Uphill Running Research Articles

Effect Of Military Training On Maximal Oxygen Uptake In Norwegian Infantry Soldiers

Completing the compulsory infantry service requires a certain level of physical fitness. It is therefore important determine whether the fitness training provided during military service improves physical fitness. Purpose To evaluate the effect of military training on maximal oxygen uptake (VO2max) in Norwegian infantry soldiers during the 10 months of compulsory service. Methods VO2 max of 107 male infantry soldiers was evaluated at the beginning and end of the 10-week basic training (BT) period, and again 7 months later prior to demobilization in 84 soldiers. VO2 max was measured using open-circuit, indirect calorimetry during a continuous uphill running treadmill protocol. The officers reported all obligatory physical training for the platoons on a weekly basis. In addition, all soldiers reported their physical training, obligatory and optional, during the basic training period. Results During BT, VO2 max increased from 54.8 ± 4.8 to 55.5 ± 4.2 ml·kg−1 ± min−1 (p<0.01). At the end of the military service, VO2 max had decreased by 3% compared with the results at the end of BT (p<0.01). To see if initial aerobic fitness had any effect on the training-induced changes on VO2 max during BT, the 107 soldiers were divided in 3 equal-sized groups according to their initial VO2 max values: high (59.7 ± 2.5 ml·kg−1 ± min−1), medium (54.6 ± 1.5 ml·kg−1 ± min−1) and low (49.4 ± 2.8 ml·kg−1 ± min−1). During BT, VO2max increased by 5% (p<0.001) in the low group, while there were no changes in VO2 max for the medium and high groups. The weekly obligatory amount of physical exercise during the basic training period was 8.5 ± 4.7 h in 3.4 ± 1.7 sessions. Around 90% of this physical exercise was military activity conducted in uniform, normally at low to moderate intensity. After the basic training period, the weekly amount of obligatory physical exercise decreased by 35% to 5.4 ± 3.5 h, with 70% being uniformed military activity. Conclusion Most of the physical training was military activity carried out at low to moderate intensity. During the BT period, this training improved VO2max only for the soldiers with the lowest initial VO2 max. After BT, VO2 max decreased in all soldiers, independent of initial VO2 max. Increasing the amount of endurance training at high intensity could increase aerobic fitness for all soldiers, especially after the initial BT period.

평지와 오르막경사의 트레드밀 걷기와 달리기 동안 발보장구가 발바닥근막염과 관련된 발아치 스트레인에 미치는 영향

There is some evidence that one of major factors to produce plantar fasciitis depends on the magnitude of the foot arch strain. The orthotics that can reduce the foot arch strain during locomotion may be effective to prevent or treat plantar fasciitis. Therefore, the purpose of this study was to investigate the effect of control condition and three types of foot orthotics on 3-dimensional foot arch strain that can produce plantar fasciitis during treadmill level and uphill walking and running. Sixteen male subjects are recruited and the arch length and height strain according to three types of foot orthotics with respect to control condition were measured by using two digital video cameras. The first hypothesis which the comfort of foot orthotics would be increased from arch pad, half length orthotics to full length orthotics was mostly accepted. It suggested that the types of the foot orthotics could be properly prescribed according foot regions that is pain or abnormal. The second hypothesis which the foot arch strain can be reduced by foot orthotics during level heel-toe walking and running and the third hypothesis which the foot arch strain can be reduced by foot orthotics during uphill heel-toe walking and running were rejected. The foot arch length and height strain during walking and running showed small and subject-specific characteristics and could not be optimal biomechanical variable to prove the overall comfort. The forth hypothesis which the foot arch strain cannot be reduced by foot orthotics during uphill toe walking and running was accepted. With the foot arch length and height strain during uphill toe walking and running the windlass mechanism suggested by Hicks can be explained successfully and excessive uphill toe walking and running can be one of cause of plantar fasciitis. The dynamic investigation on the foot arch such as walking and running should be carefully observed with integrated insights considering ligaments and foot bones as well as plantar fascia, extrinsic muscles and tendons, and intrinsic muscles and tendons.

Droplets of Fine Powders Running Uphill by Vertical Vibration

We observe "droplets" forming when an inclined surface initially covered by fine powders is vibrated vertically. Droplets move uphill in the direction of maximum local slope. The speed of droplets is nearly independent on their size whereas it is an increasing function of the plate acceleration and inclination. By evacuating the container we show that the interstitial air flow plays an important role on droplets forming and their drift.

Ground reaction forces during downhill and uphill running

We investigated the normal and parallel ground reaction forces during downhill and uphill running. Our rationale was that these force data would aid in the understanding of hill running injuries and energetics. Based on a simple spring-mass model, we hypothesized that the normal force peaks, both impact and active, would increase during downhill running and decrease during uphill running. We anticipated that the parallel braking force peaks would increase during downhill running and the parallel propulsive force peaks would increase during uphill running. But, we could not predict the magnitude of these changes. Five male and five female subjects ran at 3 m/s on a force treadmill mounted on the level and on 3°, 6°, and 9° wedges. During downhill running, normal impact force peaks and parallel braking force peaks were larger compared to the level. At −9°, the normal impact force peaks increased by 54%, and the parallel braking force peaks increased by 73%. During uphill running, normal impact force peaks were smaller and parallel propulsive force peaks were larger compared to the level. At +9°, normal impact force peaks were absent, and parallel propulsive peaks increased by 75%. Neither downhill nor uphill running affected normal active force peaks. Combined with previous biomechanics studies, our normal impact force data suggest that downhill running substantially increases the probability of overuse running injury. Our parallel force data provide insight into past energetic studies, which show that the metabolic cost increases during downhill running at steep angles.

Leukocytes, cytokines, growth factors and hormones in human skeletal muscle and blood after uphill or downhill running

Muscular adaptation to physical exercise has previously been described as a repair process following tissue damage. Recently, evidence has been published to question this hypothesis. The purpose of this study was to investigate inflammatory processes in human skeletal muscle and epimysium after acute physical exercise with large eccentric components. Three groups of subjects (n= 19) performed 45 min treadmill running at either 4 deg (n= 5) or 8 deg (n= 9) downhill or 4 deg uphill (n= 5) and one group served as control (n= 9). One biopsy was taken from each subject 48 h post exercise. Blood samples were taken up to 7 days post exercise. Compared to the control group, none of the markers of inflammation in muscle and epimysium samples was different in any exercised group. Only subjects in the Downhill groups experienced delayed onset of muscle soreness (DOMS) and increased serum creatine kinase activity (CK). The detected levels of immunohistochemical markers for T cells (CD3), granulocytes (CD11b), leukaemia inhibitory factor (LIF) and hypoxia-inducible factor 1beta (HIF-1beta) were greater in epimysium from exercised subjects with DOMS ratings >3 (0-10 scale) compared to exercised subjects without DOMS but not higher than controls. Eccentric physical exercise (downhill running) did not result in skeletal muscle inflammation 48 h post exercise, despite DOMS and increased CK. It is suggested that exercise can induce DOMS by activating inflammatory factors present in the epimysium before exercise. Repeated physical training may alter the content of inflammatory factors in the epimysium and thus reduce DOMS.

Running uphill: energy needs and Naismith's Rule

In this note we make two points, from which follows a suggestion for running uphill:(1) an athlete's energy needs in running up a slope of gradient θ at a speed V may be considered to have three additive elements: that needed to stay alive; that needed to run at a speed V on the level; that needed to lift the body at a rate V sin θ.(2) corresponding to Naismith's rule of 1 to 8, in whole numbers, for walking or running in mountainous country (1 foot of ascent is equivalent to 8 feet on the level), the rule for running on a treadmill is 1 to 3 and the rule for running on roads is 1 to 4 or 5.This result suggests that, if possible, a runner should zigzag up slopes steeper than 1 in 8 on the fells and zigzag up slopes greater than 1 in 4 or 5 on roads.

Regulation of type IV collagen gene expression and degradation in fast and slow muscles during dexamethasone treatment and exercise.

Glucocorticoids have anti-anabolic effects on many tissues and can cause muscle atrophy. However, their effects on type IV collagen gene expression and degradation in skeletal muscle have not been studied previously. Rats were treated daily with dexamethasone or saline. Half the groups of experimental and control animals were also subjected to daily endurance or uphill running exercise to determine the possible preventive effects of exercise. After an experimental period of 3 or 10 days, the extensor digitorum longus, soleus and tibialis anterior muscles were studied. Dexamethasone treatment for 10 days reduced muscle weight and type IV collagen mRNA abundance in all muscles. Gene expression of matrix metalloproteinase-2 (MMP-2) was decreased in fast muscles. However, the effects of this decrease were possibly attenuated by the simultaneous decrease in the activity of tissue inhibitor of metalloproteinases (TIMP-2). The amount of type IV collagen was not changed during dexamethasone treatment or exercise. The regulation of type IV collagen degradation during dexamethasone treatment varied between slow and fast muscles. Although endurance running prevented muscle atrophy, exercise could not compensate the changes observed in the regulation of type IV collagen gene expression and degradation during dexamethasone treatment.

Running Uphill: Political Opportunity in Non-democracies

AbstractThis study analyzes twenty-four cases of occurrence/non-occurrence of mobilization in non-democratic states to determine conditions of political opportunity in high-risk authoritarian contexts. Ragin's (1987) Boolean method of qualitative comparison (QCA 3.0) is used to identify specific configurations of conditions that constitute political opportunity in non-democracies. We find that political opportunity is sensitive to conditions created by divided elites, changes in repression, media access, influential allies, and social networks. Our analysis identifies four configurations that create an opening for mobilization under authoritarian conditions. The key factors, identified by QCA in the most parsimonious model, are media access and social networks. These two factors are sufficient conditions for producing mobilization in non-democratic states.

Oxygen uptake kinetics during horizontal and uphill treadmill running in humans.

The aim of this study was to examine the effect of increasing the ratio of concentric to eccentric muscle activation on oxygen uptake (VO(2)) kinetics during treadmill running. Nine subjects [2 women; mean (SD) age 29 (7) years, height 1.77 (0.07) m, body mass 73.0 (7.5) kg] completed incremental treadmill tests to exhaustion at 0% and 10% gradients to establish the gradient-specific ventilatory threshold (VT) and maximal oxygen uptake (VO(2max)). Subsequently, the subjects performed repeated moderate intensity (80% of gradient-specific VT) and heavy intensity (50% of the difference between the gradient specific VT and VO(2max)) square-wave runs with the treadmill gradient set at 0% and 10%. For moderate intensity exercise, there were no significant differences between treadmill gradients for VO(2) kinetics. For heavy intensity exercise, the amplitude of the primary component of VO(2) was not significantly different between 0% and 10% treadmill gradients [mean (SEM) 2,940 (196) compared to 2,869 (156) ml x min(-1), respectively], but the amplitude of the VO(2) slow component was significantly greater at the 10% gradient [283 (43) compared to 397 (37) ml x min(-1); P < 0.05]. These results indicate that the muscle contraction regimen (i.e. the relative contribution of concentric and eccentric muscle action) significantly influences the amplitude of the VO(2) slow component.

THE EFFECTS OF CONTINUOUS AND DISCONTINUOUS VO2MAX TESTS ON BALANCE

PURPOSE: To validate a discontinuous treadmill protocol for assessment of VO2max through comparison to the standard Bruce protocol. To determine the effects of fatigue induced by each test on balance. METHODS: Eight healthy female subjects (mean ± SD, age: 25.9 ± 7.3 y; height: 166.6 ± 7.5 cm; body mass: 59.8 ± 4.9 kg) completed a Bruce protocol and a discontinuous protocol consisting of 3-min work stages and 3-min rests. The initial treadmill speed and grade were 8 km/h at a 1% grade. The treadmill speed was increased by 2 km/h at each stage until a speed of 16 km/h was reached and then the grade was increased in 2.5% increments until exhaustion. Subjects completed both tests in a random order within 4 to 7 days. A computerized balance assessment was performed before and after each of the VO2max tests, which required the subject to maintain bliateral static balance and one-legged static balance on each leg for 30 seconds on an unstable platform. The subjects also completed a dynamic balance test in which they moved the unstable platform in a pattern determined by watching a moving cursor on a computer screen. A balance index score was calculated based on the deviation of the platform from the level position in the static tests or from the pattern of the cursor in the dynamic test. RESULTS: The mean VO2max measurements for the discontinuous protocol and the Bruce protocol were 42.4 ± 3.7 and 41.9 ± 5.4 ml/kg/min, respectively. The VO2max values from the discontinuous protocol and the Bruce protocol were highly correlated (r = 0.90, p < 0.05). Balance was significantly worse after the VO2max tests in all four of the conditions tested (bilateral static, right leg static, left leg static, and dynamic balance decreased by 20, 11, 12, and 6 %, respectively). The decrease in balance was about 5% greater for the bilateral static and one leg static conditions following the Bruce protocol compared to the discontinuous protocol. CONCLUSIONS: The discontinuous treadmill protocol used in this study results in similar VO2max values compared to the Bruce protocol. Balance decreases following a treadmill VO2max test. The degradation in balance is greater after the Bruce protocol, perhaps due to increased fatigue of the ankle musculature induced by the greater amount of uphill running required by this protocol.

Effects of Exercise on Muscle Metabolites and Sarcoplasmic Reticulum Function in Ovariectomized Rats Treatment.

The relationships between exercise and metabolites as well as between exercise and sarcoplasmic reticulum function were studied in gastrocnemius muscle of ovariectomized-trained rats. Prolonged moderate-intensity exercise, treadmill up-hill run for 90 min with a 10° incline, decreased the muscle glycogen content. Exercise until exhaustion further lowered the glycogen concentration to 13 % of the control, together with a significant decrease of ATP and glucose-6-phosphate concentrations. Also, Ag+-induced Ca2+release, measured in whole muscle homogenate, showed a 30 % reduction on exhaustion, while Ca2+ uptake was unaffected by this exercise. ATPase activities, of both homogenate and SR vesicles, and Ca2+ transport in the latter preparation were not altered on exhaustion. It could be concluded from these results that muscular fatigue in ovariectomized rats after aerobic exercise is caused by the change in energy supply and Ca2+ release from the SR, this latter possibly due to metabolites generated by the exercise.

Function of the oblique hypaxial muscles in trotting dogs.

In trotting dogs, the pattern of activity of the obliquely oriented hypaxial muscles is consistent with the possible functions of (i) stabilization against vertical accelerations that cause the trunk to sag in the sagittal plane and (ii) stabilization against forces that tend to shear the trunk in the sagittal plane. To test these hypotheses, we compared the amount of activity of the intercostal and abdominal oblique muscles (i) when dogs carried additional mass (8-15% of body mass) supported over the limb girdles versus supported mid-trunk (test of sagittal bounce), and (ii) when dogs trotted up versus down a 10 degrees slope (test of sagittal shear). In response to the loading manipulations, only the internal oblique muscle responded in a manner that was consistent with stabilization of the trunk against forces that cause the trunk to sag sagittally. In contrast, when the fore-aft forces were manipulated by running up- and downhill, all four of the monitored muscles changed their activity in a manner consistent with stabilization of the trunk against sagittal shearing. Specifically, muscles with a craniodorsal orientation (external oblique and external intercostal muscles) showed an increase in activity when the dogs ran downhill and a decrease when they ran uphill. Muscles with a cranioventral orientation (internal oblique and internal intercostal muscles) exhibited the opposite pattern: increased activity when the dogs ran uphill and decreased activity when they ran downhill. Changes in activity of two extrinsic appendicular muscles, the serratus ventralis and deep pectoralis, during uphill and downhill running were also consistent with the sagittal shearing hypothesis. In contrast, changes in the level of recruitment of the oblique hypaxial muscles were not consistent with stabilization of the trunk against torques that induce yaw at the girdles. Hence, we suggest that the oblique hypaxial muscles of trotting dogs act to stabilize the trunk against sagittal shearing torques induced by limb retraction (fore-aft acceleration) and protraction (fore-aft deceleration).

Kinematic and postural characteristics of sprint running on sloping surfaces

The aim of this study was to identify the kinematic and postural characteristics associated with sprint running on uphill and downhill slopes of 3° and on a horizontal surface. Eight male physical education students were filmed while sprinting maximally on an uphill-downhill platform under each of three conditions: (a) uphill at 3°, (b) downhill at 3° and (c) horizontal. Running speed, step rate, step length, step time, contact time, flight time and selected postural characteristics of the step cycle were analysed. Running speed was 9.2% faster ( P < 0.05) during downhill and 3.0% slower ( P < 0.05) during uphill compared with horizontal sprint running. During downhill and uphill sprint running, step length was the main contributor to the observed changes in running speed. It increased by 7.1% ( P < 0.05) for downhill sprint running and was associated with significant changes in posture at touchdown and take-off. During uphill sprint running, step length decreased by 5.2% ( P < 0.05), which was associated with significant changes in posture and reduced flight distance. Given the interaction between the acute changes in step length and posture when sprinting on a sloping surface, our findings suggest that such changes in posture may detract from the specificity of training on such surfaces. The chronic effects of training on such slopes on the kinematics and posture of horizontal sprint running are currently unclear.

Muscle power factors and VO2max as determinants of horizontal and uphill running performance.

This study was carried out to investigate the importance of maximal oxygen uptake (VO2max) and so-called muscle power factors relating to neuromuscular and anaerobic characteristics as determinants of peak horizontal and uphill treadmill running velocity (Vmax). Muscle power factors were measured as peak velocity (VMART) and blood lactate concentration (BlaMART) in a maximal anaerobic running test and as maximal 30-m run velocity (V30m). Seven middle-distance runners, eight triathletes and eight cross-country skiers performed an incremental VO2max-test at horizontal (subscript max0) and 7 degrees uphill (subscript max7) and the MART at 3 degrees uphill on a treadmill and V30m-test on a track. The MART consisted of n x 20-s runs with a 100-s recovery between the runs and the velocity was increased by 0.41 m x s(-1) for each consecutive run until exhaustion. At 0 degrees Vmax was significantly higher but VO2max, ventilation and Bla were significantly lower than at 7 degrees inclination. Vmax0 correlated with VMART (r=0.85, P<0.001), Blamax0 (r=0.49, P<0.05) and V30m (r=0.78, P<0.001) but not with VO2max0. Vmax7 correlated with VO2max7 (r=0.78, P<0.001), VMART (r=0.61, P<0.01) and V30m (r=0.53, P<0.05). VMART correlated with BlaMART (r=0.71, P<0.01) and V30m (r=0.96, P<0.001) but not with VO2max0 or VO2max7. Middle-distance runners had a significantly (P<0.001) higher Vmax0, VMART BlaMART and V30m than triathletes and cross-country skiers, but no significant differences were found between the three groups in VO2max0, VO2max7 or Vmax7. We conclude that so-called muscle power factors, e.g. VMART, V30m and BlaMART, contribute to peak treadmill running performance and especially to horizontal running performance and that VO2max contributes more to uphill than horizontal running performance.

Neutrophil oxidative activity is differentially affected by exercise intensity and type

The differential effects of exercise intensity and type on neutrophil activation were assessed in eight well-trained male runners. Each subject undertook, on different days, three separate 40 min interval (8 x 5 min) treadmill bouts: an intense uphill run (90% VO2 max), a moderate-intensity near-level run and an eccentrically-biased downhill run (both at 52% VO2 max). Blood granulocyte count increased (p< 0.05) after all three treadmill bouts (range 25-108%). Chemiluminescence activity of isolated neutrophils decreased (p< 0.05) immediately after (-58%) and 1-h after (-72%) uphill running, but became significantly elevated (p< 0.05) at 6-h after the near-level (+71%) and downhill (+84%) runs. The ability of neutrophils to release the superoxide anion radical was reduced (p< 0.05) immediately after near-level (-29%) and uphill (-21%) running in cells stimulated with opsonized zymosan. Epinephrine concentration increased by 430% (p=0.01) after uphill but not with near-level or downhill running. The plasma concentration of elastase increased (p< 0.05) immediately after uphill and near-level running, and one hour after uphill running. These results suggest that a population of neutrophils mobilised into the circulation became directly activated in response to exercise, and that neutrophil oxidative activity is affected differentially by both the intensity and type of exercise undertaken.

The effect of exercise modality on exercise-induced hypoxemia.

To investigate the effect of exercise mode on arterial oxyhemoglobin saturation (SaO2), 13 healthy, actively training men who displayed exercise-induced hypoxemia (EIH) performed two incremental maximal exercise tests: uphill treadmill running and cycle ergometry. At maximum, treadmill running resulted in a lower SaO2 (88.6+/-2% versus 92.6+/-2.0%) a lower ventilatory equivalent for carbon dioxide (VE/VCO2; 28.8+/-0.6 versus 31.2+/-0.9), and a higher maximal oxygen consumption (VO2, MAX; 4.83+/-0.11 l x min(-1) versus 4.61+/-0.14 l x min(-1) when compared to cycle ergometry. When data were combined from maximal running and cycling. SaO2 was correlated to VE/VCO2 (r = 0.54). However, there was no relationship between the differences in SaO2 and ventilation between exercise modes. This suggests that ventilation is important in the maintenance of SaO2, but that the difference observed in SaO2 between treadmill running and cycle ergometry cannot be explained by differences in ventilation and must be due to differences in diffusion limitation or ventilation-perfusion inequality.

ACTIVE RECOVERY FOLLOWING STRENUOUS UPHILL RUNNING STIMULATES POST-EXERCISE CIRCULATING LYMPHOCYTE AND TOTAL LEUKOCYTE COUNT

1148 This study examines the differential leukocytes count in the recovery period until 2 h post-exercise in response to passive (PR) or active recovery (AR) in the 15 min period immediately after exhaustive exercise. in a randomized cross-over study. METHODS: Thirteen male athletes (24.2 ± 3.7 years, 76.7 ± 7.9 kg, 182 ± 5 cm, VO2 max 69.2 ± 6.8 ml*kg−1*min−1) completed two tests consisting of a 60 min uphill running session at 82 ± 3% of VO2 max followed by either PR or AR in a randomized order. During exercise, neither heart rate, lactate, or rated perceived exertion differed between the PR or AR trials. Differential counts were obtained at rest, then 0, 5, 10, 15, 30, 45, 60, 90, and 120 min post-exercise. Differences in plasma volume as a result of the PR/AR intervention were calculated and accounted for in the statistical analyses. RESULTS: There were no differences in the baseline values for any hematological variables. AR resulted in higher circulatory concentration of leukocytes and lymphocytes at 10 and 15 min post-exercise (p<0.05). DISCUSSION: The well-known reduction in leukocytes and lymphocytes immediately post-exercise is largely prevented by performing light exercise in the 15 min period following exhaustive running. A possible explanation for this result is a sustained catecholamine level induced by AR, compared with rapidly decreasing catecholamines during PR.

A field study of the effects of incline on the escape locomotion of a bipedal lizard, Callisaurus draconoides.

We analyzed footprints on the surface of a sand dune to estimate maximal running speeds and the incidence of bipedality in nature, as well as to investigate the effects of incline on the escape locomotion of the lizard Callisaurus draconoides. Previous laboratory tests predicted that inclines would negatively affect sprinting performance in C. draconoides. Although physiologists commonly assume that escape locomotion will be near maximal capacity, we found that only 11% of all strides were greater than 90% of maximal speed of C. draconoides. Escape paths averaged 10 m in length and were generally straight. Approximately 30% of the strides taken by C. draconoides were bipedal, and this value was three times greater than previously found for the closely related species Uma scoparia. The modal value of bipedal stride lengths was greater than that for quadrupedal strides. Inclines negatively affected velocity of only the first meter of C. draconoides escape paths. The location of nearest cover had better predictive value for the initial orientation of C. draconoides escapes than incline. On steep slopes (>15 degrees), C. draconoides avoided running directly downhill and uphill and primarily ran horizontally, whereas on shallow slopes, lizards exhibited approximately equal amounts of horizontal, direct uphill, and direct downhill running.

EFFECT OF UPHILL AND DOWNHILL RUNNING ON LIGAMEN TOUS KNEE JOINT LAXITY

1672 The knee is constantly subject to anteroposterior and mediolateral destabilizing forces during weight bearing activities. Activities with a large eccentric component such as downhill running (DR) are associated with a high incidence of knee ligament injury due to the large impact forces acting on knee ligaments. The injury may be preceded by alterations of the physical characteristics of the ligaments. The purpose of this study was to assess the alterations of knee ligament laxity associated with DR and uphill running(UR). It is hypothesized that DR will induce larger changes in ligament laxity than UR. Twelve male students were tested for knee ligament laxity before and after either 30 min. rest; 30 min. UR and 30 min. DR both at 4.0 mph on a treadmill with 10% grade. Medial knee ligament laxity was assessed by exposing the ligaments to a constantrate bilateral stretch. The results indicated that both UR and DR significantly (p<0.05) increased the ligament laxity from pre-exercise condition (5.1% and 8.5%, respectively). However, only the change induced by DR (10.3%) was significantly (p<0.05) larger compared to the control condition. It is concluded that DR induces larger alterations in knee ligament laxity than UR.

USE OF THE RECTUS FEMORIS MUSCLE DURING HORIZONTAL AND UPHILL RUNNING

373 We used exercise-induced contrast shifts in magnetic resonance images to determine use of the rectus femoris muscle during horizontal and uphill high-intensity (115% of peak oxygen uptake) running to exhaustion (2.0-3.9 min) in 12 women. The mean percentage of the rectus femoris volume used(±SEM) was significantly (p<.05) greater during horizontal (73± 6%) compared to uphill (44 ± 6%) running. Use at the midpoint and insertion of the muscle, distal to the hip joint, were significantly(p<.05) greater during horizontal (72 ± 7% and 82 ± 6%) compared to uphill running (36 ± 9% and 42 ± 11%), respectively. Use at the origin, proximal to the hip joint, was not different (p>.05) during horizontal (63 ± 7%) compared to uphill (53±8%) running. The rectus femoris originates from the spine of the ilium and lip of acetabulun and inserts at the patella, and acts in hip flexion and knee extension. The lower use of the portion of the rectus femoris muscle distal to the hip joint in uphill compared to horizontal running is consistent with the belief that the contribution of the rectus femoris to knee extension decreases when extreme hip flexion precedes it. The results of the present study suggest that use of a two-joint muscle varies as a function of location with respect to joints it covers.