Effects of ischemic preconditioning on economy, VO2 kinetics and cycling performance in endurance athletes.

The aim of this study was to determine the effect of ischemic preconditioning (IPC) on several measures of aerobic function and 4-km cycling time-trial performance. An acute cross-over design was adopted involving eight well-trained cyclists (age 27.0 ± 7.0 years) who completed incremental and square-wave exercise tests for determination of peak O2 uptake (VO2peak), ventilatory threshold (VT) and moderate- and heavy-intensity domain VO2 kinetics, as well as 4-km time trials. All were preceded by IPC, or sham-IPC, involving repeated bouts of thigh blood flow occlusion, interspersed with reperfusion. There was no significant difference between IPC and sham-IPC with respect to VO2peak (4.4 ± 0.6 L min-1 vs 4.4 ± 0.5 L min-1, effect size - 0.01 ± 0.09), VT (3.4 ± 0.6 L min-1 vs 3.5 ± 0.5 L min-1, effect size 0.07 ± 0.28), cycling economy (4.9 ± 4.9%, ES 0.24 ± - 0.24, P > 0.05) or any moderate-domain VO2 kinetic parameter. During heavy-intensity exercise, a reduced end-exercise VO2, slow component amplitude and overall gain was observed following IPC compared to sham-IPC. Though not statistically significant, there was a possibly beneficial effect of IPC on 4-km time-trial mean power output (2.2 ± 2.0%; effect size: 0.18 ± 0.15, P > 0.05). The observed reduction in VO2 slow component and tendency for improved economy and 4-km time-trial performance, albeit small, suggests that acute IPC shows some potential as a performance-enhancing priming strategy for well-trained cyclists prior to high-intensity exercise.

Warm-up with a weighted vest improves running performance via leg stiffness and running economy.

OBJECTIVES: To determine the effects of "strides" with a weighted-vest during a warm-up on endurance performance and its potential neuromuscular and metabolic mediators. A bout of resistance exercise can enhance subsequent high-intensity performance, but little is known about such priming exercise for endurance performance. DESIGN: A crossover with 5-7 days between an experimental and control trial was performed by 11 well-trained distance runners. METHODS: Each trial was preceded by a warm-up consisting of a 10-min self-paced jog, a 5-min submaximal run to determine running economy, and six 10-s strides with or without a weighted-vest (20% of body mass). After a 10-min recovery period, runners performed a series of jumps to determine leg stiffness and other neuromuscular characteristics, another 5-min submaximal run, and an incremental treadmill test to determine peak running speed. Clinical and non-clinical forms of magnitude-based inference were used to assess outcomes. Correlations and linear regression were used to assess relationships between performance and underlying measures. RESULTS: The weighted-vest condition resulted in a very-large enhancement of peak running speed (2.9%; 90% confidence limits ±0.8%), a moderate increase in leg stiffness (20.4%; ±4.2%) and a large improvement in running economy (6.0%; ±1.6%); there were also small-moderate clear reductions in cardiorespiratory measures. Relationships between change scores showed that changes in leg stiffness could explain all the improvements in performance and economy. CONCLUSIONS: Strides with a weighted-vest have a priming effect on leg stiffness and running economy. It is postulated the associated major effect on peak treadmill running speed will translate into enhancement of competitive endurance performance.