Time in Heart Rate Zones Bar Chart — lets-plot

A vertical bar chart showing the time spent in each heart rate training zone (Z1–Z5) during a workout or training period. Each bar uses the conventional zone color semantics (grey for Z1 recovery, blue for Z2 endurance, green for Z3 aerobic, orange for Z4 threshold, red for Z5 maximum) and is annotated with its duration, making the distribution of training intensity immediately readable. This is the standard summary chart found in fitness platforms such as Garmin, Strava, and Polar, and it reveals at a glance whether a session was easy, balanced, or high-intensity.

Time in Heart Rate Zones Bar Chart rendered with lets-plot

Python source (lets-plot)

""" anyplot.ai
bar-heart-rate-zones: Time in Heart Rate Zones Bar Chart
Library: letsplot 4.10.1 | Python 3.13.13
Quality: 87/100 | Created: 2026-06-14
"""

import os

import pandas as pd
from lets_plot import (
    LetsPlot,
    aes,
    element_blank,
    element_line,
    element_rect,
    element_text,
    geom_bar,
    geom_text,
    ggplot,
    ggsave,
    ggsize,
    labs,
    layer_tooltips,
    scale_fill_manual,
    scale_x_discrete,
    scale_y_continuous,
    theme,
    theme_classic,
)


LetsPlot.setup_html()

# Theme tokens
THEME = os.getenv("ANYPLOT_THEME", "light")
PAGE_BG = "#FAF8F1" if THEME == "light" else "#1A1A17"
INK = "#1A1A17" if THEME == "light" else "#F0EFE8"
INK_SOFT = "#4A4A44" if THEME == "light" else "#B8B7B0"
INK_MUTED = "#6B6A63" if THEME == "light" else "#A8A79F"
RULE = "rgba(26,26,23,0.15)" if THEME == "light" else "rgba(240,239,232,0.15)"

# Zone colors — semantic exception: conventional fitness platform zone palette
# mapped to nearest Imprint palette members (Z1→muted grey, Z2→blue, Z3→green, Z4→ochre, Z5→red)
ZONE_COLORS = [INK_MUTED, "#4467A3", "#009E73", "#BD8233", "#AE3030"]

# Data — 60-minute tempo run session
zones = ["Z1", "Z2", "Z3", "Z4", "Z5"]
minutes = [8, 22, 15, 12, 3]
zone_names = ["Recovery", "Endurance", "Aerobic", "Threshold", "Maximum"]
hr_ranges = ["< 114 bpm", "114–133 bpm", "134–151 bpm", "152–171 bpm", "> 171 bpm"]
total = sum(minutes)  # 60

df = pd.DataFrame(
    {
        "zone": zones,
        "minutes": [float(m) for m in minutes],
        "zone_name": zone_names,
        "hr_range": hr_ranges,
        "duration_label": [f"{m} min" for m in minutes],
        "pct_label": [f"{round(m / total * 100)}%" for m in minutes],
        "bar_label": [f"{m} min  ·  {round(m / total * 100)}%" for m in minutes],
    }
)
df["zone"] = pd.Categorical(df["zone"], categories=zones, ordered=True)

# X-axis labels: zone code, zone name, and HR boundary
zone_axis_labels = {
    "Z1": "Z1  Recovery\n< 114 bpm",
    "Z2": "Z2  Endurance\n114–133 bpm",
    "Z3": "Z3  Aerobic\n134–151 bpm",
    "Z4": "Z4  Threshold\n152–171 bpm",
    "Z5": "Z5  Maximum\n> 171 bpm",
}

title = "bar-heart-rate-zones · python · letsplot · anyplot.ai"
n_chars = len(title)
title_size = round(16 * 67 / n_chars) if n_chars > 67 else 16

# lets-plot distinctive feature: formatted interactive tooltip specification
tooltips = (
    layer_tooltips()
    .title("@zone_name")
    .line("Duration|@duration_label")
    .line("Share|@pct_label")
    .line("Heart rate|@hr_range")
)

plot = (
    ggplot(df, aes(x="zone", y="minutes", fill="zone"))
    + geom_bar(stat="identity", width=0.6, color=INK_SOFT, size=0.3, tooltips=tooltips)
    + geom_text(aes(label="bar_label"), vjust=-0.5, size=4, color=INK)
    + scale_fill_manual(values=ZONE_COLORS, name="")
    + scale_x_discrete(labels=zone_axis_labels)
    + scale_y_continuous(limits=[0, 27])
    + labs(x="", y="Time (minutes)", title=title, subtitle="60-minute tempo run  ·  training intensity distribution")
    + ggsize(800, 450)
    + theme_classic()
    + theme(
        plot_background=element_rect(fill=PAGE_BG, color=PAGE_BG),
        panel_background=element_rect(fill=PAGE_BG),
        panel_grid_major_y=element_line(color=RULE, size=0.5),
        panel_grid_major_x=element_blank(),
        panel_grid_minor=element_blank(),
        axis_title_y=element_text(color=INK, size=12),
        axis_title_x=element_blank(),
        axis_text=element_text(color=INK_SOFT, size=10),
        axis_line=element_line(color=INK_SOFT),
        axis_ticks=element_line(color=INK_SOFT),
        plot_title=element_text(color=INK, size=title_size),
        plot_subtitle=element_text(color=INK_SOFT, size=10),
        legend_position="none",
    )
)

ggsave(plot, f"plot-{THEME}.png", path=".", scale=4)
ggsave(plot, f"plot-{THEME}.html", path=".")

Part of Time in Heart Rate Zones Bar Chart on anyplot.ai.

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