Summary
When muscle glycogen falls to extremely low levels (about 40 mmol/kg), anaerobic exercise
performance may be negatively affected. Individuals following a ketogenic diet who wish to lift
weights or perform sprint training must make modifications by consuming carbohydrates for
optimal performance as discussed in chapter 10 through 12.
During long term ketogenic diets, muscle glycogen maintains at about 70 mmol/kg (113-
115) leaving a ‘safety factor’ of about 30 mmol/kg at which time glycolysis will most likely be
impaired.
Section 6: Other Topics
Beyond the adaptations and effects of the ketogenic diet discussed above, there are several
other topics regarding weight training that need to be discussed. This includes the effects of
combining strength and endurance training, gender differences, and the effect of detraining.
Combining strength and endurance training
Many individuals wish to combine strength and endurance training in their exercise
program. Whether it’s a pre-contest bodybuilder looking to shed fat or an individual looking for
basic fitness, the combination of weight and aerobic training is a topic of interest. Keep in mind
that the general adaptations to aerobic/interval training are to make muscle fibers more aerobic
and enduring while the adaptations to weight training are to make the fibers larger and stronger.
These two adaptations are somewhat at odds with one another (77). Therefore, we might expect
the combination of both types of training to impair overall adaptations.
Several studies have examined the physiological effects of various combinations of aerobic
exercise with resistance training. With one exception, these studies find a decrease in the
strength gains seen in individuals performing both resistance training and high intensity aerobics
(78-80). The decrease in strength typically occurs after 8 weeks. However, these studies have
problems that need to be addressed.
First, the combined training groups (endurance and strength) typically train their legs
more total days than either the strength or endurance only groups. So, the interference effects
may simply reflect local overtraining (78). One recent study examined this possibility, having
subjects perform strength and aerobic training a total of three days per week so that all groups
only trained three days per week total (81). No decrease in strength improvements were seen
which further suggests local overtraining of the legs as the cause of the strength impairments.
Second, the studies cited used heavy resistance training in combination with interval
training (as a football player or rugby player might be expected to train) (78-80). High intensity
aerobic training recruits Type II muscle fibers, causing them to become smaller and more
aerobic. The body can generally only adapt maximally in one direction or another so it may