LITERATURE REVIEW
2.1 Human Height
Height means stature, especially of the human body. Human height or stature is the distance from the bottom of the feet to the top of the head in a human body, standing erect. It is measured using a stadiometer, usually in centimetres when using the metric system, and feet and inches when using the imperial system (Carter and Pamela, 2008). Adult height is influenced by nutrition and health throughout his or her growing years. Although final height is limited by a child genotype, environmental influences also affect his/her adult size. Panagiotopoulou et al., (2004) noted the exact body height cannot always be determined the usual way because of various deformities of the extremities or in patients who have undergone amputations or similar injuries.
In such circumstances, an estimate of body height has to be derived from other reliable anthropometric indicators, such as; hand and foot lengths (Agnihotri, Agnihotri, Jeebun & Googoolye 2008); sitting height (Fatmah 2005) as well as pattern of stature (Bidmos 2006; Bidmos & Asala 2005). Therefore, all these anthropometric indicators that are used as an alternative to estimate body height are very important in predicting age-related loss in body height (Hickson & Frost 2003).
Height is considered an important indicator of Nutrition and health of a population (Akachi and Canning 2007; Deaton, 2007). Estimation of pattern of human height from different body parts has received great attention in anthropology and forensic sciences. Stature which means standing height (NHANES, 2007) is increasingly used as measure of the health and wellness (standard of living and quality) of population (Ashizawa, 2002). Changes in body dimensions have attracted the attention of anthropologists (Ali et al., 2000) and in children of developed countries are well documented phenomenon (Loesch et al., 2000 and Adebisi, 2008).
An interest in inequality also motivates studies of the difference between male and female heights. Stature is an important and easily measurable aspect of sexual dimorphism or differences in body composition. The differences mainly emerge at puberty; at birth males are only 1% longer than females, but in adulthood men are, on average, 7% taller (Gustafsson and Lindenfors, 2004).
The difference is primarily due to men having greater leg length in part because their pubertal period is longer than women’s. Men also have a higher fat-free mass and a lower body fat percentage for a given weight. Sexual dimorphism in shape diminishes at advanced ages; both sexes tend to lose lean mass after age 40, so that even individuals with a stable weight have a higher body fat percentage as they age. The magnitude of the sexual difference in stature and body mass varies between societies, and is susceptible to environmental, social and economic influences (Wells, 2007).
A cording to Gustafsson et al., (2007) height in both sexes at a point in time is strongly influenced by socio-economic status the degree of dimorphism will be influenced by selection into and composition of the sample. Historical research on women’s height and body mass is limited by the availability of systematic sources before the late twentieth century. Golshan, Amra & Hoghoghi (2003) pointed out that people of small stature were relatively strong as compared with tall the tall ones, and quicker because the weight decrease in proportion to cube of the size, whereas the force decrease in proportion to the square of the size, being approximately proportional to the cross sectional of the muscle. Short heavy-set people are remarkably strong and make good weight-lifters, carters and heavy labourers. The “grasshoppers” types with relatively long legs make good jumpers, runners, vaulters, hurdlers, and agility athletes.
Shamim and Singh (2002) carried out a study to ascertain the difference between physical and physiological variables of high and low performance basketball players and found that the high performance basketball players had greater height, weight, lower leg, thigh, upper arm and lower arm length. They had greater shoulder and hip width and greater calf and biceps muscle girth with greater diameter of humerus and femur biepic condyle. They are meso-ectomorph and their sitting height is greater than low performance basketball player. They had lesser sum of four-skin folds measurement than that of low performance basketball players. High performance basketball player had better body proportionality in relation to mechanical advantage. They also had lesser heart rate and greater vital capacity. However there was no significant difference in the blood pressure of high and low performance basketball players (Silventoinen, 2003).
2.2 Measurement of Human Height
A portable or wall-mounted stadiometer could be used in obtaining the measurement of human height. The tool should:
Measure in 0.1 cm or 1/8 inch increments.
Be stable with a large base.
Have a horizontal headpiece at least 3 inches wide that can be brought into contact with the most superior part of the head.
Do not use cloth tapes, yardsticks, or graphics attached to wall.
Do not use metal measuring rod attached to a scale.
2.3 Methods for Measuring Human Height
The following methods are used in obtaining the height measurement of an individual according to Centre for Disease Control, (2009):
Subject removes shoes.
Subject removes hair ornaments, buns, braids to extent possible.
Subject stands on footplate portion with back against stadiometer rule (cut out feet can be placed in position to assist the student).
Bring legs together, contact at some point (whatever touches first).
Knees not bent, arms at sides, shoulders relaxed, feet flat on the floor.
Back of body touches/has contact with stadiometer at some point.
Body in straight line (mid-axillary line parallel to stadiometer).
Head in appropriate position – check Frankfort plane.
Lower headpiece snugly to crown of head with sufficient pressure to press hair. Read value at eye level.
Measure to nearest 0.1 (1/10) cm or 1/8 inch (repeat measurements should agree within .1cm or ¼ inch.)
Record value immediately on data form.
2.4 Heart Rate
Heart rate or heart beats describes the complex regulatory system between heart rate and the autonomic nervous system. Heart rate is the speed of the heartbeat measured by the number of contractions of the heart per minute (bpm). The heart rate can vary according to the body's physical needs, including the need to absorb oxygen and excrete carbon dioxide. It is usually equal or close to the pulse measured at any peripheral point (Hall and Guyton, 2005).
The heart rhythm is regulated entirely by the sinoatrial (SA) node under normal conditions heart rate is regulated by sympathetic and parasympathetic input to the sinoatrial node. The accelerans nerve provides sympathetic input to the heart by releasing norepinephrine onto the cells of the sinoatrial node and the vagus nerve provides parasympathetic input to the heart by releasing acetylcholine onto sinoatrial node cells (Schmidt-Nielsen, 1997).
Activities that can provoke change include physical exercise, sleep, anxiety, stress, illness, and ingestion of drugs. The normal resting adult human heart rate ranges from 60–100bpm. Tachycardia is a fast heart rate, defined as above 100 bpm at rest (O'Rouke and Fuster, 2001). Bradycardia is a slow heart rate, defined as below 60bpm at rest. During sleep a slow heartbeat with rates around 40–50bpm is common and is considered normal. When the heart is not beating in a regular pattern, this is referred to as an arrhythmia. These abnormalities of heart rate sometimes indicate disease (Atwal et al., 2002).
The prognostic value of heart rate variability (HRV) variables is also dependent on the left ventricular function and the severity of heart failure (Mäkikallio et al., 2005). Several factors influence the prognostic value of Heart beat measurements. The timing of the HRV measurement after an acute myocardial infarction (AMI) has a direct influence on the prognostic significance of HRV due to substantial electrical and mechanical remodeling after AMI (Exner et al., 2007; Huikuri et al., 2009).
2.5 Measurement of Heart Rate
For healthy people, the Target Heart Rate or Training Heart Rate (THR) is a desired range of heart rate reached during aerobic exercise which enables one's heart and lungs to receive the most benefit from a workout. This theoretical range varies based mostly on age; however, a person's physical condition, sex, and previous training also are used in the calculation. Below are two ways to calculate one's THR. In each of these methods, there is an element called "intensity" which is expressed as a percentage. The THR can be calculated as a range of 65–85% intensity. However, it is crucial to derive an accurate HRmax to ensure these calculations are meaningful.
Example for someone with a HRmax of 180 (age 40, estimating HRmax As 220 − age):
65% Intensity: (220 − (age = 40)) × 0.65 → 117 bpm
85% Intensity: (220 − (age = 40)) × 0.85 → 153 bpm
2.5.1 Karvonen method:
The Karvonen method factors in resting heart rate (HRrest) to calculate target heart rate (THR), using a range of 50–85% intensity:
THR = ((HRmax − HRrest) × % intensity) + HRrest
Example for someone with a HRmax of 180 and a HRrest of 70:
50% Intensity: ((180 − 70) × 0.50) + 70 = 125 bpm
85% Intensity: ((180 − 70) × 0.85) + 70 = 163 bpm
2.5.2 Zoladz method:
An alternative to the Karvonen method is the Zoladz method, which derives exercise zones by subtracting values from HRmax:
THR = HRmax − Adjuster ± 5 bpm
Zone 1 Adjuster = 50 bpm
Zone 2 Adjuster = 40 bpm
Zone 3 Adjuster = 30 bpm
Zone 4 Adjuster = 20 bpm
Zone 5 Adjuster = 10 bpm
Example for someone with a HRmax of 180:
Zone 1(easy exercise): 180 − 50 ± 5 → 125 − 135 bpm
Zone 4(tough exercise): 180 − 20 ± 5 → 155 − 165 bpm
2.6 Method for Measuring Heart rate
The pulse rate is a measurement of the heart rate, or the number of times the heart beats per minute. As the heart pushes blood through the arteries, the arteries expand and contract with the flow of the blood. The pulse can be found on the side of the lower neck, on the inside of the elbow, or at the wrist (Baljinder et al., 2009). Resting Heart Rate (RHR) is the heart rate upon waking up in the morning. To measure RHR, the index and middle finger are place on either the radial artery on the wrist or at the carotid artery in the neck. Then, the number of beats in 10 seconds is counted and the number is multiplied by 6 (Sherwood 2008).
2.7 Calculating the Difference between two Means and Variances of Human Height and Heart beat
In this case, the researcher is interested in comparing the means of the two groups of height and heart beat of males and female students. His research question is: Does the mean height heart beat of male students who enroll at a university college differ from the mean height of female students who enroll at a university college. Hence, hypotheses could be applied in obtaining the significant difference.
H0:
H1:
Where;
= mean height and heart beat of all beginning male students at the university college
= mean height and heart beat of all beginning female students at the university college
If there is no difference in population means, subtracting them will give a difference of zero. If they are different, subtracting will give a number other than zero. Occasionally, there will be a few large differences due to chance alone, some positive and others negative. If the differences are plotted, the curve will be shaped like the normal distribution and have a mean of zero, as shown in Figure 1 below;
The variance of the difference is equal to the sum of the individual variances of and . That is,
So the standard deviation of is
In the comparison of two sample means, the difference may be due to chance, in which case the null hypothesis will not be rejected, and the researcher can assume that the means of the populations are basically the same.
2.8 Empirical Studies
A study conducted by Ramesh et al., (2013) to find the correlation of anthropometric parameters and heart rate variability among medical students in south India using two hundred and forty medical students (120 males & 120 females) respectively selected on the basis of their BMI into four groups: viz. Normal (N), Underweight (UW), Overweight (OW) & Obese (OB), [n=30 each]. Results from the study showed that the body fat was significantly higher in OW and OB groups as reflected in increased W/H ratio and lower LBM (p<0.001) and significantly lesser in the UW group when compared to Normal subjects. This implies that there is a strong correlation between the Obesity levels measured in terms of BMI, LBM and weight and Height ratio and the heart rate variability, reflecting sympatho-vagal balance on heart. Obese persons may suffer from an increased mortality risk due to cardiovascular disorders related to either continuously lowered parasympathetic or altered sympathetic activation.
Chukwujekwu et al., (2014) conducted an anthropometric study of weight, height and blood pressure in children from Nnewi North Local Government of Anambra State, South East Nigeria. The study was carried out on 320 primary school children whose age ranged from 6-14 at a gender ratio of 1:1. Their heights, weights and blood pressures were measured using height meter, weighing scale, sphygmomanometer and stethoscope. The results showed that weight and height values correlated with systolic and diastolic blood pressure for males in all age groups except in age groups 6-8years. In females, weight values correlated with systolic and diastolic blood pressure in all age groups while height correlated with blood pressure only in age groups 6-8years and 9-11 years. Females also showed higher mean weight values than the males in all age groups except in groups 6-8yearrs.
A similar study conducted by Anna, (2009) to assess the anthropometric and cardio-respiratory indices and aerobic capacity of male and female students differing in the level of physical activity, under resting and exercise conditions. A group of 87 male and 75 female students volunteered to participate in the study. The Anthropometric (body height and mass, body fat content, BMI and WHR) and physiological indices (heart rate, blood pressure, VO2max and minute ventilation) were evaluated. Results obtained from their studies showed that male and female students expended 10.24.6 and 8.45.3 kcal/kg/day, respectively, the VO2max amounting to 48.4 6.4 and 41.1 4.7 ml/kg/min, respectively. Subjects having high VO2max had significantly higher energy expenditure on physical activities, fat-free mass, body water content and maximal ventilation, and lower body mass, BMI, body fat content, resting heart rate and diastolic pressure. Their findings revealed that when investigating into the relationships between physical activity and physiological features, the latter ought to be related to VO2max rather than to energy expenditure which may depend on other than physiological variables
Another recent study was carried out by Ogedengbe et al., (2015) to investigate gender and Height in relation to blood pressure and heart rate of medical students of University of Abuja. It was a cross-sectional study that recruited Ninety one (91) medical students aged 18-30 years at University of Abuja, Nigeria. The blood pressure, the pulse rate and the height of the participants were adequately measured. Results obtained from their study revealed that there was positive correlation between blood pressure and heart rate in males, though not statistically significant, while in females a negative correlation was observed. Hence, males had higher systolic and diastolic blood pressure while females had higher heart rate. The blood pressure and heart rate increased with increasing height in males but both reduced with increasing height in females. BMI was positively associated with increase in blood pressure and reduction in heart rate for both sexes. This study found that systolic blood pressure increased significantly with diastolic blood pressure and BMI was positively associated with height, increase in blood pressure and reduction in heart rate for both sexes.
Samaras, (2013) in his study discovered that a variety of cardiovascular disease (CVD) problems are related to having a taller height. These include: higher blood pressure, greater left ventricular hypertrophy, increased work load on the heart, atrial fibrillation, blood clots and lower heart pumping efficiency. The lower heart rate of taller people is considered a longevity advantage; however, centenarians are usually small with higher heart rates, which conflicts with the slow heart advantage. A larger left ventricular mass (LVM) is related to increased all-cause mortality, CVD and stroke, independent of other risk factors (Bouzas et al., 2012). Rider et al. (2009) report that LVM is positively correlated with increasing height, weight, fat mass and BMI. During the first year of life, the heart grows by increasing the number of cells. After that period, it grows through cell enlargement. For bigger people, the cells have to enlarge by a greater amount to create a larger heart. The laws of scaling indicate that bigger cells have lower surface area in comparison to their mass (Samaras, 2007). Thus, the exchange of energy, nutrients and waste is slower in a larger cell, because mass is related to consumption and waste products. How much of an effect this would have on health and longevity is not known; however, over a lifetime it could be significant.