Physiological and performance test correlates of prolonged, high-intensity, intermittent running performance in moderately trained women team sport athletes

A large number of team sports require athletes to repeatedly produce maximal or near maximal sprint efforts of short duration interspersed with longer recovery periods of submaximal intensity. This type of team sport activity can be characterized as prolonged, high-intensity, intermittent running (PHIIR). The primary purpose of the present study was to determine the physiological factors that best relate to a generic PHIIR simulation that reflects team sport running activity. The second purpose of this study was to determine the relationship between common performance tests and the generic PHIIR simulation. Following a familiarization session, 16 moderately trained (VO2max = 40.0 +/- 4.3 ml x kg(-1) x min(-1)) women team sport athletes performed various physiological, anthropometrical, and performance tests and a 30-minute PHIIR sport simulation on a nonmotorized treadmill. The mean heart rate and blood lactate concentration during the PHIIR sport simulation were 164 +/- 6 b x min(-1) and 8.2 +/- 3.3 mmol x L(-1), respectively. Linear regression demonstrated significant relationships between the PHIIR sport simulation distance and running velocity attained at a blood lactate concentration of 4 mmol x L(-1) (LT) (r = 0.77, p < 0.05), 5 x 6-second repeated cycle sprint work (r = 0.56, p < 0.05), 30-second Wingate test (r = 0.61, p < 0.05), peak aerobic running velocity (Vmax) (r = 0.69, p < 0.05), and Yo-Yo Intermittent Recovery Test (Yo-Yo IR1) distance (r = 0.50, p < 0.05), respectively. These results indicate that an increased LT is associated with improved PHIIR performance and that PHIIR performance may be monitored by determining Yo-Yo IR1 performance, 5 x 6-second repeated sprint cycle test work, 30-second Wingate test performance, Vmax, or LT. We suggest that training programs should focus on improving both LT and Vmax for increasing PHIIR performance in moderately trained women. Future studies should examine optimal training methods for improving these capacities in team sport athletes.     

Effects of active, passive or no warm-up on the physiological response to heavy exercise.

Six endurance-trained young men were subjected to a 4 min maximal aerobic treadmill run (100% of VO2 max), after active or passive warm-up or rest on separate days. The increase in body temperature during the active and passive warm-up was controlled, so that the temperature reached the same level, before the subject was exposed to the maximal exercise. On average the rectal temperature rose to 38.3 degrees C (range 38.1-38.6 degrees C). The standard work resulted in a significant higher oxygen uptake, lower lactate concentration and higher blood pH when the work was preceded by active warm-up as compared with passive or no warm-up. The difference in total oxygen uptake during the run between the active and passive warm-up procedure was 0.8 1. No significant difference in minute volume of expired air or respiratory quotient was found. It is concluded that the physiological effects of a thorough active warm-up may be of substantial benefit to athletic performance.     

Effects of prior exercise on muscle metabolism during sprint exercise in horses.

The effect of warm-up exercise on energy metabolism and muscle glycogenolysis during sprint exercise (Spr) was examined in six fit Standardbred horses exercised at 115% of maximal O(2) consumption (VO(2 max)) until fatigued, 5 min after each of three protocols: 1) no warm-up (NWU); 2) 10 min at 50% of VO(2 max) [low-intensity warm-up (LWU)]; and 3) 7 min at 50% VO(2 max) followed by 45-s intervals at 80, 90, and 100% VO(2 max) [high-intensity warm-up (HWU)]. Warm-up increased (P < 0.0001) muscle temperature (T(m)) at the onset of Spr in LWU (38.3 +/- 0.2 degrees C) and HWU (40.0 +/- 0. 3 degrees C) compared with NWU (36.6 +/- 0.2 degrees C), and the rate of rise in T(m) during Spr was greater in NWU than in LWU and HWU (P < 0.01). Peak VO(2) was higher and O(2) deficit lower (P < 0. 05) when Spr was preceded by warm-up. Rates of muscle glycogenolysis were lower (P < 0.05) in LWU, and rates of blood and muscle lactate accumulation and anaerobic ATP provision during Spr were lower in LWU and HWU compared with NWU. Mean runtime (s) in LWU (173 +/- 10 s) was greater than HWU (142 +/- 11 s) and NWU (124 +/- 4 s) (P < 0. 01). Warm-up was associated with augmentation of aerobic energy contribution to total energy expenditure, decreased glycogenolysis, and longer run time to fatigue during subsequent sprint exercise, with no additional benefit from HWU vs. LWU.     

The influence of whole-body vs. torso pre-cooling on physiological strain and performance of high-intensity exercise in the heat

Little research has been reported examining the effects of pre-cooling on high-intensity exercise performance, particularly when combined with strategies to keep the working muscle warm. This study used nine active males to determine the effects of pre-cooling the torso and thighs (LC), pre-cooling the torso (ice-vest in 3 degrees C air) while keeping the thighs warm (LW), or no cooling (CON: 31 degrees C air), on physiological strain and high-intensity (45-s) exercise performance (33 degrees C, 60% rh). Furthermore, we sought to determine whether performance after pre-cooling was influenced by a short exercise warm-up. The 45-s test was performed at different (P<0.05) mean core temperature [(rectal+oesophageal)/2] [CON: 37.3+/-0.3 (S.D.), LW: 37.1+/-0.3, LC: 36.8+/-0.4 degrees C] and mean skin temperature (CON: 34.6+/-0.6, LW: 29.0+/-1.0, LC: 27.2+/-1.2 degrees C) between all conditions. Forearm blood flow prior to exercise was also lower in LC (3.1+/-2.0 ml 100 ml tissue(-1) x min(-1)) than CON (8.2+/-2.5, P=0.01) but not LW (4.3+/-2.6, P=0.46). After an exercise warm-up, muscle temperature (Tm) was not significantly different between conditions (CON: 37.3+/-1.5, LW: 37.3+/-1.2, LC: 36.6+/-0.7 degrees C, P=0.16) but when warm-up was excluded, T(m) was lower in LC (34.5+/-1.9 degrees C, P=0.02) than in CON (37.3+/-1.0) and LW (37.1+/-0.9). Even when a warm-up was performed, torso+thigh pre-cooling decreased both peak (-3.4+/-3.8%, P=0.04) and mean power output (-4.1+/-3.8%, P=0.01) relative to the control, but this effect was markedly larger when warm-up was excluded (peak power -7.7+/-2.5%, P=0.01; mean power -7.6+/-1.2%, P=0.01). Torso-only pre-cooling did not reduce peak or mean power, either with or without warm-up. These data indicate that pre-cooling does not improve 45-s high-intensity exercise performance, and can impair performance if the working muscles are cooled. A short exercise warm-up largely removes any detrimental effects of a cold muscle on performance by increasing Tm.     

Cooling vest worn during active warm-up improves 5-km run performance in the heat.

We investigated whether a cooling vest worn during an active warm-up enhances 5-km run time in the heat. Seventeen competitive runners (9 men, maximal oxygen uptake = 66.7 +/- 5.9 ml x kg(-1) x min(-1); 8 women, maximal oxygen uptake = 58.0 +/- 3.2 ml x kg(-1) x min(-1)) completed two simulated 5-km runs on a treadmill after a 38-min active warm-up during which they wore either a T-shirt (C) or a vest filled with ice (V) in a hot, humid environment (32 degrees C, 50% relative humidity). Wearing the cooling vest during warm-up significantly (P < 0.05) blunted increases in body temperature, heart rate (HR), and perception of thermal discomfort during warm-up compared with control. At the start of the 5-km run, esophageal, rectal, mean skin, and mean body temperatures averaged 0.3, 0.2, 1.8, and 0.4 degrees C lower; HR averaged 11 beats/min lower; and perception of thermal discomfort (5-point scale) averaged 0.6 point lower in V than C. Most of these differences were eliminated during the first 3.2 km of the run, and these variables were not different at the end. The 5-km run time was significantly lower (P < 0.05) by 13 s in V than C, with a faster pace most evident during the last two-thirds of the run. We conclude that a cooling vest worn during active warm-up by track athletes enhances 5-km run performance in the heat. Reduced thermal and cardiovascular strain and perception of thermal discomfort in the early portion of the run appear to permit a faster pace later in the run.     

Effects of stretching on maximal anaerobic power: the roles of active and passive warm-ups

The purpose of the study was to provide practical suggestions on the effect of stretching on the maximal anaerobic power preceded by active or passive warm-up. To this aim, 15 relatively fit male subjects (age 23 +/- 0.2 years, height 177 +/- 2 cm, body mass 74 +/- 2 kg; [mean +/- SE]) randomly performed a series of squat jumps (SJ) and countermovement jumps (CMJ). Jumps were preceded alternatively by: i) passive stretching of lower limbs muscles; ii) active warm-up (AWU); iii) passive warm up (PWU); and iv) the joining of stretching with either active warm-up (AWU+S) or passive warm-up (PWU+S). In control conditions (C) only jumps were required. For the 2 jumps the flight time (Ft), the peak force (Pf), and the maximal power (Wpmax) were calculated. It resulted that Ft, Pf, and Wmax values were significantly higher: i) after AWU than after PWU and PWU+S in CMJ; and ii) in AWU as compared to those of other protocols of SJ. Stretching did not negatively affect the maximal anaerobic power, per se, but seems to inhibit the effect of AWU. The results suggested that AWU seemed to increase vertical jump performance when compared to PWU, presumably due to an increase in metabolic activity as a consequence of AWU, which did not occur in PWU, despite the same skin temperature. Passive stretching alone seemed not to negatively influence vertical jump performance, whereas, if added after AWU, could reduce the power output.     

Effects of wearing a cooling vest during the warm-up on 10-km run performance

The purpose of this study was to examine whether wearing a cooling vest during an active warm-up would improve the 10-km time trial (TT) performance of endurance runners. Seven male runners completed 3 10-km TTs (1 familiarization and 2 experimental) on a treadmill after a 30-minute warm-up. During the warm-up of the experimental TTs, runners wore either a t-shirt (control [C]) or a cooling vest (V), the order of which was randomized. No differences were found between the C and V conditions for the 10-km TT times (2,533 ± 144 and 2,543 ± 149 seconds, respectively) (p = 0.746) or any of the 2-km split times. Heart rate (HR) at the start of the TT equaled 90 ± 17 b·min for C and 94 ± 16 b·min for V. The HR peaked at 184 ± 20 b·min in C and 181 ± 19 b·min in V. At the start of the TT Tc was 37.65 ± .72°C in C and 37.29 ± .73°C in V (p = 0.067). In C, Tc gradually increased until 39.34 ± 0.43°C while in V is reached 39.18 ± 0.72°C (p = 0.621). Although rating of perceived exertion (RPE) and Thermal sensation (TS) increased during both experimental TTs, there were no differences between V and C. Findings suggest wearing a cooling vest during a warm-up does not improve 10-km performance. The use of cooling vests during the warm-up did not produce any physiological (HR and Tc) or psychological (RPE and TS) benefit, perhaps accounting for the lack of improvement.     

Do compression garments enhance the active recovery process after high-intensity running?

Lovell, DI, Mason, DG, Delphinus, EM, and McLellan, CP. Do compression garments enhance the active recovery process after high-intensity running? J Strength Cond Res 25(12): 3264-3268, 2011-This study examined the effect of wearing waist-to-ankle compression garments (CGs) on active recovery after moderate- and high-intensity submaximal treadmill running. Twenty-five male semiprofessional rugby league players performed two 30-minute treadmill runs comprising of six 5-minute stages at 6 km·h, 10 km·h, approximately 85% VO(2)max, 6 km·h as a recovery stage followed by approximately 85% VO(2)max and 6 km·h wearing either CGs or regular running shorts in a randomized counterbalanced order with each person acting as his own control. All stages were followed by 30 seconds of rest during which a blood sample was collected to determine blood pH and blood lactate concentration [La]. Expired gases and heart rate (HR) were measured during the submaximal treadmill tests to determine metabolic variables with the average of the last 2 minutes used for data analysis. The HR and [La] were lower (p ≤ 0.05) after the first and second 6 km·h recovery bouts when wearing CGs compared with when wearing running shorts. The respiratory exchange ratio (RER) was higher and [La] lower (p ≤ 0.05) after the 10 km·h stage, and only RER was higher after both 85% VO(2)max stages when wearing CGs compared with when wearing running shorts. There was no difference in blood pH at any exercise stage when wearing the CGs and running shorts. The results of this study indicate that the wearing of CGs may augment the active recovery process in reducing [La] and HR after high-intensity exercise but not effect blood pH. The ability to reduce [La] and HR has important consequences for many sports that are intermittent in nature and consist of repeated bouts of high-intensity exercise interspersed with periods of low-intensity exercise or recovery.     

Core stabilization exercises enhance lactate clearance following high-intensity exercise

Dynamic activities such as running, cycling, and swimming have been shown to effectively reduce lactate in the postexercise period. It is unknown whether core stabilization exercises performed following an intense bout would exhibit a similar effect. Therefore, this study was designed to assess the extent of the lactate response with core stabilization exercises following high-intensity anaerobic exercise. Subjects (N = 12) reported twice for testing, and on both occasions baseline lactate was obtained after 5 minutes of seated rest. Subjects then performed a 30-second Wingate anaerobic cycle test, immediately followed by a blood lactate sample. In the 5-minute postexercise period, subjects either rested quietly or performed core stabilization exercises. A final blood lactate sample was obtained following the 5-minute intervention period. Analysis revealed a significant interaction (p = 0.05). Lactate values were similar at rest (core = 1.4 +/- 0.1, rest = 1.7 +/- 0.2 mmol x L(-1)) and immediately after exercise (core = 4.9 +/- 0.6, rest = 5.4 +/- 0.4 mmol x L(-1)). However, core stabilization exercises performed during the 5-minute postexercise period reduced lactate values when compared to rest (5.9 +/- 0.6 vs. 7.6 +/- 0.8 mmol x L(-1)). The results of this study show that performing core stabilization exercises during a recovery period significantly reduces lactate values. The reduction in lactate may be due to removal via increased blood flow or enhanced uptake into the core musculature. Incorporation of core stability exercises into a cool-down period following muscular work may result in benefits to both lactate clearance as well as enhanced postural control.     

Acute effects of static, dynamic, and proprioceptive neuromuscular facilitation stretching on muscle power in women

The purpose of this study was to investigate the acute effects of 3 types of stretching-static, dynamic, and proprioceptive neuromuscular facilitation (PNF)-on peak muscle power output in women. Concentric knee extension power was measured isokinetically at 60 degrees x s(-1) and 180 degrees x s(-1) in 12 healthy and recreationally active women (mean age +/- SD, 24 +/- 3.3 years). Testing occurred before and after each of 3 different stretching protocols and a control condition in which no stretching was performed. During 4 separate laboratory visits, each subject performed 5 minutes of stationary cycling at 50 W before performing the control condition, static stretching protocol, dynamic stretching protocol, or PNF protocol. Three submaximal warm-up trials preceded 3 maximal knee extensions at each testing velocity. A 2-minute rest was allowed between testing at each velocity. The results of the statistical analysis indicated that none of the stretching protocols caused a decrease in knee extension power. Dynamic stretching produced percentage increases (8.9% at 60 degrees x s(-1) and 6.3% at 180 degrees x s(-1)) in peak knee extension power at both testing velocities that were greater than changes in power after static and PNF stretching. The findings suggest that dynamic stretching may increase acute muscular power to a greater degree than static and PNF stretching. These findings may have important implications for athletes who participate in events that rely on a high level of muscular power.     

The effects of nightly normobaric hypoxia and high intensity training under intermittent normobaric hypoxia on running economy and hemoglobin mass.

We investigated the effects of nightly intermittent exposure to hypoxia and of training during intermittent hypoxia on both erythropoiesis and running economy (RE), which is indicated by the oxygen cost during running at submaximal speeds. Twenty-five college long- and middle- distance runners [maximal oxygen uptake (Vo(2max)) 60.3 +/- 4.7 ml x kg(-1) x min(-1)] were randomly assigned to one of three groups: hypoxic residential group (HypR, 11 h/night at 3,000 m simulated altitude), hypoxic training group (HypT), or control group (Con), for an intervention of 29 nights. All subjects trained in Tokyo (altitude of 60 m) but HypT had additional high-intensity treadmill running for 30 min at 3,000 m simulated altitude on 12 days during the night intervention. Vo(2) was measured at standing rest during four submaximal speeds (12, 14, 16, and 18 km/h) and during a maximal stage to volitional exhaustion on a treadmill. Total hemoglobin mass (THb) was measured by carbon monoxide rebreathing. There were no significant changes in Vo(2max), THb, and the time to exhaustion in all three groups after the intervention. Nevertheless, HypR showed approximately 5% improvement of RE in normoxia (P < 0.01) after the intervention, reflected by reduced Vo(2) at 18 km/h and the decreased regression slope fitted to Vo(2) measured during rest position and the four submaximal speeds (P < 0.05), whereas no significant corresponding changes were found in HypT and Con. We concluded that our dose of intermittent hypoxia (3,000 m for approximately 11 h/night for 29 nights) was insufficient to enhance erythropoiesis or Vo(2max), but improved the RE at race speed of college runners.     

The effects of creatine loading on thermoregulation and intermittent sprint exercise performance in a hot humid environment

The purpose of this study was to determine the effects creatine (Cr) loading may have on thermoregulatory responses during intermittent sprint exercise in a hot/humid environment. Ten physically active, heat-acclimatized men performed 2 familiarization sessions of an exercise test consisting of a 30-minute low-intensity warm-up followed by 6 x 10 second maximal sprints on a cycle ergometer in the heat (35 degrees C, 60% relative humidity). Subjects then participated in 2 different weeks of supplementation. The first week, subjects ingested 5 g of a placebo (P, maltodextrin) in 4 flavored drinks (20 g total) per day for 6 days and were retested on day 7. The second week was similar to the first except a similar dose (4 x 5 g/day) of creatine monohydrate (Cr) replaced maltodextrin in the flavored drinks. Six days of Cr supplementation produced a significant increase in body weight (+1.30 +/- 0.63 kg), whereas the P did not (+0.11 +/- 0.52 kg). Compared to preexercise measures, the exercise test in the heat produced a significant increase in core temperature, a loss of body water determined by body weight change during exercise, and a relative change in plasma volume (%PVC); however, these were not significantly different between P and Cr. Sprint performance was enhanced by Cr loading. Peak power and mean power were significantly higher during the intermittent sprint exercise test following 6 days of Cr supplementation. It appears that ingestion of Cr for 6 days does not produce any different thermoregulatory responses to intermittent sprint exercise and may augment sprint exercise performance in the heat.     

The effect of exercise in cool, control and hot environments on cardioprotective HSP70 induction

A number of environmental and metabolic stimuli rapidly induce the expression of several highly conserved proteins such as heat shock proteins (HSPs) or stress proteins. The purpose of this study was to investigate the effects of a single bout of submaximal exercise in varying ambient temperatures on cardiac and skeletal muscle. Adult male Sprague-Dawley rats were randomly placed in one of three ambient temperature groups; control (23 degrees C), hot (41 degrees C) and cool (11 degrees C). Each exercise bout consisted of treadmill running at 17 m/min and 0% grade. Tissue HSP70 levels for all groups were determined using analysis of variance in two factorial design (2 x 3). Baseline rectal temperature was similar for all three groups. In the control and hot temperature groups, final rectal temperatures differed from the baseline values (p<.05). The rectal temperature from the control/exercise group were 38.5+/-0.3 degrees C at rest and 39.8+/-0.3 degrees C at exhaustion, the hot/exercise group were 38.4+/-0.3 degrees C at rest and 41.2+/-0.9 degrees C at exhaustion and the cool/exercise group were 38.2+/-0.3 degrees C at rest and 38.5+/-0.2 degrees C at exhaustion. The running time was 102.0+/-39.5 min at the control/exercise group, 44.1+/-18.0 min at the hot/exercise group, and 55.4+/-11.9 min at the cool/exercise group. The level of soleus, cardiac and extensor digitorium longus (EDL) HSP70 in cool temperature does not change during a single bout of submaximal exercise. Whereas a single bout of submaximal exercise in hot and control ambient temperatures increases HSP70 accumulation in locomotor muscles, such as the soleus and cardiac, but not in the EDL tissue. This study shows that the changes of HSP70 level induced by a single bout of submaximal exercise at various ambient temperatures (control, hot and cool) depend on the rectal temperature.     

Pre-exercise stretching does not impact upon running economy

Pre-exercise stretching has been widely reported to reduce performance in tasks requiring maximal or near-maximal force or torque. The purpose of this study was to compare the effects of 3 different pre-exercise stretching routines on running economy. Seven competitive male middle and long-distance runners (mean +/- SD) age: 32.5 +/- 7.7 years; height: 175.0 +/- 8.8 cm; mass: 67.8 +/- 8.6 kg; V(.-)O2max: 66.8 +/- 7.0 ml x kg(-1) x min(-1)) volunteered to participate in this study. Each participant completed 4 different pre-exercise conditions: (a) a control condition, (b) static stretching, (c) progressive static stretching, and (d) dynamic stretching. Each stretching routine consisted of 2 x 30-second stretches for each of 5 exercises. Dependent variables measured were sit and reach test before and after each pre-exercise routine, running economy (ml x kg(-1) x km(-1)), and steady-state oxygen uptake (ml x kg(-1) x min(-1)), which were measured during the final 3 minutes of a 10-minute run below lactate threshold. All 3 stretching routines resulted in an increase in the range of movement (p = 0.008). There was no change in either running economy (p = 0.915) or steady-state V(.-)O2 (p = 0.943). The lack of change in running economy was most likely because it was assessed after a period of submaximal running, which may have masked any effects from the stretching protocols. Previously reported reductions in performance have been attributed to reduced motor unit activation, presumably IIX. In this study, these motor units were likely not to have been recruited; this may explain the unimpaired performance. This study suggests that pre-exercise stretching has no impact upon running economy or submaximal exercise oxygen cost.     

A comparison of two warm-ups on joint range of motion

The purpose of this study was to compare a 5-minute treadmill activity at 70% maximum heart rate (MHR) and 5 to 6 minutes of ballistic stretching to a 5-minute treadmill activity at 60% of MHR and 5 to 6 minutes of static stretching. Thirty healthy college students, 7 men and 23 women, volunteered. Most volunteers were moderately active. All participants signed an informed consent. Participants received the aforementioned warm-ups in random order with 48 to 72 hours between warm-ups. The stretching exercises were a back stretch, a quadriceps stretch, and a hamstring stretch. Three trials for 30 seconds each were given. After each warm-up the participants performed the modified-modified Schober test for low back flexibility, active knee extension test for hamstring flexibility, and plantar flexion for ankle flexibility. There were no significant differences on any of the 3 range of motion (ROM) tests although the ankle ROM test was almost significantly greater (68.8 degrees ) after the warm-up with static stretching compared with 65.9 degrees after the warm-up with ballistic stretching. A more intense cardiovascular activity and ballistic stretching were similar to a less intense cardiovascular activity and static stretching on flexibility. If athletes perform a warm-up and static or ballistic stretching before their workouts, then they should continue to perform the warm-up and the stretching routine with which they are most familiar and comfortable.     

Effects of active and passive hyperthermia on heat shock protein 70 (HSP70)

Summary. The purpose of this study was to delineate the effects of hyperthermia and physical exercise on the heat shock protein 70 (HSP70) response in circulating peripheral blood mononuclear cells (PBMCs). Six healthy, young (age: 24 ± 3 yrs), moderately trained males (VO_2max: 48.9 ± 2.7 ml · kg · min⁻¹) undertook two experimental trials in a randomised fashion in which the core temperature (T _c) was increased and then maintained at 39 °C during a 90 min bout by either active (AH) or passive (PH) means. AH involved subjects cycling at 90% of their lactate threshold in attire designed to impede heat loss mechanisms. In the PH trial, subjects were immersed up to the neck in a hot bath (40.2 ± 0.4 °C), once the critical T _c was achieved, intermittent cycling and water immersions were prescribed for the AH and PH conditions, respectively, to maintain the T _c at 39 °C. HSP70 was measured intracellularly pre, post and 4 h after trials, from circulating PBMCs using an ELISA technique. T _c reached 39 °C quicker in PH than during AH trials (PH: 21 ± 4 min vs. AH: 39 ± 6 min; P < 0.01), thereafter T _c was maintained around 39 °C (PH: 39.1 ± 0.2 °C; AH: 38.8 ± 0.3 °C; P > 0.05). AH induced a marked leukocytosis in all sub-sets (P < 0.05). PH generated significant monocytosis and granulocytosis (P < 0.05), without changes in lymphocyte counts (P > 0.05). There were no significant increases in intracellular HSP70 at 0 h (AH: Δ − 21.1 ± 44.8; PH: Δ + 12.5 ± 32.4 ng/mg TP/10³/μl PBMCs; P > 0.05) and 4 h (AH: Δ − 30.0 ± 40.1; PH: Δ + 36.3 ± 70.4 ng/mg TP/10³/μl PBMCs; P > 0.05) post active and passive heating. Peak HSP70 expressed as a fold-change from rest was also not increased by AH (1.1 ± 0.9; P > 0.05) or PH (3.2 ± 4.8; P > 0.05). There were no significant differences between the AH and PH trials at any time-point, and the HSP70 response appeared to be individual specific. These results did not allow us to delineate the effects of hyperthermia and other exercise associated stressors on the heat shock response and therefore further work is warranted. Authors’ address: Ric Lovell, Department of Sport, Health and Exercise Science, University of Hull, Hull HU6 7RX, U.K.     

Changes in spring-mass model parameters and energy cost during track running to exhaustion

The purpose of this study was to determine whether exhaustion modifies the stiffness characteristics, as defined in the spring-mass model, during track running. We also investigated whether stiffer runners are also the most economical. Nine well-trained runners performed an exhaustive exercise over 2000 meters on an indoor track. This exhaustive exercise was preceded by a warm-up and was followed by an active recovery. Throughout all the exercises, the energy cost of running (Cr) was measured. Vertical and leg stiffness was measured with a force plate (Kvert and Kleg, respectively) integrated into the track. The results show that Cr increases significantly after the 2000-meter run (0.192 +/- 0.006 to 0.217 +/- 0.013 mL x kg(-1) x m(-1)). However, Kvert and Kleg remained constant (32.52 +/- 6.42 to 32.59 +/- 5.48 and 11.12 +/- 2.76 to 11.14 +/- 2.48 kN.m, respectively). An inverse correlation was observed between Cr and Kleg, but only during the 2000-meter exercise (r = -0.67; P < or = 0.05). During the warm-up or the recovery, Cr and Kleg, were not correlated (r = 0.354; P = 0.82 and r = 0.21; P = 0.59, respectively). On track, exhaustion induced by a 2000-meter run has no effect on Kleg or Kvert. The inverse correlation was only observed between Cr and Kleg during the 2000-meter run and not before or after the exercise, suggesting that the stiffness of the runner may be not associated with the Cr.     

Does Increasing Active Warm-Up Duration Affect Afternoon Short-Term Maximal Performance during Ramadan?

AimThe purpose of this study was to examine the effect of active warm-up duration on short-term maximal performance assessed during Ramadan in the afternoon.MethodsTwelve healthy active men took part in the study. The experimental design consisted of four test sessions conducted at 5 p.m., before and during Ramadan, either with a 5-minute or a 15-minute warm-up. The warm-up consisted in pedaling at 50% of the power output obtained at the last stage of a submaximal multistage cycling test. During each session, the subjects performed two vertical jump tests (squat jump and counter movement jump) for measurement of vertical jump height followed by a 30-second Wingate test for measurement of peak and mean power. Oral temperature was recorded at rest and after warming-up. Moreover, ratings of perceived exertion were obtained immediately after the Wingate test.ResultsOral temperature was higher before Ramadan than during Ramadan at rest, and was higher after the 15-minute warm-up than the 5-minute warm-up both before and during Ramadan. In addition, vertical jump heights were not significantly different between the two warm-up conditions before and during Ramadan, and were lower during Ramadan than before Ramadan after both warm-up conditions. Peak and mean power were not significantly different between the two warm-up durations before Ramadan, but were significantly higher after the 5-minute warm-up than the 15-minute warm-up during Ramadan. Moreover, peak and mean power were lower during Ramadan than before Ramadan after both warm-up conditions. Furthermore, ratings of perceived exertion were higher after the 15-minute warm-up than the 5-minute warm-up only during Ramadan.ConclusionThe prolonged active warm-up has no effect on vertical jump height but impairs anaerobic power assessed during Ramadan in the afternoon.     

Cardiorespiratory response to low-intensity walking in water and on land in elderly women.

The purpose of the present study was to determine whether or not the exercise intensity of water-walking for elderly women could be accurately prescribed by heart rate data obtained during treadmill exercise on land. Six healthy female volunteers, with a mean age of 62.2 +/- 4.2 years, took part in this study. Walking on land was performed on a treadmill. Each subject completed three consecutive 4-minute walks at a progressively increasing velocity (40, 60 and 80 m.min-1), with a 1-minute rest after both the first and second walks. The room temperature and relative humidity were 24.5 +/- 0.2 degrees C and 54.8 +/- 4.0%, respectively. Walking in water was performed in a Flowmill, which is a treadmill positioned at the base of a water flume. Each subject completed three consecutive 4-minute walks at a progressively increasing belt and water-flow velocity (20, 30 and 40 m.min-1), with a 1-minute rest after both the first and second walks. The water depth was at the level of the xiphoid process of each subject. The water temperature was 30.7 +/- 0.1 degrees C. The exercise intensity at the highest workrate was equivalent to 44.2 +/- 10.3% of the heart rate reserve (HRR) during water-walking and 38.4 +/- 4.7% of the HRR during land-walking. There was a highly significant linear relationship between heart rate (HR) and oxygen uptake (VO2) during both water-walking and land-walking. The relationship between HR and VO2 in both exercise modes was similar. Thus, the relationship of HR to VO2 derived from a treadmill-graded walking test on land may be used to prescribe exercise intensity for water-walking in thermoneutral water.     

Passive energy absorption by human muscle-tendon unit is unaffected by increase in intramuscular temperature.

The present study measured hamstring intramuscular temperature and muscle-tendon unit viscoelastic properties in healthy young men before and after 10 and 30 min of running with (day S) or without stretch (day NS). On day NS, passive energy absorption and intramuscular temperature were measured before running (Preex), after 10 min of running at 70% of maximum O(2) uptake (Postex10), and after 30 min of running at 75% of maximum O(2) uptake (Postex30). On day S, the protocol was repeated with three stretches (stretches 1-3) added after Postex10. Intramuscular temperature was elevated Postex10 (P < 0.01) and further Postex30 (P < 0.05). On day NS, the total energy absorbed Preex (14.3 +/- 2.3 J), Postex10 (14.5 +/- 3.2 J), and Postex30 (13.5 +/- 2.4 J) was not different. On day S, the total energy absorbed in stretch 3 (10.8 +/- 1.8 J) was lower than that Preex (14.5 +/- 1.7 J, P < 0.01) and Postex10 (13.5 +/- 1.9 J, P < 0.05) but not Postex30 (13.3 +/- 1.8 J). The total energy absorbed Postex30 did not differ from Preex. In conclusion, warm-up and continuous running elevated intramuscular temperature but did not affect the passive energy absorption. Repeated passive stretching reduced the energy absorption immediately; however, the effect did not remain after 30 min of running. These data suggest that passive energy absorption of the human skeletal muscle is insensitive to physiological increases in intramuscular temperature.