Jackson, JK, Shepherd, TR, and Kell, RT. The influence of periodized resistance training on recreationally active males with chronic nonspecific low back pain. J Strength Cond Res 25(1): 242-251, 2011-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 similar to 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.

Kell, RT, Risi, AD, and Barden, JM. The response of persons with chronic nonspecific low back pain to three different volumes of periodized musculoskeletal rehabilitation. J Strength Cond Res 25(4): 1052-1064, 2011-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.

In front-crawl swimming, it has been shown that the point at which a non-linear increase in stroke rate (SR) occurs is consistent with a swimmer's critical speed (CS). This non-linear change in SR is known as the critical stroke rate (CSR), and can be predicted based on a swimmer's baseline SR (defined as the minimum SR that occurs at low-intensity exercise). Consequently, if the baseline SR is known, it is theoretically possible to use the critical stroke rate (CSR) relationship to approximate a swimmer's CS. PURPOSE: To determine whether the CSR relationship can be used to accurately predict CS in competitive front-crawl swimming. METHODS: Eight elite competitive swimmers (6 female, 2 male; 17.9 ± 0.86 yrs) performed three timed maximal effort swims (200 m, 400 m and 1000 m front crawl) to determine CS. The participants then completed a 4 × 200 m interval training set (60 s rest) at progressively increasing exercise intensities, with the 3rd 200 performed at CS: 1) LT1 = 91% of CS; 2) MLSS = 96.5% of CS; 3) 100% of CS and 4) VO2 Max. = 110% of CS. SR was recorded for each 25 m length of each 200 m repetition and CSR was calculated based on the relationship CSR = SR min.* 1.23. A paired Student's t-test compared mean CS to the 3rd 200 speed and the predicted CSR to the actual 3rd 200 SR to demonstrate there were no differences between the compared variables. A Pearson r correlation statistic was also used to quantify the relationship between the predicted CSR and the 3rd 200 SR. RESULTS: No differences were found between mean CS and the 3rd 200 speed (p > 0.35), indicating that the participants successfully performed the 3rd 200 m repetition at CS (the mean difference between the two parameters was 0.03 m·s-1). There were also no differences between the predicted CSR and the actual 3rd 200 SR (p > 0.65). Most importantly, the mean difference between the predicted CSR and the 3rd 200 SR (i.e., the SR at CS) was 0.07 cycles·min-1 or 0.18%. Further, the predicted CSR was highly correlated with the actual SR recorded during the 3rd/CS 200 (r = 0.99). CONCLUSION: The findings demonstrate that predicted CSR values (based on a participant's baseline SR) are consistent with the actual SR's used by participants when swimming at CS. As such, the results show that the CSR relationship can be used to accurately approximate CS in elite competitive front-crawl swimming.

Many physiological measures can be used to monitor training of endurance athletes. These measures range from maximal oxygen uptake (VO2max) to economy of movement. We used a variety markers to monitor changes in physiological function in an elite (e.g., World University Games) college female athlete competing since 2007 in cross-country (xc-) running, xc-skiing and biathlon. We monitored a variety of physiological variables in a female endurance athlete from the start of off-season (OS) to the conclusion of pre-Season (PS). PURPOSE: To measure changes in running economy, cardiorespiratory function and strength through 5 months of training. METHODS: Participant, one female college multi-sport endurance athlete. Training took place from OS through PS 5-7 days/week with a regimen of running, roller-skiing, cycling, weight lifting, and plyometrics. Testing began at the start of OS (May 10) concluding at the end of PS (Sept. 10). Tests included: maximal exercise variables (e.g., VO2max); morning, submaximal, and maximum HRs; running economy; and upper and lower body strength. RESULTS: The following changes from OS to the end of PS were noted: body weight (-0.18%), morning HR (0.0), VO2max absolute (+3.4%) and relative (+3.5%), VE (+4.2%), HRmax (-1.1), leg press (+11.1), and bench press (+23.8%). HRs (±beats/min) were reduced during and following (Rec) a 1-mile run test at 7.5 miles/hr (0.5 mile=-7, 1 mile=-10, 1 min Rec=-18, 3 min Rec=-8, 5 min Rec=-6). See Table 1 - running economy. CONCLUSION: Large improvements occurred from OS to the end of PS in this elite multi-sport endurance athlete, with the most important changes being running economy and strength.Table 1: Oxygen consumption (VO2 mL/kg/min) at submaximal running speeds.

Apel, JM, Lacy, RM, and Kell, RT. A comparison of traditional and weekly undulating periodized strength training programs with total volume and intensity equated. J Strength Cond Res 25(3): 694-703, 2011-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−1 (approximately 135 min·wk−1) from weeks 1 to 2 and 4 d·wk−1 from week 3 to week 12 (approximately 180 min·wk−1). 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 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.

Kell, RT. The influence of periodized resistance training on strength changes in men and women. J Strength Cond Res 25(3): 735-744, 2011-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−1 (324 repetitions [reps]·wk−1) and thereafter 4 d·wk−1 (mean 642 reps·wk−1). The mean volume and intensity over the 12 weeks was 571 reps·wk−1 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.

"Exercise as an intervention for non-specific low back pain." Physical Therapy Reviews, 15(1), pp. 36–37

Low back pain (LBP) is a considerable health and socioeconomic hindrance on western society. Chronic (≥3 months) non-specific (soft tissue) low back pain (CLBP) is the most common diagnosis. Recently, periodized strength training was successfully used as a form of CLBP rehabilitation. Thirteen weeks of periodized strength training (i.e., musculoskeletal rehabilitation) by CLBP participants produced ∼40% increases in strength; these increases are similar to other research studies using healthy participants. PURPOSE: To clearly establish if females with and without CLBP show similar increases in muscular strength following 11 weeks of periodized strength training. METHODS: Forty five females (24±3.2 yrs) volunteered for the study. The CLBP (n=15) and no LBP (non-LBP) (n=15) groups completed 16-weeks of testing (5 test sessions) and periodized strength training (11 weeks; 3-4 days. week-1). The control group (C, n=15) was disallowed to strength train during the study, but maintained other recreational activities and took part in all testing sessions. Average weekly training volume and intensity were 1,563 repetitions and 67% 1 repetition maximum (RM), respectively. All participants received instruction on exercise technique and RM protocol. Testing occurred at pre-familiarization, pre-strength, and at weeks 4, 8 and 12 of strength training. The participants completed 2-weeks of familiarization, followed by 9-weeks of strength training. The CLBP group's mean pain score (10-point scale) was 4.9 prior to familiarization testing. RESULTS: The p-level was set at ≤0.05. At baseline no significant (p≤0.05) differences were noted between the groups on age, height, body mass, body fat, or strength. Significant (p≤0.05) increases in strength from pre-strength to week 12 were found in both groups: CLBP (Week 4: leg press=13%, bench press=14%; Week 12: leg press=55%, bench press=39%); and non-LBP (Week 4: leg press=10%, bench press=11%; Week 12: leg press=40%, bench press=34%). No significant (p≤0.05) differences were noted between the training groups at any testing points. CONCLUSION: Females with CLBP are able make significant increases in strength following 11 weeks of periodized strength training, attaining similar strength increases as no LBP females. Sponsored by the Augustana Research and Travel grant.

Approximately 80% of North Americans suffer from low back pain, and 85% of these are diagnosed as chronic non-specific low back pain (CLBP). In 2005, the economic cost associated with back pain was ∼$38 million as reported by Workers' Compensation Board-Alberta. PURPOSE: To determine the impact of 3 different volumes of CLBP rehabilitation (exercise therapy) on the outcome measures of strength, pain, and quality of life (QOL). METHODS: One hundred and twenty (N=30/group) CLBP males were randomly assigned to one of the following groups: 2 days/wk (2D), 3 days/wk (3D), 4 days/wk (4D) rehabilitation, or Control (C; no rehabilitation). Rehabilitation group participants completed a 2-wk exercise familiarization period. Musculoskeletal (repetition maximum) testing occurred following familiarization at baseline, wks 8 and 12. The participant's pain (11-point visual analogue scale; VAS) and QOL (Short Form-36: Physical and Mental Composite Summaries) were measured at baseline, wks 8 and 12. RESULTS: The p-level was set at ≤0.05. There were no significant differences between groups at baseline, but significant differences were present within groups across time and between groups on strength, pain, and QOL (Table). All rehabilitation groups were significantly different than the control group at wk 12.TABLECONCLUSION: A volume of 4 days/wk demonstrated greater improvement in outcome measures, especially pain and QOL, than either 2 or 3 day/wk programs. Sponsored by the Augustana Research grant.

Studies of stroke parameter relationships in swimming have shown that the basic strategy used by elite swimmers to increase speed is to increase stroke rate (SR) while attempting to maintain stroke length (SL). Recently, it has been shown that non-linear changes in SR and SL occur immediately after a swimmer reaches critical speed. The specific intra-cyclic mechanisms responsible for producing these changes, namely the duration of the propulsive and recovery phases of the stroke cycle, have not been investigated. PURPOSE: To determine temporal changes in the propulsion and recovery time associated with increased SR in front-crawl swimming. METHODS: Eight elite competitive swimmers (6 female, 2 male; 17.9 ± 0.86 yrs) performed a 4 x 200 m interval training set (60 s rest) in a 25 m pool according to target times that were based on a critical speed test (1 = submax. intensity, 2 = max. lactate steady state, 3 = critical speed, 4 = VO2 max.). Velocity, SR, SL, propulsion time and recovery time were recorded for each 25 m length of each 200 m repetition. The data were normalized (1st length %) to compare the relative stroke parameter changes between the 4 x 200s using repeated measures ANOVA. RESULTS: As speed increased, SR increased significantly (p < 0.05) for each repetition (+26.5 ± 7.8% from 1st to last repetition), whereas SL decreased significantly (p < 0.05) for the 3rd and 4th repetitions (-2.6 ± 1.6% & -4.8 ± 2.8%, respectively). In addition, SR increased markedly during the 3rd (critical speed) 200 (+12.0% vs. the previous increase of +3.4%). Changes in SR were associated with significant decreases (p < 0.01) in the propulsion time for each repetition (-25.6 ± 8.1% from the 1st to 4th repetition) as well as the recovery time (p < 0.05) for the 3rd and 4th repetitions (-6.9 ± 4.9% & -13.2 ± 5.7%, respectively). An asymmetric change in the stroke cycle was shown by a significant drop (p < 0.05) in the propulsion/recovery ratio from the 1st to 4th repetition (-9.3 ± 11.2%). CONCLUSION: Progressive speed related increases in SR are associated with simultaneous decreases in the duration of the propulsion and recovery phases of the stroke cycle, such that propulsion time decreases more than recovery time. This suggests that pulling/pushing the arm through the water faster contributes more to the elevation of SR than increasing the tempo of the recovery.

Kell, RT, and Asmundson, GJG. A comparison of two forms of periodized exercise rehabilitation programs in the management of chronic nonspecific low-back pain. J Strength Cond Res 23(2): 513 -523, 2009 -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 (>= 3 months; >= 3 d.wk(-1)) 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 <= 0.05. No significant differences were noted among the groups at baseline. The RT group significantly decreased body fat percent from baseline to week 8 and from baseline to week 16, whereas the AT group significantly decreased body fat percent and body mass from baseline to week 16. The RT group significantly improved most musculoskeletal fitness, pain, disability, and QOL outcomes from baseline to week 8, baseline to week 16, and weeks 8 to 16. However, the AT group showed significant improvements in flexibility from baseline to week 8 and in cardiorespiratory and peak leg power from baseline to week 8 and baseline to week 16. The AT groups showed no significant improvements in pain, disability, or QOL. The primary finding was that periodized RT was successful at improving many fitness, pain, disability, and QOL outcome measures, whereas AT was not. This study indicates that whole-body periodized RT can be used by training and conditioning personnel in the rehabilitation of those clients suffering with CLBP.

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.

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 (∼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.

The World Anti-Doping Agency (WADA) has recently made a decision to allow the use of hypoxic tents amid a significant amount of controversy over the morality of their use for athletic training purposes. Currently, altitude training is considered moral, but other means of improving aerobic performance are not; for example, blood doping. Altitude training and blood doping have similar results, but the methods by which the results are achieved differ greatly. The controversy lies in how the use of a hypoxic device falls within WADA's philosophy, which will then dictate future policy. This paper discusses the influence of a hypoxic environment on human physiology, altitude training's influence on athletic performance, the concept of authentic physiology, and moral behaviour that is the foundation for logical debate.

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.

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 ~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 ½ 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.

Differences may exist between healthy (H) and low back pain (LBP) subjects both centrally and peripherally as a result of the deconditioning associated with low back pain. The examination of cardiorespiratory and muscle oxygenation was undertaken to test these two groups during lifting and lower activity. PURPOSES To compare H and LBP subjects on: (1) ventilatory threshold (VT) during a repetitive incremental lifting and lowering, (2) the relationship between VT and the psychophysically determined maximum acceptable lifting weight (MAW), and (3) muscle blood volume (Mbv) and oxygenation (Mox) responses in the MAW test. METHODS Informed consent was obtained from H (N=12) and LBP (N=12) subjects (Mean±SD): age (39.3±6.73 yr), height (1.72±0.09 m), and body mass (81.8±15.3 kg); age (37.7±2.3 yr), height (1.74±0.09 m), body mass (80.0±14.53 kg), respectively. The volunteers completed a 20-min psychophysical test (10 lifts/min) to determine the MAW for an 8-hour workday. Open circuit spirometry and near infrared spectroscopy were used to measure the cardiorespiratory, and Mbv and Mox responses. Mbv and Mox variables were calculated as ‘delta’ = min value during MAW - resting value; ‘range’ = max during recovery - min during MAW, and 1/2 recovery time was 50% max recovery. VT was identified non-invasively by the ventilatory equivalents. A 2-way ANOVA and an ANCOVA were used to for analysis of VT and MAW, and NIRS variables, respectively. RESULTS VO2 at VT was significantly (p ≤ 0.05) lower in the LBP compared to the H subjects. In the H subjects, VO2 at MAW was significantly lower during the psychophysical test, while in the LBP subjects MAW, HR and VE were significantly greater at VO2 at MAW. Significant correlations were observed for the absolute VO2 at VT and VO2 at MAW in the healthy (r = 0.76) and LBP subjects (r = 0.89). There were no significant differences (p>.05) between groups for the mean values of the Mox and Mbv variables. Significant correlations were noted for both groups in the cardiorespiratory responses during the psychophysical MAW and VT. At the MAW, there was a significant correlation between absolute VO2 and: Mbv-delta(r = 0.79) and Mbv-range (r = 0.70) in the LBP subjects. CONCLUSIONS The cardiorespiratory stress was significantly greater in the LBP subjects, most likely due to reduced central circulation, as no significant differences between the groups were observed in erector spinae Mox and Mbv. Localized muscle blood volume is implicated in the reduced VO2 during a psychophysical test in LBP subjects.

Repetitive lifting during occupational tasks has been associated with low back pain (LBP). Reductions in oxygen availability and aerobic capacity of the erector spinae muscles have been implicated in this phenomenon. This hypothesis, however, has not been tested in exercising humans. PURPOSE To compare the peak oxygen uptake (VO2peak) and muscle oxygenation responses between healthy (H) and LBP subjects during repetitive incremental lifting and lowering (RILL). METHODS Informed consent was obtained from 34 H and 34 LBP subjects who were age and gender matched. Subjects completed the prescribed RILL test: 2 min rest, 2.5 kg increase in lifting load every min to fatigue (10 lifts/min, lifting height 76 cm), 4 min of seated recovery. Cardiorespiratory responses were monitored using a wireless metabolic cart. Muscle oxygenation (Mox) and blood volume (Mbv) were recorded bilaterally from the erector spinae at the third lumbar vertebrae using near infrared spectroscopy. The following Mox and Mbv variables were calculated: delta, minimum value during RILL - resting value; range, maximum during recovery - minimum during RILL, and ½ recovery time (½ Rec, time taken for 50% recovery; an index of muscle aerobic capacity). Forward stepwise multiple regression analysis was used to predict the VO2peak from selected cardiorespiratory and NIRS variables. RESULTS There was no significant difference (p>.05) between H and LBP subjects for peak values of absolute VO2 (2.54 vs 2.29 L/min, heart rate (HR), ventilation rate, and oxygen pulse (O2 pulse). However, relative VO2peak was significantly lower (p < .05) in the LBP compared to H subjects (29.9 vs 34.4 ml/kg/ min). The LBP subjects demonstrated significantly lower Mox delta, Mox range and slower ½ Rec suggesting a reduction in muscle oxidative capacity. No significant differences were observed between groups for Mbv-delta and Mbv-range. In H subjects, peak values of HR and O2 pulse explained 59% and 16% of the common variance respectively in the relative VO2peak. In LBP subjects, peak HR, Mox-delta and peak O2 pulse explained 29%, 19% and 7% of the common variance respectively. CONCLUSIONS Localized Mox, independent of changes in Mbv, is an important predictor of the relative VO2peak in LBP but not H subjects. Support: Alberta Workers' Compensation Board and Millard Health