Jul 21

Physiological load

Categories: General, Glossary

Physiological load refers to the demands and stresses placed on the body’s physiological systems during activity. It encompasses various factors that affect the body’s functioning and adaptation to running. Understanding and managing physiological load is crucial for optimizing performance, preventing injuries, and promoting overall health and well-being.

Several key aspects contribute to the physiological load experienced during running:

Cardiovascular Load: Running places a significant demand on the cardiovascular system. The heart has to pump more blood to deliver oxygen and nutrients to the working muscles. This increases heart rate, stroke volume, and cardiac output, leading to a higher overall cardiovascular load.

Musculoskeletal Load: Running involves repetitive impact forces transmitted through the bones, joints, ligaments, and tendons. The musculoskeletal load depends on factors such as running technique, running surface, footwear, and the runner’s body mechanics. Higher intensity or longer duration runs can increase the load on these structures, potentially leading to fatigue, microtrauma, and injury.

Energy Systems Load: Running requires energy production to sustain muscular activity. The body primarily utilizes aerobic metabolism, supported by the respiratory and circulatory systems, to supply oxygen and fuel (glucose and fatty acids) for energy production. Higher intensity running may also engage anaerobic metabolism, leading to the accumulation of metabolic byproducts which need to be handled and eliminated.

Thermoregulatory Load: During running, the body generates heat as a byproduct of metabolic activity. To maintain optimal body temperature, the thermoregulatory system works to dissipate excess heat through sweating and enhanced blood flow to the skin. Running in hot and humid conditions or wearing excessive clothing can increase the thermoregulatory load and may lead to dehydration and heat-related illnesses.

Hormonal and Neuroendocrine Load: Running stimulates the release of various hormones and neurotransmitters, such as endorphins, adrenaline, cortisol, and growth hormone. These substances play roles in mood regulation, stress response, energy mobilization, tissue repair, and adaptation to exercise. The magnitude and duration of running can influence the hormonal and neuroendocrine load.

Managing physiological load is essential to avoid overtraining, injuries, and other adverse effects. Factors like proper training progression, adequate recovery, balanced nutrition, hydration, and sleep are crucial in optimizing performance while minimizing the risk of overload.

With respect to running, the primary factor that affects the amount of load that a workout imparts is your speed, i.e. the faster you go, the higher the load. In addition, environmental factors such as incline, temperature and wind can have considerable effects. Consequently, you should slow down when:

  • running uphill – It costs over twice the energy consumption to run up a 20% slope
  • running downhill on gradients approaching 40% or more -This isn’t just to prevent ‘jarring’ your knees!
  • running in high temperatures and humidity – Obvious really?
  • running at low temperatures – Yes running in the cold has an effect on your running too, but at an ambient air temperature above 0 degrees celsius it is too minimal to worry about, but below freezing… start to slow down
  • running with a head or side-wind

Physiological Load within TrainAsONE

In TrainAsONE the physiological load of an activity is distilled into a single value to make quantification and comprehension as simple as possible. This aids in the analysis of loading trends over time, and straightforward ‘planned vs performed’ load comparisons.

But what load is right? TrainAsONE will determine the ideal value for each workout for you and this is stated with the planned workout (presently this is displayed within square brackets after the workout distance). This can then be compared with the calculated load for your performed activity.

  • Lower than planned: then your body has not been stressed enough and will not make any adaptive (performance improvements) responses. If this level of exercise is maintained, your body may go into a period of ‘de-training’
  • Greater than planned: then the body has been stressed too much and a consequent increase in recovery time may be required for your body to recover. If persistent inadequate rest is allowed, over-training sets in and performance (and health) will suffer
  • Equivalent to planned: your body is stressed by just the right amount to induce performance enhancing responses that will be near-peak at the time of your next training session

TrainAsONE can automatically adjust the paces of your upcoming runs according to the temperature (based on the weather forecast) and predicted incline changes (based on your running history). This is called Temperature and Undulation adjustment within your Profile.

If you elect to turn off temperature and/or undulation adjustment, your TrainAsONE paces are specified assuming that you are running under ideal conditions: flat level terrain; an ambient air temperature of 10 to 15 C; a relative humidity of 50 to 60%; and no wind. If you are not, you might need to slow down.

There are numerous other factors that have an effect (for example, solar shortwave radiation) but we won’t go into those now…

So if you notice that you have significantly different measured loads compared to those scheduled, you’re probably overdoing it and should be adjusting your future pace accordingly. If in doubt, just ask us and we can advice.

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