Anti-Aging: More on Threshold, Sweet Spot and High Intensity (HIT)

By Coach John Hughes

I’ve written two related columns on how hard exercise increases longevity:

• Anti-Aging: Interval Training Increases Longevity.
• Anti-Aging: Interval or Fartlek for Longevity?

RBR reader Glen asks a good follow up question, “Can you explain the differences between threshold, sweet spot, and high intensity training? Your eBook Performance Cycling Past 50 recommends sweet spot training for century training, and both sweet spot and threshold training for improving speed. Where does HIT fit in? Is the power program better for improving climbing than the century program?”

Coach Hughes You’re asking excellent questions, Glen.  Rather than just jumping into intensity training you’re asking which kind(s) are best for you personally.

A Little Physiology

Exercising at different intensities produces different physiological changes. When you’re driving a car, as you accelerate the engine produces higher RPMs using the same fuel and drive train. Your body doesn’t work this way. As you work harder, your mix of fuels changes. You also add different drivetrains.

Every time a muscle contracts or exerts force, it uses energy produced by adenosine triphosphate (ATP), which comes from three different sources:

1. Oxidative aerobic system

Oxidative aerobic system (low power/long duration). The oxidative system is composed of two different sub-systems:

• Metabolism of triglycerides uses beta oxidation. The triglycerides are stored in adipose tissue (body fat).
• Metabolism of glucose uses a different metabolic system. Glucose is stored as glycogen in the liver and muscles.

The energy is produced in the mitochondria, a part of the cell. Aerobic exercise enhances the enzymes and the capacity of the mitochondria to produce energy. As explained in the earlier columns, intensity workouts counteract the damage done to the mitochondria by aging.

2. Glycolytic anaerobic system

Glycolytic anaerobic system (moderate power / short duration). This system metabolizes glucose without oxygen to produce the ATP. This system provides energy for very hard efforts of about 30 seconds to two minutes. The glycolytic system is anaerobic, and lactic acid (also called lactate) is a byproduct. As soon as enough oxygen is available, the lactic acid is converted to energy.

3. ATP-PC (high power/short duration)

ATP-PC (high power / short duration). This system produces energy that can be used for maximal effort — a sprint. Training this system increases your sprint from 50-100 meters to about 300 meters.

All of the energy systems are operating all the time; however, depending on the level of effort, one system predominates.

Your muscles have two kinds of muscle fibers, which fire progressively depending on the demand for power:

1. Slow-twitch fibers (ST), which refers to how fast the muscle fibers contract (not how fast your cadence is). Slow-twitch fibers have great endurance but low power.
2. Fast-twitch fibers (FT) are of two types:
   • Fast-twitch IIa (moderate power and endurance)
   • Fast-twitch IIb (high power and shorter endurance)

Intensities and Goals

Which intensities(s) are right for you depends on your goal(s). The following are in the order of increasing intensity.

1. Endurance to build an aerobic base and increase how long you can ride. Endurance riding trains some of your ST muscle fibers. Riding at conversational pace. For more information see my column: Anti-Aging: How Much Base Training?
2. Threshold (aka tempo) to improve your cruising speed on your endurance rides. Threshold riding calls into play more of your ST. A little faster than endurance riding; you can still talk comfortably but not whistle.
3. Sweet Spot to increase your power. SS efforts train your all of your ST and start to train your fast-twitch fibers. You can still talk in short phrases.
4. Hammer (aka lactate or anaerobic threshold) to get fit enough to stay with faster riders. Hammering utilizes all of your ST and more of your FT. You can’t talk but aren’t gasping for air.
5. VO2 max to increase your VO2 max, also called aerobic capacity, which is the maximum amount of oxygen that your working muscles can utilize. VO2 max intervals continue to use all of your ST and now use all of your FT.
6. Sprinting to enhance your pedaling efficiency.

A better name for high intensity training (HIT) is higher intensity training. We’re each an experiment of one.  What’s higher for you may be too high (or not high enough) for your buddy. If your riding is all endurance riding at a conversational pace, then threshold riding is HIT for you. If you ride at a conversational pace on the flats and climb at a threshold pace then sweet spot riding is HIT for you.  You may choose to go even harder. For example, if you’re an endurance rider you may choose to hammer some or even do VO2 max intervals — but I won’t fault you if you don’t want to suffer!

Sprinting is valuable for all riders even if you’re not competitive with your friends. Your ST and FT fibers don’t naturally all fire simultaneously so they’re inefficient. When you sprint you demand maximum power and over time this trains all your fibers to fire at the same time. This is like dialing in the timing on your car so all the cylinders fire at the same time.

Endurance Rides Including Centuries

To ride anything but a flat endurance ride in calm conditions you need power, which is why I recommend sweet spot training. Sweet spot training will help you to get up the climbs without struggling. Sweet spot training will also help you when it’s windy (not just breezy).

Riding at an endurance pace you’re using some of your slow twitch fibers. To ride faster you need to use more of your ST fibers. Threshold (tempo) riding recruits more of your ST fibers, which is why threshold training increases your cruising speed. You also need more power, which is what SS training does. 

The higher the intensity intervals the more recovery you need. Riding in the sweet spot is the optimal combination of the right intensity with the least recovery to produce the maximum cumulative overload on your muscles. You can read more about the SS here:

• Sweet Spot Training for Every Rider, pt. 1
• Sweet Spot Training for Every Rider, pt. 2

In this column 6 Kinds of Intensity Training Which One Is Right for You I explain the different kinds of intensity and give you training zones based on perceived exertion, heart rate and power.

The Optimal Mix of Workouts

Your body can only handle so much training. The harder the training the less volume you can do without risking injury or overtraining. I wrote this column on:

• 12 Tips to Avoid Overtraining

You asked about my eBook Performance Cycling Past 50, which has two different programs:

1. 12-week endurance program building up to a century (200K). This program prioritizes progressively longer rides every other week. The challenging long rides are more than half of the weekly training volumes. For the other rides during the week you can only handle one more challenging ride. Sweet spot is more important for climbing and headwinds than threshold training, which is why SS workouts are included in the century program but not threshold rides. (The alternate weeks are easier to provide full recovery.) Because you’re an experiment of one you could decide to include threshold workouts instead of sweet spot workouts, but not both in addition to your long rides.
2. 9-week power program. Increasing power is the priority so sweet spot workouts (SS) are the priority along with lactate (anaerobic) threshold workouts (LT). Each week also includes either a tempo ride or an endurance ride, which are much shorter than the long rides in the endurance program.

To train effectively choose several different kinds of intensity riding and give those priority.

My Cycling Past 50 bundle includes:

1. Healthy Cycling Past 50 – what happens as we age and how to incorporate cycling and other exercise activities into our daily lives to stay healthy and active for many years.
2. Off-Season Conditioning Past 50 – how to best work on your off-season conditioning given the physiological changes of aging.
3. Healthy Nutrition Past 50 – what to eat and drink to support both a healthy lifestyle and continuing performance.
4. Performance Cycling Past 50 – how to train to achieve more specific cycling goals given the physiological changes of aging.

My 95-page Cycling Past 50 bundle is just $15.96, a 10% saving.

My eBook Anti-Aging: 12 Ways You Can Slow the Aging Process includes chapters on how to meet the American College of Sports Medicine’s recommendations on aerobic, high intensity aerobic, strength training, weight-bearing exercises, balance and flexibility. I explain intensity training in detail and give you different workouts. I include sample weeks and months for different types and amounts of exercise. I give you plans to build up to 100 km and 100-mile rides. I include a plan to increase over two years your annual riding from around 4,000 miles (6,500 km) to over 5,000 miles (8,000 km) a year. You can easily modify the plans for different annual amounts of riding. I discuss the importance of recovery and how to gauge if you are getting enough recovery. I combine the different kinds of training into programs that balance training and recovery. The 106-page Anti-Aging: 12 Ways You Can Slow the Aging Process is $14.99.

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Coach John Hughes earned coaching certifications from USA Cycling and the National Strength and Conditioning Association. John’s cycling career includes course records in the Boston-Montreal-Boston 1200-km randonnée and the Furnace Creek 508, a Race Across AMerica (RAAM) qualifier. He has ridden solo RAAM twice and is a 5-time finisher of the 1200-km Paris-Brest-Paris. He has written over 40 eBooks and eArticles on cycling training and nutrition, available in RBR’s eBookstore at Coach John Hughes. Click to read John’s full bio.