HIIT

[cellochica]

Hi Chris,
I was searching for HIIT treadmill routines and came across a forum that discourages doing HIIT and strength training on the same day. It said that if you were doing the HIIT correctly you wouldn't have enough energy left to do any weight training. What is your opinion about that? I've been trying to work in 3 days of HIIT with my TYT workouts. As you have recommended, I only do the 20 minute workout on the HIIT days. I am not doing the HIIT at the intensity level this forum was recommending. They recommend intervals of 3 -4 minutes. The HIIT interval should be so intense that you can't sustain it for more than 30 seconds. I've been sustaining it for a minute with 2 minute rest periods. What would be your ideal way of working all this out?
Thanks,
Lise

[Site Administrator]

H Lise!

Below, I am going to paste an article that I wrote a couple years ago for a men's magazine explaining the three different energy systems that our bodies utilize during physical activity. I think the article will help you to understand the physiology behind aerobic training (i.e., aerobic glycolysis) versus anaerobic training (which includes both the ATP-phosphocreatine system as well as anearobic glycolysis).

The short answer to your question about the duration of intense exertion during HIIT is, with adequate conditioning, you will be able to sustain super-aerobic efforts for up to two minutes-- but it may take some time to reach this level. I recommend that people begin with 30-second intervals of all-out effort and work their way up to 60-90 seconds.

Regarding weight training: because of the high repetitions and low weights, the TYT routines recruit primarily ST fiber types-- leaving your FT fibers relatively "rested" for HIIT. Of course, there is going to be some overlap, which is why I often recommend reverting to the 20-minute routine on the days that you also do HIIT.

Thanks for your query-- I hope this clarifies!

Best Wishes,
Chris


GOT LACTATE?
Chris Lydon, M.D.

Four mornings a week you make your way to the gym, head for the cardio theater and put five miles on the treadmill, always remaining within your target aerobic zone (60-80% MHR) for optimal fat burning. Your heart and lungs are those of someone born during the Reagan administration. Four evenings a week you make your way to the gym, don headphones which ooze heavy metal and attack the weights with the intensity of a lover scorned. Truth be told, your body should be immortalized in marble. Your friends envy your dedication. Women extol the virtues of your toned physique.

Then comes the extreme mountain bike trip you and your girlfriend have been planning for months. Escorted by a trained guide, you will be tackling unpredictable, even dangerous terrain. You size up your guide: he’s smaller, less powerful, less built. He’s checking out your girlfriend. You chuckle to yourself as he warns you to pace yourself. The day unfolds like a bad horror movie. Your legs rapidly fatigue. Your heart races. Your lungs rattle. Meanwhile, your skinny guide rides on, pedaling effortlessly, popping wheelies and catching air. You glance over at your girlfriend. She’s pushing forward like a trooper. A trooper who just happens to be staring at the guide with undisguised admiration. How is this possible? You wonder. You know that you are aerobically fit, well-muscled; a veritable picture of the robust mountain man you believe yourself to be. Where did you go wrong?

Three Ways to ATP
Every cell in the body, including muscle cells, relies on adenosine triphosphate (ATP) for immediate energy requirements. Human physiology utilizes three distinct energy systems to generate ATP for working muscles. A combination of genetic predisposition, training patterns, and overall activity level determines which energy system prevails.

1: Aerobic Glycolysis
Marathon runners and centurians require long-term, low to moderate intensity energy production. These and other endurance athletes rely most heavily on aerobic glycolysis to meet their needs. During the initial phase of glycolysis, glucose molecules are cleaved to yield two molecules of pyruvate. This chemical event generates ATP. In the presence of sufficient oxygen, what follows is a complex series of reactions known as aerobic glycolysis whose end-products include additional ATP. As long as oxygen remains available, aerobic glycolysis can supply large amounts of ATP for extended periods.

The miles you bang out on the treadmill, all the while keeping your heart rate within the “target zone,” maximize your body’s potential for aerobic glycolysis. However, even if you are extremely aerobically fit, strenuous activity will eventually overcome your cardiovascular capabilities. At this point your body must substitute alternative methods of energy production.

2: ATP-Phosphocreatine System
If distance runners and cyclists exemplify one end of the conditioning spectrum, powerlifters and bodybuilders do well to depict the other. Unlike endurance athletes, power athletes require very short-term bouts of radical energy production, and rely most heavily on the ATP-Phosphocreatine (ATP-PC) System. The ATP-phosphocreatine system is responsible for maximal efforts lasting less than 20 seconds, and is central to performance during weight training, sprints, and other activities calling for explosive power. Unlike aerobic glycolysis where glucose is the master molecule, the ATP-PC system demands the presence of copious amounts of phosphorylated creatine which donates the phosphate group necessary to regenerate ATP. This process does not require oxygen.

The hours you spend pounding iron maximize your body’s ATP-PC system. But what happens when strenuous activity continues beyond the 20-second limit imposed by the ATP-PC system? What happens when you go on a mountain bike tour and your skinny guide kicks your ass? Enter the star of our show, the often overlooked and usually underrated middle sibling of energy schemes, known as anaerobic glycolysis.

3: Anaerobic Glycolysis: The Lactic Acid System
Anaerobic glycolysis, otherwise known as the lactic acid system, is pivotal to all exercises which combine aspects of power and endurance. These include activities like soccer, rugby, tennis, hockey, basketball, mountain biking, snowboarding, rock climbing, river rafting, etc! While the lactic acid system is unable to produce as much energy per unit time as the ATP-PC system, it does support high levels of activity for a considerably longer duration. As mentioned above, the initial phase of glycolysis involves cleaving glucose molecules to yield pyruvate, a chemical event which generates ATP. However, if there is not enough oxygen present to sustain aerobic glycolysis, the pyruvate molecules are converted to lactic acid or lactate and no additional ATP is generated. Under these circumstances, lactate accumulates within the muscle.

All-out exercise, sustained for 60 to 180 seconds, produces the greatest quantities of intramuscular lactate. As exercise intensity decreases, so does the rate of lactate accumulation. When oxygen becomes available, whatever lactate has amassed is either converted back to pyruvate for aerobic glycolysis or used by the liver and other tissues for gluconeogenesis (glucose production).

Maximizing Performance by Maximizing Lactate Threshold (LT)
At some point, depending on exercise duration and intensity, the rate of lactic acid appearance may become greater than the rate of disappearance. This is known as the lactate threshold (LT), and can usually be elicited at activity levels which demand between 80% and 90% of a trained athlete’s maximum heart rate (MHR). Above this threshold, the acidic environment (low pH) created by the presence of high concentrations of lactate not only impairs muscular contraction, but also prevents enzyme activity necessary for glycolysis. At this point, local energy production ceases, and generalized fatigue sets in. This unfortunate state of affairs remains until surplus oxygen again makes it possible to clear lactic acid.

In a nutshell, the lactate threshold represents the maximum effort at which lactic acid remains in a steady state (without additional accumulation) for a sustained period of time. Provided the athlete can disregard the physical discomfort this pace entails, his or her muscles will perform well for a considerable interval despite the pain. Good News! It is possible to significantly raise your lactate threshold through a combination of training methods, warm-up and cool-down techniques, and supplementation.

Conditioning: submaximal and interval training
If oxidative energy systems are functioning sub-optimally, scant oxygen availability limits lactate clearance and LT is rapidly reached at a low exercise intensity. One of the most effective ways to raise LT is to enhance aerobic capacity through a combination of prolonged submaximal and high intensity interval training. Prolonged submaximal training (at 60-80% MHR) induces muscular adaptations such as increased capillary density and mitochondrial function. Interval training, on the other hand, maximizes cardiovascular output. By optimizing intracellular oxygen availability, these physiological modifications help to reduce lactic acid accumulation as they both prevent lactate formation and facilitate its clearance.

To combine submaximal and high-intensity training into a single session, Kenny De Meirleir, M.D., a cardiologist and exercise physiologist at the Free University of Brussels, Belgium, recommends punctuating a submaximal-intensity run (try 30-45 minutes) with 100-yard sprints at every mile. This method, aptly nick-named the “speed sandwich,” has been experimentally shown to stimulate fast-twitch muscle fibers without appreciable lactic acid accumulation.

Lactic Acid Saturation For Increased Buffering Power
Another approach to raising LT involves deliberately saturating the muscles with lactic acid in order to enhance the muscle's alkaline buffering mechanism. Peak Performance recommends a version of the following routine for competitive runners, but it is useful for anyone who wants to increase LT. Note: Any activity performed at peak effort can be substituted for running, i.e. cycling, swimming, or hitting a punching bag will also do the trick.

Once-A-Week Lactic Acid Saturation Drill
8 x 30 second sprint at 100% effort (4 minute recovery between sets)
4 x 75 second sprint at 100% effort (5 minute recovery between sets)
5 x 60 second sprint at 100% effort (2 minute recovery between sets)
3 x 90 seconds at the maximum pace you would use to run a half mile
(4 minute recovery between sets)
3 x 120 seconds at the maximum pace you would use to run a mile
(5 minute recovery between sets)

Warm-up
A properly executed 10-15 minute warm-up (just enough to break a sweat) helps to prevent lactic acid accumulation via several mechanisms. First, as body temperature increases, blood’s affinity for oxygen is reduced. Translation: more oxygen leaves the circulation to enter muscle fibers. In addition, specific hormonal activity leads to increased serum glucose and free fatty acids, making more fuel substrates available for ATP production. And lastly, the body's ability to process energy improves. For every one-degree rise in body temperature, metabolism within a muscle cell increases by approximately 13%.

Cool-down: choose active recovery
Active recovery in the form of mild exercise speeds the removal of lactic acid from the blood and muscles and helps your circulatory and metabolic systems return to their resting states. Low-intensity activity also increases blood flow and lactate transport (see SIDEBAR), enhancing lactate clearance and decreasing systemic acidity.

Supplementation
Since its identification in 1977, many mammalian enzyme systems (including human) have been shown to utilize N,N-Dimethylglycine as a supplier of one-carbon units during metabolic processes. A recent study out of the Institute of Human Fitness in Escondito, California revealed that supplementation with this compound resulted in a 27.6% increase in exhaustion time and lower blood lactic acid levels in trained athletes.

A double-blind, crossover study conducted at St. Cloud State University, Minn., studied the effects of a formulation of standardized herbal ingredients including Asian ginseng (Panex ginseng), cordyceps (Cordyceps cinensis), enoki mushroom (Flammulina velutipes), green tangerine peel (Citrus reticulata blanco), reishi mushroom (Ganoderma lucidum) and Siberian ginseng (Eleutherococcus senticosus), and sold under the brand names of Metaflex and 2nd Wind, on lactate accumulation during high-intensity cycling. Researchers found that taking the herbal mix led to significantly less lactic acid accumulation and and the herbal group finished the time trial an average of 56 seconds faster than the placebo group.
SIDE BAR
Slow versus Fast Twitch Muscle Fibers and the Lactate Shuttle

All muscle fibers contract to their greatest possible tension when stimulated. However, they do so at different rates of contraction. Due to their high aerobic capacity, Slow twitch (ST) or red muscle fibers can contract repeatedly every 0.1 seconds without fatiguing, provided sufficient oxygen is available. On the other hand, fast twitch (FT) or white muscle fibers develop tension much more rapidly (roughly five times faster than slow twitch fibers) but fatigue easily regardless of oxygen availability. As you might guess, ST and FT muscle fibers possess vastly different aerobic and anaerobic capacities, with FT fibers coming out on top when short-term, intense contractions are called for. High concentrations of certain enzymes present in FT muscle fibers favor the conversion of pyruvic acid to lactate. Conversely, other enzymes present in greater abundance in slow-twitch fibers favor the opposite reaction, converting lactate back to pyruvate.

During sustained exercise, some of the lactate produced in FT fibers diffuses or is transported to ST fibers. Alternatively, other lactate can reach ST fibers through the circulation. By this mechanism of shuttling lactate between cells, glycogenolysis in one cell can supply the fuel for oxidation to another. Consequently, much of the lactate produced in a working muscle is consumed within the same tissue and never reaches the circulation. This process by which lactate moves quickly about the body for use by appropriate tissues is called the Lactate Shuttle. Not only is this arrangement efficient in terms of energy production, but it may promote enzyme activity and delay overall fatigue.