The effect of external loading upon power output in stair climbing

Evaluation of Margaria staircase test: the effect of body size

The purpose of this study was to evaluate the methodology of Margaria staircase test (MT) for assessment of muscle anaerobic power. Specifically, we hypothesized that due to the scaling effects the outcome of MT calculated using the standard formula that suggests the power output to be proportional to body mass [P = (m . g . h)/T; P = power output, m = body mass, g = 9.81 m/s(2), h = height of stairs climbed, T = running time] overestimates the effect of body size on the calculated muscle power output. Young and physically active subjects (N = 111) were tested and the relationship between P and body size (S; either body mass or height) was assessed by standard allometric model (i.e., P = a . S ( b ); where a and b were the constant multiplier and allometric parameter, respectively). The results supported the hypothesized relationship by revealing b = 0.66 (95%CI = 0.49-0.83; r = 0.59; P < 0.001) and b = 1.13 (95%CI = 0.49-0.83; r = 0.34; P < 0.001) for body mass and body height, respectively. The obtained values of b (i.e., b < 1 for body mass and b < 3 for body height) suggest that the standard formula of MT overestimates the power output of larger subjects and underestimates the power of smaller ones. Since the results were mainly in line with both the experimental findings and theoretical predictions regarding the general effects of scale on human muscle power, we propose a modified formula that provides normalized power: P ( n ) = P/m (0.67) = [(m . g . h)/T]/m (0.67) = (m (0.33) . g . h)/T. The modified formula could provide a body size independent index of muscle power that would both allow for establishing standards and enable comparison of individuals and groups of individuals of different body dimensions.

Influence of gender, age and BMI on lower limb muscular power output in a large population of obese men and women

OBJECTIVE

To depict the general trends of muscle anaerobic performance in obese subjects within a wide range of age and body weight.

DESIGN

Cross-sectional study for the measurement of lower limb maximal anaerobic power output with a modification of the Margaria stair climbing test in a large population of obese subjects of both genders within a wide span of age (18-80 y) and body mass index (BMI, 30-68 kg m(-2)). Furthermore, body composition was also determined by bioimpedance analysis in a representative subgroup, in order to evaluate the relationships between fat-free mass (FFM) and power output.

SUBJECTS

A total of 1298 obese subjects (486 males, 812 females) from an Italian population seeking medical support for body weight reduction. Within this sample, a consistent subgroup of 193 subjects (59 males, 134 females) was also selected for accessory study of body composition.

RESULTS

In general, male subjects developed significantly higher lower limb power output (W) than female subjects (P<0.001-0.01), both in absolute terms and per unit body mass. In both genders, W was influenced negatively by age (P<0.001) and positively by BMI (P<0.001). While the effect of age was similar in both genders, BMI had a different positive effect in male and in female subjects, being more definite in male subjects. In the subgroup, FFM was found to depend both on age and BMI, in a fashion comparable with that displayed by W. The gender-related differences in W disappeared when expressed per unit FFM and a significant linear correlation was found between FFM and W, both in male and female subjects (R2=0.32-0.51, P<0.001).

CONCLUSIONS

The lower limb maximal power output is significantly higher in obese male subjects than in female subjects, being negatively influenced by age but positively related to BMI. Female subjects appear to be at a greater disadvantage for effect of obesity, the major motor limitations being suffered by older women with higher BMI. These gender differences in age- and BMI-dependent W changes seem to be related to changes in FFM in the subgroup in whom body composition was studied.

High intensity exercise assessment: relationships between laboratory and field measures of performance

The purpose of this study was to examine the relationship between high intensity cycle ergometry when resistive forces were optimised and field tests of high intensity performance in an elite sprint trained group (n = 12). Body mass, stature and age of the group were determined prior to testing (66.3 +/- 9.8kg, 177 +/- 7.6cm and 17 +/- 0.74 yrs respectively). Field tests of high intensity performance examined included sprinting. maximal shuttle running and jumping ability (vertical and horizontal). Significant correlations existed between all field tests (P < 0.01). Only moderate correlations were observed for values generated on the cycle ergometer and performance tests (P > 0.05). The results of the present study suggest that the optimised cycle ergometer test and the performance tests are unrelated when evaluated statistically. These findings also suggest that the sprinting and jumping tests examined are highly related and may be substituted for each other as possible predictors of high intensity ability.

Lower limb alactic anaerobic power output assessed with different techniques in morbid obesity

Short-term alactic anaerobic performance in jumping (5 consecutive jumps with maximal effort), sprint running (8 m) and stair climbing (modified Margaria test) were measured in 75 obese subjects (BMI: 40.3+/-5.0 kg/m2) and in 36 lean control subjects (BMI: 22.4+/-3.2 kg/m2) of the same age and gender distribution. The results show that obese subjects attained a significantly lower specific (per unit body mass) power output both in jumping (W(spec,j); p<0.001) and stair climbing (W(spec,s); p<0.001) and run at a significantly lower average velocity (v; p<0.001) during sprinting. In spite of the different motor skillfulness required to accomplish the jumping and climbing tests, W(spec,s) (and hence the vertical velocity in climbing, v(v)) was closely correlated with W(spec,j) (R2=0.427, p<0.001). In jumping, although the average force during the positive work phase was significantly higher in obese subjects (p<0.001), no difference between the 2 groups was detected in absolute power. In stair climbing the absolute power output of obese resulted significantly higher (18%) than that of lean controls (p<0.001). In sprint running, the lower average horizontal velocity attained by obese subjects also entailed a different locomotion pattern with shorter step length (L(s); p<0.001), lower frequency (p<0.001) and longer foot contact time with ground (T(c,r); p<0.001). W(spec,j) seems to be a determinant of the poorer motor performance of obese, being significantly correlated with: I) the vertical displacement of the centre of gravity (R2=0.853, p<0.001) in jumping; II) with v(v) in stair climbing; and III) with T(c,r) (R2=0.492, p<0.001), L(s) (R2=0.266, p<0.001) and v (R2=0.454, p<0.001) in sprinting. The results suggest that obese individuals, although partially hampered in kinetic movements, largely rely on their effective specific power output to perform complex anaerobic tasks, and they suffer from the disproportionate excess of inert mass of fat. Furthermore, in view of the sedentary style of life and the consequent degree of muscle de-conditioning accompanying this condition, it may prove useful to implement rehabilitation programs for obesity with effective power training protocols.

Effects of external loading on power output in a squat jump on a force platform: a comparison between strength and power athletes and sedentary individuals

The aim of this study was to determine the effects of external loading on power output during a squat jump on a force platform in athletes specializing in strength and power events (6 elite weight-lifters and 16 volleyball players) and in 20 sedentary individuals. Instantaneous power was computed from time-force curves during vertical jumps with and without an external load (0, 5 or 10 kg worn in a special vest). The jumps were performed from a squat position, without lower limb counter-movement or an arm swing. Peak instantaneous power corresponded to the highest value of instantaneous power during jumping. Average power throughout the push phase of the jump was also calculated. A two-way analysis of variance showed significant interactions between the load and group effects for peak instantaneous power (P< 0.01) and average power (P< 0.001). Peak instantaneous power decreased significantly in sedentary individuals when moderate external loads were added. The peak instantaneous power at 0 kg was greater than that at 5 and 10 kg in the sedentary individuals. In contrast, peak instantaneous power was independent of load in the strength and power athletes. Mean power at 0 kg was significantly lower than at 5 kg in the athletes; at 0 kg it was significantly higher than at 10 kg in the sedentary males and at 5 and 10 kg in the sedentary females. In all groups, the force corresponding to peak instantaneous power increased and the velocity corresponding to peak instantaneous power decreased with external loading. The present results suggest that the effects of external loading on peak instantaneous power are not significant in strength and power athletes provided that the loads do not prevent peak velocity from being higher than the velocity that is optimal for maximal power output.

A comparison of the effect of external loading upon power output in stair climbing and running up a ramp

Previous studies have shown that external loading increases the power output measured during stair climbing. However, it was noted in an earlier study that stairtreads form mechanical contraints which limit the extent to which a subject can be externally loaded, and, thereby, make it impossible to observe maximal power output for this type of activity. The purpose of this study was to compare the effects of external loading upon power output when running up stairs or a ramp. Since a ramp is free of the mechanical constraints of stairtreads, it was felt that higher power output values would be achieved using the ramp, and that it would be possible to observe an asymptote in power output which could not be obtained for stair climbing. Seven male subjects performed maximal ramp and stair climbing tests under five experimental loading conditions (no external load, 10.1, 19.2, 24.2, and 29.2 kg). For the ramp, it was possible to employ a sixth loading condition of 34.2 kg. For stair climbing, the mean (+/- SD) power output values under the five experimental conditions were 16.6 +/- 0.7, 17.3 +/- 1.3, 18.5 +/- 1.0, 18.6 +/- 1.5, and 18.9 +/- 1.7 W X kg-1, respectively. In contrast, the mean (+/- SD) power output values observed while running up the ramp were 18.8 +/- 1.4, 19.9 +/- 1.6, 20.5 +/- 1.6, 20.1 +/- 2.1, 20.3 +/- 2.1, and 19.8 +/- 1.9 W X kg-1, respectively. At each experimental condition, the differences between the ramp and stairs was significant (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of external loading on short term power output in children and young male adults

The effects of external loading, in the form of small weights distributed evenly over the limbs and torso, on physical performance and power output have been studied during vertical jumping in 10 children and four young adults and the results compared with maximal cycling. The results show under control (unloaded) conditions the absolute peak power output (W) achieved by children and adults was 572 W (45%) and 765 W (25%) respectively higher in cycling than jumping. The addition of weights during jumping served only to increase this difference. External loading produced a linear decrease of W in both groups of subjects. The reduction in W was entirely due to a decrease of take-off velocity (VT). The relationship between VT and added weights (delta wt) could be described by the equations: VT (ms-1) = 1.91 - 0.042 delta wt (kg); r = -0.96 (children); VT (ms-1) = 2.49 - 0.021 delta wt (kg); r = -0.99 (adults). Thus, contrary to the recent work of Caiozzo and Kyle (1980) which involved stair-climbing, body size and speed of movement in children and young adults would appear to be optimally matched for the production of lifting work during vertical jumping. External loading reduces the generation of power output immediately prior to take-off of a maximal jump from a force platform.