Test-retest reliability of ski-specific aerobic, sprint, and neuromuscular performance tests in highly trained cross-country skiers.

Laboratory tests are commonly performed by cross-country (XC) skiers due to the challenges of obtaining reliable performance indicators on snow. However, only a few studies have reported reliability data for ski-specific test protocols. Therefore, this study examined the test-retest reliability of ski-specific aerobic, sprint, and neuromuscular performance tests. Thirty-nine highly trained XC skiers (26 men and 13 women, age: 22 ± 4 years, V̇O <sub>2max</sub> : 70.1 ± 4.5 and 58.8 ± 4.4 mL·kg <sup>-1</sup> ·min <sup>-1</sup> , respectively) performed two test trials within 6 days of a diagonal V̇O <sub>2max</sub> test, n = 27; skating graded exercise test to assess the second lactate threshold (LT <sub>2</sub> ), n = 27; 24-min double poling time trial (24-min DP, n = 25), double poling sprint test (Sprint <sub>DP1</sub> , n = 27), and 1-min self-paced skating sprint test (Sprint <sub>1-min</sub> , n = 26) using roller skis on a treadmill, and an upper-body strength test (UB-ST, n = 27) to assess peak power (P <sub>peak</sub> ) with light, medium, and heavy loads. For each test, the coefficient of variation (CV), intraclass correlation coefficient (ICC), and minimal detectable change (MDC) were calculated. V̇O <sub>2max</sub> demonstrated good-to-excellent reliability (CV = 1.4%; ICC = 0.99; MDC = 112 mL·min <sup>-1</sup> ), whereas moderate-to-excellent reliability was found for LT <sub>2</sub> (CV = 3.1%; ICC = 0.95). Performance during 24-min DP, Sprint <sub>DP1</sub> , and Sprint <sub>1-min</sub> showed good-to-excellent reliability (CV = 1.0%-2.3%; ICC = 0.96-0.99). Absolute reliability for UB-ST P <sub>peak</sub> was poor (CV = 4.9%-7.8%), while relative reliability was excellent (ICC = 0.93-0.97) across the loads. In highly trained XC skiers, sport-specific aerobic and sprint performance tests demonstrated high test-retest reliability, while neuromuscular performance for the upper body was less reliable. Using the presented protocols, practitioners can assess within- and between-season changes in relevant performance indicators

Association of Hematological Variables with Team-Sport Specific Fitness Performance.

PURPOSE: We investigated association of hematological variables with specific fitness performance in elite team-sport players. METHODS: Hemoglobin mass (Hbmass) was measured in 25 elite field hockey players using the optimized (2 min) CO-rebreathing method. Hemoglobin concentration ([Hb]), hematocrit and mean corpuscular hemoglobin concentration (MCHC) were analyzed in venous blood. Fitness performance evaluation included a repeated-sprint ability (RSA) test (8 x 20 m sprints, 20 s of rest) and the Yo-Yo intermittent recovery level 2 (YYIR2). RESULTS: Hbmass was largely correlated (r = 0.62, P<0.01) with YYIR2 total distance covered (YYIR2TD) but not with any RSA-derived parameters (r ranging from -0.06 to -0.32; all P>0.05). [Hb] and MCHC displayed moderate correlations with both YYIR2TD (r = 0.44 and 0.41; both P<0.01) and RSA sprint decrement score (r = -0.41 and -0.44; both P<0.05). YYIR2TD correlated with RSA best and total sprint times (r = -0.46, P<0.05 and -0.60, P<0.01; respectively), but not with RSA sprint decrement score (r = -0.19, P>0.05). CONCLUSION: Hbmass is positively correlated with specific aerobic fitness, but not with RSA, in elite team-sport players. Additionally, the negative relationships between YYIR2 and RSA tests performance imply that different hematological mechanisms may be at play. Overall, these results indicate that these two fitness tests should not be used interchangeably as they reflect different hematological mechanisms

Comparison of "Live High-Train Low" in Normobaric versus Hypobaric Hypoxia.

We investigated the changes in both performance and selected physiological parameters following a Live High-Train Low (LHTL) altitude camp in either normobaric hypoxia (NH) or hypobaric hypoxia (HH) replicating current "real" practices of endurance athletes. Well-trained triathletes were split into two groups (NH, n = 14 and HH, n = 13) and completed an 18-d LHTL camp during which they trained at 1100-1200 m and resided at an altitude of 2250 m (PiO2  = 121.7±1.2 vs. 121.4±0.9 mmHg) under either NH (hypoxic chamber; FiO2 15.8±0.8%) or HH (real altitude; barometric pressure 580±23 mmHg) conditions. Oxygen saturations (SpO2) were recorded continuously daily overnight. PiO2 and training loads were matched daily. Before (Pre-) and 1 day after (Post-) LHTL, blood samples, VO2max, and total haemoglobin mass (Hbmass) were measured. A 3-km running test was performed near sea level twice before, and 1, 7, and 21 days following LHTL. During LHTL, hypoxic exposure was lower for the NH group than for the HH group (220 vs. 300 h; P<0.001). Night SpO2 was higher (92.1±0.3 vs. 90.9±0.3%, P<0.001), and breathing frequency was lower in the NH group compared with the HH group (13.9±2.1 vs. 15.5±1.5 breath.min-1, P<0.05). Immediately following LHTL, similar increases in VO2max (6.1±6.8 vs. 5.2±4.8%) and Hbmass (2.6±1.9 vs. 3.4±2.1%) were observed in NH and HH groups, respectively, while 3-km performance was not improved. However, 21 days following the LHTL intervention, 3-km run time was significantly faster in the HH (3.3±3.6%; P<0.05) versus the NH (1.2±2.9%; ns) group. In conclusion, the greater degree of race performance enhancement by day 21 after an 18-d LHTL camp in the HH group was likely induced by a larger hypoxic dose. However, one cannot rule out other factors including differences in sleeping desaturations and breathing patterns, thus suggesting higher hypoxic stimuli in the HH group

Tapering for marathon and cardiac autonomic function.

The purpose of this study was to investigate changes in post-exercise heart rate recovery (HRR) and heart rate variability (HRV) during an overload-tapering paradigm in marathon runners and examine their relationship with running performance. 9 male runners followed a training program composed of 3 weeks of overload followed by 3 weeks of tapering (-33±7%). Before and after overload and during tapering they performed an exhaustive running test (Tlim). At the end of this test, HRR variables (e.g. HRR during the first 60 s; HRR60 s) and vagal-related HRV indices (e.g. RMSSD5-10 min) were examined. Tlim did not change during the overload training phase (603±105 vs. 614±132 s; P=0.992), but increased (727±185 s; P=0.035) during the second week of tapering. Compared with overload, RMSSD5-10 min (7.6±3.3 vs. 8.6±2.9 ms; P=0.045) was reduced after the 2(nd) week of tapering. During tapering, the improvements in Tlim were negatively correlated with the change in HRR60 s (r=-0.84; P=0.005) but not RMSSD5-10 min (r=-0.21; P=0.59). A slower HRR during marathon tapering may be indicative of improved performance. In contrast, the monitoring of changes in HRV as measured in the present study (i.e. after exercise on a single day), may have little or no additive value

“Live High–Train low and high” Hypoxic training improves Team-Sport performance

Purpose This study aims to investigate physical performance and hematological changes in 32 elite male team-sport players after 14 d of “live high–train low” (LHTL) training in normobaric hypoxia (≥14 h·d−1 at 2800–3000 m) combined with repeated-sprint training (six sessions of four sets of 5 × 5-s sprints with 25 s of passive recovery) either in normobaric hypoxia at 3000 m (LHTL + RSH, namely, LHTLH; n = 11) or in normoxia (LHTL + RSN, namely, LHTL; n = 12) compared with controlled “live low–train low” (LLTL; n = 9) training. Methods Before (Pre), immediately after (Post-1), and 3 wk after (Post-2) the intervention, hemoglobin mass (Hbmass) was measured in duplicate [optimized carbon monoxide (CO) rebreathing method], and vertical jump, repeated-sprint (8 × 20 m–20 s recovery), and Yo-Yo Intermittent Recovery level 2 (YYIR2) performances were tested. Results Both hypoxic groups similarly increased their Hbmass at Post-1 and Post-2 in reference to Pre (LHTLH: +4.0%, P < 0.001 and +2.7%, P < 0.01; LHTL: +3.0% and +3.0%, both P < 0.001), whereas no change occurred in LLTL. Compared with Pre, YYIR2 performance increased by ∼21% at Post-1 (P < 0.01) and by ∼45% at Post-2 (P < 0.001), with no difference between the two intervention groups (vs no change in LLTL). From Pre to Post-1, cumulated sprint time decreased in LHTLH (−3.6%, P < 0.001) and LHTL (−1.9%, P < 0.01), but not in LLTL (−0.7%), and remained significantly reduced at Post-2 (−3.5%, P < 0.001) in LHTLH only. Vertical jump performance did not change. Conclusions “Live high–train low and high” hypoxic training interspersed with repeated sprints in hypoxia for 14 d (in season) increases the Hbmass, YYIR2 performance, and repeated-sprint ability of elite field team-sport players, with benefits lasting for at least 3 wk postintervention

Haemogoblin mass is positively correlated with sport-specific aerobic fitness, but not with repeated-sprint ability, in elite team-sport players

Purpose We investigated association of hematological variables with specific fitness performance in elite team-sport players. Methods Hemoglobin mass (Hb mass) was measured in 25 elite field hockey players using the optimized (2 min) CO-rebreathing method. Hemoglobin concentration ([Hb]), hematocrit and mean corpuscular hemoglobin concentration (MCHC) were analyzed in venous blood. Fitness performance evaluation included a repeated-sprint ability (RSA) test (8 x 20 m sprints, 20 s of rest) and the Yo-Yo intermittent recovery level 2 (YYIR2). Results Hb mass was largely correlated (r = 0.62, P0.05). [Hb] and MCHC displayed moderate correlations with both YYIR2 TD (r = 0.44 and 0.41; both P0.05). Conclusion Hb mass is positively correlated with specific aerobic fitness, but not with RSA, in elite team-sport players. Additionally, the negative relationships between YYIR2 and RSA tests performance imply that different hematological mechanisms may be at play. Overall, these results indicate that these two fitness tests should not be used interchangeably as they reflect different hematological mechanisms

&quot;Live High-Train Low and High&quot; Hypoxic Training Improves Team-Sport Performance.

PURPOSE: This study aims to investigate physical performance and hematological changes in 32 elite male team-sport players after 14 d of "live high-train low" (LHTL) training in normobaric hypoxia (≥14 h·d at 2800-3000 m) combined with repeated-sprint training (six sessions of four sets of 5 × 5-s sprints with 25 s of passive recovery) either in normobaric hypoxia at 3000 m (LHTL + RSH, namely, LHTLH; n = 11) or in normoxia (LHTL + RSN, namely, LHTL; n = 12) compared with controlled "live low-train low" (LLTL; n = 9) training. METHODS: Before (Pre), immediately after (Post-1), and 3 wk after (Post-2) the intervention, hemoglobin mass (Hbmass) was measured in duplicate [optimized carbon monoxide (CO) rebreathing method], and vertical jump, repeated-sprint (8 × 20 m-20 s recovery), and Yo-Yo Intermittent Recovery level 2 (YYIR2) performances were tested. RESULTS: Both hypoxic groups similarly increased their Hbmass at Post-1 and Post-2 in reference to Pre (LHTLH: +4.0%, P &lt; 0.001 and +2.7%, P &lt; 0.01; LHTL: +3.0% and +3.0%, both P &lt; 0.001), whereas no change occurred in LLTL. Compared with Pre, YYIR2 performance increased by ∼21% at Post-1 (P &lt; 0.01) and by ∼45% at Post-2 (P &lt; 0.001), with no difference between the two intervention groups (vs no change in LLTL). From Pre to Post-1, cumulated sprint time decreased in LHTLH (-3.6%, P &lt; 0.001) and LHTL (-1.9%, P &lt; 0.01), but not in LLTL (-0.7%), and remained significantly reduced at Post-2 (-3.5%, P &lt; 0.001) in LHTLH only. Vertical jump performance did not change. CONCLUSIONS: "Live high-train low and high" hypoxic training interspersed with repeated sprints in hypoxia for 14 d (in season) increases the Hbmass, YYIR2 performance, and repeated-sprint ability of elite field team-sport players, with benefits lasting for at least 3 wk postintervention

Do male athletes with already high initial haemoglobin mass benefit from ‘live high-train low’ altitude training?

What is the central question of this study? It has been assumed that athletes embarking on an 'live high-train low' (LHTL) camp with already high initial haemoglobin mass (Hbmass ) have a limited ability to increase their Hbmass further post-intervention. Therefore, the relationship between initial Hbmass and post-intervention increase was tested with duplicate Hbmass measures and comparable hypoxic doses in male athletes. What is the main finding and its importance? There were trivial to moderate inverse relationships between initial Hbmass and percentage Hbmass increase in endurance and team-sport athletes after the LHTL camp, indicating that even athletes with higher initial Hbmass can reasonably expect Hbmass gains post-LHTL. It has been proposed that athletes with high initial values of haemoglobin mass (Hbmass ) will have a smaller Hbmass increase in response to 'live high-train low' (LHTL) altitude training. To verify this assumption, the relationship between initial absolute and relative Hbmass values and their respective Hbmass increase following LHTL in male endurance and team-sport athletes was investigated. Overall, 58 male athletes (35 well-trained endurance athletes and 23 elite male field hockey players) undertook an LHTL training camp with similar hypoxic doses (200-230 h). The Hbmass was measured in duplicate pre- and post-LHTL by the carbon monoxide rebreathing method. Although there was no relationship (r = 0.02, P = 0.91) between initial absolute Hbmass (in grams) and the percentage increase in absolute Hbmass , a moderate relationship (r = -0.31, P = 0.02) between initial relative Hbmass (in grams per kilogram) and the percentage increase in relative Hbmass was detected. Mean absolute and relative Hbmass increased to a similar extent (P ≥ 0.81) in endurance (from 916 ± 88 to 951 ± 96 g, +3.8%, P < 0.001 and from 13.1 ± 1.2 to 13.6 ± 1.1 g kg-1 , +4.1%, P < 0.001, respectively) and team-sport athletes (from 920 ± 120 to 957 ± 127 g, +4.0%, P < 0.001 and from 11.9 ± 0.9 to 12.3 ± 0.9 g kg-1 , +4.0%, P < 0.001, respectively) after LHTL. The direct comparison study using individual data of male endurance and team-sport athletes and strict methodological control (duplicate Hbmass measures and matched hypoxic dose) indicated that even athletes with higher initial Hbmass can reasonably expect Hbmass gain post-LHTL

Similar Hemoglobin Mass Response in Hypobaric and Normobaric Hypoxia in Athletes

PURPOSE: To compare hemoglobin mass (Hbmass) changes during an 18-d live high-train low (LHTL) altitude training camp in normobaric hypoxia (NH) and hypobaric hypoxia (HH). METHODS: Twenty-eight well-trained male triathletes were split into three groups (NH: n = 10, HH: n = 11, control [CON]: n = 7) and participated in an 18-d LHTL camp. NH and HH slept at 2250 m, whereas CON slept, and all groups trained at altitudes &lt;1200 m. Hbmass was measured in duplicate with the optimized carbon monoxide rebreathing method before (pre-), immediately after (post-) (hypoxic dose: 316 vs 238 h for HH and NH), and at day 13 in HH (230 h, hypoxic dose matched to 18-d NH). Running (3-km run) and cycling (incremental cycling test) performances were measured pre and post. RESULTS: Hbmass increased similar in HH (+4.4%, P &lt; 0.001 at day 13; +4.5%, P &lt; 0.001 at day 18) and NH (+4.1%, P &lt; 0.001) compared with CON (+1.9%, P = 0.08). There was a wide variability in individual Hbmass responses in HH (-0.1% to +10.6%) and NH (-1.4% to +7.7%). Postrunning time decreased in HH (-3.9%, P &lt; 0.001), NH (-3.3%, P &lt; 0.001), and CON (-2.1%, P = 0.03), whereas cycling performance changed nonsignificantly in HH and NH (+2.4%, P &gt; 0.08) and remained unchanged in CON (+0.2%, P = 0.89). CONCLUSION: HH and NH evoked similar Hbmass increases for the same hypoxic dose and after 18-d LHTL. The wide variability in individual Hbmass responses in HH and NH emphasizes the importance of individual Hbmass evaluation of altitude training