Notes on Undulation Training for Hierarchical Firefighter Fitness (JSCR 2008)
Abstract
Topic: undulation training (UT) for development of hierarchical fitness and transfer to firefighter job performance.
Participants: 14 well-trained firefighter academy attendees randomized into two groups (n = 7 each): undulation training (UT) and standard training control (STCo).
Intervention duration: 9 weeks of resistance training (27 sessions; three sessions per week).
UT what: daily nonlinear fluctuations in prescription variables to preferentially elicit multiple muscular fitness components. STCo: traditional periodization with targeted fitness components per mesocycle.
Outcomes measured: upper- and lower-body muscular strength; lower-body power output; sprint speed; jumping ability; anthropometry; firefighter Grinder performance (a battery of job-specific tests).
Key findings:
Nearly all fitness and performance measures improved in both groups (p < 0.05).
UT yielded significantly greater improvements than STCo in Grinder performance (p < 0.05).
Effect sizes (computed as per Hedges and Olkin) identified meaningful between-group differences (effect size > 0.50) in favor of UT for thigh circumference, vertical jump, 1RM squat, Grinder performance, and peak power output.
Conclusion: UT may provide a greater multidimensional stimulus for hierarchical fitness development and transfer to firefighter-specific performance than a periodized standard control model.
Keywords: undulating periodization, fire service, muscular strength, occupation safety.
Introduction
Firefighting is one of the most physically demanding and dangerous nonathletic occupations; high injury and cardiovascular risk burden.
Occupational health strategies should combine resources to promote healthy behaviors and reduce injury risk; primary prevention targets cardiovascular disease and musculoskeletal injuries.
Cross-sectional epidemiology suggests firefighting demands exceed many occupations; injury incidence is high (nearly four times higher than private industry in some data).
A coordinated, hierarchical fitness approach is needed: simultaneous development of cardiovascular fitness, joint mobility, muscular endurance, absolute/relative strength, and muscular power.
Traditional periodization targets one fitness attribute at a time; for occupations needing concurrent development of many attributes, a more diverse training stimulus may be advantageous.
Undulation training (UT): frequent nonlinear fluctuations in training variables to elicit multiple fitness adaptations concurrently. Prior work suggests daily undulating periodization can yield greater gains in singular fitness components (e.g., strength, endurance) compared with standard linear periodization when training volume is equated.
Rationale: UT could be especially suitable for firefighters who require multidimensional fitness to perform multiple job tasks safely and effectively and to mitigate overtraining by altering neuromuscular stimuli frequently.
Hypotheses:
UT would yield greater improvements in muscular strength and power than STCo after 9 weeks.
UT would produce superior transfer to firefighter-specific job tasks (Grinder performance).
Context: Findings may inform guidelines for hierarchical fitness development in fire service and aging populations; discussion includes potential neuromuscular and morphological underpinnings and practical applications.
Methods
Experimental design
Design: longitudinal, two-arm trial comparing UT vs. STCo during resistance training.
Groups: UT (n = 7) and STCo (n = 7).
Randomization: stratified by baseline body-mass–adjusted muscular strength capacity to balance relative lower-body strength.
Testing window: assessments before and after 9 weeks of training (+ testing/ familiarization sessions).
Attendance/exclusion: training three times/week for 1.0–1.5 h per session; exclusion if more than two missed workouts during the 9-week intervention.
Study timeline: testing and training required about 12 weeks total (including testing and familiarization); the actual intervention spanned 9 weeks (27 sessions).
Ethical: informed consent obtained; procedures approved by institutional review board.
Subjects
14 well-trained firefighter academy attendees; mean (SD): age ~21.9 ± 1.8 years; height ~180.9 ± 5.7 cm; weight ~85.6 ± 9.9 kg.
Inclusion criteria: no pending medical problems affecting testing or training; no recent ankle/knee/back pathology; cleared for progressive conditioning.
All participants completed testing and training; no external workouts during the study period.
Testing procedures
Anthropometry:
Standing height (cm), body mass (kg), and circumferences of upper-arm, chest, and thigh (cm).
Muscular strength:
1RM back squat (lower body) and 1RM bench press (upper body) following NSCA guidelines; 90° knee angle criterion for squat depth; reliable testing (retest ICC ≥ 0.90).
Power and speed:
Countermovement vertical jump (VJ; cm) using Vertec; three to five trials.
Standing broad jump (SBJ; cm); three to five trials.
40-yard dash (s) using infrared timing; three trials; fastest used.
Rate of force development (RFD) and peak power output (PP) during squat efforts at relative loads of 30% and 60% 1RM, measured with the TENDO FiTRO-dyne system.
Power computed as PP (W) using body mass + load (concentric phase).
Reliability: test-retest ICCs reported as ≥ 0.90.
Job-specific testing battery: Grinder
Six tasks performed in sequence, as fast as possible, timed for total score:
1) Equipment hoist (30-kg pipe hoisted to second floor and back).
2) Hose pull (65.6 m, uncharged hose, with weight secured to trunk).
3) Keiser sled and sledgehammer (drive a 150-lb weight 5 ft with a 3.5-kg sledge).
4) Stair climb with 10-kg hose pack over five flights.
5) Attic crawl (15 m, 3 x 3 ft crawl space) in turnout gear.
6) Simulated civilian carry/drag (drags two 25-kg packs 20 m).Gear: turnout clothing and a 25-kg SCBA considered during Grinder testing; Grinder sequence kept fixed to control fatigue/strategy effects.
Training protocols
Common elements:
All sessions began with a 10–15 min general cardio warm-up and a movement-specific dynamic warm-up.
Core resistance training focused on barbell back squat (lower body) and bench press (upper body) with supplementary exercises and ballistic movements (e.g., vertical jumps, box jumps, sprinting, plyometrics).
Training frequency: 3 days/week; session length 60–90 min; rest between sessions at least 1 day.
Training volume, intensity, and frequency were equated between groups; the key difference lay in how dosages were manipulated (nonlinear undulation vs. traditional mesocycle progression).
UT protocol (Figure 1A; 9 weeks): daily fluctuations to emphasize one of three objectives per session and across a 3-week mesocycle, with deliberate sequencing to avoid overtraining:
Day 1: upper-body endurance/hypertrophy + lower-body muscular strength.
Day 2: upper-body strength + lower-body speed/power.
Day 3: upper-body speed/power + lower-body endurance/hypertrophy.
Progressive overload: expanded overall dosage across weeks; dosage manipulation designed to target each objective weekly.
STCo protocol (Figure 1B): conventional periodization with fixed objectives per mesocycle:
Mesocycle 1 (weeks 1–3): muscular endurance and hypertrophy.
Mesocycle 2 (weeks 4–6): basic/functional strength capacity.
Mesocycle 3 (weeks 7–9): RFD and PP output.
Statistical analyses
Analytic approach: repeated-measures ANOVA; Tukey post hoc tests for pairwise comparisons when needed.
Significance threshold: or $$ ext{$\