Well i havent see any studies comparing the different rep ranges and their effect on muscle preservation, but there have been studies comparing lifting at different %of 1rep max and the effect it has on metabolism.
<div></div><div id="QUOTEHEAD">QUOTE</div><div id="QUOTE">Hunter et al (2) investigated the influence of the resistance load on metabolic rate. Seventeen subjects performed a bench press a intensities range from 20% to 80% of one repetition maximum. They found that the economy of the weight training exercise decreased as the resistance load increased. This indicates less muscular efficiency at the heavier weights, and/or that stabilizing muscles participated more, which in turn will increases the energy utilization during exercise. For example, the subjects used almost 12 times as much energy (calories) doing one repetition at 80 percent of 1 RM as opposed to one repetition at 20 percent 1 RM even though work only increased by a magnitude of four. Within each bench press load (20%-80%) there was a high relationship between work performed and energy expended. This finding is in agreement with research performed by Kuehl et al (3) who found the caloric expenditure during resistance training correlates with the total weight lifted. Hunter and colleagues indicate those individuals who are interested in body composition changes should train at 60 to 80 percent 1 RM. The metabolic rate is higher at increased loads, thus causing a greater number of calories utilized.
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Also
<div></div><div id="QUOTEHEAD">QUOTE</div><div id="QUOTE">The other factor to consider with the post-exercise is the fuel which is utilized. Strength training exercise tends to burn/utilize carbohydrate during the actual training session. However, after a workout more fat is burned to meet the energy demands of your body. The more carbohydrate burned during an exercise period, the more fat burned after exercise. Research performed by Brooks and Gaesser (5) as well as Bahr and Sejersted (6) confirm that the higher the exercise intensity, proportionately more fat will be burned during the recovery phase. Recent research at Colorado State University (7) examining the effect of a resistance training on postexercise energy expenditure and resting metabolic rate, concluded that strenuous strength training can elevate metabolic rate for extended periods, and that this enhanced metabolism is due to oxidation of body fat.</div>
The entire article is here with all the references etc
http://www.saskcoach.ca/index_files/StrengthMetabolism.htm
And:
<div></div><div id="QUOTEHEAD">QUOTE</div><div id="QUOTE">Current research of resistance weight training and EPOC has noted a relationship between exercise intensity and elevated metabolic rate. As weight lifting intensity increases, the EPOC duration also increases.
Intermittent, high-intensity weight training appears to have the greatest effect on EPOC (Melby et al. 1993; Laforgia et al 1997)</div>
References and rest of article from:
http://www.drlenkravitz.com/Articles/epoc.html
If he thinks its going to define the muscle or tone or whatever just tell him to do a google search on "high reps cutting myth" theres loads of articles on it.
Heres another, the high reps burn more fat myth is at the bottom
http://www.exrx.net/WeightTraining/Myths.html
If someone wants to burn more bodyfat it makes no sense to be trying to make the workout more aerobic.