In practical WLAN deployments, the capture effect has been shown to enhance the performance of stations residing close to the AP, while putting at disadvantage the distant nodes. In this paper, we introduce an analytical model to characterise the performance of 802.11 devices with heterogeneous capture probabilities and different network loads, and explore the interaction between the MAC operation and PHY capture. Unlike previous studies, we reveal that the throughput of stations experiencing low capture probabilities can also benefit from the capture effect when the stations retaining high capture probabilities are not saturated. Following these findings, we design a power-hopping scheme for 802.11 MAC that exploits the benefits of the capture effect to improve performance in dense deployments where nodes experience similar channel conditions. We investigate the potential gains of this mechanism by implementing a practical approximation using commercial off-the-shelf hardware and open-source drivers and, by conducting experiments in a real testbed, we show that our scheme can significantly outperform the standard 802.11 protocol in terms of throughput.