The effect of critical speed and exercise intensity on stroke phase duration and bilateral asymmetry in 200-m front crawl swimming.

The main aim of this study was to determine the absolute temporal relationship between the power and recovery phases of the stroke cycle in front crawl swimming in response to progressive changes in exercise intensity that occurred before and after critical speed. A second objective was to determine whether intensity-related changes in the power/recovery phase relationship affects the bilateral symmetry of the stroke. Stroke parameters were recorded for each 25-m length during a progressive 200-m interval training set, in which eight (2 males, 6 females) national-level swimmers swam at intensities below, above, and at critical speed. The results demonstrated that substantial increases in stroke rate (P < 0.01) occurred at critical speed, and that these increases were related to a greater decrease in the duration of the power phase than the recovery phase (P < 0.01). The results also show that the degree of bilateral asymmetry was greater for the power phase than the recovery phase, and was inversely related to intensity in both phases of the stroke cycle. The findings of this study suggest that critical speed-related increases in stroke rate are an indirect consequence of increased force production in the power phase of the stroke, and that bilateral asymmetry is both intensity- and stroke-phase dependent.

The influence of periodized resistance training on strength changes in men and women.

The purpose of this study was to contrast the response of previously resistance-trained male and female recreational athletes with a traditionally periodized resistance training program. Sixty subjects (age = 22.8 ± 4.5 years) were assigned to 3 groups: male training (MT), n = 20; female training (FT), n = 20; and control, n = 20 (men, n = 10; women, n = 10). The MT and FT groups completed 12 weeks of traditional periodized strength training, with strength testing at baseline and at weeks 8 and 12. The training programs were identical (e.g., rest time, exercises, volume, and intensity) in both groups. In weeks 1 and 2, the FT and MT groups were trained 3 d·wk (324 repetitions [reps]·wk) and thereafter 4 d·wk (mean 642 reps·wk). The mean volume and intensity over the 12 weeks was 571 reps·wk and 69.7% of 1 repetition maximum. Results indicated that the men were significantly (p ≤ 0.05) stronger in absolute terms at baseline and at weeks 8 and 12. The FT group (increase = 26.2% at week 8 and 38.1% at week 12) made significantly (p ≤ 0.05) greater percent increases in strength than the MT group (increase = 17.7% at week 8 and 28.0% at week 12). The FT and MT groups made significant (p ≤ 0.05) changes in relative strength at all time points, but the MT group demonstrated greater relative strength on lateral pull-down and dumbbell shoulder press. In practical terms, the men were absolutely stronger than the women, but the women were more responsive to the periodized resistance training program. Twelve weeks of traditionally periodized resistance training induced meaningful strength gains in women (≥ 30%) and men (≥ 25%) with prior (approximately 11 months) nonperiodized resistance training experience.

The influence of periodized resistance training on recreationally active males with chronic nonspecific low back pain.

The most common musculoskeletal health issue is chronic nonspecific low back pain (CLBP). CLBP increases pain and disability, which reduces quality of life (QoL). Generally, pain, disability, and QoL are improved with a moderate volume and intensity of physical activity. Recently, periodized resistance training (PRT) was shown to be effective at improving CLBP in sedentary young, middle-age, and older adults. The purpose of this study was to determine if PRT would increase strength, reduce pain and disability, and improve QoL in recreationally active, moderately trained middle- and older-age males. Forty-five male subjects were divided according to age into 1 of 3 groups: (a) middle-age exercise (ME), (b) old-age exercise (OE), or (c) control (C). All subjects suffered from CLBP and were considered to be moderately trained, participating in recreational ice hockey for 60 minutes, 2 times per wk(-1) for ∼5 months/year along with other recreational activities. The study ran for 16 weeks (3-week familiarization and 13 weeks of testing and PRT) with 5 repetition maximum testing at baseline and weeks 8 and 12. The PRT program systematically and progressively overloaded all major muscle groups (whole-body workout). The results indicate that middle- and old-age recreationally active males with CLBP respond similarly in magnitude to PRT, with improvements in all outcome measures (strength, pain, disability, QoL) across all time points of the study. Clinical significance (≥ 25%) in outcome measures was reached on most variables for the ME and OE groups. The results suggest that PRT may be effectively applied as rehabilitation for moderately trained recreational athletes with CLBP.

A comparison of traditional and weekly undulating periodized strength training programs with total volume and intensity equated.

The purpose of this study was to compare the training adaptations attained during 12 weeks of traditional (TD) and weekly undulating (WUD) periodized strength training. Forty-two recreationally active men (age = 22 ± 2.3 years) were randomly assigned to 1 of 3 groups: control (C) (n = 14), TD (n = 14), or WUD (n = 14). Ten-repetition maximum (10RM) laboratory testing was carried out for the free weight back squat and the free weight flat bench press at baseline, week 8, and week 12. The subjects trained 3 d·wk (approximately 135 min·wk) from weeks 1 to 2 and 4 d·wk from week 3 to week 12 (approximately 180 min·wk). The TD and WUD groups trained using a periodized strength program with all program variables controlled (e.g., volume and intensity). The independent variable was the manipulation of intensity. The TD group used a linear increase in intensity, whereas the WUD group had a varied intensity. The results showed that both the TD and WUD groups made significant (p ≤ 0.05) increases in strength at weeks 8 and 12, but by week 12, the TD group was significantly (p ≤ 0.05) stronger than the WUD group. These results indicate that TD periodization with a linear increase in intensity was more effective at eliciting strength gains than WUD periodization with a varied intensity. The differences in strength gains between the TD and WUD groups may be related to extended periods of muscle soreness and fatigue that were present in the WUD group but not in the TD group. Thus, during long-term training, individuals may benefit more from TD periodized programs because there may be less muscle soreness and fatigue to disrupt practice and training.

The response of persons with chronic nonspecific low back pain to three different volumes of periodized musculoskeletal rehabilitation.

Chronic nonspecific low back pain (CLBP) is a common musculoskeletal health issue associated with pain and disability reduced quality of life (QoL). Pain initiates a fear-avoidance cycle, which needs to be broken if rehabilitation is to work. To break this cycle, exercise must be gradual and focused on strengthening the weakened musculature. Recently, periodized resistance training was effectively used as a musculoskeletal rehabilitation for adults with CLBP. The purpose of this study was to determine if the volume of periodized musculoskeletal rehabilitation (PMR) influences strength, pain, disability, and QoL in untrained persons. Subjects (n = 240) were age and sex matched, with attempts made to match on strength and pain, and randomly assigned to groups after baseline testing: (a) 4 days per week (4D; n = 60), (b) 3 days per week (3D; n = 60) (c), 2 days per week (2D; n = 60) training volume or control (C; n = 60) with no training. The PMR program progressively overloaded muscle groups, with mean training volumes of 4D (1,563 repetitions [reps] per week), 3D (1,344 reps per week), and 2D (564 reps per week). Three weeks of familiarization and 13 weeks of PMR were employed. The 4D training volume significantly (p ≤ 0.05) outperformed all other training volumes by weeks 9 and 13. However, all training volumes made significant (p ≤ 0.05) improvements in strength, pain, disability, and QoL across time. The effect sizes (ESs) associated with the group means of the outcome measures ranged from moderate to strong, with the 4D training volume consistently demonstrating the largest ESs. The 4D training volume is most effective at treating CLBP. Periodization cannot only be applied to athlete training but also to the rehabilitation setting.

A comparison of two forms of periodized exercise rehabilitation programs in the management of chronic nonspecific low-back pain.

The purpose of this study was to determine the influence of 2 different periodized exercise rehabilitation programs (resistance training [RT] and aerobic training [AT]) on musculoskeletal health, body composition, pain, disability, and quality of life (QOL) in chronic (>or=3 months; >or=3 d.wk) nonspecific low-back pain (CLBP) persons. Twenty-seven CLBP subjects were randomly assigned to 1 of 3 groups, 1) RT (n = 9), 2) AT (n = 9), or 3) control (C; n = 9). Subjects were tested at baseline and at weeks 8 and 16 of training. Intensity and volume were periodized in the training groups. Significance was set at p

Relationship between erector spinae muscle oxygenation via in vivo near infrared spectroscopy and static endurance time in healthy males.

The purpose of the study was to confirm the trends in right and left side muscle blood volume (Mbv) and muscle oxygenation (Mox) during the Biering-Sorensen muscular endurance (BSME) test, compare right and left side Mbv and Mox responses, and predict BSME time via Mox variables. Research suggests that during moderate intensity (approximately 20% of maximal volitional contraction) muscle contraction blood flow will decrease as a result of increased intramuscular pressure. Moreover, decreased muscle oxygenation is believed to be associated with diminished musculoskeletal endurance time, but until the development of near infrared spectroscopy (NIRS) it was not possible to non-invasively monitor these changes in erector spinae muscle. Nineteen healthy males completed the BSME in a prone position. The NIRS probes were placed on the left and right erector spinae muscle at the third lumbar vertebra level. The test protocol was: 2 min resting baseline, BSME to volitional fatigue, and 4 min recovery. The results indicated Mbv initially increased reaching asymptote before returning to baseline at termination. The Mox increased then declined systematically until BSME termination, returning to near baseline in recovery. No significant difference between sides was noted for Mbv or Mox. Mox best predicted BSME time. In conclusion, Mbv increased and then reaches asymptote as indicated in previous research, and oxygen availability was associated with the duration of erector spinae static contraction. Thus, prolonged static postures using the erector spinae muscles may diminish muscle oxygenation increasing susceptible to fatigue and injury.

Relationships between stroke parameters and critical swimming speed in a sprint interval training set.

The aim of this study was to determine whether a relationship exists between stroke parameters and critical swimming speed (which is defined as the speed that can theoretically be maintained without exhaustion). Stroke parameters (stroke rate and length) and velocity were recorded for each 25-m length during a controlled sprint interval training set in which participants swam one of the four competitive strokes at a range of intensities below, at, and above critical speed. Eleven participants (8 females, 3 males; age 17.9 +/- 0.9 years) completed a progressive (descending) set of 8 x 100 m repetitions in a 25-m pool according to target times that ranged in intensity from 65% to 100% of the swimmer's best time (the intensity for each repetition increased by 5% throughout the set). The data showed that participants reached critical speed on the fourth repetition and that substantial and unpredictable changes in stroke parameters occurred once critical speed had been reached. Specifically, post-critical speed stroke rate and stroke length were significantly (P < 0.01) greater and less, respectively, than the pre-critical speed values, and these changes occurred in an abrupt and non-linear manner. Overall, the findings suggest that critical speed represents a transition point between two different sets of stroke parameter relationships--one for low-intensity aerobic swimming and one for high-intensity anaerobic swimming.

Relationship between erector spinae static endurance and muscle oxygenation-blood volume changes in healthy and low back pain subjects.

The purposes of this study were to: (1) compare the muscle blood volume (Mbv) and oxygenation (Mox) responses on the right and left side erector spinae during the Biering-Sorensen muscle endurance (BSME) test between healthy, low back pain active (LBP-A) and LBP-sedentary (LBP-S) subjects using near infrared spectroscopy (NIRS), and (2) determine the relationships between the BSME time and Mbv and Mox. Informed consent was obtained from 30 healthy and 30 chronic LBP subjects. The latter group was subdivided into an active (LBP-A; n = 18) and sedentary (LBP-S; n = 12) subgroups based on physical activity patterns. The groups were age and sex matched. The NIRS probes were placed bilaterally on the erector spinae muscle at the level of the third lumbar vertebrae. The testing protocol was: 2-min resting baseline, BSME to voluntary fatigue, and 4-min recovery. During the BSME Mbv immediately increased for approximately 30-60 s, then showed an asymptote, and a steady decline towards the baseline at termination. Mox demonstrated either an initial increase followed by a systematic decrease until the termination of the BSME, or a systematic decrease throughout the BSME until termination. The LBP-S subjects showed a reduced Mox-range and slower Mox (1/2) recovery time on the left side suggesting a reduced aerobic capacity of the erector spinae muscle in this group. Significant correlations were noted between BSME time and the pooled values of Mox-delta and-range only in the LBP-A group. These observations suggest that factors other than erector spinae aerobic capacity can influence BSME performance.

In vivo erector spinae muscle blood volume and oxygenation measures during repetitive incremental lifting and lowering in chronic low back pain participants.

STUDY DESIGN: A case control study. OBJECTIVES: Using metabolic gas analysis and near infrared spectroscopy, a comparison was made between healthy controls and chronic low back pain (LBP) participants on cardiorespiratory, erector spinae muscle blood volume, and oxygenation responses, and these variables were used to determine factors that best predict peak oxygen consumption (VO2peak). SUMMARY OF BACKGROUND DATA: To date, it is unknown how the cardiorespiratory and erector spinae muscles of chronic LBP persons respond to repetitive incremental lifting and lowering. With the advent of near infrared spectroscopy technology, it is now possible to noninvasively examine erector spinae muscle oxygen supply and utilization in vivo. Thus, by using metabolic gas analysis and near infrared spectroscopy technology simultaneously, it is now possible to compare the cardiorespiratory and erector spinae muscle responses of chronic LBP participants to that of healthy controls (no history of LBP) during incremental work to volitional fatigue. METHODS: Thirty-four participants with chronic LBP and 34 healthy controls completed the repetitive incremental lifting and lowering (2.25 kg x min) protocol from floor to table (height 76 cm) at 10 lifts . min to voluntary fatigue. RESULTS: The healthy controls had significantly greater VO2peak (mL x kg x min) and VO2peak (mL x kgLBM x min), peak mass lifted, test duration, and breathing frequency. Furthermore, healthy controls showed significantly greater change in muscle oxygenation and faster one-half recovery times. Multiple regression analysis indicated that approximately 97% of the variance in absolute VO2peak was predicted by cardiorespiratory variables in both groups, while muscle oxygenation aided in predicting VO2peak relative in the LBP participants. CONCLUSIONS: The results indicated that the chronic LBP participants demonstrated a reduced cardiorespiratory and erector spinae muscle response during repetitive incremental lifting and lowering to volitional fatigue as compared to the healthy controls.

Cardiorespiratory and hemodynamic responses during repetitive incremental lifting and lowering in healthy males and females.

The purposes of this study were twofold. First, to evaluate the cardiorespiratory and muscle oxygenation (OXY)/blood volume (BV) responses during repetitive incremental lifting and lowering (RILL) in healthy males and females. Second, to develop a predictive equation for predicting peak aerobic power (VO(2peak)) during RILL from the cardiorespiratory, OXY/BV and body composition variables. Fourteen males and 18 females [mean (SD) for age, height and body mass were: 29.6 (8.2) years; 1.75 (0.07) m; 78.9 (10.4) kg and 23.9 (2.1) years; 1.63 (0.06) m; 62.3 (6.3) kg, respectively] completed a RILL from floor to table height at 10 lifts/min to voluntary fatigue. Cardiorespiratory responses were measured using open circuit spirometry and hemodynamic trends were monitored bilaterally at the third lumbar vertebra via near infrared spectroscopy. Significant sex differences ( p<0.05) were observed for the peak values of oxygen uptake (VO(2peak)), ventilation rate (V(E)), oxygen pulse, BV-max and BV-delta. Erector spinae OXY decreased systematically until VO(2peak )was attained, while BV decreased until approximately 50% of VO(2peak) and then leveled off. Stepwise regression analysis indicated that approximately 75% of the variance in VO(2peak )was predicted from cardiorespiratory, hemodynamic and body composition variables, with the most important predictors for absolute and relative VO(2peak )being V(E) ( r=0.75) and fat mass ( r=-0.63) respectively. Inclusion of left side OXY/BV responses increased the predictability of the common variance in VO(2peak )from 40% to 74%, implying that muscle hemodynamics play an important role in determining VO(2peak )during RILL.

Reliability of erector spinae oxygenation and blood volume responses using near-infrared spectroscopy in healthy males.

The purpose of this investigation was to (1). describe the trends in oxygenation (OXY) and blood volume (BV) of the right and left paraspinal muscles during the Biering-Sorensen muscle endurance (BSME) test using near infrared spectroscopy (NIRS), and (2). assess the test-retest reliability of OXY and BV changes during the BSME in healthy males. Seventeen healthy males [age=28.4 (9.8) years, height=1.75 (0.05) m, body mass=82.7 (9.1) kg; mean (SD)] completed two BSME trials within 1 week. NIRS probes were placed bilaterally at lumbar 3. The test was performed with the subject in the prone position using the following protocol: 2 min baseline, BSME, and 4 min recovery. The delta and range values of OXY and BV were used for analysis. Acceptable intra-class correlations were observed for endurance time and all the NIRS variables at the point of fatigue and at each 10% segment of the BSME during the two trials. Bland-Altman plots confirmed the reproducibility of the bilateral NIRS responses of the paravertebral muscles. The BV responses were more reliable than the OXY responses during the two trials. The OXY and BV responses of the paravertebral muscles during static contractions can be measured reliably using NIRS. Future studies should focus primarily on BV for analysis.