A Theoretical Estimation Of The Range Of The Unknown Parameter K, Presented In The Model Of Carter Et.,Al., (1987) For The Case Of Distance-Running
al., carter’s et., distal-end of the femur, distance –running, model 1987, range of k, unknown parameters m and k
M Tsili. A Theoretical Estimation Of The Range Of The Unknown Parameter K, Presented In The Model Of Carter Et.,Al., (1987) For The Case Of Distance-Running. The Internet Journal of Bioengineering. 2008 Volume 4 Number 1.
In this work we theoretically determined the range of the unknown parameter K, presented in Carter’s et., al.,(1987) theory for the case of distance-running.We expressed the density of the distal- end of the femur of a distance-runner, in terms of his (her) training history. After that we used some published data and we concluded that 0 < K <0.3206 mg.cm3/ N1/2.
Many years ago Carter et., al., (1987) proposed a theory for inter-nal bone remodeling. The basic idea of this theory was that the ap-parent bone density ρ, is expressed in terms of daily loading histo-ry. The last mathematically is approximated by the following equa-tion:
where ρ, ni, σi are respectively the bone apparent density, the number of loading circles and the peak effective stress for the i th activity of the day, c is the average number of daily activities, while K, m are coefficients that have not been experimentally determined. However Whalen et., al.,( 1988) initially specified that 2<m <12 for the physi-cal activity and at continuity they accounted the running studies of Williams et., al., (1984); Dalen and Olsson (1974) and concluded that 2< m< 7. Also Carter et., al., (1989) determined the range of the un- known parameter K,for the case of normal activity and for the as- sumed values of m =1 and m=4.
The purpose of this work is to theoretically predict the range of the unknown parameter K, for the case of distance-running. For that reason we will use the model of Carter et., al., (1987), in order to express the density of the distal-end of the femur of a distance -run- ner, in terms of his (her) loading history. During these past years, the loads of his (her) bones due: as to training as to daily normal acti-vities that are common for all people, like normal -walking. However the loads generated by the walking ( Andriacchi et., al., 1977; Rorhle et., al.,1984) are small,compared with the loads generated by the dis- tance- running (Alexander and Jayes, 1980; Bates et., al., 1983; Cavag-na, 1964;Cavanagh and La-Fortune,1980; Fukanaga et., al., 1980; Win-ter,1983) and therefore contribute insignificantly to the regulation of bone density.For that reason,we assume that athlete’s loading history due exclusively to his (her) training- practice.
We assume that we deal with a distance- runner (with an athlete who participates to 5000, or 10000, or Marathon race men/ women)
with N years exersizing background. During these N years, he (she) was training by following an annual exersizing program. Accordin-gly to Clisouras (1984), the annual exersizing of an athlete is divi-ded: to the preparation, to the gaming and to the relaxation periods. Suppose that the athlete was exersizing, accordingly to the training schedules of Tables 1., 2. and 3., taken from Clisouras (1984), as fol-lows: Initially the runner was following the instructions of Table 1. and he (she) was repeating this kind of exersize 6 times, that is the training program was performed for a period of 24 weeks.At con- tinuity he (she) was following the instructions of Table 2. and was repeating this king of training 6 times, that is the total duration of this program was also 24 weeks.Finally he (she) was completing his (her) annual training - schedule, by following the instructions of Tab-le 3.The total duration of the last program, was 4 weeks.In the be- ginning of a new athletic year,the athlete was exersizing as we des-cribed earlier,following the instructions of Tables 1., 2. and 3. With other words, the runner was training with the same manner for N years.We assume that during these years, his (her) body weight was constant.
Accordingly to Carter et., al., (1987) the density of the distal-end of the femur of the athlete, for the first day of exersizing ρ1 is gi-ven by:
where ρο is the initial density of the distal- end of his (her) femur and is independent of the exersizing and σi, ni, βi are respectively: the peak cyclic stress, the number of loading circles (per minute) and the total duration of running activity (in minutes) for the first day of exersizing.
By the same way, the density of the distal- end of the femur of the athlete for the second day ρ2, is given by:
where σ2, n2 and β2 are respectively: the peak effective stress, the number of loading circles (per minute) and the total duration of run- ning activity (in minutes) for the second day of training. Then (2.2) because of (2.1) becomes:
Consequently the density of the distal- end of the femur of the ath-lete for the first year of training background ρ̅ is given by:
Since the runner had N years training background, the final density of his (her) distal–end of the femur is:
The units of the parameter K can be defined accounting that ρ, ρο are measured in units of mg.cm 2 , while βi, σi and ni are measured in units of minutes, N /cm 2 and circles/ minute respectively. Therefore from (2.5), it follows that K is measured in units of mg.cm 3 /N 1/2 .
The physical approximation of our problem
The peak effective stress of the distal- end of the femur of the athlete during the distance -running, due to the groung reaction force at late stance phase, denoted by Gd.Τhe last is not an axial load,be- cause during the abovementioned phase, an angle α is formed by the femoral neck of the runner and by the vertical direction, as it seems in Figs.1. taken from Clisouras (1984) and 2.This angle satis-fies 0 <α<π/2.The running load Gd can be analysed into two com- ponents: the vertical Gdv and the horizontal Gdh (see Fig. 2), where:
From (3.1)1-2 it is possible to obtain:
The magnitude of the running load Gd is:
Replacing (3.2) into (3.3), it is possible to find:
The vertical component Gdv is given by:
where Gfi, Wf, Wt, are respectively: the vertical component of ground reaction force at late stance phase during running for the foot, the weights of tibia and foot. Alexander and Jayes (1980); Bates et.,al., (1983); Cavagna (1964); Cavanagh and La- Fortune (1980); Fukanaga et., al., (1980); Winter (1983), calculated the magnitude of bone’s load
for certain values of the magnitude of the running velocity. Selec-ting the experimental data from the abovementioned cites and using a linear regression analysis, is possible to obtain:
where vi is the running velocity of the athlete for the i day. Accor-dingly to Harless (1860):
Then (3.5) because of (3.6) and (3.7) is written as:
Τhe peak effective stress σi for the i day of training, is given by:
where: i =1., 2.,…,365 and B is the body weight of the runner in u- nits of N. Finally S is the cross − section area of the distal – end of the femur given by:
where a, b are the radii that correspond to endosteal and periosteal surfaces of the (distal-end) femur and are constants, since in present work we deal only with the internal remodeling (Frost, 1964; Cowin and Van - Buskirk, 1978; Cowin and Van- Buskirk, 1979).
Substituting (3.4), (3.8) and (3.10) into (3.9), it follows:
Also Fukanaga et., al.,(1980); Ito et., al., (1983) calculated the magni-tude of the number of loading circles,for certain values of the mag- nitude of the running velocity. Selecting these data from the above-mentioned cites and using a second- order regression analysis, it is possible to find:
The study of Whalen et., al., (1988, p. 830) contains a table that de-fines the magnitudes of the velocities which correspond to different physical activities: slow walking, walking, fast walking, jogging and distance- running.Accordingly to this table, the distance-running activi-ty corresponds to a velocity v2, whose magnitude is at least of the order of:
that is vi ≥ v2. Then (3.11), (3.12) because of (3.13), take the forms respectively:
n(vi) = 0.66vi 2 – 1.524vi + 84.159 ≥ 0.66v2 2 −1.524v2 +84.159 =n(v2) (3.14)1-2
Since 0 <cosα <1, from (3.14)1 we obtain:
Consequently (2.5) because of (3.14)1-2 and (3.15) takes the form:
Accordingly to (distance) running studies of Dalen and Olsson (1974); Williams (1984) and Whalen et., al., (1988), the range of the unknown parameter m is :
Therefore from (3.16) we conclude:
and it is possible to determine that the range of K is the fol-lowing :
Evaluation of the range of the parameter K
In order to specify the range of K, some data will be used. The values of the initial and final density of the distal-end of the femur of the athlete, as well his (her) mean mass :
are taken from Nilsson and Westlin (1971). Consequently the mean weight of the runner, is:
Accordingly to Clisouras (1984), the ideal age for starting an ath-letic carrier in distance- running,is between 16 - 20 years old. Suppose that the athlete started his (her) track - carrier in the age of 16. Also in the work of Nilsson and Westlin (1971),the mean age of the ath- letes who participated in their measurements, was 22. Therefore we conclude that:
Also the values:
are taken from Cowin and Van- Buskirk (1978). Substituting (3.13), (4.2) and (4.4)1-2 into (3.15) and (3.14)2 , it is possible to obtain res-pectively that :
From Table 1, it is possible to obtain that:
Also from Table 2. it is possible to obtain:
Finally from Table 3., it is possible to conclude that:
Substituting (4.1)1-2, (4.3), (4.5)1-2 and (4.6) through (4.25) into (3.19), it is possible to find that:
0 < K < 0.3206
Discussion - Conclusions
Accordindly to all that we stated earlier, it is possible to conclude the following: The value of the unknown parameter K is not unique for all individuals, because (even we knew the accurate value of the stress exponent m) it depends from the following factors:
where vo is the walking velocity. The last belongs to the range [0.5m/sec, 2m/sec] starting with slow and ending with fast walking (Whalen et., al., 1988, p. 830). Eqn. (5.1) has been found taking the experimental data from Andriacchi et., al., (1977) and Rohrle et., al., (1984) who evaluated the magnitude of walking load for certain
magnitudes of walking velocity; and using a linear regression analy-sis (Whalen et., al., 1988) . In contrast with the abovementioned, the magnitude of foot’s load during the distance - running is given again by (3.6), where v ≥v2= 4.5m/sec.
In addition it clearly seems that it is too difficult to evaluated the accurate value of K for each individual, because a lot of infor- mations are required and practictually is impossible to be obtained. Even it was possible to concentrate the required informations, in or-der to find the value of K a lot of evaluations and time spending would be necessary. In contrast with the aboventioned, the method introduced in present study, has the advantage that it can be ap-plied to an extensive team of people who deal with the same phy- sical activity ( for example walkers, distance –runners, sprinters, bicy-cletists), since athletes belonging to the same group has similar trai-ning histories with small divergencies concerning i) the magnitudes of waking / running/ biking velocity and ii) the duration of the daily training. However the velocity magnitudes lie in a certain range and it is adequate to know the minimum value. From the other hand di-vergencies of the duration of the daily training βi, do not significan tly alter the extracted range of K, since in (3.19) we deal with the 14 th root of the total sum and not with the square or third root of it.