A flow resistive inspiratory muscle training mask worn during high-intensity interval training does not improve 5 km running time-trial performance.

PURPOSE: There is little evidence of the ergogenic effect of flow-resistive masks worn during exercise. We compared a flow-resistive face mask (MASK) worn during high-intensity interval training (HIIT) against pressure threshold loading inspiratory muscle training (IMT). METHODS: 23 participants (13 males) completed a 5 km time trial and six weeks of HIIT (3 sessions weekly). HIIT (n = 8) consisted of repeated work (2 min) at the speed equivalent to 95% [Formula: see text]O2 peak with equal rest. Repetitions were incremental (six in weeks 1, 2 and 6, eight in weeks 3 and 4 and ten in week 5). Participants were allocated to one of three training groups. MASK (n = 8) wore a flow-resistive mask during all sessions. The IMT group (n = 8) completed 2 × 30 breaths daily at 50% maximum inspiratory pressure (PImax). A control group (CON, n = 7) completed HIIT only. Following HIIT, participants completed two 5 km time trials, the first matched identically to pre-intervention trial (ISO time), and a self-paced effort. RESULTS: Time trial performance was improved in all groups (MASK 3.1 ± 1.7%, IMT, 5.7 ± 1.5% and CON 2.6 ± 1.0%, p < 0.05). IMT improved greater than MASK and CON (p = 0.004). Post intervention, PImax and diaphragm thickness were improved in IMT only (32% and 9.5%, respectively, p = 0.003 and 0.024). CONCLUSION: A flow-resistive mask worn during HIIT provides no benefit to 5 km performance when compared to HIIT only. Supplementing HIIT with IMT improves respiratory muscle strength, morphology and performance greater than HIIT alone.

Functional training of the inspiratory muscles improves load carriage performance.

Inspiratory Muscle Training (IMT) whilst adopting body positions that mimic exercise (functional IMT; IMTF) improves running performance above traditional IMT methods in unloaded exercise. We investigated the effect of IMTF during load carriage tasks. Seventeen males completed 60 min walking at 6.5 km·h-1 followed by a 2.4 km load carriage time-trial (LCTT) whilst wearing a 25 kg backpack. Trials were completed at baseline; post 4 weeks IMT (consisting of 30 breaths twice daily at 50% of maximum inspiratory pressure) and again following either 4 weeks IMTF (comprising four inspiratory loaded core exercises) or maintenance IMT (IMTCON). Baseline LCTT was 15.93 ± 2.30 min and was reduced to 14.73 ± 2.40 min (mean reduction 1.19 ± 0.83 min, p < 0.01) after IMT. Following phase two, LCTT increased in IMTF only (13.59 ± 2.33 min, p < 0.05) and was unchanged in post-IMTCON. Performance was increased following IMTF, providing an additional ergogenic effect beyond IMT alone. Practitioner Summary: We confirmed the ergogenic benefit of Inspiratory Muscle Training (IMT) upon load carriage performance. Furthermore, we demonstrate that functional IMT methods provide a greater performance benefit during exercise with thoracic loads. Abbreviations: [Lac-]B: blood lactate; FEV1: forced expiratory volume in one second; FEV1/FVC: forced expiratory volume in one second/forced vital capacity ratio; FVC: forced vital capacity; HR: heart rate; IMT: inspiratory muscle training; IMTCON: inspiratory muscle training maintenance; IMTF: functional inspiratory muscle training; LC: load carriage; LCTT: load carriage time trial; Pdi: transdiaphragmatic pressure; PEF: peak expiratory flow; PEmax: maximum expiratory mouth pressure; PImax: maximum inspiratory mouth pressure; RPE: rating of perceived exertion; RPEbreating: rating of perceived exertion for the breathing; RPEleg: rating of perceived exertion for the legs; SEPT: sport-specific endurance plank test; V̇ O2: oxygen consumption; V̇ O2peak: peak oxygen consumption.

Impact of Weekly Swimming Training Distance on the Ergogenicity of Inspiratory Muscle Training in Well-Trained Youth Swimmers.

Lomax, M, Kapus, J, Brown, PI, and Faghy, M. Impact of weekly swimming training distance on the ergogenicity of inspiratory muscle training in well-trained youth swimmers. J Strength Cond Res 33(8): 2185-2193, 2019-The aim of this study was to examine the impact of weekly swimming training distance on the ergogenicity of inspiratory muscle training (IMT). Thirty-three youth swimmers were recruited and separated into a LOW and HIGH group based on weekly training distance (≤31 km·wk and >41 km·wk, respectively). The LOW and HIGH groups were further subdivided into control and IMT groups for a 6-week IMT intervention giving a total of 4 groups: LOWcon, LOWIMT, HIGHcon, and HIGHIMT. Before and after the intervention period, swimmers completed maximal effort 100- and 200-m front crawl swims, with maximal inspiratory and expiratory mouth pressures (PImax and PEmax, respectively) assessed before and after each swim. Inspiratory muscle training increased PImax (but not PEmax) by 36% in LOWIMT and HIGHIMT groups (p ≤ 0.05), but 100- and 200-m swims were faster only in the LOWIMT group (3 and 7% respectively, p ≤ 0.05). Performance benefits only occurred in those training up to 31 km·wk and indicate that the ergogenicity of IMT is affected by weekly training distance. Consequently, training distances are important considerations, among others, when deciding whether or not to supplement swimming training with IMT.

Active recovery strategy and lactate clearance in elite swimmers.

BACKGROUND: Swimming requires sustained high performance, with limited recovery between heats, recovery strategies are essential to performance but are often self-regulated and sub-optimal. Accordingly, we investigated a physiologically determined recovery protocol. METHODS: Fifteen (m=9, f=6) international junior age group swimmers participated in this study. The average age of the participants was 15.8±1.5 years. All participants completed a lactate elevation protocol (8 x 50 m sprints), followed by one of three recovery strategies: 1) velocity at lactate threshold (VLT); 2) coach prescribed protocol (COA); and 3) national governing body recommendations (NGB) and thereafter a 200-m time trial. RESULTS: [lac-]B was similar between trials at baseline (pooled data: 1.3±0.4 mmol.l-1, P>0.05) but increased following 8x50 m sprints (pooled data 9.5±3.5 mmol.l-1, P<0.05) and reduced in all conditions (mean reduction 6.4±1.7 mmol.l-1). [lac-]B remained elevated following NGB (5.6±0.8 mmol.l-1, P<0.05) compared with COA (2.3±1.7 mmol.l-1) and VLT (1.7±1.2 mmol.l-1) but was blunted during the 200-m time trial in VLT (6.4±1.7 mmol.l-1, P<0.05). Time trial performance was similar between trials; VLT (2.24±0.12 min), COA (2.23±0.14 min) and NGB (2.22±0.13 min, P>0.05). CONCLUSIONS: Despite similar performance, individually prescribed recovery strategy with a physiological basis will preserve repeated exercise performance performed on the same day.

Whole-body active warm-up and inspiratory muscle warm-up do not improve running performance when carrying thoracic loads.

Whole-body active warm-ups (AWU) and inspiratory muscle warm-up (IMW) prior to exercise improves performance on some endurance exercise tasks. This study investigated the effects of AWU with and without IMW upon 2.4-km running time-trial performance while carrying a 25-kg backpack, a common task and backpack load in physically demanding occupations. Participants (n = 9) performed five 2.4-km running time-trials with a 25-kg thoracic load preceded in random order by (i) IMW comprising 2 × 30 inspiratory efforts against a pressure-threshold load of 40% maximal inspiratory pressure (PImax), (ii) 10-min unloaded running (AWU) at lactate turnpoint (10.33 ± 1.58 km·h-1), (iii) placebo IMW (PLA) comprising 5-min breathing using a sham device, (iv) AWU+IMW, and (v) AWU+PLA. Pooled baseline PImax was similar between trials and increased by 7% and 6% following IMW and AWU+IMW (P < 0.05). Relative to baseline, pooled PImax was reduced by 9% after the time-trial, which was not different between trials (P > 0.05). Time-trial performance was not different between any trials. Whole-body AWU and IMW performed alone or combination have no ergogenic effect upon high-intensity, short-duration performance when carrying a 25-kg load in a backpack.

Effects of load mass carried in a backpack upon respiratory muscle fatigue.

PURPOSE: The purpose of this study was to investigate whether loads carried in a backpack, with a load mass ranging from 0 to 20 kg, causes respiratory muscle fatigue. METHODS: Eight males performed four randomised load carriage (LC) trials comprising 60 min walking at 6.5 km h(-1) wearing a backpack of either 0 (LC0), 10 (LC10), 15 (LC15) or 20 kg (LC20). Inspiratory (PImax) and expiratory (PEmax) mouth pressures were assessed prior to and immediately following each trial. Pulmonary gas exchange, heart rate (HR), blood lactate and glucose concentration and perceptual responses were recorded during the first and final 60 s of each trial. RESULTS: Group mean PImax and PEmax were unchanged following 60-min load carriage in all conditions (p > .05). There was an increase over time in pulmonary gas exchange, HR and perceptions of effort relative to baseline measures during each trial (p < .05) with changes not different between trials (p > .05). CONCLUSIONS: These findings indicate that sub-maximal walking with no load or carrying 10, 15 or 20 kg in a backpack for up to 60 min does not cause respiratory muscle fatigue despite causing an increase in physiological, metabolic and perceptual parameters.

Training the inspiratory muscles improves running performance when carrying a 25†kg thoracic load in a backpack.

Load carriage (LC) exercise in physically demanding occupations is typically characterised by periods of low-intensity steady-state exercise and short duration, high-intensity exercise while carrying an external mass in a backpack; this form of exercise is also known as LC exercise. This induces inspiratory muscle fatigue and reduces whole-body performance. Accordingly we investigated the effect of inspiratory muscle training (IMT, 50% maximal inspiratory muscle pressure (PImax) twice daily for six week) upon running time-trial performance with thoracic LC. Nineteen healthy males formed a pressure threshold IMT (n = 10) or placebo control group (PLA; n = 9) and performed 60 min LC exercise (6.5 km h(-1)) followed by a 2.4 km running time trial (LCTT) either side of a double-blind six week intervention. Prior to the intervention, PImax was reduced relative to baseline, post-LC and post-LCTT in both groups (pooled data: 13 ± 7% and 16 ± 8%, respectively, p < .05) and similar changes were observed post-PLA. Post-IMT only, resting PImax increased +31% (p < .05) and relative to pre-IMT was greater post-LC (+19%) and post-LCTT (+18%, p < .05), however, the relative reduction in PImax at each time point was unchanged (13 ± 11% and 17 ± 9%, respectively, p > .05). In IMT only, heart rate and perceptual responses were reduced post-LC (p < .05). Time-trial performance was unchanged post-PLA and improved 8 ± 4% after IMT (p < .05). In summary, when wearing a 25 kg backpack, IMT attenuated the cardiovascular and perceptual responses to steady-state exercise and improved high-intensity time-trial performance which we attribute in part to reduced relative work intensity of the inspiratory muscles due to improved inspiratory muscle strength. These findings have real-world implications for occupational contexts.

Preloaded time trial to assess load carriage performance.

The relevance and importance of load carriage in recreational and occupational tasks has stimulated a large body of research. Exercise protocols have been criticized for a lack of relevance to occupational activities; accordingly, the aim of this study was to assess the reliability of a preloaded time-trial protocol for load carriage assessment. After full familiarization, 8 healthy males performed 2 trials separated by 1 week. Each trial comprised 60-minute walking at 6.5 km·h and 0% gradient (LC), 15 minutes seated recovery followed by a 2.4-km time-trial (LCTT). All trials were performed wearing a 25-kg backpack. Performance time was 16.71 ± 1.82 minutes and 16.37 ± 1.78 minutes for LCTT 1 and 2, respectively with a mean difference of -0.34 ± 0.89 minutes. Using log ratio limits of agreement, the mean bias was 1.02 and random error component of the agreement ratio was 1.11. The intraclass correlation was 0.85, coefficient of variation was 10.5%, and Cohen's d was 0.35. The protocol demonstrated a very good level of reliability. We present a novel and reliable preloaded time-trial protocol that more closely reflects operational activities and can be used to quantify load carriage performance. This protocol provides greater ecologically validity regarding physical demands of load carriage activities than those adopted previously and provides an excellent tool for the strength and conditioning practitioner to assess individual load carriage performance.

Determinants of inspiratory muscle strength in healthy humans.

We investigated (1) the relationship between the baseline and inspiratory muscle training (IMT) induced increase in maximal inspiratory pressure (P(I,max)) and (2) the relative contributions of the inspiratory chest wall muscles and the diaphragm (P(oes)/P(di)) to P(I,max) prior to and following-IMT. Experiment 1: P(I,max) was assessed during a Müeller manoeuvre before and after 4-wk IMT (n=30). Experiment 2: P(I,max) and the relative contribution of the inspiratory chest wall muscles to the diaphragm (P(oes)/P(di)) were assessed during a Müeller manoeuvre before and after 4-wk IMT (n=20). Experiment 1: P(I,max) increased 19% (P<0.01) post-IMT and was correlated with baseline P(I,max) (r=-0.373, P<0.05). Experiment 2: baseline P(I,max) was correlated with P(oe)/P(di) (r=0.582, P<0.05) and after IMT PI,max increased 22% and Poe/Pdi increased 5% (P<0.05). In conclusion, baseline P(I,max) and the contribution of the chest wall inspiratory muscles relative to the diaphragm affect, in part, baseline and IMT-induced P(I,max). Great care should be taken when designing future IMT studies to ensure parity in the between-subject baseline P(I,max).

Thoracic load carriage-induced respiratory muscle fatigue.

PURPOSE: We investigated the effect of carrying a 25 kg backpack upon exercise-induced respiratory muscle fatigue, pulmonary function and physiological and perceptual responses to exercise. METHODS: Nineteen healthy males performed 60 min walking at 6.5 km h(-1) and 0 % gradient with a 25 kg backpack (load carriage; LC). Following 15 min recovery participants then completed a 2.4 km time trial with the load (LCTT) and on a different day, repeated the trials without the load [control trial (CON) and control time trial (CONTT), respectively]. Respiratory muscle fatigue was determined by the transient change in maximal inspiratory (P Imax) and expiratory (P Emax) pressure prior to and immediately following exercise. RESULTS: P Imax and P Emax were reduced from baseline by 11 and 13 % (P < 0.05), respectively, post-LC but remained unchanged post-CON. Following the time trial P Imax and P Emax were reduced 16 and 19 %, respectively, post-LCTT (P < 0.05) and by 6 and 10 %, respectively (P < 0.05), post-CONTT compared to baseline. Both forced vital capacity and forced expiratory volume in 1 s were reduced by 4 ± 13 and 1 ± 9 %, respectively, during LC when compared to CON. Relative to CON all physiological and perceptual responses were greater in LC, both post-LC and -LCTT (P < 0.01). Time trial performance was faster during CONTT (11.08 ± 1.62 min) relative to LCTT (15.93 ± 1.91 min; P < 0.05). CONCLUSION: This study provides novel evidence that constant speed walking and time trial exercise with 25 kg thoracic load carriage induces significant inspiratory and expiratory muscle fatigue and may have important performance implications in some recreational and occupational settings.

Prior upper body exercise reduces cycling work capacity but not critical power.

PURPOSE: This study examined whether metabolite accumulation, induced by prior upper body exercise, affected the power-duration relationship for leg cycle ergometry. METHODS: Seven males performed, to the limit of tolerance and both without (L) and with (AL) prior severe-intensity arm-cranking exercise, an incremental cycling test and four constant power cycling tests to determine the parameters of the power-duration relationship: critical power (CP) and W'. RESULTS: At the onset of cycling exercise plasma lactate (L vs AL: 1.2 ± 0.1 vs 11.6 ± 2.9 mEq · L) and hydrogen ion (40.4 ± 1.3 vs 53.1 ± 4.3 nEq · L), concentrations were higher during AL compared with L, whereas the strong ion difference (37.8 ± 1.8 vs 32.4 ± 2.0 mEq · L) and bicarbonate concentration (25.7 ± 0.7 vs 18.3 ± 1.9 mEq · L) were lower during AL compared with L (P < 0.01). During incremental exercise, maximum cycling power (358 ± 15 vs 332 ± 21 W) and peak oxygen uptake (VO2peak) (4.31 ± 0.36 vs 3.71 ± 0.44 L · min) were lower during AL compared with L (P < 0.05). The rate of increase in plasma potassium concentration during constant power cycling was greater during AL compared with L (0.09 ± 0.08 vs 0.14 ± 0.13 mEq · L · min) (P < 0.05), and exercise duration was 35 ± 15% shorter (P < 0.01). CP was not different between L and AL (267 ± 19 vs 264 ± 20 W), whereas W' was lower in AL (17.3 ± 5.7 vs 11.8 ± 4.2 kJ) (P < 0.01). CONCLUSION: The reduced W' after prior upper body exercise indicates that the magnitude of W' is partly dependent on metabolite accumulation.

Ventilatory muscle strength, diaphragm thickness and pulmonary function in world-class powerlifters.

PURPOSE: Resistance training activates the ventilatory muscles providing a stimulus similar to ventilatory muscle training. We examined the effects of elite powerlifting training upon ventilatory muscle strength, pulmonary function and diaphragm thickness in world-class powerlifters (POWER) and a control group (CON) with no history of endurance or resistance training, matched for age, height and body mass. METHODS: Body composition was assessed using single-frequency bioelectrical impedance. Maximal static volitional inspiratory (P(I,max)) and expiratory (P(E,max)) mouth pressures, diaphragm thickness (T(di)) derived from ultrasound measurements and pulmonary function from maximal flow volume loops were measured. RESULTS: There were no differences in physical characteristics or pulmonary function between groups. P(I,max) (22 %, P < 0.05, effect size d = 1.13), P(E,max) (16 %, P = 0.07, effect size d = 0.86) and T(di) (27 %, P < 0.01, effect size d = 1.59) were greater in POWER than CON. Correlations were observed between both T(di) and P(I,max) (r = 0.518, P < 0.05), T(di) and P(E,max) (r = 0.671, P < 0.01) and T(di) and body mass (r = 0.502, P < 0.05). CONCLUSIONS: We conclude that manoeuvres performed by world-class powerlifters improve ventilatory muscle strength and increases diaphragm size. Whole-body resistance training may be an appropriate training mode to attenuate the effects of ventilatory muscle weakness experienced with ageing and some disease states.

Respiratory-related limitations in physically demanding occupations.

Respiratory muscle work limits high-intensity exercise tolerance in healthy human beings. Emerging evidence suggests similar limitations exist during submaximal work in some physically demanding occupations. In an occupational setting, heavy loads are routinely carried upon the trunk in the form of body armor, backpacks, and/or compressed air cylinders by military, emergency service, and mountain rescue personnel. This personal and respiratory protective equipment impairs respiratory muscle function and increases respiratory muscle work. More specifically, thoracic load carriage induces a restrictive ventilatory limitation which increases the elastic work of breathing, rendering the respiratory muscles vulnerable to fatigue and inducing a concomitant reduction in exercise tolerance. Similarly, breathing apparatus worn by occupational personnel, including fire fighters and military and commercial divers, increases the inspiratory elastic and expiratory resistive work of breathing, precipitating significant inspiratory and expiratory muscle fatigue and a reduction in exercise tolerance. An argument is presented that the unique respiratory challenges encountered in some occupational settings require further research, since these may affect the operational effectiveness and the health and safety of personnel working in physically demanding occupations.

Inspiratory muscle training abolishes the blood lactate increase associated with volitional hyperpnoea superimposed on exercise and accelerates lactate and oxygen uptake kinetics at the onset of exercise.

We examined the effects of inspiratory muscle training (IMT) upon volitional hyperpnoea-mediated increases in blood lactate ([lac(-)](B)) during cycling at maximal lactate steady state (MLSS) power, and blood lactate and oxygen uptake kinetics at the onset of exercise. Twenty males formed either an IMT (n = 10) or control group (n = 10). Prior to and following a 6-week intervention, two 30 min trials were performed at MLSS (207 ± 28 W), determined using repeated 30 min constant power trials. The first was a reference trial, whereas during the second trial, from 20 to 28 min, participants mimicked the breathing pattern commensurate with 90% of the maximal incremental exercise test minute ventilation ([Formula: see text]). Prior to the intervention, the MLSS [lac(-)](B) was 3.7 ± 1.8 and 3.9 ± 1.6 mmol L(-1) in the IMT and control groups, respectively. During volitional hyperpnoea, [Formula: see text] increased from 79.9 ± 9.5 and 76.3 ± 15.4 L min(-1) at 20 min to 137.8 ± 15.2 and 135.0 ± 19.7 L min(-1) in IMT and control groups, respectively; [lac(-)](B) concurrently increased by 1.0 ± 0.6 (+27%) and 0.9 ± 0.7 mmol L(-1) (+25%), respectively (P < 0.05). Following the intervention, maximal inspiratory mouth pressure increased 19% in the IMT group only (P < 0.01). Following IMT only, the increase in [lac(-)](B) during volitional hyperpnoea was abolished (P < 0.05). In addition, the blood lactate (-28%) and phase II oxygen uptake (-31%) kinetics time constants at the onset of exercise and the MLSS [lac(-)](B) (-15%) were reduced (P < 0.05). We attribute these changes to an IMT-mediated increase in the oxidative and/or lactate transport capacity of the inspiratory muscles.

Health, fitness, and responses to military training of officer cadets in a Gulf Cooperation Council country.

OBJECTIVE: To quantify the health, fitness, and physiological responses to military training of Officer Cadets from a Gulf Cooperation Council country. METHODS: One hundred and nineteen Officer Cadets volunteered; body composition, core body temperature, aerobic fitness, hydration status (urine osmolality), cardiovascular strain, physical activity (3-dimensional accelerometry), and energy expenditure (doubly labelled water) were measured over 5-days of Basic Training (BT), Army Training (AT), Navy Training (NT), and Air Force Training (AFT). RESULTS: There were no differences between courses for body mass index (mean all courses: 24.1 +/- 4.1 kg x m2) or peak core body temperature (mean all courses: 38.1 +/- 0.4 degrees C) (p > 0.05). AT body fat (19.8 +/- 3.6%) and BT VO2 max (36.8 +/- 11.6 mL x kg(-1) x min(-1)) were lower than the other courses (BT, 26.1 +/- 8.1; NT, 26.0 +/- 6.0; AFT, 24.7 +/- 6.1%) and (AT, 44.8 +/- 9.6; NT, 45.0 +/- 7.5; AFT, 44.6 +/- 5.2 mL x kg(-1) x min(-1)), respectively (p < 0.05). NT urine osmolality (979 +/- 90 mOsmol x kg(-1)) was similar to BT (946 +/- 181 mOsmol x kg(-1) p > 0.05) but lower in AT (868 +/- 144 mOsmol x kg(-1), p < 0.05) and AFT (883 +/- 121 mOsmol x kg(-1), p < 0.05). Cardiovascular strain during NT (22 +/- 5% HRR) was lower than other courses (range, 25 +/- 4-29 +/- 3% Heart Rate Reserve) (p < 0.05). Physical activity level during AFT (1.70 +/- 0.18 AU) was lower than other courses (range, 1.86 +/- 0.21-1.92 +/- 0.18 AU) (p > 0.05). CONCLUSION: Positive developments were apparent from BT leading into other courses. Potential exists to increase physical training volume on all courses, which may improve participants' aerobic fitness, body composition, and health.

Influence of hydration volume and ambient temperature on physiological responses while wearing CBRN protective clothing.

This study examined a low (L; 5 ml/kg per h) and high (H, 10 ml/kg per h) rate of fluid replacement in moderate (18°C) and hot (30°C) conditions on physiological responses while wearing personal protective equipment (PPE). PPE included the gas-tight suit (GTS), the powered respirator protective suit (PRPS) and the civil responder 1 (CR1). Relative to the moderate condition, physiological responses were greater in the hot condition. The percentage change in body mass was different (p < 0.05) between L and H in the hot (L vs. H, GTS: -0.83 vs. -0.38%; PRPS: -1.18 vs. -0.71%; CR1: -1.62 vs. -0.57%) and moderate conditions, although in GTS and CR1 body mass increased (L vs. H, GTS: -0.48 vs. 0.06%; PRPS: -0.66 vs. -0.11%; CR1: -0.18 vs. 0.67%). Fluid replacement strategies for PPE should be adjusted for environmental conditions in order to avoid >1% body mass loss and/or net body mass gain. STATEMENT OF RELEVANCE: Currently, the UK Emergency Services do not have specific evidence-based fluid replacement guidelines to follow when wearing chemical, biological, radiological and/or nuclear (CBRN) PPE. Although ad libitum fluid replacement is encouraged (when breathing apparatus permits), recommendations from evidence-based findings specific to different PPE and to different environmental conditions are lacking. This study provides novel evidence supporting the need to develop fluid replacement strategies during CBRN deployments in both moderate and hot environmental conditions for CBRN PPE.

Loading of trained inspiratory muscles speeds lactate recovery kinetics.

PURPOSE: The purpose of this study was to investigate the effects of inspiratory threshold loading (ITL) and inspiratory muscle training (IMT) on blood lactate concentration ([lac(-)]B) and acid-base balance after maximal incremental cycling. METHODS: Eighteen subjects were divided into a control (n = 9) or an IMT group (n = 9). Before and after a 6-wk intervention, subjects completed two maximal incremental cycling tests followed by 20 min of recovery with (ITL) or without (passive recovery (PR)) a constant inspiratory resistance (15 cm H2O). The IMT group performed 6 wk of pressure threshold IMT at 50% maximal inspiratory mouth pressure. Throughout recovery, acid-base balance was quantified using the physicochemical approach by measuring the strong ion difference ([SID] = [Na+] + [K+] - [Cl-] + [lac-]), the total concentration of weak acids ([Atot-]), and the partial pressure of carbon dioxide (PCO2). RESULTS: After the intervention, maximal inspiratory mouth pressure increased in the IMT group only (+34%). No differences in lactate clearance were observed between PR and ITL before the intervention in both groups and after the intervention in the control group. After IMT, relative to PR, [lac-]B was reduced throughout ITL (minutes 2-20) by 0.66 +/- 1.28 mmol x L(-1) (P < 0.05), and both the fast (lactate exchange) and the slow (lactate clearance) velocity constants of the lactate recovery kinetics were increased (P < 0.05). Relative to pre-IMT, ITL reduced plasma [H], which was accounted for by an IMT-mediated increase in [SID] due almost exclusively to a 1.7-mmol x L(-1) reduction in [lac-]B. CONCLUSIONS: After maximal exercise, ITL affected lactate recovery kinetics only after IMT. Our data support the notion that the inspiratory muscles are capable of lactate clearance that increases [SID] and reduces [H+]. These effects may facilitate subsequent bouts of high-intensity exercise.

Inspiratory muscle training reduces blood lactate concentration during volitional hyperpnoea.

Although reduced blood lactate concentrations ([lac(-)](B)) have been observed during whole-body exercise following inspiratory muscle training (IMT), it remains unknown whether the inspiratory muscles are the source of at least part of this reduction. To investigate this, we tested the hypothesis that IMT would attenuate the increase in [lac(-)](B) caused by mimicking, at rest, the breathing pattern observed during high-intensity exercise. Twenty-two physically active males were matched for 85% maximal exercise minute ventilation (.V(E) max) and divided equally into an IMT or a control group. Prior to and following a 6 week intervention, participants performed 10 min of volitional hyperpnoea at the breathing pattern commensurate with 85% .V(E) max. The IMT group performed 6 weeks of pressure-threshold IMT; the control group performed no IMT. Maximal inspiratory mouth pressure increased (mean +/- SD) 31 +/- 22% following IMT and was unchanged in the control group. Prior to the intervention in the control group, [lac(-)](B) increased from 0.76 +/- 0.24 mmol L(-1) at rest to 1.50 +/- 0.60 mmol L(-1) (P < 0.05) following 10 min volitional hyperpnoea. In the IMT group, [lac(-)](B) increased from 0.85 +/- 0.40 mmol L(-1) at rest to 2.02 +/- 0.85 mmol L(-1) following 10 min volitional hyperpnoea (P < 0.05). After 6 weeks, increases in [lac(-)](B) during volitional hyperpnoea were unchanged in the control group. Conversely, following IMT the increase in [lac(-)](B) during volitional hyperpnoea was reduced by 17 +/- 37% and 25 +/- 34% following 8 and 10 min, respectively (P < 0.05). In conclusion, increases in [lac(-)](B) during volitional hyperpnoea at 85% .V(E) max were attenuated following IMT. These findings suggest that the inspiratory muscles were the source of at least part of this reduction, and provide a possible explanation for some of the IMT-mediated reductions in [lac(-)](B), often observed during whole-body exercise.

The effect of warm-up on high-intensity, intermittent running using nonmotorized treadmill ergometry.

The aim of this study was to investigate the effect of previous warming on high-intensity intermittent running using nonmotorized treadmill ergometry. Ten male soccer players completed a repeated sprint test (10 x 6-second sprints with 34-second recovery) on a nonmotorized treadmill preceded by an active warm-up (10 minutes of running: 70% VO2max; mean core temperature (Tc) 37.8 +/- 0.2 degrees C), a passive warm-up (hot water submersion: 40.1 +/- 0.2 degrees C until Tc reached that of the active warm-up; 10 minutes +/- 23 seconds), or no warm-up (control). All warm-up conditions were followed by a 10-minute static recovery period with no stretching permitted. After the 10-minute rest period, Tc was higher before exercise in the passive trial (38.0 +/- 0.2 degrees C) compared to the active (37.7 +/- 0.4 degrees C) and control trials (37.2 +/- 0.2 degrees C; p < 0.05). There were no differences in pre-exercise oxygen consumption and blood lactate concentration; however, heart rate was greater in the active trial (p < 0.05). The peak mean 1-second maximum speed (MxSP) and group mean MxSP were not different in the active and passive trials (7.28 +/- 0.12 and 7.16 +/- 0.10 m x s(-1), respectively, and 7.07 +/- 0.33 and 7.02 +/- 0.24 m x s(-1), respectively; p > 0.05), although both were greater than the control. The percentage of decrement in performance fatigue was similar between all conditions (active, 3.4 +/- 1.3%; passive, 4.0 +/- 2.0%; and control, 3.7 +/- 2.4%). We conclude that there is no difference in high-intensity intermittent running performance when preceded by an active or passive warm-up when matched for post-warm-up Tc. However, repeated sprinting ability is significantly improved after both active and passive warm-ups compared to no warm-up.