Some important issues for future HIIE research include optimization of type and nature of HIIE protocols, individual fat loss response to HIIE, and suitability of HIIE for special populations. The most utilized protocol has been the Wingate test (30 s of all-out sprint). This protocol amounts to 3 to 4 min of cycle exercise per session with each session being typically performed 3 times a week. This protocol, although remarkably short in duration, is extremely hard and subjects have to tolerate significant discomfiture. Thus, the Wingate protocol is likely to be unsuitable for most overweight, sedentary individuals interested in losing fat. Other less demanding HIIE protocols have included an 8-second cycle sprint followed by 12 s of low intensity cycling for a period of 20 min [5], a 15-second cycle sprint followed by 15 s of low intensity cycling for a period of 20 min [45], and a 2-minute cycle sprint followed by 3 min of low intensity cycling for a period of 20 min [8]. A challenge for future research is to identify the minimal dose of HIIE for the maximum health benefit. As discussed earlier, reducing the length of HIIE training from 15 to 12 weeks still resulted in significant subcutaneous and abdominal fat loss [46]. Thus, more research is needed to identify the optimal length and intensity of the HIIE protocol for achieving varying health outcomes.