaerobic physical performance.

Effects of vitamin D and quercetin, alone and in combination, on cardiorespiratory fitness and muscle function in physically active male adults.

INTRODUCTION: Vitamin D and the antioxidant quercetin, are promising agents for improving physical performance because of their possible beneficial effects on muscular strength and cardiorespiratory fitness. PURPOSE: The purpose of this study was to determine the effects of increased intakes of vitamin D, quercetin, and their combination on antioxidant status, the steroid hormone regulators of muscle function, and measures of physical performance in apparently healthy male adults engaged in moderate-to-vigorous-intensity exercise training. METHODS: A total of 40 adult male participants were randomized to either 4,000 IU vitamin D/d, 1,000 mg/d quercetin, vitamin D plus quercetin, or placebo for 8 weeks. Measures of cardiorespiratory fitness and muscle function, blood markers for antioxidant and vitamin D status, and hormones 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) and testosterone were measured pre- and postsupplementation. RESULTS: At enrollment, 88.6% of participants were vitamin D sufficient (serum 25-hydroxyvitamin D >50 nmol/L) and had normal serum testosterone levels. Supplementation with vitamin D significantly increased serum 25(OH)D concentration (by 87.3% in the vitamin D group, P<0.001) and was associated with an increasing trend of testosterone concentration. There were no changes in concentration of 1,25(OH)2D3 and markers of antioxidant status associated with vitamin D or quercetin supplementation. No improvements in physical performance measures associated with vitamin D and quercetin supplementation were found. CONCLUSION: The findings obtained demonstrate that long-term vitamin D and quercetin supplementation, alone or in combination, does not improve physical performance in male adults with adequate vitamin D, testosterone, and antioxidant status.