Effect of Postactivation Potentiation Induced by Elastic Resistance on Kinematics and Performance in a Roundhouse Kick of Trained Martial Arts Practitioners.

Aandahl, HS, Von Heimburg, E, and Van den Tillaar, R. Effect of postactivation potentiation induced by elastic resistance on kinematics and performance in a roundhouse kick of trained martial arts practitioners. J Strength Cond Res 32(4): 990-996, 2018-The aim of this study was to examine whether kicking with elastic resistance during warm-up could initiate postactivation potentiation (PAP), and thereby positively influence kinematics and performance on subsequent explosive roundhouse kicking. Five women and 11 men (n = 16) with a background in kickboxing (n = 10) or taekwondo (n = 6) performed 2 warm-up strategies with 3 subsequent test kicks 5-8 minutes after a PAP-inducing exercise. Kicking performance, defined as roundhouse kicking velocity with the foot, was measured using 3D motion capture (500 Hz) with a 15 marker lower-body 3D model. In addition, electromyography of the prime movers-vastus lateralis, vastus medialis, and rectus femoris muscles-was measured to confirm the presence of PAP. Kicking velocity of the foot increased by 3.3% after performing a warming-up strategy including kicking with elastic resistance (p = 0.009, η = 0.32). Increases were also recorded in muscle activity in vastus medialis (35.2%, p = 0.05, η = 0.18) and rectus femoris (43.9%, p = 0.04, η = 0.20). These findings indicate that performing a warm-up strategy including kicking with elastic resistance can have a positive effect on kicking performance in a roundhouse kick.

Effects of Short or Long Warm-up on Intermediate Running Performance.

van den Tillaar, R, Vatten, T, and von Heimburg, E. Effects of short or long warm-up on intermediate running performance. J Strength Cond Res 31(1): 37-44, 2017-The aim of the study was to compare the effects of a long warm-up (general + specific) and a short warm-up (specific) on intermediate running performance (3-minute run). Thirteen experienced endurance-trained athletes (age 23.2 ± 2.3 years, body mass 79.8 ± 8.2 kg, body height 1.82 ± 0.05 m) conducted 2 types of warm-ups in a crossover design with 1 week in between: a long warm-up (10 minutes, 80% maximal heart rate, and 8 × 60 m sprint with increasing intensity and 1 minute rest in between) and a short warm-up (8 × 60 m sprint with increasing intensity and 1 minute rest in between). Each warm-up was followed by a 3-minute running test on a nonmotorized treadmill. Total running distance, running velocity at each 30 seconds, heart rate, blood lactate concentration, oxygen uptake, and rate of perceived exertion were measured. No significant differences in running performance variables and physiological parameters were found between the 2 warm-up protocols, except for the rate of perceived exertion and heart rate, which were higher after the long warm-up and after the 3-minute running test compared with the short warm-up. It was concluded that a short warm-up is as effective as a long warm-up for intermediate performance. Therefore, athletes can choose for themselves if they want to include a general part in their warm-up routines, even though it would not enhance their running performance more compared with only using a short, specific warm-up. However, to increase efficiency of time for training or competition, these short, specific warm-ups should be performed instead of long warm-ups.

Comparison of Two Types of Warm-Up Upon Repeated-Sprint Performance in Experienced Soccer Players.

van den Tillaar, R and von Heimburg, E. Comparison of two types of warm-up upon repeated-sprint performance in experienced soccer players. J Strength Cond Res 30(8): 2258-2265, 2016-The aim of the study was to compare the effects of a long warm-up and a short warm-up upon repeated-sprint performance in soccer players. Ten male soccer players (age, 21.9 ± 1.9 years; body mass, 77.7 ± 8.3 kg; body height, 1.85 ± 0.03 m) conducted 2 types of warm-ups with 1 week in between: a long warm-up (20 minutes: LWup) and a short warm-up (10 minutes: SWup). Each warm-up was followed by a repeated-sprint test consisting of 8 × 30 m sprints with a new start every 30th second. The best sprint time, total sprinting time, and % decrease in time together with heart rate, lactate, and rate of perceived exertion (RPE) were measured. No significant differences in performance were found for the repeated-sprint test parameters (total sprint time: 35.99 ± 1.32 seconds [LWup] and 36.12 ± 0.96 seconds [SWup]; best sprint time: 4.32 ± 0.13 seconds [LWup] and 4.30 ± 0.10 seconds [SWup]; and % sprint decrease: 4.16 ± 2.15% [LWup] and 5.02 ± 2.07% [SWup]). No differences in lactate concentration after the warm-up and after the repeated-sprint test were found. However, RPE and heart rate were significantly higher after the long warm-up and the repeated-sprint test compared with the short warm-up. It was concluded that a short warm-up is as effective as a long warm-up for repeated sprints in soccer. Therefore, in regular training, less warm-up time is needed; the extra time could be used for important soccer skill training.

Energy cost of the Trondheim firefighter test for experienced firefighters.

AIM: The aim of this study was to measure aerobic demands of fire fighting activities including exercise in the heat. METHODS: Twenty-two experienced firefighters performed the Trondheim test simulating fire fighting tasks including work in the heat. Maximal oxygen uptake (VO2 max), heart rate (HR) and ventilation were recorded continuously. Data were compared with results obtained during a treadmill test during which the participants were dressed as smoke divers. RESULTS: The participants completed physical parts of the Trondheim test in ˜12 min (range: 7.5-17.4). Time to complete the test was closely related to the participant's VO2 max. HR of ˜170 beats/min and pulmonary ventilation of ˜100 L/min were higher than at lactate threshold (LT) during laboratory tests. VO2 averaged over the test's physical part was 35 ± 7 ml/min/kg, which was at the same or below the level corresponding to the participants' LT. Physically fit participants completed the test faster than less fit participants. Slower and physically less fit participants consumed more air and used more oxygen than faster and physically more fit participants. CONCLUSION: The Trondheim test is physically demanding; it distinguishes physically fit and less fit participants.

Performance on a work-simulating firefighter test versus approved laboratory tests for firefighters and applicants.

AIM: Firefighters must meet minimum physical demands. The Norwegian Labour Inspection Authority (NLIA) has approved a standardised treadmill walking test and 3 simple strength tests for smoke divers. The results of the Trondheim test were compared with those of the NLIA tests taking into account possible effects of age, experience level and gender. METHODS: Four groups of participants took part in the tests: 19 young experienced firefighters, 24 senior male firefighters and inexperienced applicants, 12 male and 8 female. RESULTS: Oxygen uptake (VO2) at exhaustion rose linearly by the duration of the treadmill test. Time spent on the Trondheim test was closely related to performance time and peak VO2 on the treadmill test. Senior experienced firefighters did not perform better than equally fit young applicants. However, female applicants performed poorer on the Trondheim test than on the treadmill test. Performance on the Trondheim test was not closely related to muscle strength beyond a minimum. CONCLUSION. Firefighters completing the Trondheim test in under 19 min fit the requirements of the NLIA treadmill test. The Trondheim test can be used as an alternative to the NLIA tests for testing aerobic fitness but not for muscular strength. Women's result of the Trondheim test were poorer than the results of the NLIA treadmill test, probably because of their lower body mass.

Comparison of a Traditional Graded Exercise Protocol With a Self-Paced 1-km Test to Assess Maximal Oxygen Consumption.

PURPOSE: To compare the assessment of the maximal oxygen consumption (VO2max) in a traditional graded exercise test (GXT) with a 1-km self-paced running test on a nonmotorized treadmill in men and women. METHODS: A total of 24 sport-science students (12 women: age 23.7 [7.7] y, body height 1.68 [0.02] m, body mass 66.6 [4.3] kg; 12 men: 22.1 [3.1] y, body height 1.82 [0.06] m, body mass 75.6 [11.0] kg) performed a traditional GXT on a motorized treadmill and a 1-km self-paced running test on a nonmotorized treadmill. VO2max, blood lactate, heart rate, and rating of perceived exertion, together with running velocity and duration at each test, were measured. RESULTS: The main findings of the study were that the 1-km test produced significantly higher VO2max values (53.2 [9.9] vs 51.8 [8.8] mL/kg/min ) and blood lactate concentrations (11.9 [1.8] vs 11.1 [2.2] mmol/L) than the GXT (F ≥ 4.8, P ≤ .04, η2 ≥ .18). However, after controlling for sex, these differences were only present in men (60.6 [8.1] vs 58.1 [8.0] mL/kg/min , P = .027). Peak running velocity was higher in the GXT than in the 1-km test (15.7 [2.7] vs 13.0 [2.8] km/h). Men had higher VO2max values and running velocities than women in both tests. However, men and women used approximately similar pacing strategies during the 1-km test. CONCLUSIONS: Higher VO2max values were observed in a 1-km self-paced test than in the GXT. This indicates that a 1-km running test performed on a nonmotorized treadmill could serve as a simple and sport-specific alternative for the assessment of VO2max.

The steady-state load of five firefighting tasks.

Purpose. Physiologic demands of five common tasks in firefighting have been examined. Methods. Eight male volunteers, dressed up as smoke divers (+21 kg extra load), carried out the following tasks at constant pace for 5 min: walking at 1.4 m·s-1, walking (all walks at the same speed) while carrying a 10-kg ladder, walking carrying two hose packs of 16 kg together, walking carrying a 32-kg spreader tool and, finally, climbing up and down a ladder at a preset pace. A 5-min break separated each exercise. The heart rate, oxygen uptake and lung ventilation were measured continuously, and the blood lactate concentration was recorded after each task. Results. The end-exercise heart rate rose from 108 to 180 bpm from the first to last task, blood lactate concentration rose from 1 to 7 mmol·L-1, oxygen uptake rose from 19 to 48 ml·kg-1 min-1 and lung ventilation rose from 38 to 124 L·min-1. Discussion. Walking was an easy task even when dressed up as a smoke diver. Adding loads increased demands; ladder climbing taxed >90% of the subjects' aerobic power. Conclusions. The physiologic demands varied considerably between different tasks.

Comparison of three types of warm-up upon sprint ability in experienced soccer players.

PURPOSE: The study aimed to compare the effects of a long general warm-up, a long specific warm-up, and a short specific warm-up upon sprint ability in soccer players. METHODS: Twelve male soccer players (age: 18.3 ± 0.8 years, mean ± SD; body mass: 76.4 ± 7.2 kg; body height: 1.79 ± 0.05 m) conducted 3 types of warm-ups with 1 week in between: a long general warm-up, a long specific warm-up, and a short specific warm-up followed by 3 sprints of 40 m each. The best, average, and total sprinting times together with heart rate and ratings of perceived exertion were measured. RESULTS: The sprint times (best, average, and total time) were significantly better when performing a long specific or short specific warm-up compared with the long general warm-up (all p < 0.05). The received perception exertion was significantly lower during the specific short warm-up (4.92 ± 0.90) compared with the longer ones (6.00 ± 0.74 and 6.25 ± 0.87, respectively). CONCLUSION: Specificity is more important in a warm-up routine before sprint performance than the duration of the warm-up.

Physiological and perceptual strain of firefighters during graded exercise to exhaustion at 40 and 10 °C.

Purpose. To study whether perceptual identification should be included as a measure to evaluate physiological stress. Methods. Physiological variables oxygen uptake (VO2), ventilation, heart rate, blood lactate concentration, rectal temperature (Trec) and mean skin temperature, and perceptual variables rate of perceived exertion, thermal sensation and time to exhaustion, were measured at submaximal and maximal intensities during graded exercise on a treadmill to exhaustion in 12 firefighters wearing protective clothing and extra mass at 40 and 10 °C. Physiological strain index (PhSI) and perceptual strain index (PeSI) were calculated. Results. Apart from Trec, all physiological and perceptual variables were higher at submaximal intensities of 40 °C. Time to exhaustion was 16% shorter and the corresponding VO2 was reduced by 7% in the heat. A high correlation (r = 89) between PhSI and PeSI was found at both temperatures. PeSI scores were equal to PhSI at both ambient temperatures, except at the two highest intensities in the heat, where PeSI was higher. Conclusions. These findings support use of perceptual identification to evaluate physiological stress. However, at very high intensities under hot conditions the perceptual strain was estimated higher than the physiological strain. More precise indexes are needed to include perceptual measures in safety standard.

Comparison of Long and Short High-Intensity Interval Exercise Bouts on Running Performance, Physiological and Perceptual Responses.

This study compared the effects of long (4×4 min) and short intervals (4×8×20 s) of high-intensity interval exercise bouts (HIIT) on running performance, physiological and perceptual responses, and excess postexercise oxygen consumption (EPOC). Twelve healthy college students (8 men, 4 women; mean age=22±2 years) performed long (90-95% of peak heart rate) and short intervals (maximal intensity) of high-intensity training (running on a non-motorized treadmill) with the same total duration on separate days. The total volume of consumed oxygen during recovery was the same in both cases ( P =0.21), whereas the short intervals of high-intensity training were performed at a faster mean running velocity (3.5±0.18 vs. 2.95±0.07 m/s) and at a lower RPE breath compared with the long intervals of high-intensity training. The blood lactate concentration also tended to be lower during the short intervals of high-intensity training, indicating that short-interval training was perceived to be easier than long-interval training, even though the cardiovascular and metabolic responses are similar. Furthermore, EPOC lasted significantly longer (83.4±3.2 vs. 61.3±27.9 min, P =0.016) and tended to be higher (8.02±4.22=vs. 5.70±3.75 L O 2 , P =0.053) after short intervals than after long intervals of training.

Influence of different soccer-specific maximal actions on physiological, perceptual and accelerometer measurement loads.

BACKGROUND: The aim of this study was to compare the effect of different soccer-specific maximal actions (Continuous run, Sprint, Sprint with change of direction [Sprint COD], Jump and Shot) upon physiological (oxygen uptake and heart rate) and perceptual (rating of perceived exertion [RPE]) responses and accelerometer load. MATERIALS AND METHODS: Ten moderately to well-trained male soccer players volunteered to serve as subjects in this study. A repeated within-subject design was used in which each subject was tested on five occasions on different days, one test each day, during a period of 2 weeks. Each of the five tests had a distance of 900 m and lasted 5 minutes, thus the mean speed for all five tests was 3 m/s. During the test, oxygen uptake, heart rate and accelerometer load were measured. Immediately after each test, RPE was recorded, and after the test, oxygen uptake was measured for 5 minutes while the subject sat in an upright position on a chair. RESULTS: In the comparison of different soccer-specific maximal actions upon physiological and perceptual responses and accelerometer load, this study found that the total accelerometer load was lowest in Sprint and Sprint COD conditions, although the physiological (oxygen uptake and heart rate) and perceptual (RPE) responses were highest in the respective conditions. The Jump condition experienced lower RPE than Sprint and Sprint COD but achieved the highest accelerometer load. CONCLUSION: Accelerometer load is not a valid measurement for energy costs or RPE but may function as a complementary tool to investigate the player loads during matches and training.

Energy cost of free technique and classical cross-country skiing at racing speeds.

PURPOSE: First, to measure the O(2) uptake ([OV0312]O(2)) and the blood lactate concentration during cross-country skiing at competition speed. Second, to compare these entities for the free technique and the classical technique. Further, to establish the subjects' [OV0312]O(2max) and the [OV0312]O(2) corresponding to the onset of blood lactate accumulation (OBLA, 4 mmol.L-1) during skiing, and finally to relate these entities to those of treadmill running. METHODS: Five high-level female junior cross-country skiers with a mean [OV0312]O(2max) of 63 mL.kg-1.min-1 served as subjects in five tests: examination of the [OV0312]O(2max) and the [OV0312]O(2) corresponding to the OBLA during up-hill cross-country skiing (both styles), inclined treadmill running, and a 6-km simulated cross-country ski race (both styles). RESULTS: The [OV0312]O(2max) obtained during up-hill cross-country skiing did not differ from that during treadmill running, nor did it differ between the two skiing styles. The peak heart rate was significantly lower during uphill cross-country skiing than during treadmill running. During the simulated competitions, the [OV0312]O(2) averaged 84% of the [OV0312]O(2max) or 95% of the [OV0312]O(2) at the OBLA found for uphill skiing. CONCLUSION: High-level female junior cross-country skiers are unable to ski at intensities close to their [OV0312]O(2max) or maintain an average intensity above that corresponding to their OBLA even during races lasting less than 25 min. Thus, training at intensities around the OBLA may be particularly relevant for cross-country skiers.

Physiological responses of firefighters and performance predictors during a simulated rescue of hospital patients.

There is incomplete information about how physically demanding rescue work may be. The aim therefore of this paper was to examine the physiological responses of firefighters during a simulated rescue of hospital patients and to relate the firefighters' performance to their endurance, strength and working technique. Fourteen part-time male firefighters with a maximal oxygen uptake (VO(2max)) of 4.4 +/- 0.3 l/min (mean +/- SD) served as subjects in this study. First, each firefighter ascended six floors (a 20.5 m vertical ascent) carrying tools, wearing protective clothing and a breathing apparatus, an extra mass of 37 kg. He thereafter 'rescued' six persons by dragging each person on a fire-sheet on a flat floor. The technique used was recorded and the O(2) uptake and the heart rate were measured continuously during the whole operation. The blood lactate concentration and the subjective rating of perceived exertion were measured during and just after the rescue. The VO(2max) and the muscle strength were measured in the laboratory. The whole operation was carried out in the course of 5-9 min. The operation was a virtual all-out effort and the peak blood lactate concentration was 13 +/- 3 mmol/l. The peak oxygen uptake was 3.7 +/- 0.5 l/min (84% of the VO(2max)) during the operation. Large and heavy firefighters carried out the task faster than smaller ones. The VO(2max) in absolute terms and the dragging technique used were both related to the rescue performance. Rescuing patients at a hospital was physically very demanding and the time needed to complete the task depended on the VO(2max) in absolute values and the working technique used. A minimum VO(2max) of 4 l/min for firefighters was recommended.