- Zied Abbes

# Swimming Performance Analysis Deterministic models – Front Crawl

Updated: Apr 7

### By Zied Abbes

# I. Introduction:

In many ﬁelds of study, a model (a graphical or mathematical description of a system or process) can be used as a basis for theoretical or empirical understanding of that system or process. Deterministic models serve such purposes in biomechanics, and their use could help to promote the use of theoretical models in sports and exercise biomechanics research. Over the years the utility of a deterministic model approach in biomechanical research has been illustrated in several sports, especially in swimming.

Since 2006, the trend in swimming research is the “Interdisciplinary assessment”. This “Interdisciplinary assessment” is based on the “holistic approach”.

According to Hay (1984), all the factors included at one level of the model must completely determine the factors included at the next highest level. It can be used as a basis for qualitative analysis of sports skills (Hay, 1984; Hay & Reid, 1988):

1. The ﬁrst step is to identify the primary goal, result/outcome of the performance to be investigated.

2. The next step is to identify those factors that produce the result

# II. Performance Analysis in Swimming:

Performance analysis is the investigation of sporting performance, with the aim being to develop an understanding of sports that can:

1. inform decision-making,

2. Enhance performance

3. inform the coaching process, through the means of objective data collection and feedback.

**Figure 1: A digital systems diagram showing the interactions of the data collected with various other team members. Developed from work by Hughes 2004 (4, 6)**

# III. Front Crawl

The arms contribute more to propulsion than the legs in front crawl swimming, with reports of up to 90%, but generally agreed at 85%7, 8, 9, 10. In addition to this, the swimmer's arm motions, and the coordination of them, are of importance in relation to performance.

Biomechanics has tended to break into two sections, focusing on Kinematic and Kinetic factors of the stroke.

** Kinematics:** Motion of a body or system of bodies without consideration of the forces involved.

** Kinetics:** the action of forces in producing or changing motion

**An example of the start of a deterministic model, adapted from work by Hey 1993 (13)**
**Blue represents Kinematic elements. Orange represents Kinetics**

# 1. Front Crawl Kinematic:

### A. TIME

The competitive swimmers objective is to swim the full distance in as short a time as possible where the time will consist of the time starting, time stroking and time turning :

**a. Stroking Time:**

The goal of competitive swimming is to travel the event distance at the maximal velocity since the performance is assessed by the time spent to cover that same distance:

Determined by **two factors**: the **distance of the race** and the **average speed** of the swimmer.

Calculated as the product of Stroke Length (SL) and Average Stroke Frequency/Rate (SF /SR)

--> Stroke length has been identified as the **“ single best predicator of swimming performance”**

--> As stroke length increases, swimmers will tend to find they need longer to complete the stroke, leading to a decrease in stroke rate.

**b. Stroking efficiency **

The product of Speed and Stroke Length (SL) are used to create a Stroke Index (SI) as a method of measuring stroke efficiency.

--> Elite level swimmers have a higher Stroke Index.

C__. Propelling efficiency (__*ƞp)*__:__

The fraction of mechanical power (Wtot) that can be utilized, in water, to overcome hydrodynamic resistance is termed propelling efficiency (ηp):

Wd = Hydrodynamic resistance

– Fd = drag force

“l” : represents the Arm’s Length.

*-->ƞp* should remain constant

--> Whereas ˙ Wtot increases with the swimming speed, propelling efficiency decreases with it

# 2. Front Crawl Kinetics

### A. Acceleration:

Swimmers present a uniform accelerated movement. Therefore, the Δ*v*, considering a given period of time, defines the acceleration*. Δv *is the change of the velocity with the stroke cycle

This variable is dependent on the applied resultant **mechanical force (F)** and the **inertial term of Newton’s law (Mass = m): **

*F *is the result of the vector adding of propulsive forces and drag forces, which have two opposed forces: F = Fp + D

Fp = Sum of all components of the propulsive forces

D = Sum of all components of the drag force.

### B. EFFECTIVE PROPELLING FORCE

Effective propelling force is the component of the resultant vector in the displacement direction:

*Dp *represents the drag force,

*L *the lift force

α the absolute angle of the resultant vector in the displacement direction (i.e., horizontal axis).

** C. DRAG FORCE**

Drag force (*D*) represents the resistance to move forward in a fluid environment. It can be expressed by Newton’s friction equation:

D represents the drag force,

*ρ *is the fluid density,

*v *is the swimming velocity,

*S *is the projection surface of the swimmer

*CD *is the drag coefficient.

The total drag force is the sum of the all drag components:

· *D*f is the swimmer’s Skin-friction drag à slow the water flowing along the body surface of the swimmer

· *D*p is the swimmer’s pressure drag à caused by the pressure differential between the front and the rear of the swimmer.

· *D*w is the swimmer’s wave dragà displacement of the swimmer at the water surfaces, which catches and compresses water, leading to the formation of surface waves.

Wave drag can be neglected when a swimmer is at least 0.60m deep (i.e., ~1.8 chest depths)18

__Partial contribution of each drag component to total drag depends:__

__Partial contribution of each drag component to total drag depends:__

(i) swim or gliding velocity; (ii) underwater dolphin kicking after start and turn; (iii) body position while gliding and swimming; (iv) drafting

# VI. REFERENCES:

1. Chow, JW, Knudson, DV. Use of deterministic models in sports and exercise biomechanics research*. *2011;1476-3141 (Print)): 2011 Sep

2. Vilas-Boas, JP. *Biomechanics and Medicine in Swimming: Past, present, future. *Oslo: Norwegian School of Sport Science

3. Barbosa, TM, Bragada Ja Fau - Reis, VM, Reis Vm Fau - Marinho, DA, Marinho Da Fau - Carvalho, C, Carvalho C Fau - Silva, AJ, Silva, AJ. Energetics and biomechanics as determining factors of swimming performance: updating the state of the art*. *2010;1878-1861 (Electronic)): 2010 Mar

4. Hughes, M. Performance analysis – a 2004 perspective. *International Journal of performance analysis in sport. *2004;4(1): 103-109.

5. Hughes, M, Bartlett, RM. *What is performance analysis? *Oxon: Taylor & Francis.

.

6. Hughes, M. Notational analysis – a mathematical perspective. *International journal of performance analysis in sport. *2004;4(2): 97-139.

7. Toussaint, HM. Differences in propelling efficiency between competitive and triathlon swimmers*. *1990;0195-9131 (Print)): 1990 Jun

8. Di Prampero , Pendergast Dr Fau - Wilson, DW, Wilson Dw Fau - Rennie, DW, Rennie, DW. Energetics of swimming in man*. *1974;0021-8987 (Print)): 1974 Jul

9. Hollander, AP, De Groot, G, Van Ingen Schenau, GJ, Kahman, R., and Toussaint, H. M., . Contribution of the legs to propulsion in front crawl swimming. *Swimming science V,. *1988;39-43.

10. Zamparo, P, Lazzer S Fau - Antoniazzi, C, Antoniazzi C Fau - Cedolin, S, Cedolin S Fau - Avon, R, Avon R Fau - Lesa, C, Lesa, C. The interplay between propelling efficiency, hydrodynamic position and energy cost of front crawl in 8 to 19-year-old swimmers*. *2008;1439-6319 (Print)): 2008 Nov

11. Seifert, L, Boulesteix L Fau - Carter, M, Carter M Fau - Chollet, D, Chollet, D. The spatial-temporal and coordinative structures in elite male 100-m front crawl swimmers*. *2005;0172-4622 (Print)): 2005 May

12. Barbosa, TM, Marinho, DA, Costa, MJ, and Silva, A. *Biomechanics of competitive swimming strokes. *

13. Hay, JG. The biomechanics of sports techniques. *Prentice-Hall. *1993;

14. Costill, Kovaleski J, Porter D, J, K, King, FR. Energy expenditure during front crawl swimming: predicting success in middle-distance events*. *1985;0172-4622 (Print)): 1985 Oct

15. Sanders, RH. *New analysis procedure for givign feedback to swimming coaches and swimmers. *1-14Caceres: University of Extramedura.

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16. Fritzdorf, S, Hibbs A Fau - Kleshnev, V, Kleshnev, V. Analysis of speed, stroke rate, and stroke distance for world-class breaststroke swimming*. *2009;0264-0414 (Print)): 2009 Feb 15

17. Toussaint, HM, Carol A Fau - Kranenborg, H, Kranenborg H Fau - Truijens, MJ, Truijens, MJ. Effect of fatigue on stroking characteristics in an arms-only 100-m front-crawl race*. *2006;0195-9131 (Print)): 2006 Sep

18. Lyttle, A, Blanksby, B, Elliott, B, & Lloyd, D. *Optimal depth for streamlined gliding. *Jyväskylä: Gummerus Printing