I read with great interest the article by Slentz and co-workers entitled “The Effects of Aerobic versus Resistance Training on Visceral and Liver Fat Stores, Liver Enzymes and HOMA from STRRIDE AT/RT: A Randomized Trial” published in the August 16, 2011, issue of American Journal of Physiology - Endocrinology and Metabolism (13).
This paper clearly demonstrates that aerobic training had a significantly greater effect than resistance training on liver fat, visceral fat, alanine aminotransferase (ALT), HOMA and both total and subcutaneous abdominal fat. Undoubtedly aerobic training is a useful training method that can improve body composition (4) and, as well demonstrated by Slentz and co authors in this article, had a beneficial effect on liver fat. I agree in general with the findings of Slentz et al., but also with Sundell’s statement “Resistance training has favourable effect on metabolic syndrome since it decreases fat mass including abdominal fat. It also enhances insulin sensitivity, improves glucose tolerance, and reduces blood pressure values” (14). This is only an apparent contradiction because there are some unresolved questions about exercise variables. The conflicting results regarding the effects on body composition and insulin sensitivity of resistance training and aerobic training (5,6,10,12) can be explained by the extremely wide range of exercise variables, for example aerobic training may be performed in many different ways to achieve the same results (3). Also resistance training may be carried out via different methods that have been shown to have differing effects on muscle metabolism and signalling pathways related to insulin (9). Recently our group has demonstrated the different effects of circuit training carried out at low or high intensity on some anthropometric and metabolic variables (8). In our opinion there is something that maybe best described as a “scotoma” in research on various training methodologies; if we don’t consider the extremely wide range of different exercise execution we risk underestimating the importance and the effects of the different kinds of exercise. In Slentz’s study the classical 3 sets of 8 to 12 repetitions scheme was used but its effectiveness is, at least, questionable (1). A resistance training program is a composite of several important variables including: 1) muscle action used, 2) type of resistance used, 3) volume (total number of sets and repetitions), 4) exercises selected and workout structure (e.g., the number of muscle groups trained), 5) the sequence of exercise performance, 6) rest intervals between sets, 7) repetition velocity and 8) training frequency (7,9,12). It is in the interests of researcher to carefully consider the exercise study design with specific regard to these variables, in order to avoid underestimating the effectiveness of certain kinds of exercise. The following sentence “… in sedentary, overweight and obese adults, aerobic training was consistently more effective than resistance training at improving visceral fat, total abdominal fat, liver fat, and the liver derived enzyme alanine aminotransferase” should contain the adjunctive information “aerobic training performed at 75% VO2max, 3 times a week, 117 min a week” and “resistance training performed at 3 times a week, 3 sets for 8-12 reps”. I hope that this invitation to greater precision in training description can be taken into account in order to better define the most effective kinds of exercise, especially for resistance training that may be considered the multifaceted side of exercise