Exercise can blunt the physical effects of aging. It has been estimated that 30% of all deaths from heart disease, diabetes, and colon cancer are related to inadequate physical activity. And even though we have data that supports the benefits of exercise, one study revealed that no more than 20% (and more likely less than 10%) of adults in the US exercise enough obtain enough to have a measurable impact on their health and fitness levels.

And what about the effects of aging on athletic performance? Two quotes from this web article summarize the key points:

• "...a gradual and fairly linear decline in most physiological and performance measures of 5 to 10 percent per decade after 30."
• "...you generally (see a) decrease both your maximal (performance) ceiling and your mean Time Trial wattage at an even rate"
• The specific impacts:
  • a decreased maximal power during ramp test, 30 W (7 percent) per decade.
  • a decreased mean power output during TT, 24 W (7 percent) per decade.
  • a decreased maximal heart rate (8 beats per minute, 4 percent) and mean HR during the TT (7 bpm, 3.8 percent) per decade.
  • a slight but significant decrease in cadence (3 revolutions per minute, 3.1 percent) per decade.

The 2 reasons behind this decrease in performance are

• a decrease in VO2 max and
• decrease in muscle strength

Second, the decrease in muscle strength. Again to quote: "Muscles are made up of thousands of individual muscle fibers. Each muscle fiber is innervated by a single nerve. With aging, humans lose the nerves that innervate muscle fibers and with each nerve loss, they lose the associated muscle fiber. For example, the vastus medialis muscle in the front of your thigh contains approximately 800,000 muscle fibers when you are 20 years old, but by age 60, it will have only about 250,000 fibers. The average person loses about eight percent of muscle size in the decade between 40 and 50 years of age, and the rate of loss increases to 15 percent per decade after age 75."

And coping strategies .... "You can slow the loss of muscle fibers as you age and can enlarge the remaining muscle fibers by exercising against resistance, but you cannot increase the number of fibers once they are lost. In one study, older men gained more muscle strength by spending more time lifting lighter weights, whereas younger men gained more muscle strength by lifting heavier weights. In younger men, doubling exercise volume by spending more time lifting weights produced limited added muscle enlargement. In older men, it resulted in much larger muscles and far more strength."

Or in a simple mantra, "use it or lose it (more quickly)". Regular training and stressing the CV and muscular systems will blunt the effects of aging and help keep you ahead of your peers.

Another plus for aging is that it gives us perspective and enjoyment beyond charging up the hills or racing to the next power pole. I think the author of the blog says it well. "I'm enjoying riding and racing more than ever before. I'm still mixing it up in the club hammer sessions. I'm riding on much nicer equipment now than what was available (or what I could afford as a poor starving grad student). I get to share my joy of cycling with our two boys, and I have the perspective of enjoying cycling as a lifelong activity that the young 'uns just don't have."

THE AGING MUSCLE AND THE MASTER ATHLETE

The impact of aging on our muscle (and indeed every) cells is inexorable. And it is reflected in a decrease in strength and performance in aerobic activities.

On average, muscle mass decreases approximately 3-8 % per decade after the age of 30 with this rate of decline accelerating over the age of 60. Some muscle loss (sarcopenia) is inevitable no matter what we do. But we can minimize the rate of loss by paying attention to our level of physical activity (more will minimize muscle loss) and our nutrition (adequate dietary protein) is required to maintain muscle repair and growth.

As a cyclist, you already minimizing muscle loss in your quads but what about other muscle groups (upper body strength) as well as in the winter when you are off the bike? I thought this NYT article nicely summarized options and strategies.You can turn things around within 3 months on a 3 times a week resistance training program that includes adequate dietary protein.

Proper technique is critical to getting the desired results without incurring an injury. And you should use your perceived level of exertion to determine the amount of resistance to use. Do 2 reps. Judge your effort. It should be "somewhat hard". (More on using a "feeling scale" to set resistance training levels.) Do 8 to 12 reps at this level of exertion - which should bring you to the point at which you would normally stop from fatigue.

And don't forget to review you daily protein intake as your muscles need adequate protein to respond to the resistance training. We know that older people absorb protein less effectively, so you will need at least 0.54 grams of protein per pound of ideal body weight, an amount well above what older people typically consume.

Along with a decrease in the total volume of the muscle (the cross sectional area of the entire muscle or it's "contractile mass"), a second factor in the progressive weakness experienced with aging is a decrease in the contractile force each muscle fiber can develop.

This study (full article http://ajpcell.physiology.org/content/ajpcell/early/2015/12/02/ajpcell.00289.2015.full.pdf) compared the force of individual muscle cell contraction in 3 groups - 80 year old master athletes, a cohort of sedentary peers (~80 y/o), and a group of 23 year olds. Although it has been speculated that the regular training of master athletes blunts aging's effects on individual muscle cell performance, the data show otherwise. The study normalized the force of contraction of individual muscle fibers "... when force was normalized to cross sectional ...both old (masters aged) groups did not differ, and the MA (masters) and NA (sedentary) were approximately 43% and 48% weaker, respectively, compared with young."

The final, third factor in the decreased performance (strength) of the aging muscle is a decrease in the effectiveness of neural activation (the nerve stimuli that initiate muscle cell contraction).

We know that regular exercise minimizes the expected loss of "motor units" (MU), the basic contractile unit in an intact muscle, with aging. (A motor unit is a single motor neuron and the several muscle fibers that will respond if it is firing. A single neuron may innervate several muscle fibers, so a motor unit is not necessarily limited to a single nerve/muscle fiber unit but rather a single nerve/multiple fibers unit.). This study, from 2010, showed us that the number of functioning motor units in the tibialis anterior of masters runners (approximately 65 y/o) were comparable to the values in the recreationally active young (approximately 25 y/o), and significantly more than healthy age-matched controls (approximately 65 y/o). "The estimated number of MU did not differ between masters runners and young, but MU number estimates were lower in the old (91 +/- 22 MU) compared with the masters runners (140 +/- 53 MU) and young (150 +/- 43 MU)."

The current study confirmed this. ".....greater preservation of muscle fiber number rather than contractile function may be contributing to the MA exceptional athletic performance. Additionally, fewer denervated muscle fibers (thus, a greater maintenance of muscle fiber number) and the ability of the MA (master athletes) to activate their muscle to a greater extent than NA (non-athletes) may influence EC-coupling and Ca2+ kinetics ..." So we see that although aging impact on individual cells cannot be stopped, regular exercise provides a tool to compensate by maintaining more active muscle motor units as well as preserving larger muscle fibers. So keep up those intervals and that weight work at the gym.

AGING AND OTHER ASPECTS OF HUMAN PHYSIOLOGY

Physiologic and performance measures peak in the late teens and 20s, and then decline with age. However they do not all decline at the same rate, and the rates of deterioration vary according to lifestyle (the old use it or lose it philosophy).

a) Bones (osteoporosis)

Aging is accompanied by a loss of bone mineral content. Aside from using calcium supplements to minimize bone loss, there is no support for a role of diet in preventing this natural process. On the other hand, there is excellent evidence on the benefits of regular physical activity to maintain muscle and bone structure.

Physical activity is necessary for bone health, but not all exercise is equal in that regard. Exercise that involves running and hopping, that cause microscopic bone deformity and in turn induce a compensatory response are much better for your bone health than non jarring activities such as swimming and cycling.

This study compared elite runners and cyclists. Even though the cyclists included weight lifting in their off season training, it was not enough to compensate for the lack of "jarring" activity. The result? The cyclists, as a group, all had thinner bones than the runners, and more than half of them met medical criteria for low bone mineral density in some portion of their skeleton.

So if you do not regularly cross train, consider adding some regular bone-stressing activities such s these to your weekly routine:

• Hiking
• Jogging/running
• Jumping Rope
• Stair climbing
• racquet sports

b) Muscles

Strength levels for men and women are at their peak between the ages of 20 and 30. Without a regular exercise program, there is then a decrease in muscle mass from muscle fiber atrophy hat becomes particularly apparent at age 60 . However, this is a combination of aging effects on the muscle/ nerve unit AND a decrease in daily muscle loading. One study of men between the ages of 60 and 72 years, training with standard muscle resistance exercises, demonstrated an improvement rate equal to young adults. Another group of 70 year olds who had regularly trained from age 50, had a muscle cross sectional area equivalent to a group of 28 year old students. (more details below)

c) Nervous system

Reflexes do slow with age, but as with muscular strength, activity minimizes the effects. Active men in their 70s had reaction times equivalent to inactive men in their 20s.

And the odds of developing dementia if you exercise regularly decreases as well. This blog post from Dr. Mirkin provides more details as well as references. And a few additional direct excerpts from one of his later blogs (these may be repetitive - I did not review the references and include these for those interested):

• Researchers followed the physical activity and did brain MRIs of 3700 men and women over 60 years of age for more than 10 years and found that the most active people had larger hippocampi (the part of the brain that controls short-term memory) and that those over 75 had the greatest benefit from exercise (J of Geron Ser A: Biol Sci and Med Scien, August 2016).

• Canadian researchers analyzed brain scans of 330 healthy adults, ages of 19 and 79, and showed that those who walked up and down stairs regularly had younger-appearing and larger brains (Neurobiology of Aging, April 2016;40:138-144). They estimated that every added flight of stairs walked each day reduced the person's brain age by half a year.

• A group of 100 men, aged 55-68, with mild cognitive impairment (progressive impaired memory) did a supervised program of lifting increasingly heavy weights twice a week for six months. Compared to those who had a program of just stretching, the weightlifters had a significant improvement in their memories and ability to solve problems and the greater the gain in strength, the greater their improvement in mental function (J of American Geriatrics, Nov 30, 2016).

• A study of 3050 twins, followed for 25 years, showed that moderately vigorous physical activity is associated with higher memory and better problem solving (J of Alzheimer's Disease, September 2, 2016).

• Very strong data show that regular exercise improves memory. Exercising muscles produce and release into the bloodstream a substance called Cathepsin B (CTSB) that has been shown to increase memory and grow nerves in mice, monkeys and humans (Cell Metabolism, June 12, 2016). Many previous studies show that the higher the blood level of CTSB, the greater the improvement in fitness level and memory. Researchers showed that after just one week of exercise, a normal mouse's memory improved dramatically. However, mice who were genetically engineered to be unable to produce CTSB gained no improvement in memory tests from exercise. Other studies are proceeding to find out if CTSB can be given to people to help prevent and treat the amyloid plaques that characterize Alzheimer's disease.

• When healthy, regularly-exercising master athletes, ages 50-80 years, stopped exercising for just 10 days, MRI brain scans showed a marked reduction in blood flow to the hippocampus, which controls memory. As people start to develop Alzheimer's disease, the hippocampus in their brains become smaller. (Frontiers in Aging Neuroscience, August 5, 2016).

This article documents the neurologic benefits of aerobic training, but similar benefits have been found in the musculoskeletal and cardiovascular systems as well.

There were 3 study groups.

1. A control group (with no intervention)
2. An exercise only group (six months of of aerobic exercise, three times a week, 45 minutes, at greater than 65 percent of their max heart rate)
3. An exercise AND diet group (adopted the Dietary Approaches to Stop Hypertension (DASH) diet).

So if you have been mourning over opportunities lost, it is never too late to take up an aerobic exercise program - and consider improving your diet as well (less meat and less sugar being the two biggest factors).

d) Lung (pulmonary) function

Once again, there is a decrease in lung function with age that can be blunted with regular activity. These studies indicate that a lifetime of regular physical activity may retard the decline in pulmonary function associated with aging.

e) Cardiovascular function

• aerobic capacity declines twice as fast in sedentary individuals and may even plateau with a regular training program.
• the maximum heart rate does decline with age
• cardiac output also falls with age - partially related to heart rate, but also from a decrease in stroke volume

f) The immune system

This interesting study on exercise and immunity found that "..125 long-distance cyclists, some now in their 80s, .....had the immune systems of 20-year-olds."

As nicely summarized by Dr. Mirkin "T-cells recognize foreign proteins on the surface of invading germs and cancers to tell your immunity to attack and kill these cells. They then stimulate your immune system to make antibodies to attach to and kill invading germs and cancer cells, and produce chemicals called cytokines that activate other T-cells to remove germs and cancer cells from your body. Other regulatory T-cells dampen down your immunity so that your immunity does not attack and destroy your own healthy cells."

The study suggests that this weakening of the aging immune system is from a significant reduction in thymic activity and the production of T cells. This senescence is blunted in regular cyclists, and to quote: "....many features of immune senescence may be driven by reduced physical activity with age."

TRAINING SLOWS THE AGING PROCESSS

Ben Franklin once said that the only constants in this world were death and taxes. The negative effects of aging on physical performance should probably be added to this list. However numerous studies have demonstrated the dramatic effect a regular exercise program (riding three to four times a week) can have on blunting the inevitable changes.

• 41% less likely to die from heart disease
• 58% less likely to develop diabetes

And the training effect is so effective that the aging process may be held at bay for up to a decade or more. In fact, for any age group regular riders are 150% less like to die from all causes.

Why is exercise so effective in blunting the effects of aging? There are multiple possibilities.

• Exercise changes our Metabolome - the complete set of metabolites (organic molecules) in a cell, tissue, organ or organism, which are involved in or are end products of cellular metabolism.The last few years have seen a dramatic increase in the number and type of tools for metabolomic investigations. This paper is a fascinating example of how detailed these investigations into exercise physiology have become.

  I am going to quote from a NYT article review of the paper. Scientists "decided ....to complete a full census of almost every molecule that (might) change when we work out."

  Study participants were "asked ....to complete a standard treadmill endurance test, running at an increasing intensity until exhaustion, usually after about nine or 10 minutes of exercise." Blood was drawn at time 0, immediately after this exertion, and again 15, 30 and 60 minutes later.

  The scientists "...measured the levels of 17,662 different molecules. Of these, (the concentrations of) 9,815 - or more than half - changed after exercise, compared to their levels before the workout. Some increased. Others declined. Some gushed immediately after the exercise, then fell away, while others lingered in heightened or lowered amounts for an hour after the workout. The types of molecules ....ranged widely, with some involved in fueling and metabolism, others in immune response, tissue repair or appetite."

  The answer to the question on positive health effects is almost certainly buried in this collection of 9815 organic molecules.

• A second possibility is a direct effect of aerobic exercise on our chromosomes. With aging, our chromosomes, and specifically the DNA at the end of the chromosomes (telomeres), shorten. And at a critical telomere length, cells become unable to replicate or enter a process called programmed cell death.

  As this process of aging is common to all cells, any strategy that delays (or better yet, reverses) this shortening process will extend cell life. This study suggests that aerobic training does just that.

• Another possibility may be via its effect on our mitochondria to preserve a cells energy supply. Although this reference is focused on the energy supply for nerve tissue, I suspect there is a similar process in mitochondria many cell types throughout the body.

  To quote: "Researchers ....discovered that an enzyme called SIRT3 that is located inside mitochondria may protect mice brains from loss of their energy supply (Cell Metabolism, November 19, 2015). Normal mice who ran on a spinning wheel increased their levels of SIRT3 in nerve cells, maintained brain function with aging ..... A special group of mice that were genetically engineered to be unable to produce SIRT3 gained no benefit from running on a spinning wheel..... This implies that SIRT3 strengthens brains and that blocking SIRT3 prevents exercise from benefiting brain function."

Although there is a trend towards an increased percentage of body fat after age 30, there is good evidence that a resistance training program will minimize the loss of muscle mass, and good eating habits and self awareness will prevent weight gain.

The protein needs of older athletes increases with age. The US Recommended Dietary Allowance (RDA) for protein intake is 0.8 g/kg/day for adults. But as we have just read, this may be on the low side for an athlete. How did that happen? Most likely as the recommendation is based on nitrogen-balance studies in average young adults who almost certainly have varying athletic leanings.

And it is probably too low for older adults who are less efficient in their protein digestion and absorption. It has been speculated that too little dietary protein and as a result being relatively relative protein deficient, may be an aggravating factor in the loss of muscle mass that accompanies aging.

Taking both aging and activity level into account, an international panel of experts recommended protein intakes of 1.0 - 1.2 g/kg/day for all adults 65 years or older, with even higher intakes for those who are more physically active.

So for all of us who are riding regularly, and often competitively - even if just with friends on the weekend, it is important to keep an eye on the protein content of our diets.

I have never been a fan of the over response with the paleo diets as the red meat comes along with a lot of undesirable fats. So if you want to err on the side of caution, there are plenty of non meat sources of protein to add to your diet.

There is also less "physiologic forgiveness" or latitude to skip the pre-event carbohydrate meal, and an increased sensitivity to major fluid shifts from sweating and inadequate replacement. But aside from this decreased tolerance for physiologic abuse, and a slightly higher daily protein requirement, the general principles of nutrition are exactly the same for all age groups including vitamin, mineral, and electrolyte replacement as well as the use of ergogenic aids such as diet supplements and unusual food products.

USE IT OR LOSE IT...PERHAPS FOREVER

Regular exercise has a powerful effect on many metabolic processes (beyond beefing up your VO2max and limiting the loss of muscle mass). This is especially true of insulin metabolism where a lack of exercise directly affects the tendency to obesity, insulin resistance and type 2 diabetes.

Generally, we think that taking some time off from aerobic activity, and the resulting impact on our metabolism is reversible when we get back to the gym or on the bike. This study suggests that is not the case, especially for older adults.

So the old adage "use it or lose it" has a new level of significance for older adults in that once they lose it, it may be gone forever no matter what they do. So on that business trip, or family vacation, it is worth taking the time for a 30 to 60 minute daily walk or other activity that will boost your heart rate.

NYT article

USE THE "RPE" OR "FS" SCALE TO TARGET TRAINING INTENSITY

This article is jargon heavy, but suggest you could use an RPE type scale (called the FS or "feeling scale") to guide resistance and aerobic training. Maintaining an exercise program is to a significant degree based on our perception of discomfort (pleasure) from the exercise sessions. Too much discomfort and our commitment to continue quickly wanes.

For aerobic exercise we have the RPE scale based on our perception as to how hard we "feel" we are exerting. It correlates well with more objective measures such as heart rate or power meter readings.

The study validated that a participant could use the Feeling Scale (FS) to self-regulate exercise intensity. Again, less discomfort = more likely to continue with future sessions. The FS was originally described as spanning -5 (I feel very bad) to +5 (I feel very good) with 0 being neutral.

We know that to improve muscle strength (and muscle mass) you need to maintain a resistance exercise intensity between 55% to 85% of your personal 1 repetition maximum (1RM). How does that translate into a FS rating for resistance exercise? Using a group of non exercisers, exerting to a level between feeling "good" (+3) to "fairly bad" (-1) matched up with weights (or resistance intensities) between 55% to 85% of the 1RM.

If you wanted to use the FS system for aerobic training, the same general relationship applies. For aerobic training (running and cycling exercise), the exercising to feel "good" (+3) and/or "fairly good" (+1) did produce an exercise intensity that generated cardiovascular improvements.

I was able to find this table which shows the relationship between the traditional 10 point RPE scale and how you feel (although not the specific FS number scale).

STRATEGIES TO STAY AHEAD OF THE CURVE

Is it safe to exercise as you age? If one uses common sense, the long term health benefits far outweigh any potential cardiac complications. One should avoid the extremes such as exercising above and beyond the level you have trained for, environmental extremes of temperature and humidity, and exercising when not feeling well. But even orthopedic injuries, which might be expected to be more common in the older athlete, do not appear to be increased with activities of moderate intensity and duration. A few thoughts:

• It's not just the miles you put in. Athletes who maintain or increase workout intensity tend to see their VO2 max decline at a lower rate than those who focus on higher mileage but at a slower pace. Stay with those intervals - year round. Aim to keep the heart rate is at 85 - 90 % of max.
• There is a drop off in muscle volume near age 60. Keep lifting those weights.
• You will need a little more recovery time than when you were 25. So take factor in a little off the bike rest time to let those muscles heal between workouts.
• Stay on that balanced diet with an emphasis on fruit, vegetables, more whole grains and enough protein to help main muscle volume (remember you will need more as you age, not less). And, of course, plenty of carbs to replace the Calories you will be using on those rides.
• Keep your life in emotional balance and enjoy family, friends and other activities. Don't just focus on the biking to the exclusion of all else.

These strategies were reinforced in a recent NYT article, "Age is irrelevant when it comes to fitness." Several quotes from the article:

• "Even if you can't quite turn back the clock, you can actually slow it considerably and maintain a high level of performance deep into your sunset years."

• "As much as 70 percent of your athletic power after turning 50 remains under your control."

• You can minimize the factors working against you:
  • declining aerobic capacity
  • more body fat
  • shrinking muscles
  • decreased mobility

But even if you slacked off on those intervals, just keeping to a routine including regular aerobic activity will pay off with huge anti-aging dividends. How big? This recently published study provides some insight.

• There were 28 in the active study group, average age 73. They exercised because they enjoyed it and only rarely competed. Running, cycling, and swimming, for more than 50 years they averaged 5 days/wk for a total of 7 hrs/wk.
• They measured cardiovascular health defined as aerobic capacity (Vo2max) and found that the active elderly group had
  • aerobic capacities that were 40 percent higher than those of their sedentary peers and
  • equivalent to that of people 30 years younger than themselves!!

• The measurement of VO2max was supplemented with muscle biopsies measuring the degree of muscle vascularity (capillary density) and cellular aerobic metabolism enzyme levels. And again they found both measures in the study group to be equivalent to the younger athletes.

1. reducing training volumes (number of rides a week). As you age you need more rest to recover from the minor physiologic traumas of hard physical activity. And if you are more rested, you can then push yourself harder during interval training. So the first challenge for those of us who have been used to pushing ourselves for years is decreasing the number of hours (or days) a week on the bike.
2. Make aerobic activity part of your lifestyle. Five days a week. A solid hour.
3. If possible, add intervals (or a period of aerobic stress) several days a week.
4. Supplement your aerobic program with resistance training (lifting weights) and increased dietary protein.

A.If you don't stress the CV system, you will lose aerobic capacity over time. But you can minimize that loss by regular riding - and by pushing yourself. I would consider doing intervals once or twice a week as one part of a program (if you are not now). And that means getting your heart rate up into Zone 4 for you. As to the knees, make sure you have a good fit on the bike, pedals (if you have clips) with good play (like frogs/speedplay), and then keep that RPM between 90 and 100. Don't lug on the hills, or spin too fast - it plays havoc with the knees.

Q. I am 69 years old, female. I ride about 130 miles a week and am working on interval training and sprinting to get stronger and faster. I ride a minimum of 20 miles a day. I have osteoarthritis in my back and hands. I don't take anything for the osteoarthritis and find that cycling is my key to living with OA and hopefully preventing it from getting worse. Today, I did 4 intervals of 1/2 mile. From a dead start, I was able to ride 18.8 on the 2nd interval and 18.7 on the 4th. My goal is to ride the 5K and 10K in the Senior Games in October at 18 mph. On a dead start, I can sprint up to 23 mph in the first few seconds, but it poops me out quicker and I ride slower, on the 1/2 mile interval, i.e., 17.7. My question involves maximum heart rate. I have noticed that my heart rate number is going higher, before I get exhausted, than a couple of months ago.

A.This question suggested that you may have fallen into a deadly trap in training, the "if a little is good, a lot is better" approach. It is really important to warm up before you do the intervals. If you are not doing so (5 miles or so at a modest pace) you risk injury and, as the CV system is not yet into its rhythm, you won't get maximum benefit from the intervals before feeling fatigued.

I don't see any advantage to a 23 MPH sprint for a few seconds - the whole interval should be at a steady pace you pick. If you can't hold 23 for the full interval, either decrease the interval duration or the speed.

It is really important to take off a few days a week off the bike. I'm not sure what to say about "your MHR going higher" but it is possible this is a sign of overtraining, not ideal training.

And finally, I did get the following question which raises a point I'd like to reemphasize:

Q.It seems your website is mostly designed for much stronger riders than I. Perhaps, you will see the benefit of gearing part of it to someone on my level, although there is a really small percentage of women my age, who have the drive to "push their limits." Presently, I know only one other female with that drive.

A.As to age, if you key your training to your personal max heart rate (less as you age) the general approach to a training program (how you divide up the rides during a week)should be age independent.