To Örebro University

Artistic swimming combines prolonged breath-hold periods with high-intensity movements, resulting in unique physiological demands. Direct measurement of key variables such as oxygen uptake (VO₂) during routines is limited by frequent immersion. However, VO₂ monitoring is essential for understanding the balance between aerobic and anaerobic energy contributions, guiding training strategies and reducing injury risk. This study aimed to analyze the acute physiological responses, VO₂, blood lactate concentration, and heart rate, during free duet routines in elite artistic swimmers, using a segmented protocol that emphasized the two longest apneas. Sixteen elite artistic swimmers performed both complete and segmented versions of the routine. VO₂ was estimated using retro-extrapolation, while lactate was measured after each phase, and heart rate was continuously monitored. The protocol included six measurement points: pre-routine, pre- and post-apnea 1 and 2, and post-routine. VO₂ increased rapidly, reaching nearly 90% of VO₂ peak within 67 seconds (mean: 61.8 ± 15.1 mL·min ⁻ ¹·kg ⁻ ¹). Blood lactate concentration rose progressively, peaking at 5.93 ± 1.41 mmol·L ⁻ ¹. Heart rate exhibited large fluctuations, with a maximum of 203.8 ± 5.0 beats·min ⁻ ¹ and a minimum of 71.9 ± 16.6 beats·min ⁻ ¹, reflecting a bradycardic response during apneas. No significant changes were observed in VO₂ or lactate between pre- and post-apnea values, as measured around the two longest apneas within the routine. These findings suggest that, under the specific conditions of this study, short-duration apneas (< 20 s) may be insufficient on their own to elicit distinct physiological shifts. However, the progressive increases observed in blood lactate and heart rate throughout the full routine suggest that the overall physiological load may be influenced more by sustained exercise intensity and the cumulative effect of repeated apneas than by isolated breath-hold events.

Purpose: To compare external and internal training load markers during resistance training (RT) in normoxia (N), intermittent hypobaric hypoxia (HH), and intermittent normobaric hypoxia (NH).

Methods: Thirty-three volunteers were assigned an 8-week RT program in either N (690 m, n = 10), HH (2320 m, n = 10), or NH (inspired fraction of oxygen = 15.9%; ~ 2320 m, n = 13). The RT program (3x/week) consisted of six exercises, with three sets of six to 12 repetitions at ~ 70% of one repetition maximum (1RM) with the first session of each week used for analysis. 1RM in back squat and bench press was used to evaluate muscle strength before and after the program. External load was assessed by the volume load relative to body mass (RVL, kg·kg-1). Internal load was assessed by the ratings of perceived exertion (RPE) and heart rate (HR).

Results: Smaller relative improvements were found for the back squat in the N group (11.5 ± 8.8%) when compared to the NH group (22.2 ± 8.2%, P = 0.01) and the HH group (22 ± 8.1%, P = 0.02). All groups showed similar RVL, HR responses and RPE across the program (P˃0.05). However, reduced HR recovery values, calculated as the difference between the highest HR value (HRpeak) and the resting heart rate after a two min rest, were seen in the N and NH groups across the program (P < 0.05).

Conclusion: It seems that 8 weeks of intermittent RT in hypoxic environments could maximize time-efficiency when aiming to improve strength levels in back squat without evoking higher levels of physiological stress. Performing RT at hypobaric hypoxia may improve the cardiorespiratory response, which in turn could speed recovery.

INTRODUCTION: The extent to which additional health benefits of accumulating twice the minimum amount of time in moderate-to-vigorous physical activity (MVPA) affects indicators of physical function in older adults is unclear. Therefore, the aim of the present study was to assess indicators of physical function in older adults who accumulate at least 150 but less than 300 min/week of MVPA compared to those accumulating at least 300 min/week.

METHODS: Indicators of physical function, including handgrip strength, 5 times sit-to-stand test (5-STS), squat jump and 6-min walk test (6MWT) were assessed in a sample of 193 older men (n = 71, 67 ± 2 years), and women (n = 122, 67 ± 2 years), who all accumulated at least 150 weekly minutes of MVPA. Time in MVPA was assessed by accelerometry during 1 week and engagement in muscle strengthening activities (MSA) was assessed by self-report. Protein intake was assessed by a food-frequency-questionnaire. Participants were classified as physically active (≥150 but <300 min of MVPA per week) or as highly physically active (≥300 min of MVPA per week).

RESULTS: Factorial analysis of variance revealed that older adults accumulating at least 300 min of MVPA per week had a significantly (p < 0.05) better 6MWT performance and overall physical function compared to the less active group. These findings remained significant after further adjustment for MSA, sex, waist circumference and protein intake. In contrast, no significant differences in indicators of muscle strength were observed between the two groups.

DISCUSSION: Adherence to twice the recommended minimum amount of weekly MVPA time is related to a better physical function, evidenced by a better walking performance compared to adherence to the minimum weekly amount of MVPA. This finding emphasizes the benefits of accumulating daily MVPA beyond the minimum recommended amount to optimize the ability to perform activities of daily living, thus reducing the burden of physical disability and related health-care costs.

Although high and simulated altitude training has become an increasingly popular training method, no study has investigated the influence of acute hypoxic exposure on balance in team-sport athletes. Therefore, the purpose of this study was to investigate whether acute exposure to normobaric hypoxia is detrimental to balance performance in highly-trained basketball players. Nine elite and nine sub-elite male basketball players participated in a randomized, single-blinded, cross-over study. Subjects performed repeated trials of a single-leg balance test (SLBT) in an altitude chamber in normoxia (NOR; approximately sea level) with FiO2 20.9% and PiO2 ranging from 146.7 to 150.4 mmHg and in normobaric hypoxia (HYP; ~3,800 m above sea level) with FiO2 13.0% and PiO2 ranging from 90.9 to 94.6 mmHg. The SLBT was performed three times: 15 min after entering the environmental chamber in NOR or HYP, then two times more interspersed by 3-min rest. Peripheral oxygen saturation (SpO2) and heart rate (HR) were recorded at four time points: after the initial 15-min rest inside the chamber and immediately after each SLBT. Across the cohort, the balance performance was 7.1% better during NOR than HYP (P < 0.01, η2p = 0.58). However, the performance of the elite group was not impaired by HYP, whereas the sub-elite group performed worse in the HYP condition on both legs (DL: P = 0.02, d = 1.23; NDL: P = 0.01, d = 1.43). SpO2 was lower in HYP than NOR (P < 0.001, η2p = 0.99) with a significant decline over time during HYP. HR was higher in HYP than NOR (P = 0.04, η2p = 0.25) with a significant increase over time. Acute exposure to normobaric hypoxia detrimentally affected the balance performance in sub-elite but not elite basketball players. 

Purpose: To determine whether heart-rate variability (HRV) was correlated with other training-load and training-tolerance markers for monitoring the effect of a training session on elite synchronized swimmers.

Methods: The authors recorded the resting HRV of 12 elite swimmers (mean age = 21.5 [3.5] y) 3 times over 1 wk with a cadence of 48 h prior to the 2015 World Swimming Championships. They continuously monitored heart rate and obtained salivary cortisol (SC) samples before and after the last training session of the week. The authors measured capillary blood lactate (La) 2, 4, and 8 min after the last training session and monitored recovery HRV. They assessed rating of perceived exertion (RPE) over the entire session and tested the association between the highest La concentration (Lapeak), SC, and RPE and relative changes (Δ%) in the natural logarithm of the root-mean-square successive difference of intervals (LnRMSSD). The authors also calculated the smallest worthwhile change of the averaged pre and post LnRMSSD measurements.

Results: There were periods of pronounced bradycardia (60.5 [16.7] beats/ min) during training exercises corresponding to apneic exercise. The magnitude-based inferences showed nonclinically meaningful changes of LnRMSSD. Lapeak (6.8 [2.7] mmol/L) correlated positively with Δ%LnRMSSD and Δ%SC (r = .89, P = .001 and r = .61, P = .04, respectively). Conclusions: There was no change in LnRMSSD and Lapeak, Δ%SC, and RPE indicated reduced sympathetic activation and positive adaptation to the stress imposed by the session. Isolated HRV assessment may reveal a controversial interpretation of autonomic nervous system status or the training tolerance in elite synchronized swimming athletes due to the influence of the diving response.

(SaO₂)To facilitate recovery from hypoxia, many freedivers use a breathing method called "hook breathing" (HB) after diving, involving an interrupted exhale to build up intrapulmonary pressure. Some divers experience a delay in recovery of arterial oxygen saturation (SaO₂) after diving, interpreted as symptoms of mild pulmonary edema, and facilitated recovery may be especially important in this group to avoid hypoxic "blackout." We examined the influence of HB on recovery of (SaO₂) in freedivers with slow recovery (SR) and fast recovery (FR) of (SaO₂) after deep "free immersion" (FIM) apnea dives to 30 m depth. Twenty-two male freedivers, with a mean (SD) personal best in the discipline FIM of 57(26) m, performed two 30 m deep dives, one followed by HB and one using normal breathing (NB) during recovery, at different days and weighted order. (SaO₂) and heart rate (HR) were measured via pulse oximetry during recovery. The SR group (n = 5) had a faster (SaO₂) recovery using HB, while the FR group (n = 17) showed no difference between breathing techniques. At 105 s, the SR group reached a mean (SD) SaO(2) of 95(5)% using HB, while using NB, their (SaO₂) was 87(5)% (p < 0.05), and 105-120 s after surfacing(SaO₂) was higher with HB (p < 0.05). In SR subjects, the average time needed to reach 95% (SaO₂) with HB was 60 s, while it was 120 s at NB (p < 0.05). HR was similar in the SR group, while it was initially elevated at HB in the FR group (p < 0.05). We conclude that HB efficiently increases (SaO₂) recovery in SR individuals, but not in the FR group. The proposed mechanism is that increased pulmonary pressure with HB will reverse any pulmonary edema and facilitate oxygen uptake in divers with delayed recovery.

We examined the viability of using mean propulsive velocity (MPV) to adjust the load in the countermovement jump (CMJ) at moderate altitude. Twenty-four volunteers were assigned to a 4-week power-oriented resistance training (RT) program in either normoxia (N, 690 m) or intermittent hypobaric hypoxia (IH, 2,320 m). The load was adjusted to maintain execution velocity of CMJ at 1m·s⁻¹ of MPV. Relative peak power output (Prel), and percentage of velocity loss throughout the sets (VL) were determined for each session. The internal load was measured by the rating of perceived exertion (RPE). The absolute load lifted was higher in IH compared to N (75.6 ± 8.4 vs. 58.5 ± 12.3 kg P < 0.001). However, similar relative increases for both groups were found when comparing the final values (IH: 8.2%, P = 0.007; N: 9.8%, P = 0.03) with no changes in VL between groups (P = 0.36). Post-study Prel improved significantly only in IH (+7% W·kg⁻¹, P = 0.002). Mean RPE was greater in IH vs. N (6.8 ± 1.5 vs. 5.6 ± 2, P < 0.001). The MPV seems to be a viable method for adjusting external load during RT at moderate altitude. However, given that RT at moderate altitude increases RPE, it is prudent to monitor internal load when using the MPV to best determine the actual physiological stress of the session.

BACKGROUND: The purpose of this study was to determine the cardiorespiratory demands of standing and wheelchair (seated) fencing in a group of able-bodied fencers during simulated competitive bouts.

METHODS: Participants were ten male able-bodied fencers of regional level with previous training experience in wheelchair fencing. After a standardised warm-up participants performed two series of simulated competitive épée bouts (5 and 15 touches) in a random order, either while standing or while sitting in a wheelchair. Expired gas was analyzed for oxygen consumption (V̇ O2) and respiratory exchange ratio (RER) and heart rate were continually monitored. Energy expenditure (EE) was subsequently calculated.

RESULTS: V̇ O2, HR and EE peak responses were greater during standing than seated fencing (p< .05). Mean V̇ O2 during all ST bouts (5 and 15 touch) was 43% greater than in WC fencing (44.2 ± 7.8 vs. 25.1 ± 5.4 ml·kg-1·min-1). Mean HR during the standing 5 and 15 touch bouts was 91% ± 20% and 84% ± 7% of that recorded during the seated bouts. HR,V̇O2 and EE data also indicated that the 15-touch bouts were more physiologically demanding than the 5-touch bouts (P < .01). The HR-V̇ O2 relationship was similar between both fencing modes. The duration of the 5 and 15 touch bouts were shorter for the seated than the standing bouts (P < .01).

CONCLUSIONS: The physiological demands of wheelchair fencing are lower than those for standing fencing. Furthermore, the physiology of 5 vs. 15 touch bouts, similar to those undertaken in fencing competition, also differs.

A number of competitive water sports are performed while breath-holding (apnea). Such performances put large demands on the anaerobic system, but the study of lactate accumulation in apneic sports is limited. We therefore aimed to determine and compare the net lactate accumulation (NLA) during competition events in six disciplines of competitive freediving (FD) and three disciplines of synchronized swimming (SSW). The FD disciplines were: static apnea (STA; n = 14); dynamic apnea (DYN; n = 19); dynamic apnea no fins (DNF; n = 16); constant weight (CWT; n = 12); constant weight no fins (CNF; n = 8); free immersion (FIM; n =10). The SSW disciplines were solo (n = 21), duet (n = 31) and team (n = 34). Capillary blood lactate concentration was measured before and three minutes after competition performances, and apneic duration and performance variables were recorded. In all nine disciplines NLA was observed. The highest mean (SD) NLA (mmol·L-1) was found in CNF at 6.3 (2.2), followed by CWT at 5.9 (2.3) and SSW solo at 5 (1.9). STA showed the lowest NLA 0.7 (0.7) mmol·L-1 compared to all other disciplines (P ⟨ 0.001). The NLA recorded shows that sports involving apnea involve high levels of anaerobic activity. The highest NLA was related to both work done by large muscle groups and long apneic periods, suggesting that NLA is influenced by both the type of work and apnea duration, with lower NLA in SSW due to shorter apneic episodes with intermittent breathing.

PURPOSE: The assessment of body hydration is a complex process, and no measurement is valid for all situations. Bioelectrical impedance vector analysis (BIVA) has emerged as a relatively novel technique for assessing hydration status in sports. We applied BIVA a) to determine hydration changes evoked by an intense synchronized swimming (SS) training session; b) to characterize the sample of young elite swimmers in relation with a nonathletic reference population; and c) to generate its 50%, 75% and 95% percentiles of the bioelectrical variables.

METHODS: Forty-nine elite SS female swimmers of two age categories, comen (Co: 13.9 ± 0.9 years, n = 34) and junior (Jr: 16.3 ± 0.6 years, n = 15), performed a long, high intensity training session. Body mass (BM) and bioelectrical variables (R, resistance; Xc, reactance; PA, phase angle; and Z, impedance module) were assessed pre- and post-training. BIVA was used to characterize 1) the distribution pattern of the bioelectrical vector (BIA vector) for both age groups, and 2) pre- to post-training BIA vector migration. Bioelectrical variables were also correlated with BM change values.

RESULTS: Most swimmers were mostly located outside the 75% and some beyond the 95% percentile of the bioelectrical tolerance ellipses of the general population. The BIA vector showed statistically significant differences in both Co (T2 = 134.7, p = 0.0001) and Jr (T2 = 126.2, p < 0.001). Both groups were also bioelectrically different (T2 = 17.6, p < 0.001). After the training session, a decrease in BM (p = 0.0001) and an increase in BIA variables (p = 0.01) was observed. BIVA also showed a significant pre-post vector migration both in Co (T2 = 82.1; p < 0.001) and Jr (T2 = 41.8; p < 0.001). No correlations were observed between BM changes and bioelectrical variables.

CONCLUSIONS: BIVA showed specific bioelectrical characteristics in young elite SS athletes. Considering the decrease in BM and the migration of the BIA vector, we conclude that the homeostatic hydration status of these young elite female swimmers was affected by the execution of intense training sessions. From a methodological perspective, BIVA appears to be sensitive enough to detect subtle hydration changes, but further research is needed to ensure its validity and reliability. Moreover, these findings highlight the importance of ensuring adequate fluid intake during training in young SS athletes.