Concurrent endurance and explosive type strength training increases activation and fast force production of leg extensor muscles in endurance athletes

The purpose of this experiment was to examine the effects of concurrent endurance and explosive strength training on electromyography (EMG) and force production of leg extensors, sport-specific rapid force production, aerobic capacity, and work economy in cross-country skiers. Nineteen male cross-country skiers were assigned to an experimental group (E, n = 8) or a control group (C, n = 11). The E group trained for 8 weeks with the same total training volume as C, but 27% of endurance training in E was replaced by explosive strength training. The skiers were measured at pre- and post training for concentric and isometric force-time parameters of leg extensors and EMG activity from the vastus lateralis (VL) and medialis (VM) muscles. Sport-specific rapid force production was measured by performing a 30-m double poling test with the maximal velocity (V(30DP)) and sport-specific endurance economy by constant velocity 2-km double poling test (CVDP) and performance (V(2K)) by 2-km maximal double poling test with roller skis on an indoor track. Maximal oxygen uptake (Vo(2)max) was determined during the maximal treadmill walking test with the poles. The early absolute forces (0-100 ms) in the force-time curve in isometric action increased in E by 18 +/- 22% (p < 0.05), with concomitant increases in the average integrated EMG (IEMG) (0-100 ms) of VL by 21 +/- 21% (p < 0.05). These individual changes in the average IEMG of VL correlated with the changes in early force (r = 0.86, p < 0.01) in E. V(30DP) increased in E (1.4 +/- 1.6%) (p < 0.05) but not in C. The V(2K) increased in C by 2.9 +/- 2.8% (p < 0.01) but not significantly in E (5.5 +/- 5.8%, p < 0.1). However, the steady-state oxygen consumption in CVDP decreased in E by 7 +/- 6% (p < 0.05). No significant changes occurred in Vo(2)max either in E or in C. The present concurrent explosive strength and endurance training in endurance athletes produced improvements in explosive force associated with increased rapid activation of trained leg muscles. The training also led to more economical sport-specific performance. The improvements in neuromuscular characteristics and economy were obtained without a decrease in maximal aerobic capacity, although endurance training was reduced by about 20%.     

Are Gender Differences in Upper-Body Power Generated by Elite Cross-Country Skiers Augmented by Increasing the Intensity of Exercise?

In the current study, we evaluated the impact of exercise intensity on gender differences in upper-body poling among cross-country skiers, as well as the associated differences in aerobic capacity, maximal strength, body composition, technique and extent of training. Eight male and eight female elite skiers, gender-matched for level of performance by FIS points, carried out a 4-min submaximal, and a 3-min and 30-sec maximal all-out test of isolated upper-body double poling on a Concept2 ski ergometer. Maximal upper-body power and strength (1RM) were determined with a pull-down exercise. In addition, body composition was assessed with a DXA scan and training during the previous six months quantified from diaries. Relative to the corresponding female values (defined as 100%), the power output produced by the men was 88%, 95% and 108% higher during the submaximal, 3-min and 30-sec tests, respectively, and peak power in the pull-down strength exercise was 118% higher (all P<0.001). During the ergometer tests the work performed per cycle by the men was 97%, 102% and 91% greater, respectively, and the men elevated their cycle rate to a greater extent at higher intensities (both P<0.01). Furthermore, men had a 61% higher VO₂peak, 58% higher 1RM, relatively larger upper-body mass (61% vs 56%) and reported considerably more upper-body strength and endurance training (all P<0.05). In conclusion, gender differences in upper-body power among cross-country skiers augmented as the intensity of exercise increased. The gender differences observed here are greater than those reported previously for both lower- and whole-body sports and coincided with greater peak aerobic capacity and maximal upper-body strength, relatively more muscle mass in the upper-body, and more extensive training of upper-body strength and endurance among the male skiers.     

Comparison of the aerobic performance of leg and arm muscles in cross-country skiers

In the last fifteen years, a trend has appeared in cross-country ski racing to increase the use of double poling and, therefore, to increase the load on the shoulder girdle (arm) muscles. The purpose of this study was to compare the aerobic performance of elite cross-country skiers in incremental running (treadmill) and double poling (with manual ski ergometer) tests to exhaustion. Four junior cross-country skiers and four biathletes ( $ \dot V_{O_{2max} } $ = 70 (66?C72) mL/min per kg body weight) participated in the experiment. In the double poling test, the lactate concentration increased more rapidly than in the running test, and the peak oxygen consumption ( $ \dot V_{O_{2peak} } $ ) in the double poling test was 88 (84?C93)% of the maximal oxygen consumption ( $ \dot V_{O_{2max} } $ ) in the running test. The relative anaerobic threshold, which characterizes the relative level of current aerobic performance, in the double poling test was significantly lower than in the running test (79 (57?C83)% vs 94 (90?C98)%, respectively). On the basis of these data, it can be concluded that the main reserve for a further increase in the aerobic performance of cross-country skiers and biathletes is the increase in the aerobic capacity of arm and trunk muscles.     

Aerobic capacity and force-velocity characteristics in cross-country skiers at the end of preparatory period and at the beginning of period of competitions

The goal of this study is to compare the dynamics of aerobic and force–velocity characteristics of the shoulder girdle muscles and leg muscles during high-volume aerobic training in junior cross-country skiers in the time interval from the end of the preparatory period to the beginning of the competition period. Eleven junior cross-country skiers were repeatedly tested from December to February. In this period, the volume of aerobic training was 22–23 h per week. During the experimental period, the knee extensors torque in the range of angular velocities of 30–300 degrees/s was observed to decrease, with no changes in the volume of the quadriceps muscle of thigh and knee flexor muscles. The maximal oxygen consumption rate (VO₂ max) was observed to decrease by 6% (P < 0.05) in the treadmill test, while the oxygen consumption at anaerobic threshold (VO₂ at La = 4 mmol/L) was unchanged. On the contrary, the functional capacity of the shoulder girdle muscles was enhanced. The force-velocity characteristics of the shoulder girdle muscles that were estimated in the maximal anaerobic power test at a double poling ergometer increased by 16% (P < 0.01), and the volume of the triceps muscle of arm increased by 4.6 (P < 0.01). The aerobic capacity of the shoulder girdle muscles that were estimated by the VO₂ at La = 4 mmol/L increased by 30% (P < 0.05). The potential for increasing the performance of junior cross-country skiers seems to be associated with the increased functional capacity of the shoulder girdle muscles.     

Effects of explosive type strength training on physical performance characteristics in cross-country skiers

To investigate the effects of a combination of simultaneous strength and endurance training on selected neuromuscular and aerobic performance characteristics seven male cross-country skiers underwent training for a period of 6 weeks. The experimental group trained 6-9 times per week with a programme consisting of 34% explosive type strength training and 66% endurance training during the first 3 weeks of the experiment and 42% and 58% respectively during the last 3 weeks of the experiment. The total volume of training of the control group (eight skiers) was of the same magnitude but consisted of 85% pure endurance training and 15% endurance type strength training. The experimental training regime resulted in specific changes in neuromuscular performance. This was demonstrated by improvements (P less than 0.01) in the maximal heights of rise of the centre of gravity in the squat and countermovement jumps. A significant decrease (P less than 0.05) took place also in the time of rapid isometric force production during experimental training, while no changes occurred in the maximal force of the trained muscles. Aerobic performance characteristics of the experimental group did not change during the experimental training period. No significant changes occurred in neuromuscular or aerobic performance characteristics in the control group. These findings indicated that training-induced improvements in explosive force production may not be fully inhibited by this kind of aerobic training. They also suggested that endurance athletes could undertake explosive type strength training programmes without a concomitant reduction in aerobic capacity, if the overall loading of training were within predefined limits.     

Development of upper body power in junior cross-country skiers

With the advent of the ski-skating technique, upper body power has increasingly been shown to be a major factor in cross-country skiing success. The purpose of this study was to evaluate 4 commonly used training methods (weight, circuit, rollerboard, and ski-specific training) for the development of upper body power (UBP) in junior cross-country skiers. Fifty-eight adolescent cross-country skiers (Boys: n = 29, age = 16.0 +/- 1.2 y and Girls: n = 29, age = 15.5 +/- 1.5 y) were assigned to one of the UBP training methods for a 10-week training program. Fourteen cross-country runners served as controls (boys: n = 7, age = 15.8 +/- 1.7 y; girls: n = 7, age = 14.9 +/- 1.3 y). Skiers were evaluated pre- and post-training for upper body strength (UBS) using a 10 repetition maximum (RM) rollerboard test, for UBP using a double-poling ergometer and for upper body endurance (UBE) with a 3-km, arms-only, rollerski endurance time trial. Competitive race results were collected during the winters before and after training as were all training data. Only the rollerboard training group improved significantly greater than the control group (p < 0.05) in UBP and UBS. Improvements in UBP, UPS, and UBE were significantly related (r = 0.545, 0.303, and 0.407, respectively) to improvements in competitive performance. These data suggest that training using a rollerboard with 5-12RM and explosive speed is more effective in developing UBP than other common training methods for adolescent cross-country skiers. The practical importance of these data was verified by the significant relationships between improvements in UBP, UBS, and UBE related to improvements in competitive race performance.     

Effects of an eight-week training program on upper-body power in women cross-country skiers

A distinguishing feature of elite cross-country skiers is their superlative upper-body power (UBP). Recently, roller board training was shown to be superior for improving UBP in cross-country skiers; however, the newly developed wind machine had not yet been tested. The purpose of this study was to determine if wind machine training was as effective as roller board training at increasing UBP. Forty-four women cross-country skiers, age 23-59 years, were matched on initial UBP, measured in watts (W), and placed into 1 of 2 experimental groups (roller board or wind machine). All women underwent 8 weeks of UBP training. Although both groups improved significantly pre-post (p < 0.05) in UBP, t-tests indicated that there was no significant difference (p > 0.05) between the 2 groups' improvements (roller board, pre 74.5 +/- 30.9, post 95.9 +/- 29.8 W; wind machine, pre 74.5 +/- 33.5, post 99.3 +/- 34.3 W). Thus the wind machine was as effective at enhancing UBP as the roller board.     

Noninvasive determination of the anaerobic threshold in canoeing, cross-country skiing, cycling, roller, and ice-skating, rowing, and walking

The relationship between velocity (V) and heart rate (HR) was determined in four canoeists, 42 cross-country skiers, 73 cyclists, nine ice-skaters, 10 roller-skaters, 32 rowers, and 20 walkers. The athletes were asked to increase their work intensity progressively, from low to submaximal velocities; HRs were determined by ECG in roller-, ice-skating, and walking, or read on a cardiofrequency meter in canoeing, cross-country skiing, cycling, and rowing. In all the athletes examined the linearity of the V-HR relationship was maintained up to a submaximal speed (deflection velocity, Vd), beyond which the increase in work intensity exceeded the increase in HR. Vd and anaerobic threshold (AT), determined through blood lactate measurements, were coincident in 19 athletes (6 cross-country skiers, 3 cyclists, 2 roller-skaters, 3 rowers, and 5 walkers). Vd was correlated with the average speeds maintained in walking (20 km, n = 13, r = 0.88), cross-country skiing (15 km, n = 20, r = 0.80; 30 km, n = 8, r = 0.82; 12 km, n = 7, r = 0.86; 11 km, n = 7, r = 0.86) and cycling (1,000 m flying-start, n = 68, r = 0.83), thus showing that AT is a limiting factor in these aerobic events.     

A Comparison of Frontal Theta Activity During Shooting among Biathletes and Cross-Country Skiers before and after Vigorous Exercise

Background

Previous studies using electroencephalography (EEG) to monitor brain activity have linked higher frontal theta activity to more focused attention and superior performance in goal-directed precision tasks. In biathlon, shooting performance requires focused attention after high-intensity cross-country skiing.

Purpose

To compare biathletes (serving as experts) and cross-country skiers (novices) and examine the effect of vigorous exercise on frontal theta activity during shooting.

Methods

EEG frontal theta (4–7 Hz) activity was compared between nine biathletes and eight cross-country skiers at comparable skiing performance levels who fired 100 shots on a 5-m indoor shooting range in quiescent condition followed by 20 shots after each of five 6-min high-intensity roller skiing sessions in the skating technique on a treadmill.

Results

Biathletes hit 80±14% and 81±10% before and after the roller skiing sessions, respectively. For the cross-country skiers these values were significantly lower than for the biathletes and amounted to 39±13% and 44±11% (p<0.01). Biathletes had on average 6% higher frontal theta activity during shooting as compared to cross-country skiers (F1,15 = 4.82, p = 0.044), but no significant effect of vigorous exercise on frontal theta activity in either of the two groups were found (F1,15 = 0.14, p = 0.72).

Conclusions

Biathletes had significantly higher frontal theta activity than cross-country skiers during shooting, indicating higher focused attention in biathletes. Vigorous exercise did not decrease shooting performance or frontal theta activity during shooting in biathletes and cross-country skiers.     

Final blood lactate concentration after incremental test and aerobic performance

The goal of this study was to test the hypothesis that, in groups of highly trained endurance athletes (first and junior national teams), the final blood lactate concentration at maximum aerobic performance decreased as their training status increased. This study was performed with 20 physically active volunteers and 45 highly trained middle- and long-distance endurance athletes (speed skaters, triathletes, and cross-country skiers). Significant negative correlations (r = ?0.59 to ?0.87) between the final blood lactate concentration after incremental tests until exhaustion and aerobic performance (anaerobic threshold (AT)) were found only for the groups of highly trained endurance athletes, but not for the group of physically active subjects. It was shown for highly trained speed skaters that the final lactate concentration in their blood decreased and the oxygen consumption at AT increased with an increase in the volume of type I muscle fibers in the working muscle (r = ?0.84 and r = 0.7, respectively).     

A Study on the Effect of Core Strength Strengthening Training on Exercise-Induced Lumbar Injuries

Objective: This study aims to analyze the effect of core strength strengthening training on exercise-induced lumbar injuries. Methods: Sixteen athletes suffering from lumbar injuries were randomly divided into two groups, group A and group B. Group A performed core strength strengthening training, while group B only performed normal study and life. Before and after the experiment, the Visual Analogue Scale (VAS) score, lumbar spine mobility, Oswestry Disability Index (ODI) and overall effect evaluation of the two groups were recorded and compared. Results: After the experiment, the VAS score of group A decreased to 2.78 ± 1.89 points, the anterior flexion distance was 0.85 ± 0.03 cm, the left lateral flexion distance was 4.97 ± 0.02 cm, and the right lateral flexion distance was 3.32 ± 0.02 cm, and the ODI was 15.68 ± 6.73% (p < 0.05 compared to group B before and after the experiment). Overall, in group A, two athletes were cured, four athletes had significant improvements, and two athletes had a mild response, while the treatment was ineffective in group B. Conclusion: Core strength strengthening training enhances lumbar muscle strength and improves lumbar stability, showing a significant improvement effect on lumbar injuries.     

Endurance training and sprint performance in elite junior cross-country skiers

The purpose of the present study was to investigate the relationship between aerobic characteristics and sprint skiing performance, and the effects of high-intensity endurance training on sprint skiing performance and aerobic characteristics. Ten male and 5 female elite junior cross-country skiers performed an 8-week intervention training period. The intervention group (IG, n = 7) increased the volume of high-intensity endurance training performed in level terrain, whereas the control group (CG, n = 8) continued their baseline training. Before and after the intervention period, the skiers were tested for 1.5-km time-trial performance on roller skis outdoors in the skating technique. Maximal oxygen uptake (VO?max) and oxygen uptake at the ventilatory threshold (VO?VT) were measured during treadmill running. VO?max and VO?VT were closely related to sprint performance (r = ~0.75, both p < 0.008). The IG improved sprint performance, VO?max, and VO?VT from pre to posttesting and improved sprint performance and VO?VT when compared to the CG (all p < 0.01). This study shows a close relationship between aerobic power and sprint performance in cross-country skiing and highlights the positive effects of high-intensity endurance training in level terrain.     

Seasonal fluctuations of selected physiological characteristics of elite alpine skiers

The effects of heavy resistance training and jumping exercise were examined during the 1989–1990 season in 12 international level alpine skiers. The athletes were tested before, during, immediately after training and during the period off training (June, July, October 1989, April 1990). Their mechanical behaviour was investigated using firstly squat jumps performed without (SJ) or with low extra loads (20 kg, SJ_20kg) and high extra loads (equivalent to body mass on the shoulders, SJ_bm) and secondly 15–30 s continuous jumping. These tests allowed the assessment of explosive dynamic strength production (SJ and SJ_20kg), slow dynamic strength (SJ_bm) and maximal mechanical power (continuous jumping). The training adopted resulted in specific changes in neuromuscular performance; in fact all the variables studied showed a significant improvement (P<0.01) from the beginning compared to the end of training. The range of improvement was between 55.4% (SJ_bm) and 12.5% (average power during 15-s continuous jumping). The enhancement of SJ had become significant by July. Surprisingly, even when no strength or jumping training was performed during the competition period (November-April), no deterioration in the neuromuscular performance was observed, there being no significant difference between the test values obtained in October 1989 and April 1990. It was concluded that the demanding competition programme of alpine skiers may provide a training stimulus adequate to maintain the neuromuscular improvement induced by training throughout the competition season.     

Effect of strength training and the practice of Alpine skiing on bone mass density, growth, body composition, and the strength and power of the legs of adolescent skiers

This work examines the influence of practicing strength training and Alpine skiing over 2 years on bone mineral density (BMD), growth, body composition, and the strength and power of the legs of adolescent skiers. The study subjects were 20 adolescent skiers (10 girls and 10 boys) and 19 sedentary adolescents (9 girls and 10 boys), all 13-16 years of age. The BMDs of the lumbar column (L2-L4) and hip (neck of the femur, trochanter, and Ward's triangle) were determined by dual x-ray photon absorptiometry at the beginning and end of the experimental period. The increase in height and the percentage fat and muscular masses of the subjects were also recorded, as was their ability to jump (countermovement jump [CMJ]), their leg strength and power (squat test), and their leg anaerobic power (continuous jump test [CMJ15″]). No significant differences were seen in the increase in height, body weight, or percentage fat mass between the skiers and sedentary subjects, although the boy skiers showed a significant increase in percentage muscular mass (p < 0.05) compared to the sedentary boys. The improvement in the values of the different CMJ variables was significantly greater among the boy skiers than among the sedentary boys (p < 0.001-0.01). The same was true for the girls (p < 0.001), except for CMJ15″. The skiers experienced a significantly greater increase in L2-L4 BMD than the sedentary subjects (boys p < 0.05; girls p < 0.01). These results suggest that Alpine skiing combined with rational strength training involves no special risk for the physical development of young people, has a positive effect on the power and the percentage of muscle mass in the legs, and helps to have a higher bone density in the lumbar spine (L2-L4).     

The Road to Gold: Training and Peaking Characteristics in the Year Prior to a Gold Medal Endurance Performance

Purpose

To describe training variations across the annual cycle in Olympic and World Champion endurance athletes, and determine whether these athletes used tapering strategies in line with recommendations in the literature.

Methods

Eleven elite XC skiers and biathletes (4 male; 28±1 yr, 85±5 mL. min⁻¹. kg⁻¹ , 7 female, 25±4 yr, 73±3 mL. min⁻¹. kg⁻¹ ) reported one year of day-to-day training leading up to the most successful competition of their career. Training data were divided into periodization and peaking phases and distributed into training forms, intensity zones and endurance activity forms.

Results

Athletes trained ∼800 h/500 sessions.year⁻¹, including ∼500 h. year⁻¹ of sport-specific training. Ninety-four percent of all training was executed as aerobic endurance training. Of this, ∼90% was low intensity training (LIT, below the first lactate threshold) and 10% high intensity training (HIT, above the first lactate threshold) by time. Categorically, 23% of training sessions were characterized as HIT with primary portions executed at or above the first lactate turn point. Training volume and specificity distribution conformed to a traditional periodization model, but absolute volume of HIT remained stable across phases. However, HIT training patterns tended to become more polarized in the competition phase. Training volume, frequency and intensity remained unchanged from pre-peaking to peaking period, but there was a 32±15% (P<.01) volume reduction from the preparation period to peaking phase.

Conclusions

The annual training data for these Olympic and World champion XC skiers and biathletes conforms to previously reported training patterns of elite endurance athletes. During the competition phase, training became more sport-specific, with 92% performed as XC skiing. However, they did not follow suggested tapering practice derived from short-term experimental studies. Only three out of 11 athletes took a rest day during the final 5 days prior to their most successful competition.     

The effectiveness of stretch–shortening cycling in upper-limb extensor muscles during elite cross-country skiing with the double-poling technique

This investigation was designed to evaluate the effectiveness of stretch–shortening cycling (SSC_EFF) in upper-limb extensor muscles while cross-country skiing using the double-poling technique (DP). To this end, SSC_EFF was analyzed in relation to DP velocity and performance. Eleven elite cross-country skiers performed an incremental test to determine maximal DP velocity (V_max). Thereafter, cycle characteristics, elbow joint kinematics and poling forces were monitored on a treadmill while skiing at two sub-maximal and racing velocity (85% of V_max). The average EMG activities of the triceps brachii and latissimus dorsi muscles were determined during the flexion and extension sub-phases of the poling cycle (EMG_FLEX, EMG_EXT), as well as prior to pole plant (EMG_PRE). SSC_EFF was defined as the ratio of aEMG_FLEX to aEMG_EXT. EMG_PRE and EMG_FLEX increased with velocity for both muscles (P < 0.01), as did SSC_EFF (from 0.9 ± 0.3 to 1.3 ± 0.5 for the triceps brachii and from 0.9 ± 0.4 to 1.5 ± 0.5 for the latissimus dorsi) and poling force (from 253 ± 33 to 290 ± 36 N; P < 0.05). Furthermore, SSC_EFF was positively correlated to V_max, to EMG_PRE and EMG_FLEX (P < 0.05). The neuromuscular adaptations made at higher velocities, when more poling force must be applied to the ground, exert a major influence on the DP performance of elite cross-country skiers.     

Assessment of Heart Rate Variability Thresholds from Incremental Treadmill Tests in Five Cross-Country Skiing Techniques

The assessment of heart rate variability (HRV) thresholds (HRVTs) as an alternative of Ventilatory thresholds (VTs) is a relatively new approach with increasing popularity which has not been conducted in cross-country (XC) skiing yet. The main purpose of the present study was to assess HRVTs in the five main XC skiing-related techniques, double poling (DP), diagonal striding (DS), Nordic walking (NW), V1 skating (V1), and V2 skating (V2).Ten competitive skiers completed these incremental treadmill tests until exhaustion with a minimum of one to two recovery days in between each test. Ventilatory gases, HRV and poling frequencies were measured. The first HRV threshold (HRVT₁) was assessed using two time-domain analysis methods, and the second HRV threshold (HRVT₂) was assessed using two non-time varying frequency-domain analysis methods. HRVT₁ was assessed by plotting the mean successive difference (MSD) and standard deviation (SD) of normalized R-R intervals to workload. HRVT₁ was assessed by plotting high frequency power (HFP) and the HFP relative to respiratory sinus arrhythmia (HFP_RSA) with workload. HRVTs were named after their methods (HRVT_1-SD; HRVT_1-MSD; HRVT_2-HFP; HRVT_2-HFP-RSA). The results showed that the only cases where the proposed HRVTs were good assessors of VTs were the HRVT_1-SD of the DS test, the HRVT_1-MSD of the DS and V2 tests, and the HRVT_2-HFP-RSA of the NW test. The lack of a wider success of the assessment of HRVTs was reasoned to be mostly due to the high entrainment between the breathing and poling frequencies. As secondary finding, a novel Cardiolocomotor coupling mode was observed in the NW test. This new Cardiolocoomtor coupling mode corresponded to the whole bilateral poling cycle instead of corresponding to each poling action as it was reported to the date by the existing literature.     

“Negative phase” of the heart rate and stroke volume in young athletes after the Harvard step test

Changes in the heart rate (HR) and stroke volume (SV) after the Harvard step test have been studied in young athletes at different stages of multiyear training. At the initial stage of training, the HR of young swimmers and skiers transiently decreased after the test below the starting values; i.e., during the recovery period, a “negative phase” of the HR was observed. After the test, the SVs of these athletes also decreased below the starting values, following the pattern of the pulse negative phase. However, the HR and SV negative phases were not synchronous. With advancement in the training level of the young swimmers and skiers, decreases in the HR and SV below the starting values were observed more seldom, and such decreases were virtually absent at the advanced stage. No decreases in the HR or SV after the Harvard step test were observed in young ice hockey players or gymnasts.     

Comparison of heart rate deflection and ventilatory threshold during a field cross-country roller-skiing test

This study was to assess whether the point of deflection from linearity of heart rate (HRd) could be an accurate predictor of ventilatory threshold (VT2) during a specific cross-country roller-skiing (RS) test. Ten well-trained cross-country skiers performed a maximal and incremental RS test in the field and a standardized maximal and incremental treadmill running (TR) test in the laboratory. Values of oxygen uptake (VO2) and heart rate (HR) were continuously recorded during all exercises by a portable breath-by-breath gas exchange measurement system and a wireless Polar monitoring system, respectively. The VT2 and HRd points were individually determined by visual analysis during RS. Maximal VO2 (VO2 max) and HR were higher (p < 0.05) during TR (67.1 +/- 7.3 ml x min(-1) x kg(-1) and 196.0 +/- 14.1 bpm, respectively) compared with RS (64.2 +/- 7.3 ml x min(-1) x kg(-1) and 191.5 +/- 13.1 bpm, respectively). However, a high correlation (r = 0.94, p < 0.01) between TR and VO2 max was observed. Paired t-tests showed no significant differences in HR (183.6 +/- 15.1 vs. 185.2 +/- 13.9 bpm) and VO2 (55.5 +/- 7.1 vs. 55.8 +/- 6.1 ml x min(-1) x kg(-1)) at intensities corresponding to HRd and VT2 during the RS test, respectively; Pearson product-moment correlation coefficients demonstrated significant relationships for HR at the HRd and VT2 points (r = 0.99, p < 0.001) as well as for VO2 (r = 0.95, p < 0.001). Our results indicate that the specific incremental RS test is effective in eliciting HRd in the field for all skiers and is an accurate predictor of VT2. These findings give very interesting practical applications to cross-country coaches and skiers to evaluate and control specific aerobic training loads.     

Early-phase adaptations to intrahospital training in strength and functional mobility of children with leukemia

Improvements in chemotherapy and radiotherapy have contributed to the high survival rate (approximately 70%) of childhood acute lymphoblastic leukemia (ALL). However, during treatment, lack of physical activity and treatment cause various short- to long-term side effects, such as muscle atrophy and physical deconditioning. The purpose of this study was to determine the effects of an intrahospital, short-duration (8 weeks) exercise training program on muscle strength and endurance and functional mobility of children with ALL. Seven children (4 boys and 3 girls; 4-7 years of age) who were in the maintenance phase of treatment for ALL were selected as subjects. Three training sessions of 90- to 120-minute duration were performed each week. Each session included 11 different strength exercises engaging the major muscle groups and aerobic training. Gains in strength and endurance were assessed with a 6 repetition maximum test for upper (seated bench press and seated lateral row) and lower extremities (leg press). Gains in functional mobility were assessed with the time up and go test (TUG) and the timed up and down stairs test (TUDS). Performance was significantly improved after the training program in all strength tests (p < 0.01 for seated bench press and p < 0.05 for both seated lateral row and seated leg press) and in the TUG test (p < 0.05). In summary, a period of time as short as 8 weeks is enough to produce clinically relevant early-phase adaptations in children receiving treatment against ALL (i.e., improved functional mobility and muscle strength). Although more research is needed in the area of exercise training and pediatric cancer, exercise sciences can play a beneficial role in assisting both oncologists in treating cancer and improving children's quality of life during and after treatment.