How Intensity Helps Repair Effects of Aging on Your Muscle Cells

By Coach John Hughes

Aging damages the cells in your muscles, which is especially severe, because they do not regenerate easily. They become weaker as their mitochondria, where energy is produced, diminish in vigor and number. An interesting new study tested the effects of different training protocols on the cells of younger and older sedentary individuals.

The Study

To test the effects of exercise, researchers at the Mayo Clinic tested different training protocols with 29 participants aged 18 to 30, and a second set of 26 participants aged 65 to 80. The age groups had approximately equal numbers of men and women. The participants did not exercise regularly before the study.

Baseline measurements were done and the participants were randomized into three groups. The research protocol for 12 weeks was:

• Interval training (HIIT) by 11 younger and 8 older participants three times a week on a stationary bike. The intervals were: repeat 4 times [4 minutes at 90% of VO2 max and 3 minutes very easy]. This group also walked for 45 minutes twice a week on a treadmill at 70% of VO2 max.
• Vigorous resistance training (RT) by 10 younger and 8 older participants twice a week, doing 4 sets of 8–12 repetitions of lower and upper body exercises.
• Combined training (CT) by 8 younger and 7 older participants. For 12 weeks they did no structured exercise and their daily activities were measured were by accelerometers. They then did 5 days per week moderate cycling at 70% of VO2 max for 30 minutes per session and 4 days per week weight lifting with fewer repetitions than the vigorous weight training.

After these training blocks, the same physiological measurements were taken as before the study.

The Results

The high-intensity interval training exercise produced mitochondrial increases of 49% in the younger group and 65% in the older group. The CT moderate exercise produced mitochondrial increases in the younger group by 38% but not in the older adults. The vigorous weight training did not produce any improvement in either group.

The HIIT increased VO2 max in the younger group by approximately 28%, CT increased VO2 max by approximately 17% and RT made no significant difference. At the start of the experiment, the older group’s VO2 max was approximately 30% lower than the younger group. In the older group HIIT increased their VO2 max by approximately 17% and CT increased VO2 max by approximately 21%! RT made no change in VO2 max.

Another consequence of aging is the decrease in fat-free mass (FFM) and increase in muscle wasting and weakness. Whole body FFM increased in all groups. The training groups with resistance training (RT and CT) had increased leg strength; however, leg strength did not change significantly with HIIT, possibly due to the specificity associated with cycling versus leg press exercises.

Importantly, the study notes that, “Younger adults demonstrated more robust increase of VO2 peak in response to HIIT, unlike older adults who responded equally to HIIT and CT.”

The study is relevant to roadies because both the HIIT and CT groups got their aerobic exercise by cycling as well walking for the HIIT group. However, there are two important caveats:

1. The study was done on previously sedentary people. The increases certainly would not be as dramatic with already fit cyclists.
2. The testing groups were very small for the different protocols, and studies with larger individuals may produce different results.

The Takeaway

HIIT sometimes means very short, very intense intervals. In the experiment the intervals were 4 minutes very hard / 3 minutes very easy. The intensity was equivalent to a Rate of Perceived Exertion of about 6 – 7 on a 10-point scale, over about 106% of lactate threshold and 106 – 120% of Functional Threshold Power.

Bearing in mind the above caveats, there are three important results for older roadies:

1. High-intensity training produced mitochondrial increases in older participants, but resistance training and lower intensity training did not produce significant changes.
2. Both high-intensity and moderate-intensity training produced similar increases in VO2 max in the older participants.
3. Specificity is important: cycling did not increase leg strength, and resistance training didn’t increase the mitochondrial functioning or VO2 max.

The full research study is published in Cell Metabolism.

My new eBook will describe in detail how best to use aerobic, intense aerobic and resistance training to combat the effects of aging.  Look for Anti-Aging: How You Can Slow the Aging Process later this month.

My eArticle Intensity Training 2016 shows you how to build or maintain your hard-earned fitness through the use of intensity training – across 10 different training objectives, each with 5-10 specific workouts.