Gunnar Treff

Oxygen saturation increases over the course of the night in mountaineers at high altitude (3050–6354 m)

Background Blood oxygen saturation (SpO 2 ) is frequently measured to determine acclimatization status in high-altitude travellers. However, little is known about nocturnal time course of SpO 2 (SpO 2N ), but alterations in SpO 2N might be practically relevant as well. To this end, we describe the time-course of SpO 2N in mountaineers at high altitude. Methods SpO 2N was continuously measured in ten male mountaineers during a three-week expedition in Peru (3,050-6,354m). Average SpO 2N of the first (SpO 2N1 ) and second half (SpO 2N2 ) of an individuals sleep duration was calculated from 2h intervals of uninterrupted sleep. Heart rate oscillations and sleep dairies were used to exclude periods of wakefulness. SpO 2 was also measured at rest in the morning. Results SpO 2N significantly increased from SpO 2N1 to SpO 2N2 . The magnitude of this increase (ΔSpO 2 ) was reduced with time spent at altitude. On night 1 (3,050m) SpO 2 increased from 83.4% (N1) to 86.3% (N2). At the same location on night 21, SpO 2 increased from 88.3% to 90.1%, which is a relative change of 4.7% and 2.0%, respectively. This pattern of increase in SpO 2N was perturbed when individual acclimatization was poor or altitude was extreme (5630m). SpO 2N was significantly lower than SpO 2 at rest in the morning. Conclusions This study is the first to demonstrate an increase of SpO 2 during the night in mountaineers at high altitude (3,050-6,354m) with high consistency between and within subjects. The magnitude of ΔSpO 2N decreased as acclimatization improved, suggesting that these changes in ΔSpO 2 between nights might be a valuable indicator of individual acclimatization. In addition, the failure of any increase in SpO 2N during the night might indicate insufficient acclimatization. Even though underlying mechanisms for the nocturnal increase remain unclear, the timing of SpO 2N measurement is obviously of utmost importance for its interpretation. Finally our study illustrates the detailed effects of ventilatory acclimatization over several weeks.

Carbohydrate Intake in Form of Gel Is Associated with Increased Gastrointestinal Distress but Not with Performance Differences Compared with Liquid Carbohydrate Ingestion during Simulated Long-Distance Triathlon

The ingestion of exogenous carbohydrates (CHO) during prolonged endurance exercise, such as long-distance triathlon, is considered beneficial with regard to performance. However, little is known about whether this performance benefit differs among different forms of CHO administration. To this end, the purpose of our study was to determine the impact of CHO ingestion from a semisolid source (GEL) on measures of performance and gastrointestinal (GI) comfort compared with CHO ingestion from a liquid source (LIQ). Nine well-trained triathletes participated in this randomized crossover study. Each participant completed a 60-min swim, 180-min bike exercise, and a 60-min all-out run in a laboratory environment under 2 conditions, once while receiving 67.2 ± 7.2 g · h-1 (M ± SD) of CHO from GEL and once while receiving 67.8 ± 4.2 g · h-1 of CHO from LIQ. The amount of fluid provided was matched among conditions. Respiratory exchange ratio (RER), blood glucose, and lactate as well as GI discomfort were assessed at regular intervals during the experiment. The distance covered during the final all-out run was not significantly different among participants ingesting GEL (11.81 ± 1.38 km) and LIQ (11.91 ± 1.53 km; p = .89). RER, blood glucose, and lactate did not differ significantly at any time during the experiment. Seven participants reported GI discomfort with GEL, and no athlete reported GI discomfort with LIQ (p = .016). This study suggests that administration of GEL does not alter long-distance triathlon performance when compared with LIQ, but GEL seems to be associated with reduced GI tolerance. Athletes should consider this a potential disadvantage of GEL administration during long-distance triathlon.

The effect of westward travel across five time zones on sleep and subjective jet-lag ratings in athletes before and during the 2015's World Rowing Junior Championships.

ABSTRACT This study examined sleep-wake habits and subjective jet-lag ratings of 55 German junior rowers (n = 30 male, 17.8 ± 0.5 years) before and during the World Rowing Junior Championships 2015 in Rio de Janeiro, Brazil. Athletes answered sleep logs every morning, and Liverpool John Moore’s University Jet-Lag Questionnaires each evening and morning. Following an 11-h westward flight with 5-h time shift, advanced bedtimes (−1 h, P < .001, ηp2 = 0.68), reduced sleep onset latency (P = .002, ηp2 = 0.53) and increased sleep duration (P < .001, ηp2 = 0.60) were reported for the first two nights. Jet-lag symptoms peaked upon arrival but were still present after 6 days. Sleep quality improved (P < .001, ηp2 = 0.31) as well as some scales of the Recovery-Stress Questionnaire for Athletes. Participation was successful as indicated by 11 of 13 top 3 placings. Overall, the initial desynchronisation did not indicate negative impacts on competition performance. As travel fatigue probably had a major effect on perceptual decrements, sleep during travel and time to recover upon arrival should be emphasised. Coaches and practitioners should consider higher sleep propensity in the early evening by scheduling training sessions and meetings until the late afternoon.

Assessment of subcutaneous adipose tissue using ultrasound in highly trained junior rowers

Abstract Introduction: There is a large variety of body fat (BF) measurements, which differ in validity and reliability. The aim of this study was to measure subcutaneous adipose tissue (SAT) using ultrasound (US) in highly trained junior rowers in a field setting, establish fat patterning profiles, and compare the profiles between male and female athletes. Skinfold thickness (SKF) measurements were also taken and compared to US measurements. Methods: Sixteen athletes participated. US measurements were taken at eight sites and reported as a sum of SAT (D): DExcl (without embedded structures) and DIncl (including embedded structures). SKF was measured at three sites and reported as a sum of adipose tissue thickness (SUMSKF). Results: Mean SAT thickness (DIncl) was 27.6 ± 12.4 mm for males and 65.5 ± 11.8 mm for females. Females had significantly more embedded structures than males (P = .016). Significant correlations were found (P < .001, r = 0.92) comparing SUMSKF to DIncl and between SKF and US measurements at the thigh site (P < .001, r = 0.86). Conclusion: US is a suitable tool to measure BF in the field testing of athletes and enables measurements of SAT with an accuracy and reliability not reached before. The sum of thicknesses (DIncl or DExcl) can be used to represent subcutaneous fat based on accurate measurements of uncompressed SAT thicknesses.

Sedentary Behavior among National Elite Rowers during Off-Training—A Pilot Study

The aim of this pilot study was to analyze the off-training physical activity (PA) profile in national elite German U23 rowers during 31 days of their preparation period. The hours spent in each PA category (i.e., sedentary: <1.5 metabolic equivalents (MET); light physical activity: 1.5–3 MET; moderate physical activity: 3–6 MET and vigorous intense physical activity: >6 MET) were calculated for every valid day (i.e., >480 min of wear time). The off-training PA during 21 weekdays and 10 weekend days of the final 11-week preparation period was assessed by the wrist-worn multisensory device Microsoft Band II (MSBII). A total of 11 rowers provided valid data (i.e., >480 min/day) for 11.6 week days and 4.8 weekend days during the 31 days observation period. The average sedentary time was 11.63 ± 1.25 h per day during the week and 12.49 ± 1.10 h per day on the weekend, with a tendency to be higher on the weekend compared to weekdays (p = 0.06; d = 0.73). The average time in light, moderate and vigorous PA during the weekdays was 1.27 ± 1.15, 0.76 ± 0.37, 0.51 ± 0.44 h per day, and 0.67 ± 0.43, 0.59 ± 0.37, 0.53 ± 0.32 h per weekend day. Light physical activity was higher during weekdays compared to the weekend (p = 0.04; d = 0.69). Based on our pilot study of 11 national elite rowers we conclude that rowers display a considerable sedentary off-training behavior of more than 11.5 h/day.

Eleven-Week Preparation Involving Polarized Intensity Distribution Is Not Superior to Pyramidal Distribution in National Elite Rowers

Polarized (POL) training intensity distribution (TID) emphasizes high-volume low-intensity exercise in zone (Z)1 (< first lactate threshold) with a greater proportion of high-intensity Z3 (>second lactate threshold) compared to Z2 (between first and second lactate threshold). In highly trained rowers there is a lack of prospective controlled evidence whether POL is superior to pyramidal (PYR; i.e., greater volume in Z1 vs. Z2 vs. Z3) TID. The aim of the study was to compare the effect of POL vs. PYR TID in rowers during an 11-wk preparation period. Fourteen national elite male rowers participated (age: 20 ± 2 years, maximal oxygen uptake (V˙O2max): 66 ± 5 mL/min/kg). The sample was split into PYR and POL by varying the percentage spent in Z2 and Z3 while Z1 was clamped to ~93% and matched for total and rowing volume. Actual TIDs were based on time within heart rate zones (Z1 and Z2) and duration of Z3-intervals. The main outcome variables were average power in 2,000 m ergometer-test (P2,000 m), power associated with 4 mmol/L [blood lactate] (P4[BLa]), and V˙O2max. To quantify the level of polarization, we calculated a Polarization-Index as log (%Z1 × %Z3 / %Z2). PYR and POL did not significantly differ regarding rowing or total volume, but POL had a higher percentage of Z3 intensities (6 ± 3 vs. 2 ± 1%; p < 0.005) while Z2 was lower (1 ± 1 vs. 3 ± 2%; p < 0.05) and Z1 was similar (94 ± 3 vs. 93 ± 2%, p = 0.37). Consequently, Polarization-Index was significantly higher in POL (3.0 ± 0.7 vs. 1.9 ± 0.4 a.u.; p < 0.01). P2,000 m did not significantly change with PYR (1.5 ± 1.7%, p = 0.06) nor POL (1.5 ± 2.6%, p = 0.26). V˙O2max did not change (1.7 ± 5.6%, p = 0.52 or 0.6 ± 2.6, p = 0.67) and a small increase in P4[BLa] was observed in PYR only (1.9 ± 4.8%, p = 0.37 or −0.5 ± 4.1%, p = 0.77). Changes from pre to post were not significantly different between groups in any performance measure. POL did not prove to be superior to PYR, possibly due to the high and very similar percentage of Z1 in this study.

Monitoring rowers to determine under-performance

Over the past few years, training load and performance in competition has continuously increased and is fraught with risk to result in the accumulation of fatiguing conditions. The coach determines training success by controlling boat speed, performance, power and soft parameters like stability of rowing technique, capacity to teamwork, and mood state. However, in team sports like rowing, monitoring of individual rowers fatigue to optimize regeneration is difficult. While training should voluntarily cause acute fatigue, the accumulation of training leads to more severe fatigue, which is called “overreaching”. When fatigue is more prolonged and recovery is impaired, the condition is defined as “non-functional overreaching” ending in a primarily unexplained, long-term, and unplanned decreasing performance, a condition defined as “Unexplained Underperformance Syndrome” (UUPS) or “overtraining syndrome” (OTS). Good standards and appropriate markers for diagnosis and treatment are currently lacking.

Speckle tracking-derived bi-atrial strain before and after eleven weeks of training in elite rowers

The left (LA) and right (RA) atria undergo adaptive remodeling in response to hemodynamic stress not only induced by endurance exercise but also as part of several cardiovascular diseases thereby confounding differential diagnosis. Echocardiographic assessment of the atria with novel speckle tracking (STE)-derived variables broadens the diagnostic spectrum compared to conventional analyses and has the potential to differentiate physiologic from pathologic changes. The purpose of this study was to assess and categorize baseline values of bi-atrial structure and function in elite rowers according to recommended cutoffs, and to assess the cardiac changes occurring with endurance training. Therefore, fifteen elite rowers underwent 2D-echocardiographic analysis of established variables of cardiac structure and function as well as STE-derived variables of bi-atrial function. Measurements were performed at baseline and after eleven weeks of extensive training. 40% of athletes displayed mildly enlarged LA and 47% mildly enlarged RA at baseline, whereas no athlete fell below the lower reference values of LA and RA reservoir strain. Average power during a 2000 m ergometer rowing test (P2000 m) improved from 426 ± 39 W to 442 ± 34 W (p = 0.010) but there were no changes of echocardiographic variables following training. In elite rowers, longitudinal bi-atrial strain assessment indicates normal resting function of structurally enlarged atria and thereby may assist to differentiate between exercise-induced versus disease-associated structural cardiac changes in which function is commonly impaired.

Acute exercise-induced irisin release in healthy adults: Associations with training status and exercise mode

Abstract There is a growing interest in exploring irisin response to acute exercise; however, the associations of acute exercise-induced irisin release with training status and exercise mode are not fully understood. This study was primarily designed to evaluate these associations. Sixteen healthy adults (8 trained versus 8 untrained) underwent a bout of cycling at 80% of maximal oxygen uptake (VO2max) for 50 min, with blood drawn pre-, 10-, and 180-min post-exercise. Another 17 healthy adults performed 2 bouts of graded exercise (cycling and running) until exhaustion on separate days using a randomized cross-over design, with blood taken pre-, 0-, 10-, and 60-min post-exercise. Circulating irisin, creatine kinase (CK), aspartate aminotransferase (AST), and myoglobin (Mb) were measured, and their respective areas under the curves (AUCs) were calculated. Irisin increased 10-min after 50 min of cycling at 80% of VO2max, while its changes from baseline to post-exercise and the amount of exercise-induced irisin release (presented as AUC) were comparable between trained and untrained adults (all P > .05). Irisin remained elevated 10-min post-exhausting running but decreased towards baseline 10-min post-exhausting cycling. Exhausting running induced an increase in irisin release for the whole course of exercise and recovery periods, but cycling did not. Acute exercise-induced irisin changes seemed not related to changes of CK, aspartate AST, and Mb in general. In conclusion, acute exercise-induced irisin release is not associated with training status but might be affected by training mode. Future studies are required to investigate which exercise mode might be most efficient in altering irisin.

Anthropometric profiles are associated with long-term career attainment in elite junior rowers: A retrospective analysis covering 23 years

ABSTRACT Introduction: Successful rowers are heavier and taller than their opponents, but the effect of these variables on long-term career attainment in juniors has not been examined. We therefore analysed this in a large sample of elite German junior rowers. Methods: Former German Junior National Team rowers (N = 910; 399 females) were grouped according to their highest career attainment, i.e., participation in U19-, U23-, Senior World Championships or Olympic Games (OG). Differences in standing height (SH), body mass (BM) and body mass index (BMI) between groups were analysed using unpaired t-tests and magnitude-based inferences (MBI), effects of anthropometrics on career attainment were analysed with a proportional odds model. Interquartile ranges of the OG group were used to define normative data ranges. Results: SH and BMI very likely differed between career attainment in females. The same was found in males for SH and BM. BM (odds ratio (OR) = 0.958, P = .0171) and BMI (OR = 0.787, P = .0004) had a significant effect on career attainment in females as SH (OR = 1.072, P = .0002) and BM (OR = 1.049, P = .0004) had in males. Interquartile ranges of SH and BM were 178–184 cm and 68–73 kg in females, 190–196 cm and 84–93 kg in males. Conclusion: Anthropometric characteristics at junior age affect long-term career attainment even within elite U19 National Team rowers, underlining the relevance of anthropometric assessments and their consideration for talent identification and development programmes in rowing. We provide evidence-based normative data that rule out an anthropometric limitation of junior rowers for career progression to Olympic level.