Summer 1, Week 1: Technical and Conditioning Focus: March 23 – March 29: Email 3 of 3: Capillary Beds (More than you ever wanted to know about flutter kick)
Summer 1, Week 1: Technical and Conditioning Focus: March 23 – March 29: Email 3 of 3: Capillary Beds
Why is Flutter Kick so Important?
- Macrocycle: Summer 1: March 24 – June 1
- Mesocycle: March 24 – April 13: General Preparation
- Microcycle: March 24 – March 30
- Catch, Pull, & Body Position
Hello Swim Families!
You’re really getting hit with a lot of swimming content this week!
Today, I want to talk about why I highly emphasize flutter kick in Marlin’s training. While it might seem intuitive for a freestyle or a backstroke specialist to do a lot of flutter kick in their training, it is not so obvious why a breaststroke or butterfly specialist should also do a significant amount of flutter kick.
Whether with a board, on their back, or streamlined prone with a snorkel, flutter kick is vital to any swimmer’s conditioning. Flutter kick with a board or with a snorkel in a prone streamlined position, however, tends to promote the best results.
Why do we emphasize flutter kick, even if with a board?
While a kickboard can lower the hips due to the head and shoulders being placed above water level, ultimately, intense flutter kick with a board is a proven method of increasing the strength and endurance of capillary beds, meaning, an increase in an athlete’s blood-oxygen levels.
As described by legendary University of Texas Men’s Swim & Dive Head Coach Eddie Reese, “…and back then, breaststrokers flutter kicked for like eight weeks for the first half of every kick set due to capillarization or circulation. You can build capillary beds in the lower extremities, which is hard to do, only through freestyle kick, because you can only kick that fast enough to create the oxygen need—breaststroke’s too slow, fly kick’s too slow. So, they do that to make, help their circulation down the line,” (Hawke, 2021).
Essentially, establishing a strong flutter kick is vital to overall kick strength and endurance, regardless of a swimmer’s stroke specialization.
Before we launch into why building strong capillary beds is important, let’s establish the vocabulary used in this email.
Blood Oxygen (Sp02): "[T]he percentage of oxygen-containing hemoglobin in the blood, measured invasively via oximetry of arterial blood," (Abu, Khraiche, Amatoury, 2024).
Capillary: "[The] smallest of blood vessels where physical exchange occurs between the blood and tissue cells surrounded by interstitial fluid," (University of Queensland, 2021).
Capillary Bed: "[The] network of 10–100 capillaries connecting arterioles to venules," (ibid).
Capillary Hydrostatic Pressure (CHP): "[The] force blood exerts against a capillary," (ibid).
Capillarization: "Muscle capillarization is central for the delivery of oxygen and nutrients to the exercising muscle, and thus, capillarization is vital for exercise capacity. A high muscle capillary density means a large muscle-to-blood exchange surface area, short oxygen diffusion distance, and high red blood cell mean transit time," (Gliemann, 2016).
Cardiac Muscle: "...heart muscle, under involuntary control, composed of striated cells that attach to form fibres, each cell contains a single nucleus, contracts autonomously," (University of Queensland, 2021).
Hemoglobin: "...oxygen-carrying globular protein in erythrocytes," (ibid).
Muscle Fiber: "The muscle fiber is composed of four fundamental constituents: (1) the sarcolemma that is the equivalent of the cell membrane; (2) the fibrils that represent the structural elements responsible for contraction; (3) the sarcosomes that are really the mitochondria and contribute the supply of energy for muscular contraction; (4) the sarcoplasm, which is the ground cytoplasmic substance in which the other structures of the muscle fiber are embedded; and (5) the sarcoplasmic reticulum. The nerve fiber is not a cell but a prolongation of a cell. It is a process of a neuron that is adapted for carrying nervous impulses. The functioning of the nerve fiber is a little more mysterious at the moment than the muscle fiber," (Bourne, 1970).
Smooth Muscle: "[U]nder involuntary control, moves internal organs, cells contain a single nucleus, are spindle-shaped, and do not appear striated; each cell is a fibre," (University of Queensland, 2021).
Skeletal Muscle: "[U]sually attached to bone, under voluntary control, each cell is a fibre that is multinucleated and striated," (ibid).
Feel like you’re back in a human biology class? Well, we’re only going to go further down the rabbit hole. Strap yourselves in.
What is this capillary bed stuff?
Here, I am going to defer to Norwegian sports exercise experts Sigmund B. Strømme and Frank Ingjer for further details on these biological systems. If some words seem to be spelled funny it’s because the document I reference (Strømme, Ingjer, 1982) is written in British English.
Strømme and Ingjer state that:
“Emphasis is laid upon recent studies of the effects of training on the heart and on the capillary supply of skeletal muscles. Regular systematic training leads to adaptational changes in the size of the heart, its function and its pump capacity. Recent studies based upon echocardiography have enabled us to differentiate between increased heart size due to thickening of the walls and increased myocardial mass, and increase in heart size primarily due to increase in ventricular volume. The results indicate that those who undergo typical aerobic endurance training, which includes continuing haemo-dynamic loading of the heart and therefore optimal venous filling, develop greater left ventricular end-diastolic volume and myocardial mass together with better systolic emptying than others. These changes are accompanied by increased stroke volume and lowered heart rate at rest and submaximal workload, and increased stroke volume and cardiac output during maximal muscular work,” (Strømme, S.B., Ingjer, F, 1982).
“On the other hand, the total haemoglobin mass may rise. The rise in aerobic power which takes place as a result of endurance training is due not only to increase in the heart capacity as a pump but also to increase in maximal arterio-venous oxygen difference. This may be explicable on a basis of adaptive change in the biochemical qualities of the muscle fibres and functional adaptations in the peripheral parts of the circulatory system. Recent studies have shown that the capillary supply to muscle fibres differs for the different types of muscle fibre (highest for type I and lowest for type IIB). Regular physical training over a prolonged period influences capillary density in a positive direction,” (sic)
“Increase in the number of capillaries as a result of training appears to be specific for muscle fibres mobilized during training. It has also been shown that there is an approximately linear relationship between the capillary density and aerobic power,” (sic).
Musch, Poole, Copp, and Ferguson say “The capillary bed presents a prodigious surface area that facilitates blood–tissue interchange of O2, substrates and metabolites, as well as hormones and other bioactive/signaling molecules. Of all capillary beds, that of skeletal muscle represents by far the largest and, especially during exercise, plays the dominant role in whole-body O2, glucose, lactate and fatty acid dynamics,” (Musch, Poole, Copp, Ferguson, 2013).
While my citations relate to humans and mammals, there is a vast amount of scientific literature about the capillary beds of marine animals available online, which I think is somewhere between coincidental and, dare I say, poetical.
Sources
Bompa, T.O., Buzzichelli, C.A. (2015). Periodization Training for Sports: Third Edition. Human Kinetics. ISBN: 978-1-4504-6943-2
Bourne, G.H. (1970). SEVEN - Specialized cells: gland cells, muscle fibers, and nerve fibers. Division of Labor in Cells (Second Edition). Pages 236-283. Elsevier, Inc. 978-0-12-119259-4.
DeWeese, B.H., Hornsby, G., Stone, M., Stone, M.H. (2015). The training process: Planning for strength–power training in track and field. Part 2: Practical and applied aspects. ScienceDirect. Journal of Sport and Health Science 4 (2015) 318–324.
Hawke, B. (2021). Inside with Brett Hawke: Eddie Reese the GOAT. https://www.youtube.com/watch?v=FayDPtjvCpk&t=1734s
Gliemann, L. (2016). Training for skeletal muscle capillarization: a Janus‑faced role of exercise intensity? European Journal of Applied Physiology. https://link.springer.com/article/10.1007/s00421-016-3419-6
Poole, D.C., Copp, S.W., Ferguson, S.K., Musch, T.I. (2013). Skeletal muscle capillary function: contemporary observations and novel hypotheses. Departments of Kinesiology, Anatomy and Physiology, Kansas State University, Manhattan, KS, USA. Experimental Physiology. The Physiological Society. https://physoc.onlinelibrary.wiley.com/doi/epdf/10.1113/expphysiol.2013.073874
Strømme, S.B., Ingjer, F. (1982). The Regular Effect of Training on the Cardiovascular System. From the laboratory of Physiology, Norwegian College of Physical Education and Sport, Box 40, Kringsjã, Oslo 8, Norway. Social Medicine, Suppl. 29: 37-45, 1982. https://www.jstor.org/stable/45199656?seq=1
University of Queensland. (2021). Fundamentals of Anatomy and Physiology. University of Southern Queensland. https://usq.pressbooks.pub/anatomy/back-matter/glossary/#letterc
